·· In all honesty all previous projects were designed (As far as specs and looks/layout) went.· So I was just the builder.· Once in awhile I used prototypes for my own use, but that's all they ever were, and weren't ever really my own personalized design and custom to me.· This time I intend to build an Amplifier and Controller all about me!· And I will use the BASIC Stamp just on principle.
·· I have a good idea what I want for features, and I have a good idea what I want for cabinet style/layout.· What I need to do is work toward that so that I am happy with the unit and keep it around.· I used to showcase my customer units during burn-in/testing.· But never made one just for me.· This time I am doing it for me.·
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·· Before I forget, what VFD modules did you get?· To date I haven't used one for any such project, but it might be worth pursuing depending on cost, etc.· I do have a HUGE blue inverse 20 X 4 LCD Display, but it's overkill.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Chris Savage Parallax Tech Support csavage@parallax.com
The small one on my desk is the 4x20 model in their 7000 series (GU140x32). It's actually a dot matrix display, and can do graphics, windowed writes, and a pile of other ultra cool features I'm looking forward to playing with.
-dave
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·· I'm not seeing much in the way of price on the website.· How much does that display run?· I have seen the ads in Nuts & Volts, but I don't recall a price listed there either.· Is this one of those, "If you have to ask how much it costs, you can't afford it" things?
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·· I have to admit, one of these Graphical VFD Displays would certainly look nice in my controller/pre-amp.· I could even draw little graphical symbols for the different input sources, such as a CD, etc.· You'll probably laugh, but for my current controller software, I have custom LCD characters I designed to represent a CD, an Antenna (For Tuner), a Cassette (For the Tape Monitor), a VHS Tape (For VCR input) and a little pair of RCA Plugs (Sort of) that represent Aux In.
·· I also made a Pac-Man Ghost for when the unit is in Stand-By mode.· One sits on either side of the word Stand-By, and at power up, they run away off the sides of the LCD.· It's rather humorous to people who have heard of Pac-Man.· I also have little Left and Right speaker character (That fills CGRAM, sigh) for volume, muting, etc.· Graphics Displays would make that stuff a lot nicer!· Have your rep drop me off one, will ya?·
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·· Here's the propsed layout of the new amplifier.· Really it's a lot like all the others I have done, but these pictures are not to scale, nor do they provide real detail, since I don't know exactly what buttons, knobs, etc. I will be using.· But it gives you an idea of what I was planning on doing.· I'm also not sure on the fan.· I have always mounted the fan in the back, however this time I am thinking of trying something different.· I guess it depends on room in the case.
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Nice renderings One question....is there any reason to have a control input on the amp for anything but a 12V remote on/off?
The graphical VFD is going to open up a whole host of possibilities for me in terms of the UI on my preamp, especially with the windowing. I've spent some time planning and writing pseudocode for the programming on the SX. This is going to be fun.
-dave
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·· I'm glad you asked that, because everyone who has seen my systems asks me that, and I should've mentioned it here anyway.· The control connection is a standard MIDI cable.· There are actually up to 5 different signals used by the cable.· Obviously you got the first one, which is to turn on the Power Relay in the Power Amplifier section.
·· The second signal is for the Muting Relay.· Even thought the chips we have both used include muting capability, the LM3886 has built-in muting which prevents 90% of turn-on thump, and therefore 1 second after power-up, a second smaller relay is energized via the controller which turns off muting.
·· The third signal, which is not always used is the temperature sense signal.· This is connected to a thermistor inside the amplifier section and contacting the heatsink.· It tells the controller how hot the amplifier is.· This brings us to the fourth signal, which is the cooling fan.· I prefer to have control of the fan from the audio controller, since I usually have 3 modes for the fan.· OFF/ON/AUTO.· They should be self-explanatory.·
·· The fifth signal isn't really a signal so much...I used the center pin as a common ground between the two cabinets simply because I have had some MIDI cables in the past in which the shield didn't connect on both ends, however, I think this time around I will design this system based on that connection being there and I will have that fifth signal wire for one other possible circuit I was thinking of using on the power-amp side.
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Post Edited (Chris Savage (Parallax)) : 10/3/2005 2:33:32 PM GMT
Makes sense. I prefer my amps to be dumb and self-contained, since I have so many, and I like to switch them around from time to time depending on what's going on. I put thermal breakers in the supply rails, and I usually handle muting with the old RC method, with about a 1 second time constant. I've been meaning to do something more creative with relays and such to mute it for turnoff as well, but I couldn't get it to fit into the 4x4 case so I shelved it a while back. With the idea of the highly multichannel amp for my house, I'm exploring it again. I suppose I should find an 8ch 8 bit fast 5V differential ADC for the remote control pots. Hmm. Serial bus intelligent wallplates? Maybe I'm getting ahead of myself, but I think the Stamp 1 would be perfect for that. the LCD/Keypad app note and a pair of lines for serin/serout. Add differential tranmitters and receivers to them...
