Agreed…Very nice…I have to agree with Dave on the ground planes, although none of my previous prototypes had them because the boards were hand etched. The newer stuff will certainly make use of it though. Once you get them populated take a snapshot…Looking forward to seeing them populated.
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Pre has two ground planes digital and analog. Analog plane is solid while digital is meshed so that they could be clearly identified both joined at one place via a wire connector.
Chris: for encoder knobs those which I showed along encoders they can be used with both type of shafts and I could send them over to you, whenever you want....
For now have a look at the simple version of the pre-amp boards, along OPA549 stereo boards.
I recieved them yesterday (6 boards each) and immediately started populating simple pre-amp board, will complete the pre on weekend and then onto PC for finalizing the firmware, once it is complete and bug free I intend to put it on the discussion board (board to be decided later) for non-commerical hobbyists.
Chris I will make photos of the knobs today, since there is holiday tomorrow, will post the pics day after, right now here is the PIC of simple pre being populated after putting in RCA jacks.
Now I am waiting for ICD2, so that I could program the mcu, my previous one fried due to voltage fluctuation.
Very nice! They look a lot like LM3886 Gain Clone amplifiers…Interesting…Is this board one you posted the layout to? It would be interesting to see since it’s single-sided.
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Yes·these are·the same boards whose layout I posted on the board, its a single sided proto board, with just one jumper for negative rail. Next boards are already on the way, and they will have enamel on both sides and silk screen on the top for single sided, etc. I have now about 30 boards of the gainclone. I needed about 6 of them.
PICs of the knobs are here they have screws on the front side one you fix em on any encoeder they could be tightened. The encoders along knobs are available at ebay for a mere 10$ for 10 encoders and 10$ for shipment by a seller by the name of sure electronics.
Here are populated pics of the simple pre and a few glimpses of the high end pre, controller and analog section. your would see some sticky thing on jumpers, I have experimented here by putting silicone sealant on top of them to ensure they dont move and dont get shorted with others.
Sorry for poor quality of PICs, couldnt get da** macro mode in my cam to work properly
Looks like you’re way ahead of Dave and I on current projects! Nice work…Now I need to play catch-up!
Dave,
Just got the regulators in so I shall begin populating a couple of those P/S boards so I can start testing the audio chips.· I will keep you all posted on the results.
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Thanks for the nice comments, though my progress on boards seem faster, but I know you guys will catch up faster coz now I ll have to put my head down and start programming which by the way is my grey area because of limited grey areas inside the skull·· and thats one place where you guys will go at a much faster pace.
Anyways I am always open for any help/support for open pre-amp that we intended to design here.
Nice to see the progress guys. I'm up to my ears in day job work, wedding planning, and a side project I'm doing for some fellow Honda guys (new fuel rail to adapt some injectors to our little 4cyl motors). I'll catch up...er...eventually
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Chris here are schematics of simple pre-amp which is build around a PIC16F876A and Controller and Analog section of High End Pre which is build around a PIC16F877A.
Though schematics are not as good as they should be, coz I used simple connect planes rather than databus entries, but then again I had no intention of doing simulation in ADS just simple layouts.
I ll post even layouts of the simple pre, but not high end pre, I ll rather prefer PM them to you.
I'm interested in designing an amp of my own. I don't really know where to start, so do you guys have any suggested reading that I should do? I'm looking to replace my stereo in my room with something a little more 'DIY'. All I need is an input for my computer and another for my iPod. I need about 100W per channel (the stereo I have now is about 120W per channel and I'm planning on keeping the speakers), unless it's way to complicated.
Thanks,
Dan
EDIT: I have been looking at the LM12 as an amplifier chip. It seems that you guys have used them before? I found this site that has a (what I think) good design for a stereo amp: http://www.dpaton.net/audio/lm12amp/lm12.shtml.
Let me know what you think.
