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Amp/preamp design

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-08 00:07
    Dave Paton said...
    The docs I sent are all I got with mine. They should tell you enough to get started though.
    -dave
    Dave,

    ·· I cannot seem to locate those docs you sent.· I will continue to look, in the meantime I have sent you an e-mail about them.· Most of the information seems to be in the available quick reference sheet, except that it eludes to needing to short a jumper to use the serial connector, but doesn't say for sure.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-15 20:00
    Dave,

    ·· Since my last post I figured it out on my own...The command structure for this display is somewhat complex, although I haven't used any other GRFX Displays to compare the complexity to those.· Compared to a character display many things seem more difficult, but last night I successfully placed a bitmap image on the display.· So now I just need to look into storing it off screen and bringing it (Possibly scrolling it) int the visible area/window.

    ·· I haven't yet messed with those chips as I had planned, due to the display taking up more of my time, but I think that will justify itself soon.· Right now I am just waiting for the finds for a cabinet for the Power Amp and Controller.· Even on eBay they're a little high in price.· Anyway, if you need any pointers on the display, let me know.· I've been really messing around with scrolling, flashing, etc.· Not too bad.· The small display does draw a whopping 260 mA with the whole thing lit up inverse though!

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Dave PatonDave Paton Posts: 285
    edited 2005-10-24 13:49
    Chris-

    Sorry I fell off the net...life got a little too busy for me.

    My progress has slowed t a crawl, partly because of an impending move and partly due to general busyness.

    Only 260mA? That's cheap on current compared to my 2x20 Hitachi character VFD. It pulls down 1100mA at 5V wink.gif

    I'll probably be putting together a library of functions for the Noritake VFD over the next few months. I'd appreciate any help you can give me, since I'm starting from zero right now.

    Have you had a chance to play with all those nifty analog chips yet? Regrettably, even the shiny new bags of silicon toys I've gotten recently have been relegated to a shoebox pending the relocation of my den. I can't wait to unpack the stuff and start playing with it in earnest.

    As for enclosures, I still think Par-metals is your best bet for 'relatively inexpensive and right now'. Enclosures always kill my cost models here at work. Formed metal isn't cheap. I usually budget the complete electronic BOM cost to get something in a case. It drives me nuts.

    -dave

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-24 14:31
    Dave,

    ·· Is that like falling off the wagon?· That's okay, I get busy too.· In fact I haven't yet played with any of the audio chips!· =(· They're begging to be played with, but between the Noritake and a few other small projects on my bench, I haven't even made the room for them yet!

    ·· Yes, I am slowly forming some BASIC Stamp Documentation for the Noritake Displays, although, admittedly it's mainly centered around the 2X16 module right now.· The Bitmap Graphics turned out to be easier than I thought.· My older boy did a few pictures and we uploaded them.· Of course, that display is 112X16 pixels, so it took 224 DATA statements to make one screen...And each one is made up of eight binary digits (Longer, but easier than trying to convert to decimal or hex).

    ·· It's funny you should mentioned Par-Metal...I'm at the page right now (http://www.par-metal.com/).· Someone from there e-mailed me in response to a question on eBay.· It seems I missed an auction for a Tube Cabinet, then when I asked about it, they sent me the link.· That's where I was talking about getting the cabinets from, but originally I was just on their eBay Store.

    ·· Anyway, yeah, we'll get caught up on this whole project.· For now it will give us some time to focus on the VFD code, since I too am still learning.· I am having much success, but it is not easy on a few commands that don't seem to be working as expected.

    ·· Oh, before I forget, while I didn't get to play with any of the audio chips yet, I did get the code (BASIC Stamp 2px) reformatted for this new project, including references to all the hardware I know I am using, and the base code template.· So that much is done.· I just need to add the details in as I go.


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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-29 03:38
    Dave,

    ·· What do you think of the following case for new Audio Amplifier Designs?· Sure beats fabricating one from scratch (Which I've done more than a few times and cursed it!).· These look almost perfect.· I say almost because I think they could use a double front panel, but I could make due.



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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
    648 x 312 - 17K
  • Dave PatonDave Paton Posts: 285
    edited 2005-11-08 14:56
    Rescued from the deep dark depths of page 4, the Amp/[noparse][[/noparse]reamp design thread has returned!

    Why Chris, is thast one of those fancy Par-Metal cases? wink.gif

    Look spretty spiffy to me. I've got plans for something similar, but with beefier microfinned side panel heatsinks for my big power integrated amp (pre & amp, one box).

