Both layouts do show up in this post. Thanks. Also thanks for the enlightenment…I went to the link and sure enough, a Futaba VFD. Who knew? [noparse];)[/noparse] As for LED Bar Graphs, it is true if you share a supply and aren’t careful the bouncing display can be a source of noise in your amplifier. However I use a separate supply for the displays and fully filter the board itself. Also there is a diode/RC filter on the input which also helps clean up any leakage. I always appreciate having them too when I have the volume down and still have music playing. The meters on the Pre-Amp are always on the input (pre-volume) so they show levels whether the volume is up or down or even if the pre-amp is muted. This new amplifier will only be new in the sense that I have never used the MPC507A or the PGA2311. The parts I used to use when I built so many LM3886 amplifiers in the 90’s are all obsolete/discontinued. One in particular was a single supply part but one I really liked…LM1037N. Time to play catch up!
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Yup, we have the same Noritake display. I'm still working on the code for mine, very slowly. I'm trying to build a library of sorts for the display, with drawing primatives so I can reuse it easily.
After spending some time with the data sheet, I think the OPA549 would be better suited for the lower half of a biamped setup, much like the LM12. It has a rising THD curve that I'm not a huge fan of, plus it costs a lot more than the free LM3886s I've amassed over the years
Junkie-
You might want to consider buffering the inputs of the MPC507 as well. It helps keep THD low, and generally makes them immune to differences in source impedance. A simple noninverting buffer will do. Otherwise, I think your plan sounds great.
I was planning on three function buttons (source, vol, menu) and a pushbutton rotary for my human interface before I got sidetracked by surround sound The navigation is a little different with that scheme, but both work very well.
What scheme are you going to use for your IR control?
-dave
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Also thanks for the enlightenment…I went to the link and sure enough, a Futaba VFD. Who knew?
Chris: You are welcome, I hope you are going to buy more than one (100 would be a nice figure ), 3886 is a nice chip good high and low freq response, easy to build even a P2P.
I have a VFD bar graph display though it works fine but I have never used it beyond testing once...
LM391x and LB1415 I used both of them and had the same problems that I mentioned above in·nineties when I was learning·electronics, and came to the same conclusion that you have mentioned of seperate PSU for Bargraph and RC filter. For me digipots concept is about three years old when I found TDA7448 chip and wanted to make a vol controller around it and posted about it on a DIY board like a newbie and the kind of flames I got from there convinced me to improve my learning curve and do learn mcu's myself, so three years down the road I guess I could do many things with a MCU...
Dave: I would put a buffer before MPC507, and would use an op amp with FET input stage. But as·I mentioned lack of time do leave me at difficult stages I couldn't seem to find how much current·could MPC507 tolerate in the signals (sorry for my bad english)·coz reason I didnt use SSM2404 was it had a maximum current flow of 20ma (if I remember right).
OPA549 is a nice chip I have used it many times in many amp and after comparing it with 3886 and TDA729x I have come to the conclusion that OPA and TDA are better choices (for me, others might have different opinion)
What scheme are you going to use for your IR control?
SONY I guess, coz I.R modules of sony are easy to get (here) and easy to implement for me.
I have developed a·working code, where I could make the PIC do what I want via I.R and·implemented it sucessfuly.
For the pre, if I get time this weekend I ll try to make schematics and share with you and chris so that your expert opinion could help to improve it...
Here is a smaller version, send by a friend, but now the new version developed by me has more buttons and uses 16F876A instead of 874A, has output buffers, better supply and I.R implemented, output relay to prevent powerdown thump, and 2 source switching relays
100+ LM3886 chips? Hehe, only if I go into production again…I did that once…But building each amplifier was such a tedious task that after awhile I needed a break from it. I love the electronics part, but admittedly milling out enclosures is something I don’t care for. Not to mention tuning all the individual circuits as my systems always had 3 or 4 boards in each cabinet.
The buffers Dave mentioned reminded me…I typically buffer both the input and output of the Pre-Amp circuitry. Back when I had Tape Monitor circuits the input/output of those was buffered as well. But what I had forgotten was that I also buffered the input to the Level Meters, which also helps cut down on any noise. The Op-Amps I used for buffers were high-end, low THD units made specifically for audio and dual supply. I will have to look at the part numbers some time, but I believe I used to get them from a surplus house called B.G. Micro, simply because they had them cheap and they were somewhat hard to find.
As for choice of parts everyone has their own preference and you have to go with what you know/like or just what works for you. Our interests are still common and the end goals are very similar. I’m sure we’ll all learn a lot from each others experiences in doing this. I hate to admit it but this will be the first amplifier I built with milled PC boards. In the past every board was hand made. Sometimes I had to do it twice to get it right but back then it wasn’t cost-effective to have them done professionally. Now with ExpressPCB and others it can be done pretty cost-effectively.
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Dave: I would put a buffer before MPC507, and would use an op amp with FET input stage. But as I mentioned lack of time do leave me at difficult stages I couldn't seem to find how much current could MPC507 tolerate in the signals (sorry for my bad english) coz reason I didnt use SSM2404 was it had a maximum current flow of 20ma (if I remember right).
No worries about your english...it's at least as good as mine is before I have my morning coffee The MPC507 isn't designed to move much current at all. Hence the input and output buffering. It's frequency response and THD are also related to the input and output impedances it sees. Iout is measured in microamps for the part, and for best performance, feed it with a very low input impedance (<<<1k) and let it drive a very very high output impedance (FET input op amps are good). A simple unity buffer of the right type on each end will make things happy for you. It'll also ensure that you never exceed the voltage range of the MPC, since it can run all the way to it's rails, and your buffers will likely clip a little bit before that.
-dave
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100+ LM3886 chips? Hehe, only if I go into production again
Sorry for miscommunication, I meant VFDs 100+ units of Futaba would be a good figure(·) 3886 I could get as much as I want @3-4$ per chip, its only VFDs that are difficult to get here (in fact impossible), chris I agree with you on in/out buffers.
Also·about econo prices, its always price vs benefits(economy) that one needs to calculate. 5532/33 are pretty reasonably priced here like 1$ per chip (though I have lots and lots of AD8610/20 and OPA134, OPA627 more than 30 each)
Express PCB is a good way and pretty economical as well.