This is getting dangerous.
I've been chatting with Andrew (awasson) in a thread over in the SX forum. He might be another guy interested in this stuff. As I told him, I bet if you ordered DIP samples today and dug up the right power supplies and a decent breadboard, you could put together a 4 or 6 ch controller over the weekend with some pushbuttons and LEDs for control. If you want to put input switching into the preamp, it's a little more tedious, but not complicated. I'll see about posting some of my older PCBs here later in the week if you're interested. Mainly for the DG507s and CS3310/PGA231x. One of my favorite ways to go about these things is to hack something together quickly and then build on it. It'll be ugly, but that all gets fixed when I spin a PCB and build a proper case.
That reminds me, are you happy with the layout on the LM3886 modules? I'll try and shoot them out today or tomorrow if you are. We could have a whole pile of them in the next week or two.
-dave
-dave
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Post Edited (Dave Paton) : 10/3/2005 6:39:37 PM GMT
·· I will go home and re-check the layout tonight and e-mail you.· IIRC I was waiting for a reply from you on the muting circuit, which I didn't understand (No negative voltage).· I guess I will check my e-mail on that when I get home.· As I said, I appreciate the schematic, but that's what made me realize that was different than I expected.
·· As for dumb amplifiers, I have built my share of them.· Most have a standard dual-100K pot, no tone control, no balance control, no loudness contour, etc.· The only logic was in the input selection and the muting.· Even then, on a few systems I used rotary switches for the inputs.· I was concerned about noise, but wasn't able to detect any, so I didn't worry about it.·
·· I figure this one is going to incorporate all the bells and whistles I can think of.· I can always adjust the code, but I don't want to have to modify the hardware too much on this one.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Chris Savage Parallax Tech Support csavage@parallax.com
Ahh..I see now. The muting is implemented just as it is on the datasheet. The jumper is for the switch (S1), or your muting relay contacts, to bypass the capacitive mute delay. It just looks a little funny. The cap is marked as 100u, but I'm pretty sure that was a typo from 10u. And yes, the GND should ve Vee. I goofed that too. This is why we have design reviews. I'll email you some new ones in a minute.
Mmm..bells and whistles. I'm looking forward ot having all kinds of display fun with custom characters and windowed graphic areas. And I've got a super secret trick up my sleeve I'll only show off once I'm all done. Mwahahaha...
-dave
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·· Yeah I thought something was different there.· The datasheet called for negative current/voltage.· Anyway, no fair teasing with this feature/trick...Now we have to wait until the amplifier's done!· =(· I have to get one of those displays.
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The trick is for the preamp...the amps will be nice and vanilla. This time.
The displays are in stock and ready to go at Digikey.
I haven't had a chance to play with mine with an SX or a Stamp, since it speaks real RS232 (well...Tx/Rx/Gnd at real RS232 levels anyway) and I don't have any MAX232s handy, or much spare time to mess with personal projects. Once I get my house rennovation finished and my tools moved in, things will calm down a whole lot, but that's probably a month off still (kitchen, carpet, full re-wire, and some more paint are all TBC).
Pseudocode continues to flow from my fingers on occasional evenings, and I'm nipping at the amp module layout here and there, so things are progressing, but slowly. I do have some nice big heatsinks in a box someplace, so I'm ahead of the game there, but not anywhere else.
Give the module PCB a once over with a fine toothed comb and tell me if you spot any other issues. I have clearances set for 75VDC, but that should be alright, since Vcc/Vee will be the limits, and they can't exceed 44VDC. Just make sure there are some nice fat (10-50kuF) bulk filter caps somewhere before the modules to smooth things out.
-dave
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·· I just got done going through the new schematic you sent.· I replied on that.· Meanwhile I think we'll be okay in the P/S Dept.· My supply tops out at 37-0-37 and has some nice filter caps.· Of course, I did want to re-design the supply, but I may hold off on that until the next amplifier.
·· On another note I wanted to discuss signal splitting with you.· I don't know if you have ever gone through this or not, but I sure have a few times.· If you noticed in my concept drawings, I show 4 inputs and 4 outputs, as well as a Tape Monitor circuit.
·· The interesting thing is now that I am switching chips and using one you recommended I must consider the entire Pre-Amp stage.· Now you might say I won't need one with the new chips, however my signals actually go three ways.· In the last system the inputs for each device came into the signal switcher circuit in duplicate.· That is there were two identical input circuits.· The output of one went to the N.C. contacts of a small PCB Relay (There were two, one for each channel) as well as the Input Level Meters.· The second signal switcher output went to the Tape Out Pre-Amp (A high quality Audio Op-Amp).·
·· The Tape In section also had a Pre-Amp.· It went to the N.O. contacts of a small PCB Relay.· The common lead of the relay(s) connected to the volume control chip, which connected to the Power Amplifier.· In this manner the selected output was sent to the Amplifier, but when the Tape Monitor was engaged the Relay would enabled the Tape In to the Amplifier instead.