    I've been swamped at the office (I'm part of a team of 3 inheriting a half-million LOC project with no documentation aside from header files and sparse inline comments), so I've been neglecting hobbies and such lately, but with only a few more weeks to go before my house is able to be moved in to, I should be able to jump back in soon.

    How've you been doing? Playing with the toys?

    -dave

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-11-08 17:42
    Dave,

    ·· To be honest, I too have been swamped!· I haven't had a chance to play with any hardware yet since last I mentioned.· That hasn't, however, stopped me from looking for a potential enclosure...Besides, I can order that at my leisure.· =)· I am still hashing some details out, but I sent an e-mail to John at Par-Metals and haven't yet gotten a reply.· I noticed on eBay some people have complained about their e-mail response.· But I am in no hurry so.· The only thing is, while I wait I keep looking, so they could lose my business.

    ·· I did see a GainClone project that a guy built which I really liked his case.· I was tempted to e-mail him and ask how much for the metal, machinned and ready to assemble, but it looks like he put a lot of work into it, so I would guess the Par-Metal Enclosure may be the better deal.

    ·· Have you gotten to use the Noritake Display at all?· I haven't touched it in over a week unfortunately.· But I do have example code for both text and graphics.· I haven't nailed down the windowing, but it's a matter of time.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Dave PatonDave Paton Posts: 285
    edited 2005-11-08 18:53
    To be honest, I haven't touched a single thing in close to a month. It's been that crazy.

    More later, I have 2 meetings scheduled for 1pm. Oops.

    -dave

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-11-08 18:57
    Dave,

    ·· The thing I am waiting to find out from Par-Metal (A few things, actually) is if there is a baffle plate available for behind the front panel so I can mount front panel items to it, and not have to drill mounting holes in the front panel, just cut-outs.

    ·· The other things are just regarding ordering with different finishes, thicknesses of front panel, extra panel, etc.· But as I said, nothing yet.· If you're interested (Or anyone else) I will post my information here.· These seem like nice cases/enclosures, and are very inexpensive.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Dave PatonDave Paton Posts: 285
    edited 2005-11-08 21:28
    I think you'll have to make your own U shaped standoffs to do that. I don't remember for sure, but it sticks in my mind that others have had to do that. Your other option is to get one of their rack cases with a seperate faceplate and front case plate, and recess things between them.

    -dave

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-11-08 22:00
    I saw the rack mount cases, but they're a lot bigger than I need.· Still, in the end, if it means less work for mounting I might break down and get one.· =(

    As it stands, I am trying to decide if I want black or not.· I have black rack-style handles I could mount on the front if I don't get a rack mount case.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Dave PatonDave Paton Posts: 285
    edited 2005-11-09 14:38
    I'm actually a fan of silver right now. I've done black for a lot of stuff before, and I own a whole lot fo black audio boxen, and it's getting a little old. My old Carver TX-11 with the silver face has a look that's grown on me. Plus it matches my big silver plasma TV wink.gif

    If you're crafty, you might be able to get Ken to machine you something on that CNC mill he's got. The penguin bots came out really slick. I';m sure a front panel cover plate from 0.25" Aluminium with rounded edges and some control holes would be doable wink.gif

    -dave

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-11-09 19:30
    Interesting thought Dave!· I've been sick for the last few days (Really sick today) so I am not thinking of what is right before me!· I guess I'd just have to find a good source for the Aluminum now.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Dave PatonDave Paton Posts: 285
    edited 2005-11-09 23:40
    Online Metals, a division of Little Machine Shop:

    http://littlemachineshop.com/Info/OnlineMetals.php

    -dave

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-12-27 20:43
    Dave,
    ·
    ·· As I mentioned, I am watching and bidding in an attempt to get a case for my current amplifier which is a bunch of boards tied together with wires on my desk.· The wife laughs every time I crawl under the desk to plug it in or pull the plug (no power switch).· So I am getting a case finally!· On the toroidal transformers on his eBay page, I am trying to decide if the configuration is different on the units marked as being for Stepper Motors, as opposed to the ones he lists for amplifiers.· Problem is the guy never answers questions…At least none of mine.
    ·
    http://search.ebay.com/_W0QQsassZjohnangoQQhtZ-1

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    Chris Savage
    Parallax Tech Support
  • Dave PatonDave Paton Posts: 285
    edited 2006-12-27 22:03
    Ahh! It's the return of the undead Frankenthread!

    smilewinkgrin.gif

    The toroid I'm using is one of his 1KV 12V units. It's in a motion control app (but not steppers). The amplifier ones are all in the 2xVV category, with the steppers being single secondary units...I think. He's never answered an email of mine either, just a fast auto-checkout finalization of the auction and relatively fast shipment. I've been waiting for a nice fat one with 18 or 20V secondaries (x2) for my big beefy multichannel LM3886 beast, but none have shown up in a while. I'm a patient man though.