Do you think you want to go ahead with your own design or would like to embark upon a group design with Dave and me? I am open to suggestions....
The MPC507 isn't designed to move much current at all. Hence the input and output buffering. It's frequency response and THD are also related to the input and output impedances it sees
Are the Futaba VFDs graphical? From the picture they appear to be character displays. The Noritake I am planning on currently is graphical. As for a Unique VS Group design, there’s no reason we couldn’t do both. I can continue to build my current system while contributing to a group design if that’s what Dave wants to do. I know time is a luxury for most of us these days.
What I would need to do is obtain the parts you’re using…Also, we’d have to agree on ExpressPCB or Eagle for the PCB layout as I don’t have access to anything else right now. I know in Eagle the free version is somewhat limited in board size, which I don’t know if that will matter here or not…I guess we’ll see what Dave says and go from there. Dave?
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The question of the capture program (EAGLE, DxP, Altuim, ExpressPCB, etc) is going to need to be worked out pretty fast. My copy of EAGLE is an older one (4.0) so I won't be able to edit anything anyone creates in the freeware version (it's newer). Of course, my version of Altuim/DxP is a lot newer, but I can backsave that one to any previous rev.
I'm up to my ears right now with job work, but I'd be happy to contribute some random tidbits I've got socked away already, until I can dig my way clear to actually put some hours into a design.
I suppose the next question is what precisely do we want to design?
-dave
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Are the Futaba VFDs graphical? From the picture they appear to be character displays. The Noritake I am planning on currently is graphical.
These Futaba VFDs are character display and are HD44780 compliant, easy to program and implement as easy as:
lcd clr;
& lcdout "Hello World"
he he and easy to define custom characters.
As for software for Layout you might want to email me to discuss that coz I have·registered versions·of EAGLE, DXP V7/2004, and Proteus 6.7 VSM...
I'm all for a group design.
For project outline I guess I have already posted my idea for it...
I did plot the schematics last eve, I have them here with me but dont want to post them on the board.
I would need you guys to provide some feedback and change what you want to.
I use PB Pro 2.47 which I guess (think) is BS compatible? dont know exactly
Awaiting your inputs, regarding project outlines, layout software and how to share schematics....
There’s nothing wrong with character LCDs…Before Dave swayed me over to the Noritake Display I was going to use a simple 2X16 Character LCD w/Backlight. I have designed many customer characters for HD44780 compatible displays over the years. Most are built around audio or security functions. I have speakers, CDs, Tapes, Input Jacks, etc. Of course @ 5x7 they are very clunky, but they get the job done.
As for software, as I said, I am limited to designs in Eagle or ExpressPCB. I have no intentions of picking up the packages you and Dave have since it’s not really cost effective for me, plus I would want any shared designs to be available to others who also could not afford the commercial grade software. Even the design I am working on myself will be made freely available in Eagle format with schematic and complete Bill Of Materials. I have no desire to sell the design and even with as complex a design as it may appear to some it will actually be quite simple compared to some of the stuff Dave and perhaps you are working on.
On the group design…I’m all for testing a new Power Amp design using this other chip you referred us to as well as a Pre-Amp for it.
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Aww, Chris, did I really sway you that much? I've still got a pile of character VFDs and LCDs around, and use them a lot more often than I even consider using my one Noritake graphical, mainly because they're so easy and cheap.
I don't expect anyone in the hobby world to ever own a copy of DxP...at the price they're charging for new licenses I can't afford to buy one for myself. If I didn't work at a place that already had a few seats (along with a machine shop and some really cool EE toys) my hobby efforts would be much more limited.
My current though on the software front requires a somewhat modular approach to the design. THe free version of EAGLE limits one to a eurocard area board. There's a lot we can do in that space, but I think it might be wise to consider making modules, that way we can get a lot of functionality in the box without requiring large PCBs and the associated large design tool costs.
An amp and pre pair would be fun I think. If we go modular, it'd be easy to add balanced and unbalanced input/switching modules, a digital input (DAC module), and all sorts of other interesting bits (class A output buffers, tube buffers, etc), assuming folks embrace the openness of the project and contribute.
Thoughts?
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Hey, count me in! I just picked up a few LM3886 chips for peanuts....
I think modular is the way to go, they could be building blocks to a really kick - xxx system, and are upgradeable...
Bob
Post Edited (Robert Kubichek) : 3/9/2007 7:57:41 PM GMT
I finally dug out my Audio Pre-Amp chips today to verify I still had the datasheet. They are manufactured by JRC and are part # NJM2068D. As I recall these weren’t the easiest to find in the late 90’s and I got these from B.G. Micro. They have the following features…Datasheet attached.
Operating voltage (+/-4V ~ +/-18V)
Low THD (0.001%)
High Slew Rate (6V/uS typ.)
Unity Gain B/W (27 MHz @ f=10 KHz)
DIP8 Package
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I have no intentions of picking up the packages you and Dave have since it’s not really cost effective for me, plus I would want any shared designs to be available to others who also could not afford the commercial grade software.
well to be honest you are right but I guess I could arrange for that.....
as for sharing the design I dont have any issues with it, except one concern to add disclaimer that the design and firmware is not for commercial usage. It had happened to me once that I posted design (dxp format) firmware on one of the e-board, only to find it couple of weeks later with some changes in the inputs stage and no change in the software by another gentleman's name, claiming it to be his design with even the header of the firmware having my name....
I guess posting .hex file or even pre-programmed chips wont be a bad idea.
I have no interest in commercial gains
My current though on the software front requires a somewhat modular approach to the design.
Agreed.
I·did a 5 channel power amp· around OPA549, board is double sided available in PCAD.PCB, DXP.pcbdoc meaning that I could always do a gerber output. Fortunately I found it in my notebook so I am editing the post and attaching the PDF
As I have the 3886 stereo version I think doing a multichannel one is matter of half an hour or so.
BTW: MAX5406 is one hot chip have a look at its data sheet.
Dave have u checked PCM290x or 270x USB Dacs? Robert:
welcome aboard.