·· Since the Input Level Meters were connected to the output of the switcher, they always displayed the level of the input signal, regardless of the volume control, while the meters on the Amplifier showed the actual power output (With a small margin of error).
·· What I am getting at, is on this new chip (New to me) what would you say is the best way to split (Y) the audio signal to more than one device?· For example, if I wanted to be able to select one device for listening, and another for recording, like I did before, I would most likely need two of the input selector circuits again.· How would you go about getting the signal to both circuits with little noise and loss?
·· Way back when I used a similar design as to what's done with most mixers, using a resistor through an Op-Amp, but I don't think that will be required here in this case.· On the other hand I can simplify the input section by not having a separate selectable output, but I will still need to tap the audio on the output side for the Tape Monitor and Level Meters.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Chris Savage Parallax Tech Support csavage@parallax.com
You'll have to forgive my PCB misadventures. This week started out bad, and went to worse in short order. I'll get Rev 5 out to you tomorrow, once I get some sleep and recover a little. Mea culpa. Again.
As for splitting, I tend to follow the one-buffer-per-output-device school of thought. I buffer the outputs of the matrix chips, and if it goes more than one jack, I give each destination a unity gain buffer off of that signal.
In terms of inputs, I buffer things once at the input jacks and leave it at that. Inside a preamp, the runs are pretty short, and noise should be well controlled, so I don't worry as much about things. For the CS3310 I had to buffer both the input and output of each chip, due to the impedence of the attenuator. I haven't looked at the PGA parts yet, but they may require the same treatment.
Overall, you can't hurt too much with a high quality unity gain buffer here and there. It's easy to bypass them if you like to experiment too.
-dave
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·· On the layout...Don't worry about it...You saw the ExpressPCB layout I sent to you...'nuff said!·· You've got me thinking I want to maybe simplify the input/output section a little more and settle for a traditional "record what you hear" setup.· Heck, as popular as Take Decks are now, I may leave that circuit right out too...But then, I did want to be complete so I can't start second-guessing features I may use.
·· My mind is mush today...But, on the other hand I have worked out almost everything.· Oddly enough my samples still haven't arrived.· Weird.· I cannot prototype anything until they show up.· As for the display I am going to read the datasheet tonight and make a decision.· It makes a difference on the color theme.
·· If I used a backlit LCD display I will most likely use a green LED theme for the indicators to match the backlight.· However, if I go with a GRFX Display I may forgo that logic and make everything red.· I have built so many systems using both color schemes that I don't prefer one over the other anymore, but Blue would be difficult not only due to the cost of Blue LEDs, but the voltage and current requirements to drive them.· I think I would certainly have to use individual LEDs for the meters if I used Blue, and there are two problems with that.· Cost and brightness.
·· Blue LEDs tend to be water-clear ultra-bright.· I did order a few T1 LEDs from Jameco once that were diffused and perfect for the application, but looking on their website I no longer see them, unless their descriptions are wrong.· I can't remember the part #, but these would be great for indicators and metering in that they're NOT super-bright and being diffused they have even lighting.· I may save that idea for another smaller amplifier.
·· On a final note for tonight, your household audio system reminds me of something I recently found while looking for old data and information on my projects.· I once had this concept for building a computerized house.· Okay, I was young!· But in the plans I had drawn a wiring system that would go throughout the entire house networking each sub-system together and allowing for an LCD Display in each room that could emulate the configuration for other rooms if you wanted to control things from another room.
·· For example, say you had a graphical display that showed graphical representations of the things you control in that room.· In another room it's display has different controls and information.· My thought was you could access the control system for another room through that panel and it would re-configure itself.· Touch displays are coming down.· Especially ones usable by microcontrollers.
·· At the time I had dreamed of using the Z80, but now I am thinking several BASIC Stamps in a network.· Cleverly designed this could be even more powerful than I originally imagined, and the audio control could be a sub-system as well.· From any room you could select audio and see a graphical representation of the audio sub-system controls for that room.· You could then pipe the audio from any other room's source into that room, or from there re-direct other rooms.· You get the idea I think.· I will have to ponder this concept some more.· It would be extremely elaborate, but awesome!
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My thought for the room control pads wasn't anything more complicated than a BS1, a differential Tx/Rx pair, and thr 2x8 LCD AppMod. Basic souce selection and volume control, nothing outrageous. It will really depend on how much the whole thing will cost.