Post Edited (Ductapemaster) : 5/7/2007 3:30:49 AM GMT
Yeah, that’s Dave’s website…You’ll find a lot of information and links there. Speaking of which…
Dave,
This weekend I didn’t get much done that I had planned…But I DID get that Power Supply Board (one of them) you sent me populated. I kind of wish the Bridge Rectifier was on-board, but I will deal with it. After completing this I tested the board and the negative supplies were all almost spot on. The positive side was a little low, especially on the 12V side but within norms. This means I can start testing the audio stuff next weekend since I now have power for everything. I have the perfect power transformer for this board. It’s actually from Radio Shack but has 12V-0V-12V0 @ 2A secondary. I figured I’ll either use a bridge with screw terminals (overkill) or just get one with a mounting hole and wrap the supply wires to it. Thanks again!
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Chris Savage Parallax Tech Support
The LM12 design on my page should be considered only for the schematic. If you build it physically like I did, you'll spend weeks and weeks poking and prodding to get rid of hum, buzz, and general weirdness. That said, with careful design (treat it like a low noise op-amp design, and a high power layout at the same time) it's a wonderful amplifier for about 200wpc into 8R. Don't use it for anything under about 6R...the current spikes too high, and you can either blow up devices or kill speakers (the Ilimit hardware isn't load friendly). Ideally there would be a THD measurement circuit that would clamp the input when the output got wonky, like Crown's IOC circuitry, but that's a little much for me to design at this point. Life is just too busy
Chris-
I originally had the bridge on the board, but I ended up loading it pretty heavily, so I re-designed it to use an offboard bridge that could be bolted to an aluminum heatsink (the case) and re-laid the regulators so they too could be mounted flat to the case. I found some of my regulators were unhappy when being loaded asymmetrically (more positive load than negative) and ended up with outboard regulation for some of the higher current things (+5 for the VFD drive, +12 for the relays and VU meter lamps). I also had a few RatShack regulators that were fine unloaded, but fell apart under load, and likely either sweepings or...er...less than authentic, so you might want to try swapping regulators just in case.
Still working on too many things to play, but I do have time to pop in every once and a while
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I actually cut mine on the line on the bottom, so I could more easily mount them flat to a big chunk of aluminum (my regulators are mounted to the bottom of the PCB), but that way works great too. I've got one like that sitting next to me here at work, +/- 3.3, 5, and 12.
-dave
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Yeah, this was easiest for testing…If I use one in-circuit I may change the way I mount it. No doubt I will populate one with 3.3V, 5V and 12V. That would be very useful as well. Thanks again and Take care!
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I checked the speaker I have from my stereo, and they're 6 ohm ones. I'm planning on using those until I find a nice pair (and when I'm done with the project...). Funny how I found your website Dave...that was the best design that google came up with for an LM12 amp. Yeah, and I was just searching for a schematic, not a full assembly plan. I can figure most of it out on my own.
I've spent some time designing my amp and adding features that I would like. So far, they include: An LCD or VFD display, 2 inputs (computer and iPod), a 5 band graphic equalizer (found a nice IC that does it all for me) with linear pots, a simple VU meter, but with a different color scheme than green, yellow and red, and a nice big quadrature encoder for volume control. At the moment thats it, maybe I will add a serial controller for an iPod in the future...you never know.
And this isn't one of those impulse things...I plan to see it all the way through.
Oh and BTW, I didn't understand half the things you said in your post, Dave (any suggested reading for getting up to speed on audio electronics? That's why I'm doing this project...tired of all the digital stuff). I'm only 16, so I don't have my EE degree yet (planning on it though!). I'm no newbie at electronics though, I have been interested in them since I was about 4. My most recent projects include a clock based on Nixie Tubes (vintage neon display tubes) with a Basic Stamp 2 controlling it all, and a box (once again, controlled by a BS2) that counts down and launches my model rockets. Great fun...
One more thing...Chris, thanks for helping me out in tech support today with my SX-Key. I sent it out this afternoon.