Those are nifty little chips. I like the simplicity of their design...diff input, bipolar complimentary output driver, limited output protection, and not much else. Too bad they're so darn hard to find now.
Junkie said...
as for sharing the design I dont have any issues with it, except one concern to add disclaimer that the design and firmware is not for commercial usage. It had happened to me once that I posted design (dxp format) firmware on one of the e-board, only to find it couple of weeks later with some changes in the inputs stage and no change in the software by another gentleman's name, claiming it to be his design with even the header of the firmware having my name.
Two words: Locked PDFs.
It's not inherently secure, but it's a darn sight better than posting the master files. I've been bitten by the same thing a few times, once for profit, so I know the sting well. Being a consultant these days, doing development both for hire and in-house for later OEMing, IP violations like that hit extra close to home.
Junkie said... modular boards, MAX5406, USB DACs
I love modular systems
Heck, with the right motherboard design, we could engineer it so we could make a receiver out of this thing (I've run across some serial controlled FM tuner modules in the past).
The MAX5406 is a nifty little chip. Pity about the low supply voltage though. I'm a bit of a parts snob, I confess. I have trouble using anything that doesn't want at least +/-5V, preferably +/-15 (hence my affinity for the CS3310 and PGA2311).
I've actually got a layout someplace for a USB DAC based on the PCM2906(?), but it's buried at the moment. It'd be easy enough to implement though.
Here's my proposal for our system:
A motherboard, size and shape determined by the end user. Example: 10" wide x 4" deep.
"Inputs" are dual row 0.1" headers spaced every inch, on center, total qty 6.
"Outputs" are the same connector and spacing, but qty 2.
Inputs and outputs need not share a common motherboard, but can.
The bus between them will contain power, audio and control signals on seperate headers. Precise header layout below in daughter board spec.
Daughterboards, each 2" tall and as deep as required, not to exceed 8" (or the limit of the software package being used, 4" for EAGLE lite) so we can pack this into a 2U rack case.
Power connector: 2x4 dual row 0.1" header, 2.25" from back panel edge of PCB, 0.05" up from PCB bottom edge
Contents: 2 pins for ground, 2 pins each for 3 power supplies
Control connector: 2x6 dual row 0.1" header, 1.5" from back panel edge of PCB, 0.05" up from PCB bottom edge
Contents:TBD, but 12 pins should be enough, right?
Signal connector: 2x12 dual row 0.1" header, 3.25" from back panel edge of PCB, 0.05" up from PCB bottom edge
Contents: 8x 3 line inputs, to be used as seen fit. Suitable for 8 stereo sources with individual grounds. Also suitable for 6 balanced inputs using power supply ground as audio ground. Also suitable for 8 stereo sources and 2 balanced inputs with a common ground and pins left over. We should figure out 2 variants I think, one single ended, one not.
Vertical offset may change depending on the right angle header used, to keep the overall height of the mother and daughterboard under 2.5"
I'll be putting it into a design document today...we can continue to edit and things to our hearts content though. I'll post it once I'm done with the first draft.
Early input would be good though
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I understand your concerns on IP being used by others in commercial applications illegally, which is why I suggest we continue on our original designs on our own, keeping those details vague and on the collaborative effort we focus on a more generic design which could be easily modified by others. I doubt we’ll fit everyone’s needs/wants in one shot. Plus, since I will be using non-familiar parts I will have to fly blind, so to speak since I have never had a chance to really prototype with some of these new parts. I am just looking forward to trying something new and hopefully adding to the overall design parameters.
Dave,
Yes, too bad on the audio chips…It’s like the LM1037N where I had like 5 different amplifier designs using the chip (about 20 custom systems) and then it was discontinued. I had enough in case I needed replacements for my customers but after 10 years I lost touch so if they ever find me now I don’t have the chips to replace them. Then again in one of the designs the main amplifier chip was discontinued. Oh, just did a check and the LM383 was also discontinued so add that to the list…Oh well…On one hand it makes me wish I was more into discrete amplifiers but on the other hand that makes my head hurt.
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I plan to keep my personal designs personal. What I contribute to the OpenPreamp though, will be pretty cool too I think.
To that end, here's my first stab at a spec. The PDF is locked from editing (version control reasons mainly), but is printable and folks can leave notes on it. Feel free to hack it apart and tear my draft to shreds...that's what it's there for. I have some ideas about the structure of the document, and how it goes together, which I'll try and implement in version 0.2, so for now focus on the content. All of the information is open for discussion...these are just some ideas I put on paper.
The dimensions in the module drawing are incorrect, I know. That was Altium, because it can dimension things quickly. I'm working on the EAGLE version, hopefully it'll be prettier and more accurate, since it uses center points for placement instead of pin 1, unless we want dimensions for both?
Also attached is the EAGLE directory of the first stab at the module board. The schematic is horiffic, but it gets the point across.
-dave
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Post Edited (Dave Paton) : 3/13/2007 9:48:41 PM GMT
actually got a layout someplace for a USB DAC based on the PCM2906(?)
Nice Chip I would be interested in making one for me'self, though I did one around 2902 and 2706 nice little chips.
I would be more than happy to be part of group design, whatever specs you guys comeup with its fine with me.
My only limitation is that I find it difficult to work with EAGLE (despite having 4.15 registered version), always find it comfortable to work with P.DXP, however PDF would a good way to share things. I would like to give MAX chips a try, order is underway let see how much time my agent takes to get them here.
Dave·I have gone through the docs and they are alright with me, now Q is which stage should I design and who will take resposibility of different stages?
For me doing PIC and BS is easier than AVR or 8051 chips.
I understand your concerns on IP being used by others in commercial applications illegally, which is why I suggest we continue on our original designs on our own, keeping those details vague and on the collaborative effort we focus on a more generic design which could be easily modified by others.
Agreed
I plan to keep my personal designs personal. What I contribute to the OpenPreamp though, will be pretty cool too I think
& agreed Point is do our designs ourselves no prob, let put something for those who either cant do it or cant afford t. As for my personal design I guess whatever changes are to be made digital section would remain the same, keeping that in view I had been working on the programme to control PIC, PGA, input selector, vol up, vol down, mute/unmute switch and encoder. I think I have made it work pretty well now I need to tweak it a bit and add I.R codes. For MPC50x I guess I need to study a bit more to adjust TTL level out of PICs and
"VAH (Logic Level High) = +4.0V;"
of MPC chips.