Personally, I'm going for blue and red on this project. Blue for source selection and the VFD, red for power indication and the mute button. There are some wonderful LEDs available in 0603 packages that will be perfect for what I'm doing, assuming I Can get the button caps made the way I want.
I plan on having a buffered tape output on my preamp (pre volume control, maybe with a seperate trim?), but nothing fancy. I'd likely be using it as an aux-out to feed my computer or an amp and speakers in the back yard.
If I go whole hog on the home audio system, the preamp will magically morph into an 8x8 matrix, with volume on each output and trims on all the inputs, fully balanced, and probably end up in a card cage backplane instead of a slick 1U enclosure as I plan now. I have a pretty decent layout to make a modular 8x1 card with a pair of DG507AUs and PG2311s (everything is balanced you know...), but I haven't solved wire management for it yet. Small Weidmueller connectors come to mind, but they're really expensive and tough on the fingers. I'm still thinking about that one.
Then again, I might just spend some cash and buy an Ashly 24.24M and build me a 16x8 matrix with all the goodies out of the box, and spend my time souping up a Xantech Smartpad program to control it. Turnkey does have it's appeal when it comes to slickness
I'll have a fixed payout to you soon.
-dave
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·· Okay, got the new schematic and layout.· Layouts are a little hard to follow because of the way they're exported I think, but the schematic looks good, and I followed most of the layout.· Seems to be all in order.· I guess it's ready!·
·· As for the Display...I ordered a sample today.· It's a CMOS level serial version.· I had the impression they only had RS-232C, but checking the list I quickly found that they even support parallel interface on many of the models.· It will be interesting to see how "real-time" I can get, since I may actually try to implement meters
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At 37.6kBaud, meters should be relatively easy, since you'll only be updating a small portion of one user window. I hope.
The layout does export a little funny. I can't turn off the copper pours without actually deleting them, which makes doing just the traces a little difficult. Rest assured, the schematic and layout reconcile, so it seems to be all good. I'll panelize them tomorrow, and I should have boards in a week or two, barring any errors.
-dave
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Yes, only a portion of the window needs to be updated...Depending on how I lay it out, I will designate at least one area for the symbol of the input, another for status of things not shown by LEDs, and then the meters will be all that is left.· I will have to do some testing to see what kind of performance I get.· Of course, that will be directly related to reading the input through a (series of) ADC to get the signal level.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Chris Savage Parallax Tech Support csavage@parallax.com
I'm betting that if you did some trickery and used a parallel ADC, you could do a rapid 'copy and paste' operation to the VFD. Something like a shiftout (pins.lowbyte) or something?
After further review, I'm going to stick with external meters. I'm going to have enough to do with the UI and the remote control and other joys.
Panelizing now. Boards to come.
-dave
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·· Oh sure, make me second guess my plans!·· Okay, well, either way I plan on trying to implement the Display into my Pre-Amp/controller.· So we'll see what happens during prototyping/beta-testing stage.· I will mess around and see what I come up with.· Worst-case scenario I will have a really fancy display that doesn't do much more than display static information, or perhaps I will animate the input device icons.· For example, when CD is selected, maybe display a spinning CD?· VCR might show a VHS Cassette with the reels spinning?·· Ideas?
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Chris Savage Parallax Tech Support csavage@parallax.com
Animation would be killer Chris. I've been playing with the idea of doing a Tron style lightbike animation for the startup on mine, purely as eye-candy.
The boards are going to be delayed a little bit, much to my chagrin. Licensing issues are limiting me rather severely on my quest for 60sqin Gerbers right now, tho I hope I can get them resolved before the end of the week.
Kinda like the pile of fix-its that just landed on my desk. Ugh. Back to work.
-dave
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·· I'm not sure what mine will be yet.· For now I will probably do the Parallax, Inc. logo to see how that comes out, then I will worry about animated icons for various inputs and functions.· Like a Fan Blade for the fan control system.· So I can use icons for functions as well.· Speakers with a circle/slash for muting, etc.
·· Sorry about the board set back.· I have a few of those as well.· I need to still order those enclosures.· Everything on the hardware level will be well documented, including pictures.· Lots of pictures.
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·· I just had two of the aforementioned Noritake Displays dropped off to me for analysis.· The 7002 version of the displays support Parallel, Async Serial, And Sync Serial.· The 7003 series does not support Parallel, but are otherwise the same.· One thing I am disappointed by is the lack of documentation.· I had to submit a request for the PDF documentation.· So now I must wait until I have the information to continue.· From what I can tell though, these are extremely easy to work with, and run up to 115 Kbps serial.· One neat feature that has always been lacking on the Hitachi and similar displays is an external RESET feature, which these displays have.· I have a found a few situations where that would be handy in the past.