I used to be the top hit for the LM3886 and Phase Linear 700 as well..and was pretty high up for Hafler gear. Thankfully, Google has let my unloved and nearly abandoned site fall down the listings in the last couple of years, buying me time until I can give it the overhaul it really needs.
As far as the gobbldygook I spouted, I'd reccomend picking up a copy of The Art of Electronics. It's not a cheap book, and it's a little dated in it's component lists, but Horiwitz and Hill have forgotten more about electronics than anyone I've met has ever known. The books by Walt Jung and Bob Pease are also required reading in my book. None of them were part of my college curriculum, but if they had been, life would have been easier.
I built my LM12 amp at 19, so you're not out of your element at all. Good luck!
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This is not a sig. This is a duck. Quack.
I think that book will make a good 'end of my junior year' present...now I just have to talk my parents into it...
I was looking through some of the previous posts in this thread and I have a couple of questions/observations:
- A looked at that par-metal place and they have some really nice stuff. I was hoping to fit everything in one case, but I'm not sure about it. I really would like to have the 2 inch (height) case and it would make for a really clean front panel. Do you think I could shove everything in there?
- Chris, could I possible buy one of those quadrature encoders you have? I don't need 10 of them, and thats the only quantity available for a reasonable price on eBay.
- Also, what program did you do your renderings for the front/back panel in? I need a decent program for that type of stuff.
- Do either of you have a good source for slide type pots (100k ohms)? I can't find them for a reasonable price much anywhere.
Can you post a photo of the P/S boards you built? You have my attention and curiosity on how you set yours up.
Dan,
Like Dave I am willing to share a little…PM me your address and I will send you out one tomorrow USPS. I understand about eBay…I rarely buy on there and when I do I try to make it worth my while.
As for the panel designs you won’t believe me…Like my schematics they’re hand drawn in MS Paint. I don’t really have a fancy program for this stuff. Soon I will be using Eagle though. I just need to compile a decent library because my biggest gripe in Eagle is going through all those libraries to get what I need.
I think I had some linear potentiometers once years ago I purchased to try and save a BSR EQ that was in need of repair. But the units I got cost me a fortune and were supposed to fit but didn’t. I got rid of them back in the mid 90’s and haven’t ordered any since. Sorry.
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Funny...my first impression was that you used MS paint, but I figured that you used something more, but I guess not. I just went out this afternoon and bought a big graph paper pad (its 11x17 inches) for the panel design and schematics. I generally like to hand draw my stuff when testing and put it all together in the end. I'm in the habit as I never used to have a computer in the garage, but I recently upgraded mine and put the old one in the garage, so I have my schematic program out there. And FYI, for my schematics, I use Circuitmaker 2000 pro. I found a copy on a teacher's webpage, so I used it. Technically it's not piracy, as the company changed names and doesn't even support the product anymore. Being 16 I didn't have $900 to spend on software...oh well.
And BTW, when I said a source for slide pots I didn't mean do you have any, but if you knew of a good place to buy some (I need 5, 100k pots)
I don't have any current pictures (the bos the supply is in is at the bottom of a rack in the living room, and I'm loathe to disconnect it and pull it out for a photo), but this is what it looked like originally. Don't mind the hand-etched PCB or the disorganize wiring, that's a picture from when my preamp was in early alpha, and it was taken by an ooooold QuickCam VC.
It's basically the same as yours, with 0.1" headers for input and output. The regulators ended up getting moved to the bottom, and the board ended up flat on the bottom of the encolsure, instead of on an internal brace as shown, but it's pretty vanilla.
Dan-
Par-Metal makes some wonderful cases. With careful design, you can get everything into a 1.75" takk 1U rack case (~1.5" usable internal height), or even smaller if you use a miniature 1-line display. That starts getting silly though, so I always planned mine for a 2U case (3.5" outside height, 3.125" usable internal height), and had plenty of space.