Take care
Junkie said...
now Q is which stage should I design and who will take resposibility of different stages?
Well, the stuff I put in was just filler. Have we really all decided to go with those parts, those reccomendations, and that language? Do we all agree on the form factor, pinouts, etc?
I can't believe that half an hour of unilateral typing generated something everyone agrees with. That's just too easy.
I agree, I'm more comfortable in Altium than I am in EAGLE, but since (I believe) our target audience must be able to freely create parts for this project, we need to stick with something that's free, no? I think we'll need to have stock designs for the motherboard, since it'll be larger than the Lite board limits (or one of us can do it in Altuim/DxP), but everything else can happen in EAGLE Lite I think.
As far as the MPC's Vah of 4V, it means it's designed to work with 5V logic. If you plan on using a 3.3V uC, you'll need level translators. Think of Vah ans Vin(high).
Chris? Anything to chime in with?
-dave
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I think it will be more difficult to do something community oriented if we don’t use community available resources. That said I was planning on using Eagle myself…PDF is okay for showing a concept, but I find if you can’t load it in and look at it yourself it’s very difficult to offer much in the way of useful advice.
As for the controller…Of course I will be using a BASIC Stamp, however the controller board can be separate, so we should build it as if that is an unknown. As far as the audio section I don’t know about you guys but I tend to design the main amplifier and work backward from there since often the requirements of the power amplifier will affect the pre-amp design. It is rarely an issue the other way, at least for me.
Dave’s right…Standard TTL logic should be able to handle everything we’ve mentioned…My big set back is the power supply requirements since I got lucky before and was able to run everything from +/-12V and +/-5V. Now I need +/-15V so none of my current prototyping supplies will work. This means I need to break down and build a new supply.
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Chris Savage (Parallax) said...
I think it will be more difficult to do something community oriented if we don’t use community available resources. That said I was planning on using Eagle myself…PDF is okay for showing a concept, but I find if you can’t load it in and look at it yourself it’s very difficult to offer much in the way of useful advice.
My thought was that we'd provide some reference designs in PDF form and gerber-ized, ready for home photolith construction or sending to a board house. We'd also provide an EAGLE template for the module boards, kinda like a prototyping board, but electronic. That way, anyone who wanted to build their own modules for input or output could take the existing template with the physical board outline and the connector positions, and fill in the blanks with their desired bits and bobs.
Chris Savage (Parallax) said...
As for the controller…Of course I will be using a BASIC Stamp, however the controller board can be separate, so we should build it as if that is an unknown. As far as the audio section I don’t know about you guys but I tend to design the main amplifier and work backward from there since often the requirements of the power amplifier will affect the pre-amp design. It is rarely an issue the other way, at least for me.
I do just the opposite...I start at the low level side and work up, since I consider a good amplifier to be independent of it's preamp, with a nice high input impedance, ready for anything to be plugged into it. Out of curiosity, how has the amp design affected the preamp design in the past?
Chris Savage (Parallax) said...
Dave’s right…Standard TTL logic should be able to handle everything we’ve mentioned…My big set back is the power supply requirements since I got lucky before and was able to run everything from +/-12V and +/-5V. Now I need +/-15V so none of my current prototyping supplies will work. This means I need to break down and build a new supply.
I need to send you my power supply boards still. They're sitting on my desk, waiting for a day warm and dry enough to pull the table saw out. I promise it'll be soon...
-dave
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Dave Paton said...
I can't believe that half an hour of unilateral typing generated something everyone agrees with. That's just too easy.
My applogies if I misunderstood, my only thought was let do it decide amongst ourselves who would do which part and other things....
Chris Savage (Parallax) said...
I think it will be more difficult to do something community oriented if we don’t use community available resources. That said I was planning on using Eagle myself…PDF is okay for showing a concept, but I find if you can’t load it in and look at it yourself it’s very difficult to offer much in the way of useful advice.
Hmmm, nice logic
Agreed, though I feel comfortable with DXP but whatever portion is assigned to me I ll do it in EAGLE.
As for my own project please see attachment, its a view of my board in 3D, simple design Quad RCA Jacks, input buffer around OPA2134, PGA2310, Output Buffer around OPA627, with out put relay, PIC mcu.
Junkie said...
My applogies if I misunderstood, my only thought was let do it decide amongst ourselves who would do which part and other things....
No worries. I wanted to toss out some ideas, and I'd hoped everyone would add their opinions to help make things better. I don't want to make the design decisions all by myself...
To all:
Do we need a section on tone control? Should there be a processing header on the backplane board? Do we need more than 2 headers for output modules, given the size constraints I've guessed at? Is the module size reasonable? How about the power supply header? More voltages? More pins? More ground? The bus connector pinout...does it make everyone 100% happy? We still need to define the control connector...I need input here. 1x SPI, 1x I2C, and some bitwise I/O? I don't know!
Junkie said...
Agreed, though I feel comfortable with DXP but whatever portion is assigned to me I ll do it in EAGLE.
I'm more comfortable in Altium/DxP, but since I did a lot fo time in Eagle, I've got no problem with it, especially since there's a free version, and I'm happy to be the guinea pig for the limits of the Lite.
Junkie said...
As for my own project please see attachment, its a view of my board in 3D, simple design Quad RCA Jacks, input buffer around OPA2134, PGA2310, Output Buffer around OPA627, with out put relay, PIC mcu.
Looks good! I'm had to switch almost 100% to SMT for my personal designs, as the chips I like playing with don't come in DIP packages, and the high quality SMT-DIP converters are pricey. I just wish I could get the PCB3D module working on my machine...it crashes every time with a conflict with my video card. Altuim has been sympathetic, but useless in getting it fixed.
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Could the group design modules that are controlled by a Stamp cpu via a common buss??
Imagin a modular system with seperate preamps/tone/input output switchers connected to
a power amp, and controlled by a stamp with any type of custom display via a common buss
for flexibilty of configuring to suit ones needs...