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Dave Paton said...(trimmed)
I'd get a sample of the PGA2311. It's literally a drop-in replacement, and much more readily available than the Crystal/Cirrus part, mainly because TI samples them, which allows you to avoid dealing with Newark (blech). I've effectively left Cirrus behind for my newer designs, because of the easier availability of the TI cross and the friendliness of the TI dealers and saple reps.
Dave,
·· The TI Parts all came today...Actually they came over a week ago, but FedEx never left a delivery notice.· So, I had no idea they were ever delivered.· Anyway, I got them today and now have 5 each of the 2 chips you recommended.· This weekend I will be prototyping/testing those sections.· I will post back when I have news.·· Wish me luck!
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·· The RCA jacks I use mount right into the metal cabinet, and thus are inherently grounded to the cabinet.· However I have to run shielded wires inside, so there is always the worry of ground loops, although I haven't had that happen in a long time.
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Comments
·· In all honesty all previous projects were designed (As far as specs and looks/layout) went.· So I was just the builder.· Once in awhile I used prototypes for my own use, but that's all they ever were, and weren't ever really my own personalized design and custom to me.· This time I intend to build an Amplifier and Controller all about me!· And I will use the BASIC Stamp just on principle.
·· I have a good idea what I want for features, and I have a good idea what I want for cabinet style/layout.· What I need to do is work toward that so that I am happy with the unit and keep it around.· I used to showcase my customer units during burn-in/testing.· But never made one just for me.· This time I am doing it for me.·
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Chris Savage
Parallax Tech Support
csavage@parallax.com
·· Before I forget, what VFD modules did you get?· To date I haven't used one for any such project, but it might be worth pursuing depending on cost, etc.· I do have a HUGE blue inverse 20 X 4 LCD Display, but it's overkill.
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Chris Savage
Parallax Tech Support
csavage@parallax.com
-dave
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·· I'm not seeing much in the way of price on the website.· How much does that display run?· I have seen the ads in Nuts & Volts, but I don't recall a price listed there either.· Is this one of those, "If you have to ask how much it costs, you can't afford it" things?
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Chris Savage
Parallax Tech Support
csavage@parallax.com
I'm waiting for a price quote for 1k, 5k, and 10k, Digikey has them for around $100 each in singles.
-dave
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·· I have to admit, one of these Graphical VFD Displays would certainly look nice in my controller/pre-amp.· I could even draw little graphical symbols for the different input sources, such as a CD, etc.· You'll probably laugh, but for my current controller software, I have custom LCD characters I designed to represent a CD, an Antenna (For Tuner), a Cassette (For the Tape Monitor), a VHS Tape (For VCR input) and a little pair of RCA Plugs (Sort of) that represent Aux In.
·· I also made a Pac-Man Ghost for when the unit is in Stand-By mode.· One sits on either side of the word Stand-By, and at power up, they run away off the sides of the LCD.· It's rather humorous to people who have heard of Pac-Man.· I also have little Left and Right speaker character (That fills CGRAM, sigh) for volume, muting, etc.· Graphics Displays would make that stuff a lot nicer!· Have your rep drop me off one, will ya?·
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Chris Savage
Parallax Tech Support
csavage@parallax.com
·· Here's the propsed layout of the new amplifier.· Really it's a lot like all the others I have done, but these pictures are not to scale, nor do they provide real detail, since I don't know exactly what buttons, knobs, etc. I will be using.· But it gives you an idea of what I was planning on doing.· I'm also not sure on the fan.· I have always mounted the fan in the back, however this time I am thinking of trying something different.· I guess it depends on room in the case.
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Chris Savage
Parallax Tech Support
csavage@parallax.com
Nice renderings
The graphical VFD is going to open up a whole host of possibilities for me in terms of the UI on my preamp, especially with the windowing. I've spent some time planning and writing pseudocode for the programming on the SX. This is going to be fun.
-dave
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·· I'm glad you asked that, because everyone who has seen my systems asks me that, and I should've mentioned it here anyway.· The control connection is a standard MIDI cable.· There are actually up to 5 different signals used by the cable.· Obviously you got the first one, which is to turn on the Power Relay in the Power Amplifier section.
·· The second signal is for the Muting Relay.· Even thought the chips we have both used include muting capability, the LM3886 has built-in muting which prevents 90% of turn-on thump, and therefore 1 second after power-up, a second smaller relay is energized via the controller which turns off muting.
·· The third signal, which is not always used is the temperature sense signal.· This is connected to a thermistor inside the amplifier section and contacting the heatsink.· It tells the controller how hot the amplifier is.· This brings us to the fourth signal, which is the cooling fan.· I prefer to have control of the fan from the audio controller, since I usually have 3 modes for the fan.· OFF/ON/AUTO.· They should be self-explanatory.·
·· The fifth signal isn't really a signal so much...I used the center pin as a common ground between the two cabinets simply because I have had some MIDI cables in the past in which the shield didn't connect on both ends, however, I think this time around I will design this system based on that connection being there and I will have that fifth signal wire for one other possible circuit I was thinking of using on the power-amp side.