Slide pots? Ask and ye shall receive: http://www.alltronics.com/cgi-bin/category/162
-dave
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Yeah, not having thought about them in so many years I don’t know who carries them anymore. They’re more of a niche item these days it seems. As for Graph Paper, that’s always a good place to start when hammering out designs. Nothing really beats a pencil and paper for concept art…
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Chris Savage Parallax Tech Support
No minimum order and they'll ship UPS or by US Mail.
Buy·a few things from them and they'll start sending you their 3" thick catalog every 3 months. It makes finding parts a lot easier when you have the catalog to flip through.
I assume that the picture was sans heat-sinks for the regulators as well? Anyway I see how you have the heavy-duty rectifier setup on the bottom. That is what I will be doing as well.
Dan,
Your rotary encoder has been sent out today USPS this morning. Let me know (via PM) when you get it. Take care.
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I found a Mouser catalog in my room and I have been looking through it lately. I found the slide pots and they seem to be exactly what I want. Thanks.
I have some more questions though. First, the schematics you have on your webpage say they're for a subwoofer amp. Will they be appropriate for driving normal speakers? Also, do I need four LM12's? 80 watts per channel seems fine with me (the stereo I have now isn't something I crank up all the way, and it's claimed to be 120W per channel, but I doubt it). I found a schematic in the datasheet for the LM12, but will it work for my application? It doesn't have any specifications other than it being an audio amp. Furthermore, I have been searching for a good transformer to use. I'm not sure what volt-amp rating I should buy though. If I revise my schematic to use two LM12 instead of four, do I really need 500VA's? It seems like overkill, but maybe not. I am trying to fit the amp and preamp into a case thats 12x12x2 (LxWxH) inches, but I' m not sure whether it will be possible, as transformers can get big. I was also looking at some heatsinks to use for the TO-3 packages. I found one in the mouser catalog that looks promising. It's part number 567-641-A. It will fit in a 2 inch (well vented) case (it's an inch high) and I plan on using a fan(s), so size isn't a huge issue. In your experience, will it suffice or will I need something larger? I know it needs to be isolated from the case, as the case of the LM12 is V-.
Thanks for all your guys and sorry about all the questions.
Comments
Agreed…Very nice…I have to agree with Dave on the ground planes, although none of my previous prototypes had them because the boards were hand etched. The newer stuff will certainly make use of it though. Once you get them populated take a snapshot…Looking forward to seeing them populated.
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Chris Savage
Parallax Tech Support
Pre has two ground planes digital and analog. Analog plane is solid while digital is meshed so that they could be clearly identified both joined at one place via a wire connector.
Chris: for encoder knobs those which I showed along encoders they can be used with both type of shafts and I could send them over to you, whenever you want....
For now have a look at the simple version of the pre-amp boards, along OPA549 stereo boards.
I recieved them yesterday (6 boards each) and immediately started populating simple pre-amp board, will complete the pre on weekend and then onto PC for finalizing the firmware, once it is complete and bug free I intend to put it on the discussion board (board to be decided later) for non-commerical hobbyists.
Awesome, definitely keep us updated when you get that one board populated. Do you have a picture of the knobs you’re referring to?
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Chris Savage
Parallax Tech Support
Now I am waiting for ICD2, so that I could program the mcu, my previous one fried due to voltage fluctuation.
Program is almost ready to be tested.
Post Edited (Junkie) : 4/30/2007 5:56:38 AM GMT
Please comment.
Very nice! They look a lot like LM3886 Gain Clone amplifiers…Interesting…Is this board one you posted the layout to? It would be interesting to see since it’s single-sided.
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Chris Savage
Parallax Tech Support
Yes·these are·the same boards whose layout I posted on the board, its a single sided proto board, with just one jumper for negative rail. Next boards are already on the way, and they will have enamel on both sides and silk screen on the top for single sided, etc. I have now about 30 boards of the gainclone. I needed about 6 of them.
PICs of the knobs are here they have screws on the front side one you fix em on any encoeder they could be tightened. The encoders along knobs are available at ebay for a mere 10$ for 10 encoders and 10$ for shipment by a seller by the name of sure electronics.