If you look, you'll see the control bus to all modules is as yet undefined. It'd be easy to make 2 of the wires RS-485 multidrop, allowing any kind of inter-unit communication, and any amount of processing power to be put on the modules.
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I will ponder the current information and post something on Sunday...My brain's too fried today and I have a bunch of things to post tomorrow which will limit time. Dave threw out some very important things to think about though...Especially in terms of P/S design.
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Chris Savage said...
I will ponder the current information and post something on Sunday...My brain's too fried today and I have a bunch of things to post tomorrow which will limit time.
Same here, had three tough days (friday, saturday and sunday) attended Asia Oceana Regional Meeting (mutual funds and investments for which I was invited to attend) and after that had meeting of country mutual fund (of which I am also a member) and some extra curricular activities, that has virtually fried my brain too. In the office for a couple of hours and after that will take off for a well deserved rest.
Will post my thoughts tomorrow.
Dave has some important points.
As for PCB3D crashing it has not much to do with DXP/ADS rather the VGA card, hopefully it should be a GeForce and not the build in one or ATI coz both of them have some conflicts, but if its a GeForce please update to latest drivers hopefully you ll get the problem resolved.··
My thoughts on P/S design are as follows: We'll need +5 and +/-15 for digital and analog for sure...if you need less than +/-15, hang some little regulators on your module board and locally regulate your supply..it'll make for a lower noise system anyway most of the time. If you need a LOT of some other voltage, that's where Vcc2 comes in...and where we need to talk. Personally, I'm probably going to stick some random voltage on there for whatever I need...independent of what we decide the spec to be, unless we leave it 'open'.
I have some thoughts about a different arrangement of the backplane too, with more output slots, and modular config for switching, volume control, and tone control, but that's something I won't actually bring up until we have some of these more basic things nailed down.
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Just one thing that 5v digital section should have seperate return paths just to keep digital and analogue ground seperate.
For other supplies like 12v -/+ for analogue section I think regulators may be added after 15v reg.
Dave Paton said...
I have some thoughts about a different arrangement of the backplane too, with more output slots, and modular config for switching, volume control, and tone control, but that's something I won't actually bring up until we have some of these more basic things nailed down.
Look forward to hear about those ideas. What·does "more basic things nailed down" mean?
Going to have a long weekend 3Days.
Will be back on monday.
·· I’m a little confused on the supply…The PGA2311 requires a dual supply @ +5V/-5V and the MPC507A requires a dual supply @ +15V/-15V so why doesn’t the supply have -5V? In my earlier pre-amp I used the +12V/-12V to get the +5V/-5V for the audio circuits, so I could do that. The +5V logic supply is always separate. I need to confirm what you’re doing so I can integrate that into my organic memory core (brain). Thanks.
·· As a side-note I have been working on the code for the controller since I will need the basics when it comes time for testing.· It’s interesting to see how this is developing.· I will post some code once I have a good base I am working from.
[noparse][[/noparse]Edit] - Okay, organic memory core meltdown...Somehow I blew right past your answer to my question...Don't mind me...I think I am having an overload from so much information today!
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Post Edited (Chris Savage (Parallax)) : 3/26/2007 7:36:54 PM GMT
Comments
Both layouts do show up in this post. Thanks. Also thanks for the enlightenment…I went to the link and sure enough, a Futaba VFD. Who knew? [noparse];)[/noparse] As for LED Bar Graphs, it is true if you share a supply and aren’t careful the bouncing display can be a source of noise in your amplifier. However I use a separate supply for the displays and fully filter the board itself. Also there is a diode/RC filter on the input which also helps clean up any leakage. I always appreciate having them too when I have the volume down and still have music playing. The meters on the Pre-Amp are always on the input (pre-volume) so they show levels whether the volume is up or down or even if the pre-amp is muted. This new amplifier will only be new in the sense that I have never used the MPC507A or the PGA2311. The parts I used to use when I built so many LM3886 amplifiers in the 90’s are all obsolete/discontinued. One in particular was a single supply part but one I really liked…LM1037N. Time to play catch up!
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Chris Savage
Parallax Tech Support
Yup, we have the same Noritake display. I'm still working on the code for mine, very slowly. I'm trying to build a library of sorts for the display, with drawing primatives so I can reuse it easily.
After spending some time with the data sheet, I think the OPA549 would be better suited for the lower half of a biamped setup, much like the LM12. It has a rising THD curve that I'm not a huge fan of, plus it costs a lot more than the free LM3886s I've amassed over the years
Junkie-
You might want to consider buffering the inputs of the MPC507 as well. It helps keep THD low, and generally makes them immune to differences in source impedance. A simple noninverting buffer will do. Otherwise, I think your plan sounds great.
I was planning on three function buttons (source, vol, menu) and a pushbutton rotary for my human interface before I got sidetracked by surround sound
What scheme are you going to use for your IR control?
-dave
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I have a VFD bar graph display though it works fine but I have never used it beyond testing once...
LM391x and LB1415 I used both of them and had the same problems that I mentioned above in·nineties when I was learning·electronics, and came to the same conclusion that you have mentioned of seperate PSU for Bargraph and RC filter. For me digipots concept is about three years old when I found TDA7448 chip and wanted to make a vol controller around it and posted about it on a DIY board like a newbie and the kind of flames I got from there convinced me to improve my learning curve and do learn mcu's myself, so three years down the road I guess I could do many things with a MCU...
Dave: I would put a buffer before MPC507, and would use an op amp with FET input stage. But as·I mentioned lack of time do leave me at difficult stages I couldn't seem to find how much current·could MPC507 tolerate in the signals (sorry for my bad english)·coz reason I didnt use SSM2404 was it had a maximum current flow of 20ma (if I remember right).
OPA549 is a nice chip I have used it many times in many amp and after comparing it with 3886 and TDA729x I have come to the conclusion that OPA and TDA are better choices (for me, others might have different opinion) SONY I guess, coz I.R modules of sony are easy to get (here) and easy to implement for me.
I have developed a·working code, where I could make the PIC do what I want via I.R and·implemented it sucessfuly.