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Chris Savage
Parallax Tech Support
csavage@parallax.com
Post Edited (Chris Savage (Parallax)) : 10/3/2005 2:33:32 PM GMT
Makes sense. I prefer my amps to be dumb and self-contained, since I have so many, and I like to switch them around from time to time depending on what's going on. I put thermal breakers in the supply rails, and I usually handle muting with the old RC method, with about a 1 second time constant. I've been meaning to do something more creative with relays and such to mute it for turnoff as well, but I couldn't get it to fit into the 4x4 case so I shelved it a while back. With the idea of the highly multichannel amp for my house, I'm exploring it again. I suppose I should find an 8ch 8 bit fast 5V differential ADC for the remote control pots. Hmm. Serial bus intelligent wallplates? Maybe I'm getting ahead of myself, but I think the Stamp 1 would be perfect for that. the LCD/Keypad app note and a pair of lines for serin/serout. Add differential tranmitters and receivers to them...
This is getting dangerous.
I've been chatting with Andrew (awasson) in a thread over in the SX forum. He might be another guy interested in this stuff. As I told him, I bet if you ordered DIP samples today and dug up the right power supplies and a decent breadboard, you could put together a 4 or 6 ch controller over the weekend with some pushbuttons and LEDs for control. If you want to put input switching into the preamp, it's a little more tedious, but not complicated. I'll see about posting some of my older PCBs here later in the week if you're interested. Mainly for the DG507s and CS3310/PGA231x. One of my favorite ways to go about these things is to hack something together quickly and then build on it. It'll be ugly, but that all gets fixed when I spin a PCB and build a proper case.
That reminds me, are you happy with the layout on the LM3886 modules? I'll try and shoot them out today or tomorrow if you are. We could have a whole pile of them in the next week or two.
-dave
-dave
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Post Edited (Dave Paton) : 10/3/2005 6:39:37 PM GMT
·· I will go home and re-check the layout tonight and e-mail you.· IIRC I was waiting for a reply from you on the muting circuit, which I didn't understand (No negative voltage).· I guess I will check my e-mail on that when I get home.· As I said, I appreciate the schematic, but that's what made me realize that was different than I expected.
·· As for dumb amplifiers, I have built my share of them.· Most have a standard dual-100K pot, no tone control, no balance control, no loudness contour, etc.· The only logic was in the input selection and the muting.· Even then, on a few systems I used rotary switches for the inputs.· I was concerned about noise, but wasn't able to detect any, so I didn't worry about it.·
·· I figure this one is going to incorporate all the bells and whistles I can think of.· I can always adjust the code, but I don't want to have to modify the hardware too much on this one.
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Chris Savage
Parallax Tech Support
csavage@parallax.com
Ahh..I see now. The muting is implemented just as it is on the datasheet. The jumper is for the switch (S1), or your muting relay contacts, to bypass the capacitive mute delay. It just looks a little funny. The cap is marked as 100u, but I'm pretty sure that was a typo from 10u. And yes, the GND should ve Vee. I goofed that too. This is why we have design reviews. I'll email you some new ones in a minute.
Mmm..bells and whistles.
-dave
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·· Yeah I thought something was different there.· The datasheet called for negative current/voltage.· Anyway, no fair teasing with this feature/trick...Now we have to wait until the amplifier's done!· =(· I have to get one of those displays.
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Chris Savage
Parallax Tech Support
csavage@parallax.com
The displays are in stock and ready to go at Digikey.
I haven't had a chance to play with mine with an SX or a Stamp, since it speaks real RS232 (well...Tx/Rx/Gnd at real RS232 levels anyway) and I don't have any MAX232s handy, or much spare time to mess with personal projects. Once I get my house rennovation finished and my tools moved in, things will calm down a whole lot, but that's probably a month off still (kitchen, carpet, full re-wire, and some more paint are all TBC).
Pseudocode continues to flow from my fingers on occasional evenings, and I'm nipping at the amp module layout here and there, so things are progressing, but slowly. I do have some nice big heatsinks in a box someplace, so I'm ahead of the game there, but not anywhere else.
Give the module PCB a once over with a fine toothed comb and tell me if you spot any other issues. I have clearances set for 75VDC, but that should be alright, since Vcc/Vee will be the limits, and they can't exceed 44VDC. Just make sure there are some nice fat (10-50kuF) bulk filter caps somewhere before the modules to smooth things out.
-dave
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·· I just got done going through the new schematic you sent.· I replied on that.· Meanwhile I think we'll be okay in the P/S Dept.· My supply tops out at 37-0-37 and has some nice filter caps.· Of course, I did want to re-design the supply, but I may hold off on that until the next amplifier.