Here are populated pics of the simple pre and a few glimpses of the high end pre, controller and analog section. your would see some sticky thing on jumpers, I have experimented here by putting silicone sealant on top of them to ensure they dont move and dont get shorted with others.
Sorry for poor quality of PICs, couldnt get da** macro mode in my cam to work properly
I look forward to inputs from you guys.
Post Edited (Junkie) : 5/3/2007 6:09:16 AM GMT
Looks like you’re way ahead of Dave and I on current projects! Nice work…Now I need to play catch-up!
Dave,
Just got the regulators in so I shall begin populating a couple of those P/S boards so I can start testing the audio chips.· I will keep you all posted on the results.
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Chris Savage
Parallax Tech Support
Thanks for the nice comments, though my progress on boards seem faster, but I know you guys will catch up faster coz now I ll have to put my head down and start programming which by the way is my grey area because of limited grey areas inside the skull·
Anyways I am always open for any help/support for open pre-amp that we intended to design here.
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This is not a sig. This is a duck. Quack.
We’ll leave the light on for ya…
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Chris Savage
Parallax Tech Support
-dave
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No problem!
Junkie,
I know you posted layout pictures of the boards, but did you post a schematic for the boards you recently made?
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Parallax Tech Support
Though schematics are not as good as they should be, coz I used simple connect planes rather than databus entries, but then again I had no intention of doing simulation in ADS just simple layouts.
I ll post even layouts of the simple pre, but not high end pre, I ll rather prefer PM them to you.
We had already discussed the rasons for that.
Thanks,
Dan
EDIT: I have been looking at the LM12 as an amplifier chip. It seems that you guys have used them before? I found this site that has a (what I think) good design for a stereo amp: http://www.dpaton.net/audio/lm12amp/lm12.shtml.
Let me know what you think.
Post Edited (Ductapemaster) : 5/7/2007 3:30:49 AM GMT
Yeah, that’s Dave’s website…You’ll find a lot of information and links there. Speaking of which…
Dave,
This weekend I didn’t get much done that I had planned…But I DID get that Power Supply Board (one of them) you sent me populated. I kind of wish the Bridge Rectifier was on-board, but I will deal with it. After completing this I tested the board and the negative supplies were all almost spot on. The positive side was a little low, especially on the 12V side but within norms. This means I can start testing the audio stuff next weekend since I now have power for everything. I have the perfect power transformer for this board. It’s actually from Radio Shack but has 12V-0V-12V0 @ 2A secondary. I figured I’ll either use a bridge with screw terminals (overkill) or just get one with a mounting hole and wrap the supply wires to it. Thanks again!
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Chris Savage
Parallax Tech Support
The LM12 design on my page should be considered only for the schematic. If you build it physically like I did, you'll spend weeks and weeks poking and prodding to get rid of hum, buzz, and general weirdness. That said, with careful design (treat it like a low noise op-amp design, and a high power layout at the same time) it's a wonderful amplifier for about 200wpc into 8R. Don't use it for anything under about 6R...the current spikes too high, and you can either blow up devices or kill speakers (the Ilimit hardware isn't load friendly). Ideally there would be a THD measurement circuit that would clamp the input when the output got wonky, like Crown's IOC circuitry, but that's a little much for me to design at this point. Life is just too busy
Chris-
I originally had the bridge on the board, but I ended up loading it pretty heavily, so I re-designed it to use an offboard bridge that could be bolted to an aluminum heatsink (the case) and re-laid the regulators so they too could be mounted flat to the case. I found some of my regulators were unhappy when being loaded asymmetrically (more positive load than negative) and ended up with outboard regulation for some of the higher current things (+5 for the VFD drive, +12 for the relays and VU meter lamps). I also had a few RatShack regulators that were fine unloaded, but fell apart under load, and likely either sweepings or...er...less than authentic, so you might want to try swapping regulators just in case.