For the pre, if I get time this weekend I ll try to make schematics and share with you and chris so that your expert opinion could help to improve it...
Here is a smaller version, send by a friend, but now the new version developed by me has more buttons and uses 16F876A instead of 874A, has output buffers, better supply and I.R implemented, output relay to prevent powerdown thump, and 2 source switching relays
Post Edited (Junkie) : 3/7/2007 5:15:46 AM GMT
100+ LM3886 chips? Hehe, only if I go into production again…I did that once…But building each amplifier was such a tedious task that after awhile I needed a break from it. I love the electronics part, but admittedly milling out enclosures is something I don’t care for. Not to mention tuning all the individual circuits as my systems always had 3 or 4 boards in each cabinet.
The buffers Dave mentioned reminded me…I typically buffer both the input and output of the Pre-Amp circuitry. Back when I had Tape Monitor circuits the input/output of those was buffered as well. But what I had forgotten was that I also buffered the input to the Level Meters, which also helps cut down on any noise. The Op-Amps I used for buffers were high-end, low THD units made specifically for audio and dual supply. I will have to look at the part numbers some time, but I believe I used to get them from a surplus house called B.G. Micro, simply because they had them cheap and they were somewhat hard to find.
As for choice of parts everyone has their own preference and you have to go with what you know/like or just what works for you. Our interests are still common and the end goals are very similar. I’m sure we’ll all learn a lot from each others experiences in doing this. I hate to admit it but this will be the first amplifier I built with milled PC boards. In the past every board was hand made. Sometimes I had to do it twice to get it right but back then it wasn’t cost-effective to have them done professionally. Now with ExpressPCB and others it can be done pretty cost-effectively.
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Chris Savage
Parallax Tech Support
No worries about your english...it's at least as good as mine is before I have my morning coffee
-dave
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Also·about econo prices, its always price vs benefits(economy) that one needs to calculate. 5532/33 are pretty reasonably priced here like 1$ per chip (though I have lots and lots of AD8610/20 and OPA134, OPA627 more than 30 each)
Express PCB is a good way and pretty economical as well.
Do you think you want to go ahead with your own design or would like to embark upon a group design with Dave and me? I am open to suggestions.... I ll keep your guidelines in mind
Post Edited (Junkie) : 3/8/2007 9:01:21 AM GMT
Are the Futaba VFDs graphical? From the picture they appear to be character displays. The Noritake I am planning on currently is graphical. As for a Unique VS Group design, there’s no reason we couldn’t do both. I can continue to build my current system while contributing to a group design if that’s what Dave wants to do. I know time is a luxury for most of us these days.
What I would need to do is obtain the parts you’re using…Also, we’d have to agree on ExpressPCB or Eagle for the PCB layout as I don’t have access to anything else right now. I know in Eagle the free version is somewhat limited in board size, which I don’t know if that will matter here or not…I guess we’ll see what Dave says and go from there. Dave?
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Chris Savage
Parallax Tech Support
The question of the capture program (EAGLE, DxP, Altuim, ExpressPCB, etc) is going to need to be worked out pretty fast. My copy of EAGLE is an older one (4.0) so I won't be able to edit anything anyone creates in the freeware version (it's newer). Of course, my version of Altuim/DxP is a lot newer, but I can backsave that one to any previous rev.
I'm up to my ears right now with job work, but I'd be happy to contribute some random tidbits I've got socked away already, until I can dig my way clear to actually put some hours into a design.
I suppose the next question is what precisely do we want to design?
-dave
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lcd clr;
& lcdout "Hello World"
he he and easy to define custom characters.
As for software for Layout you might want to email me to discuss that coz I have·registered versions·of EAGLE, DXP V7/2004, and Proteus 6.7 VSM...
I did plot the schematics last eve, I have them here with me but dont want to post them on the board.
I would need you guys to provide some feedback and change what you want to.
I use PB Pro 2.47 which I guess (think) is BS compatible? dont know exactly
Awaiting your inputs, regarding project outlines, layout software and how to share schematics....
There’s nothing wrong with character LCDs…Before Dave swayed me over to the Noritake Display I was going to use a simple 2X16 Character LCD w/Backlight. I have designed many customer characters for HD44780 compatible displays over the years. Most are built around audio or security functions. I have speakers, CDs, Tapes, Input Jacks, etc. Of course @ 5x7 they are very clunky, but they get the job done.
As for software, as I said, I am limited to designs in Eagle or ExpressPCB. I have no intentions of picking up the packages you and Dave have since it’s not really cost effective for me, plus I would want any shared designs to be available to others who also could not afford the commercial grade software. Even the design I am working on myself will be made freely available in Eagle format with schematic and complete Bill Of Materials. I have no desire to sell the design and even with as complex a design as it may appear to some it will actually be quite simple compared to some of the stuff Dave and perhaps you are working on.
On the group design…I’m all for testing a new Power Amp design using this other chip you referred us to as well as a Pre-Amp for it.
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Chris Savage
Parallax Tech Support
I don't expect anyone in the hobby world to ever own a copy of DxP...at the price they're charging for new licenses I can't afford to buy one for myself. If I didn't work at a place that already had a few seats (along with a machine shop and some really cool EE toys) my hobby efforts would be much more limited.
My current though on the software front requires a somewhat modular approach to the design. THe free version of EAGLE limits one to a eurocard area board. There's a lot we can do in that space, but I think it might be wise to consider making modules, that way we can get a lot of functionality in the box without requiring large PCBs and the associated large design tool costs.
An amp and pre pair would be fun I think. If we go modular, it'd be easy to add balanced and unbalanced input/switching modules, a digital input (DAC module), and all sorts of other interesting bits (class A output buffers, tube buffers, etc), assuming folks embrace the openness of the project and contribute.
Thoughts?
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I think modular is the way to go, they could be building blocks to a really kick - xxx
Bob
Post Edited (Robert Kubichek) : 3/9/2007 7:57:41 PM GMT
I finally dug out my Audio Pre-Amp chips today to verify I still had the datasheet. They are manufactured by JRC and are part # NJM2068D. As I recall these weren’t the easiest to find in the late 90’s and I got these from B.G. Micro. They have the following features…Datasheet attached.