·· On another note I wanted to discuss signal splitting with you.· I don't know if you have ever gone through this or not, but I sure have a few times.· If you noticed in my concept drawings, I show 4 inputs and 4 outputs, as well as a Tape Monitor circuit.
·· The interesting thing is now that I am switching chips and using one you recommended I must consider the entire Pre-Amp stage.· Now you might say I won't need one with the new chips, however my signals actually go three ways.· In the last system the inputs for each device came into the signal switcher circuit in duplicate.· That is there were two identical input circuits.· The output of one went to the N.C. contacts of a small PCB Relay (There were two, one for each channel) as well as the Input Level Meters.· The second signal switcher output went to the Tape Out Pre-Amp (A high quality Audio Op-Amp).·
·· The Tape In section also had a Pre-Amp.· It went to the N.O. contacts of a small PCB Relay.· The common lead of the relay(s) connected to the volume control chip, which connected to the Power Amplifier.· In this manner the selected output was sent to the Amplifier, but when the Tape Monitor was engaged the Relay would enabled the Tape In to the Amplifier instead.
·· Since the Input Level Meters were connected to the output of the switcher, they always displayed the level of the input signal, regardless of the volume control, while the meters on the Amplifier showed the actual power output (With a small margin of error).
·· What I am getting at, is on this new chip (New to me) what would you say is the best way to split (Y) the audio signal to more than one device?· For example, if I wanted to be able to select one device for listening, and another for recording, like I did before, I would most likely need two of the input selector circuits again.· How would you go about getting the signal to both circuits with little noise and loss?
·· Way back when I used a similar design as to what's done with most mixers, using a resistor through an Op-Amp, but I don't think that will be required here in this case.· On the other hand I can simplify the input section by not having a separate selectable output, but I will still need to tap the audio on the output side for the Tape Monitor and Level Meters.
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Chris Savage
Parallax Tech Support
csavage@parallax.com
You'll have to forgive my PCB misadventures. This week started out bad, and went to worse in short order. I'll get Rev 5 out to you tomorrow, once I get some sleep and recover a little. Mea culpa. Again.
As for splitting, I tend to follow the one-buffer-per-output-device school of thought. I buffer the outputs of the matrix chips, and if it goes more than one jack, I give each destination a unity gain buffer off of that signal.
In terms of inputs, I buffer things once at the input jacks and leave it at that. Inside a preamp, the runs are pretty short, and noise should be well controlled, so I don't worry as much about things. For the CS3310 I had to buffer both the input and output of each chip, due to the impedence of the attenuator. I haven't looked at the PGA parts yet, but they may require the same treatment.
Overall, you can't hurt too much with a high quality unity gain buffer here and there. It's easy to bypass them if you like to experiment too.
-dave
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·· On the layout...Don't worry about it...You saw the ExpressPCB layout I sent to you...'nuff said!·
·· My mind is mush today...But, on the other hand I have worked out almost everything.· Oddly enough my samples still haven't arrived.· Weird.· I cannot prototype anything until they show up.· As for the display I am going to read the datasheet tonight and make a decision.· It makes a difference on the color theme.
·· If I used a backlit LCD display I will most likely use a green LED theme for the indicators to match the backlight.· However, if I go with a GRFX Display I may forgo that logic and make everything red.· I have built so many systems using both color schemes that I don't prefer one over the other anymore, but Blue would be difficult not only due to the cost of Blue LEDs, but the voltage and current requirements to drive them.· I think I would certainly have to use individual LEDs for the meters if I used Blue, and there are two problems with that.· Cost and brightness.
·· Blue LEDs tend to be water-clear ultra-bright.· I did order a few T1 LEDs from Jameco once that were diffused and perfect for the application, but looking on their website I no longer see them, unless their descriptions are wrong.· I can't remember the part #, but these would be great for indicators and metering in that they're NOT super-bright and being diffused they have even lighting.· I may save that idea for another smaller amplifier.
·· On a final note for tonight, your household audio system reminds me of something I recently found while looking for old data and information on my projects.· I once had this concept for building a computerized house.· Okay, I was young!· But in the plans I had drawn a wiring system that would go throughout the entire house networking each sub-system together and allowing for an LCD Display in each room that could emulate the configuration for other rooms if you wanted to control things from another room.
·· For example, say you had a graphical display that showed graphical representations of the things you control in that room.· In another room it's display has different controls and information.· My thought was you could access the control system for another room through that panel and it would re-configure itself.· Touch displays are coming down.· Especially ones usable by microcontrollers.