Still working on too many things to play, but I do have time to pop in every once and a while
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Chris Savage
Parallax Tech Support
I actually cut mine on the line on the bottom, so I could more easily mount them flat to a big chunk of aluminum (my regulators are mounted to the bottom of the PCB), but that way works great too. I've got one like that sitting next to me here at work, +/- 3.3, 5, and 12.
-dave
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This is not a sig. This is a duck. Quack.
Yeah, this was easiest for testing…If I use one in-circuit I may change the way I mount it. No doubt I will populate one with 3.3V, 5V and 12V. That would be very useful as well. Thanks again and Take care!
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Chris Savage
Parallax Tech Support
I've spent some time designing my amp and adding features that I would like. So far, they include: An LCD or VFD display, 2 inputs (computer and iPod), a 5 band graphic equalizer (found a nice IC that does it all for me) with linear pots, a simple VU meter, but with a different color scheme than green, yellow and red, and a nice big quadrature encoder for volume control. At the moment thats it, maybe I will add a serial controller for an iPod in the future...you never know.
And this isn't one of those impulse things...I plan to see it all the way through.
Oh and BTW, I didn't understand half the things you said in your post, Dave (any suggested reading for getting up to speed on audio electronics? That's why I'm doing this project...tired of all the digital stuff). I'm only 16, so I don't have my EE degree yet (planning on it though!). I'm no newbie at electronics though, I have been interested in them since I was about 4. My most recent projects include a clock based on Nixie Tubes (vintage neon display tubes) with a Basic Stamp 2 controlling it all, and a box (once again, controlled by a BS2) that counts down and launches my model rockets. Great fun...
One more thing...Chris, thanks for helping me out in tech support today with my SX-Key. I sent it out this afternoon.
-Dan
I used to be the top hit for the LM3886 and Phase Linear 700 as well..and was pretty high up for Hafler gear. Thankfully, Google has let my unloved and nearly abandoned site fall down the listings in the last couple of years, buying me time until I can give it the overhaul it really needs.
As far as the gobbldygook I spouted, I'd reccomend picking up a copy of The Art of Electronics. It's not a cheap book, and it's a little dated in it's component lists, but Horiwitz and Hill have forgotten more about electronics than anyone I've met has ever known. The books by Walt Jung and Bob Pease are also required reading in my book. None of them were part of my college curriculum, but if they had been, life would have been easier.
I built my LM12 amp at 19, so you're not out of your element at all. Good luck!
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I was looking through some of the previous posts in this thread and I have a couple of questions/observations:
- A looked at that par-metal place and they have some really nice stuff. I was hoping to fit everything in one case, but I'm not sure about it. I really would like to have the 2 inch (height) case and it would make for a really clean front panel. Do you think I could shove everything in there?
- Chris, could I possible buy one of those quadrature encoders you have? I don't need 10 of them, and thats the only quantity available for a reasonable price on eBay.
- Also, what program did you do your renderings for the front/back panel in? I need a decent program for that type of stuff.
- Do either of you have a good source for slide type pots (100k ohms)? I can't find them for a reasonable price much anywhere.
Thanks for all your help so far.
-Dan
Can you post a photo of the P/S boards you built? You have my attention and curiosity on how you set yours up.
Dan,
Like Dave I am willing to share a little…PM me your address and I will send you out one tomorrow USPS. I understand about eBay…I rarely buy on there and when I do I try to make it worth my while.
As for the panel designs you won’t believe me…Like my schematics they’re hand drawn in MS Paint. I don’t really have a fancy program for this stuff. Soon I will be using Eagle though. I just need to compile a decent library because my biggest gripe in Eagle is going through all those libraries to get what I need.
I think I had some linear potentiometers once years ago I purchased to try and save a BSR EQ that was in need of repair. But the units I got cost me a fortune and were supposed to fit but didn’t. I got rid of them back in the mid 90’s and haven’t ordered any since. Sorry.