Operating voltage (+/-4V ~ +/-18V)
Low THD (0.001%)
High Slew Rate (6V/uS typ.)
Unity Gain B/W (27 MHz @ f=10 KHz)
DIP8 Package
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Chris Savage
Parallax Tech Support
as for sharing the design I dont have any issues with it, except one concern to add disclaimer that the design and firmware is not for commercial usage. It had happened to me once that I posted design (dxp format) firmware on one of the e-board, only to find it couple of weeks later with some changes in the inputs stage and no change in the software by another gentleman's name, claiming it to be his design with even the header of the firmware having my name....
I guess posting .hex file or even pre-programmed chips wont be a bad idea.
I have no interest in commercial gains Agreed.
I·did a 5 channel power amp· around OPA549, board is double sided available in PCAD.PCB, DXP.pcbdoc meaning that I could always do a gerber output. Fortunately I found it in my notebook so I am editing the post and attaching the PDF
As I have the 3886 stereo version I think doing a multichannel one is matter of half an hour or so.
BTW: MAX5406 is one hot chip have a look at its data sheet.
Dave have u checked PCM290x or 270x USB Dacs?
Robert:
welcome aboard.
Post Edited (Junkie) : 3/12/2007 7:50:38 AM GMT
Those are nifty little chips. I like the simplicity of their design...diff input, bipolar complimentary output driver, limited output protection, and not much else. Too bad they're so darn hard to find now.
Two words: Locked PDFs.
It's not inherently secure, but it's a darn sight better than posting the master files. I've been bitten by the same thing a few times, once for profit, so I know the sting well. Being a consultant these days, doing development both for hire and in-house for later OEMing, IP violations like that hit extra close to home.
I love modular systems
Heck, with the right motherboard design, we could engineer it so we could make a receiver out of this thing (I've run across some serial controlled FM tuner modules in the past).
The MAX5406 is a nifty little chip. Pity about the low supply voltage though.
I've actually got a layout someplace for a USB DAC based on the PCM2906(?), but it's buried at the moment. It'd be easy enough to implement though.
Here's my proposal for our system:
A motherboard, size and shape determined by the end user. Example: 10" wide x 4" deep.
"Inputs" are dual row 0.1" headers spaced every inch, on center, total qty 6.
"Outputs" are the same connector and spacing, but qty 2.
Inputs and outputs need not share a common motherboard, but can.
The bus between them will contain power, audio and control signals on seperate headers. Precise header layout below in daughter board spec.
Daughterboards, each 2" tall and as deep as required, not to exceed 8" (or the limit of the software package being used, 4" for EAGLE lite) so we can pack this into a 2U rack case.
Power connector: 2x4 dual row 0.1" header, 2.25" from back panel edge of PCB, 0.05" up from PCB bottom edge
Contents: 2 pins for ground, 2 pins each for 3 power supplies
Control connector: 2x6 dual row 0.1" header, 1.5" from back panel edge of PCB, 0.05" up from PCB bottom edge
Contents:TBD, but 12 pins should be enough, right?
Signal connector: 2x12 dual row 0.1" header, 3.25" from back panel edge of PCB, 0.05" up from PCB bottom edge
Contents: 8x 3 line inputs, to be used as seen fit. Suitable for 8 stereo sources with individual grounds. Also suitable for 6 balanced inputs using power supply ground as audio ground. Also suitable for 8 stereo sources and 2 balanced inputs with a common ground and pins left over. We should figure out 2 variants I think, one single ended, one not.
Vertical offset may change depending on the right angle header used, to keep the overall height of the mother and daughterboard under 2.5"
I'll be putting it into a design document today...we can continue to edit and things to our hearts content though. I'll post it once I'm done with the first draft.
Early input would be good though
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I understand your concerns on IP being used by others in commercial applications illegally, which is why I suggest we continue on our original designs on our own, keeping those details vague and on the collaborative effort we focus on a more generic design which could be easily modified by others. I doubt we’ll fit everyone’s needs/wants in one shot. Plus, since I will be using non-familiar parts I will have to fly blind, so to speak since I have never had a chance to really prototype with some of these new parts. I am just looking forward to trying something new and hopefully adding to the overall design parameters.
Dave,
Yes, too bad on the audio chips…It’s like the LM1037N where I had like 5 different amplifier designs using the chip (about 20 custom systems) and then it was discontinued. I had enough in case I needed replacements for my customers but after 10 years I lost touch so if they ever find me now I don’t have the chips to replace them. Then again in one of the designs the main amplifier chip was discontinued. Oh, just did a check and the LM383 was also discontinued so add that to the list…Oh well…On one hand it makes me wish I was more into discrete amplifiers but on the other hand that makes my head hurt.
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Chris Savage
Parallax Tech Support
I plan to keep my personal designs personal. What I contribute to the OpenPreamp though, will be pretty cool too I think.
To that end, here's my first stab at a spec. The PDF is locked from editing (version control reasons mainly), but is printable and folks can leave notes on it. Feel free to hack it apart and tear my draft to shreds...that's what it's there for. I have some ideas about the structure of the document, and how it goes together, which I'll try and implement in version 0.2, so for now focus on the content. All of the information is open for discussion...these are just some ideas I put on paper.
The dimensions in the module drawing are incorrect, I know. That was Altium, because it can dimension things quickly. I'm working on the EAGLE version, hopefully it'll be prettier and more accurate, since it uses center points for placement instead of pin 1, unless we want dimensions for both?
Also attached is the EAGLE directory of the first stab at the module board. The schematic is horiffic, but it gets the point across.
-dave
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Post Edited (Dave Paton) : 3/13/2007 9:48:41 PM GMT
I would be more than happy to be part of group design, whatever specs you guys comeup with its fine with me.
My only limitation is that I find it difficult to work with EAGLE (despite having 4.15 registered version), always find it comfortable to work with P.DXP, however PDF would a good way to share things. I would like to give MAX chips a try, order is underway let see how much time my agent takes to get them here.
Dave·I have gone through the docs and they are alright with me, now Q is which stage should I design and who will take resposibility of different stages?
For me doing PIC and BS is easier than AVR or 8051 chips. Agreed & agreed
Point is do our designs ourselves no prob, let put something for those who either cant do it or cant afford t.