·· At the time I had dreamed of using the Z80, but now I am thinking several BASIC Stamps in a network.· Cleverly designed this could be even more powerful than I originally imagined, and the audio control could be a sub-system as well.· From any room you could select audio and see a graphical representation of the audio sub-system controls for that room.· You could then pipe the audio from any other room's source into that room, or from there re-direct other rooms.· You get the idea I think.· I will have to ponder this concept some more.· It would be extremely elaborate, but awesome!
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Chris Savage
Parallax Tech Support
csavage@parallax.com
Wow, you dreamed big
My thought for the room control pads wasn't anything more complicated than a BS1, a differential Tx/Rx pair, and thr 2x8 LCD AppMod. Basic souce selection and volume control, nothing outrageous. It will really depend on how much the whole thing will cost.
Personally, I'm going for blue and red on this project. Blue for source selection and the VFD, red for power indication and the mute button. There are some wonderful LEDs available in 0603 packages that will be perfect for what I'm doing, assuming I Can get the button caps made the way I want.
I plan on having a buffered tape output on my preamp (pre volume control, maybe with a seperate trim?), but nothing fancy. I'd likely be using it as an aux-out to feed my computer or an amp and speakers in the back yard.
If I go whole hog on the home audio system, the preamp will magically morph into an 8x8 matrix, with volume on each output and trims on all the inputs, fully balanced, and probably end up in a card cage backplane instead of a slick 1U enclosure as I plan now. I have a pretty decent layout to make a modular 8x1 card with a pair of DG507AUs and PG2311s (everything is balanced you know...), but I haven't solved wire management for it yet. Small Weidmueller connectors come to mind, but they're really expensive and tough on the fingers. I'm still thinking about that one.
Then again, I might just spend some cash and buy an Ashly 24.24M and build me a 16x8 matrix with all the goodies out of the box, and spend my time souping up a Xantech Smartpad program to control it. Turnkey does have it's appeal when it comes to slickness
I'll have a fixed payout to you soon.
-dave
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·· Okay, got the new schematic and layout.· Layouts are a little hard to follow because of the way they're exported I think, but the schematic looks good, and I followed most of the layout.· Seems to be all in order.· I guess it's ready!·
·· As for the Display...I ordered a sample today.· It's a CMOS level serial version.· I had the impression they only had RS-232C, but checking the list I quickly found that they even support parallel interface on many of the models.· It will be interesting to see how "real-time" I can get, since I may actually try to implement meters
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Chris Savage
Parallax Tech Support
csavage@parallax.com
The layout does export a little funny. I can't turn off the copper pours without actually deleting them, which makes doing just the traces a little difficult. Rest assured, the schematic and layout reconcile, so it seems to be all good. I'll panelize them tomorrow, and I should have boards in a week or two, barring any errors.
-dave
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This is not a sig. This is a duck. Quack.
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Chris Savage
Parallax Tech Support
csavage@parallax.com
I'm betting that if you did some trickery and used a parallel ADC, you could do a rapid 'copy and paste' operation to the VFD. Something like a shiftout (pins.lowbyte) or something?
After further review, I'm going to stick with external meters. I'm going to have enough to do with the UI and the remote control and other joys.
Panelizing now. Boards to come.
-dave
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This is not a sig. This is a duck. Quack.
·· Oh sure, make me second guess my plans!·
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Chris Savage
Parallax Tech Support
csavage@parallax.com
The boards are going to be delayed a little bit, much to my chagrin. Licensing issues are limiting me rather severely on my quest for 60sqin Gerbers right now, tho I hope I can get them resolved before the end of the week.
Kinda like the pile of fix-its that just landed on my desk. Ugh. Back to work.
-dave
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·· I'm not sure what mine will be yet.· For now I will probably do the Parallax, Inc. logo to see how that comes out, then I will worry about animated icons for various inputs and functions.· Like a Fan Blade for the fan control system.· So I can use icons for functions as well.· Speakers with a circle/slash for muting, etc.
·· Sorry about the board set back.· I have a few of those as well.· I need to still order those enclosures.· Everything on the hardware level will be well documented, including pictures.· Lots of pictures.
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Chris Savage
Parallax Tech Support
csavage@parallax.com
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Chris Savage
Parallax Tech Support
csavage@parallax.com
-dave
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·· The TI Parts all came today...Actually they came over a week ago, but FedEx never left a delivery notice.· So, I had no idea they were ever delivered.· Anyway, I got them today and now have 5 each of the 2 chips you recommended.· This weekend I will be prototyping/testing those sections.· I will post back when I have news.·
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Chris Savage
Parallax Tech Support
csavage@parallax.com
-dave
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·· The RCA jacks I use mount right into the metal cabinet, and thus are inherently grounded to the cabinet.· However I have to run shielded wires inside, so there is always the worry of ground loops, although I haven't had that happen in a long time.
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Chris Savage
Parallax Tech Support
csavage@parallax.com