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Chris Savage
Parallax Tech Support
Funny...my first impression was that you used MS paint, but I figured that you used something more, but I guess not. I just went out this afternoon and bought a big graph paper pad (its 11x17 inches) for the panel design and schematics. I generally like to hand draw my stuff when testing and put it all together in the end. I'm in the habit as I never used to have a computer in the garage, but I recently upgraded mine and put the old one in the garage, so I have my schematic program out there. And FYI, for my schematics, I use Circuitmaker 2000 pro. I found a copy on a teacher's webpage, so I used it. Technically it's not piracy, as the company changed names and doesn't even support the product anymore. Being 16 I didn't have $900 to spend on software...oh well.
And BTW, when I said a source for slide pots I didn't mean do you have any, but if you knew of a good place to buy some (I need 5, 100k pots)
Thanks again.
-Dan
I don't have any current pictures (the bos the supply is in is at the bottom of a rack in the living room, and I'm loathe to disconnect it and pull it out for a photo), but this is what it looked like originally. Don't mind the hand-etched PCB or the disorganize wiring, that's a picture from when my preamp was in early alpha, and it was taken by an ooooold QuickCam VC.
http://www.dpaton.net/audio/preamp/pre_ps.jpg
It's basically the same as yours, with 0.1" headers for input and output. The regulators ended up getting moved to the bottom, and the board ended up flat on the bottom of the encolsure, instead of on an internal brace as shown, but it's pretty vanilla.
Dan-
Par-Metal makes some wonderful cases. With careful design, you can get everything into a 1.75" takk 1U rack case (~1.5" usable internal height), or even smaller if you use a miniature 1-line display. That starts getting silly though, so I always planned mine for a 2U case (3.5" outside height, 3.125" usable internal height), and had plenty of space.
Slide pots? Ask and ye shall receive: http://www.alltronics.com/cgi-bin/category/162
-dave
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This is not a sig. This is a duck. Quack.
Yeah, not having thought about them in so many years I don’t know who carries them anymore. They’re more of a niche item these days it seems. As for Graph Paper, that’s always a good place to start when hammering out designs. Nothing really beats a pencil and paper for concept art…
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Chris Savage
Parallax Tech Support
http://www.mouser.com/catalog/630/536.pdf
http://www.mouser.com/catalog/630/537.pdf
No minimum order and they'll ship UPS or by US Mail.
Buy·a few things from them and they'll start sending you their 3" thick catalog every 3 months. It makes finding parts a lot easier when you have the catalog to flip through.
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- Rick
I assume that the picture was sans heat-sinks for the regulators as well? Anyway I see how you have the heavy-duty rectifier setup on the bottom. That is what I will be doing as well.
Dan,
Your rotary encoder has been sent out today USPS this morning. Let me know (via PM) when you get it. Take care.
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Chris Savage
Parallax Tech Support
I have some more questions though. First, the schematics you have on your webpage say they're for a subwoofer amp. Will they be appropriate for driving normal speakers? Also, do I need four LM12's? 80 watts per channel seems fine with me (the stereo I have now isn't something I crank up all the way, and it's claimed to be 120W per channel, but I doubt it). I found a schematic in the datasheet for the LM12, but will it work for my application? It doesn't have any specifications other than it being an audio amp. Furthermore, I have been searching for a good transformer to use. I'm not sure what volt-amp rating I should buy though. If I revise my schematic to use two LM12 instead of four, do I really need 500VA's? It seems like overkill, but maybe not. I am trying to fit the amp and preamp into a case thats 12x12x2 (LxWxH) inches, but I' m not sure whether it will be possible, as transformers can get big. I was also looking at some heatsinks to use for the TO-3 packages. I found one in the mouser catalog that looks promising. It's part number 567-641-A. It will fit in a 2 inch (well vented) case (it's an inch high) and I plan on using a fan(s), so size isn't a huge issue. In your experience, will it suffice or will I need something larger? I know it needs to be isolated from the case, as the case of the LM12 is V-.
Thanks for all your guys and sorry about all the questions.
-Dan