As for my personal design I guess whatever changes are to be made digital section would remain the same, keeping that in view I had been working on the programme to control PIC, PGA, input selector, vol up, vol down, mute/unmute switch and encoder. I think I have made it work pretty well now I need to tweak it a bit and add I.R codes.
For MPC50x I guess I need to study a bit more to adjust TTL level out of PICs and
"VAH (Logic Level High) = +4.0V;"
of MPC chips.
Take care
Post Edited (Junkie) : 3/14/2007 9:22:07 AM GMT
I can't believe that half an hour of unilateral typing generated something everyone agrees with. That's just too easy.
I agree, I'm more comfortable in Altium than I am in EAGLE, but since (I believe) our target audience must be able to freely create parts for this project, we need to stick with something that's free, no? I think we'll need to have stock designs for the motherboard, since it'll be larger than the Lite board limits (or one of us can do it in Altuim/DxP), but everything else can happen in EAGLE Lite I think.
As far as the MPC's Vah of 4V, it means it's designed to work with 5V logic. If you plan on using a 3.3V uC, you'll need level translators. Think of Vah ans Vin(high).
Chris? Anything to chime in with?
-dave
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As for the controller…Of course I will be using a BASIC Stamp, however the controller board can be separate, so we should build it as if that is an unknown. As far as the audio section I don’t know about you guys but I tend to design the main amplifier and work backward from there since often the requirements of the power amplifier will affect the pre-amp design. It is rarely an issue the other way, at least for me.
Dave’s right…Standard TTL logic should be able to handle everything we’ve mentioned…My big set back is the power supply requirements since I got lucky before and was able to run everything from +/-12V and +/-5V. Now I need +/-15V so none of my current prototyping supplies will work. This means I need to break down and build a new supply.
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Chris Savage
Parallax Tech Support
My thought was that we'd provide some reference designs in PDF form and gerber-ized, ready for home photolith construction or sending to a board house. We'd also provide an EAGLE template for the module boards, kinda like a prototyping board, but electronic. That way, anyone who wanted to build their own modules for input or output could take the existing template with the physical board outline and the connector positions, and fill in the blanks with their desired bits and bobs.
I do just the opposite...I start at the low level side and work up, since I consider a good amplifier to be independent of it's preamp, with a nice high input impedance, ready for anything to be plugged into it. Out of curiosity, how has the amp design affected the preamp design in the past?
I need to send you my power supply boards still. They're sitting on my desk, waiting for a day warm and dry enough to pull the table saw out. I promise it'll be soon...
-dave
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Agreed, though I feel comfortable with DXP but whatever portion is assigned to me I ll do it in EAGLE.
As for my own project please see attachment, its a view of my board in 3D, simple design Quad RCA Jacks, input buffer around OPA2134, PGA2310, Output Buffer around OPA627, with out put relay, PIC mcu.
Post Edited (Junkie) : 3/15/2007 4:44:32 AM GMT
To all:
Do we need a section on tone control? Should there be a processing header on the backplane board? Do we need more than 2 headers for output modules, given the size constraints I've guessed at? Is the module size reasonable? How about the power supply header? More voltages? More pins? More ground? The bus connector pinout...does it make everyone 100% happy? We still need to define the control connector...I need input here. 1x SPI, 1x I2C, and some bitwise I/O? I don't know!
I'm more comfortable in Altium/DxP, but since I did a lot fo time in Eagle, I've got no problem with it, especially since there's a free version, and I'm happy to be the guinea pig for the limits of the Lite.
Looks good! I'm had to switch almost 100% to SMT for my personal designs, as the chips I like playing with don't come in DIP packages, and the high quality SMT-DIP converters are pricey. I just wish I could get the PCB3D module working on my machine...it crashes every time with a conflict with my video card. Altuim has been sympathetic, but useless in getting it fixed.
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Imagin a modular system with seperate preamps/tone/input output switchers connected to
a power amp, and controlled by a stamp with any type of custom display via a common buss
for flexibilty of configuring to suit ones needs...
Bob
If you look, you'll see the control bus to all modules is as yet undefined. It'd be easy to make 2 of the wires RS-485 multidrop, allowing any kind of inter-unit communication, and any amount of processing power to be put on the modules.
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This is not a sig. This is a duck. Quack.
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Chris Savage
Parallax Tech Support
Will post my thoughts tomorrow.
Dave has some important points.
As for PCB3D crashing it has not much to do with DXP/ADS rather the VGA card, hopefully it should be a GeForce and not the build in one or ATI coz both of them have some conflicts, but if its a GeForce please update to latest drivers hopefully you ll get the problem resolved.··
I have some thoughts about a different arrangement of the backplane too, with more output slots, and modular config for switching, volume control, and tone control, but that's something I won't actually bring up until we have some of these more basic things nailed down.
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This is not a sig. This is a duck. Quack.
I would go with your PSU suggestions.
Just one thing that 5v digital section should have seperate return paths just to keep digital and analogue ground seperate.
For other supplies like 12v -/+ for analogue section I think regulators may be added after 15v reg.
Look forward to hear about those ideas. What·does "more basic things nailed down" mean?
Going to have a long weekend 3Days.
Will be back on monday.
·· I’m a little confused on the supply…The PGA2311 requires a dual supply @ +5V/-5V and the MPC507A requires a dual supply @ +15V/-15V so why doesn’t the supply have -5V? In my earlier pre-amp I used the +12V/-12V to get the +5V/-5V for the audio circuits, so I could do that. The +5V logic supply is always separate. I need to confirm what you’re doing so I can integrate that into my organic memory core (brain). Thanks.
·· As a side-note I have been working on the code for the controller since I will need the basics when it comes time for testing.· It’s interesting to see how this is developing.· I will post some code once I have a good base I am working from.
[noparse][[/noparse]Edit] - Okay, organic memory core meltdown...Somehow I blew right past your answer to my question...Don't mind me...I think I am having an overload from so much information today!
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Chris Savage
Parallax Tech Support
Post Edited (Chris Savage (Parallax)) : 3/26/2007 7:36:54 PM GMT