    -dave

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-12-28 00:32
    Dave,
    ·
    ·· That’s what I mean…He had an audio transformer on there one day that was 2X24V and I missed it!· Ever since then the minimum voltage he has for audio is like 2X28V which is too much (after rectification and filtering) for the LM3886T, which is what I am using.· I need 2X24V max.· I estimate using the 2X28V would be over 43 volts…With a 24V I am getting around 37V on the outputs.· Even that is pushing it.

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    Chris Savage
    Parallax Tech Support
  • T ChapT Chap Posts: 4,198
    edited 2006-12-28 01:23
    I like these rack boxes from middle atlantic. They are completely modular, with any type of mouting plate for any connector you can imagine.

    http://middleatlantic.com/rackac/ucp/frame.htm#ucp-ch

    Check out the UCP Chassis, it has rails on front and rear for mounting stuff. Not cheap though.

    middleatlantic.com/rackac/ucp/custom.htm#ucpvent
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-12-28 01:28
    Originator,
    ·
    ·· Your links don’t work as they are, however I did manage to get to the pages…These guys seem more geared toward rack-mount cases.· While I considered one before, this will be a home audio amplifier and a rack-mount case like these wouldn’t work for my approach.· Thanks for the information though.· Someone else may be looking for just that!

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    Chris Savage
    Parallax Tech Support
  • Dave PatonDave Paton Posts: 285
    edited 2007-01-05 15:19
    The M-A modular parts are OK for whacking together something quick, but I'm not a fan of their fit and finish for something that I won't be hiding in a wiring closet. They're just not slick enough for me these days. Functionally however, they rock hard. Your mileage will certainly vary however.

    smile.gif

    Chris-

    The transformers I'm looking for are the same as the ones you're looking for...it figures. In the mean time I've been using stuff I've scrounged from old receivers and the like, but I'd really like to do it right. Having a half dozen 150W units in a box doesn't appeal to me much.

    -dave

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-01-05 17:13
    Dave,

    That’s interesting since the only 3 power transformers I have consist of two recovered from commercial receivers/amplifiers and one from a company that seemed to disappear in the late 90’s called Mark V Electronics. I used to buy all my power transformers from them and use a second transformer for the line-level stuff, which was in a separate cabinet anyway.

    Anyway the two ‘recovered’ transformers have multiple taps on the outputs for additional lower voltage circuitry, such as the volume control and switching circuitry but I haven’t built a board to handle all of that yet. Perhaps I should get started. If you find a toroidal at 24V (or even as low as 20V) with the proper secondary let me know and I will also purchase one.

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    Chris Savage
    Parallax Tech Support
  • Dave PatonDave Paton Posts: 285
    edited 2007-01-05 20:13
    I remember Mark V...too bad they disappeared. Their little 36W class A amp was a nice beast. I had a pair of them in a case for a long time, until I loaned it out and it got fried by a friend who threw a party with "the heavy amp with the huge heatsinks". Grr. Learned my lesson with that one.

    There are toroids that pop up on eBay from time to time. I've also had good luck buying from Steve at Apex Jr, and from the folks at Alltronics and All Electronics. THey all have good deals from time to time on nice power transformers and other large power supply related goodies, but they go fast, so it takes sharp eyes.

    -dave

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-01-05 22:44
    Dave,

    Wow, someone who remembers Mark V! I never purchased one of their amplifier kits, but I must admit it was one of the inspiring factors to me building my own. Since Heathkit they were one of the few places that had built-it-yourself kits of high quality. But they sold the transformers separately which I appreciated. Anyway, I saved the links. I have done business with All Electronics, B.G. Micro and even Electronics Goldmine but two you listed were new to me so thanks!

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    Chris Savage
    Parallax Tech Support
  • Dave PatonDave Paton Posts: 285
    edited 2007-01-06 04:23
    Glad to help smile.gif

    Mark V was one of my favorite catalogs for a long time, it fuelled my DIY hobby pretty well. Heathkit was a feature of my youth, providing me with a meter (via my dad) and some educaiton in Jr. High with a Hero 2000 (after they were out of business), but I was born about 10 years too late for their real heyday.

    These days it's all about people like Jan at 41Hz.com (Tripath kits) and the folks at my pro sound DIY group...when I have the time.

    Oh, check out the first page of this thread, post #4. Apexjr is mentioned there wink.gif

    -dave

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-01-06 04:56
    Dave,

    So it is…I will check it out tonight! Thanks again!

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    Chris Savage
    Parallax Tech Support
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-01-11 18:48
    Dave,

    I got my amplifier case in. I have two small complaints about it…The front panel has some silvery scuffing where the screws go in, almost as if they were put in using a nut-driver and it scuffed the panel. I may be able to buff that out. Also the front panel was slightly (very slightly) warped, so that it appears to bow outward a little when looking down from the top. However, in all fairness I will be buying the other one he has of the same size now since this one is definitely too small for everything. This one will be for the Power Amp section and the other one will be for the controller. I will post pictures as I take them. Take care.

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    Chris Savage
    Parallax Tech Support
  • Dave PatonDave Paton Posts: 285
    edited 2007-01-12 15:08
    Chris-

    Sounds like a pretty good deal nonetheless. I've seen the scuffing you mentioned before on similar cases, it's always due to sloppy driver work when they're being assembled. That said, compared to Par-Metal, the price can't be beat, and I'll accept having to spend a little time with a scotch-brite pad to make them pretty.

    I'll be looking forward to seeing pictures as the project progresses. Hopefully I can toss in some of my own some day...once I get the den in order, finish the wedding plans, sell a pile of stuff on eBay, reorganize the house, rebuild the motor on my car, finish the trim, repaint the front door, take care of the plants in the side yard....

    well, you get the idea.

    -dave

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-01-12 17:43
    Dave,

    No problem! I totally understand having a life and being busy! Aren’t we all at some point? The good thing is that through it all you’ll be hashing out plans and when you’re ready to build you’ll have so many new ideas you won’t know where to start! =)

    Needless to say I am going to have to be very careful milling the front/rear panels on these since they won’t be prototypes…I want these to get me through the next 5 or 10 years or so…

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    Chris Savage
    Parallax Tech Support
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-01-17 17:18
    Dave (& all),

    Last night I sat down and finalized my draft for the controller. I was going to use an SX but in retrospect the BASIC Stamp is still quite capable, even with everything I am doing. To that end I plan on using a BS2p40 in the controller. The way I have it worked out is that the entire Main I/O will be all of the inputs while the entire Aux I/O handles the I/O and interface ICs. For example, the DS1302, 74595, PGA2311, ADC0831, VFD, Power Relay, Mute Relay, Fan Control, MPC507A, etc. will all be on that side. Since all of these devices are accessed using subroutines anyway it will be easy to swap banks, handle the I/O and return to the Main bank so when I come back I can monitor the inputs between calls.

    I will probably use three program slots total. Slot 0 for startup initialization, Slot 1 for the main routines and Slot 2 for DATA for the graphics display and a few other things. Of course that depends on how much space my code ends up taking up too since I will have a menu system for adjusting the clock, fan mode, etc. There’s even a light sensor for adjusting display brightness, though I am not yet sure if/how I will implement that.

    The DS1302 will be used for time/date stuff but primarily is my storage for certain values that need to be backed up but change too frequently to use EEPROM. These settings are always restored at power up. The 74HC595 (2) will be used for the indicator lights on the front panel. I was thinking about doubling up and using bi-directional LEDs but I am unsure there as well. One ADC will monitor the volume control POT, while the other monitors heat sink/amplifier temperature. Depending on the fan mode this information will be used to control the cooling fan.

    Anyway, I still have a lot to hash out, but this much will allow me to get the program templates up and running so I can start prototyping. Once I get that far experimenting with the optional stuff will help me decide on what stays and what goes. I originally accounted for a Tape Monitor circuit, but now I am wondering about that. One last option was to be able to select the audio source and select what goes out to record output separately. This is what made me think of bi-color LEDs, since I would show the selected audio source in green and the recording source in red. If the same was selected I would alternate the LED color. Ideas, thoughts, comments?

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    Chris Savage
    Parallax Tech Support
  • Dave PatonDave Paton Posts: 285
    edited 2007-01-18 07:01
    That sounds like a very well reasoned plan Chris. I especially like your zone/tape output idea, with the bicolor LEDs. Very slick. I'd comment more, but it's 1am and I need sleep. I'm looking forward to hearing more as your project progresses. Maybe it'll be the motivation I need to learn enough SX/B to rebuild mine into the multizone home audio system it wants to be.

    -dave

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