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Author Topic: Want a PCB please!  (Read 13941 times)

yatinejkc

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Want a PCB please!
« on: December 17, 2006, 08:25:54 AM »
I want to build my guitar amp and i have got a lot of shematics but no one was accompanied with a PCB layout, a pcb really helps to accelerate the work and is very tidy.

Can som1 give me a link where i can get shematics with the PCB layouts of a 10w-20w ss amp please, ti is very important for my college project!!! ???

joecool85

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Re: Want a PCB please!
« Reply #1 on: December 17, 2006, 08:51:04 AM »
Life is what you make it.
Still rockin' the Dean Markley K-20X
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yatinejkc

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Re: Want a PCB please!
« Reply #2 on: December 18, 2006, 05:10:29 AM »
That is really cool but im looking for pcb with the schematics like those on www.fuzzcentral.ssguitar.com and i need a really more powerful than that you gave me. sincerely, i need more quality than power and amps with only a few transistors sound horrid, i wanted to make one with valves but in Mauritius, we dont have such variety of electronic spare parts, so i must find one with transistor but that sound really good.

isn't there any other sites or any ssguitar member  who did an amp and who is putting the pcb layout on the intnet??

joecool85

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Re: Want a PCB please!
« Reply #3 on: December 18, 2006, 07:02:38 AM »
The LM1875 amps sound great!  Trust me, I have two :-)  The LM3886 is good as well, but more powerful.  If you want one based off transistors as opposed to ICs, I would have you check out Joe Davidson's guitar amp (its more than 10-20 watts though), but his schematic isn't online anymore and I don't have it on my computer :-(

You could look into the schematics at deanmarkley.com, some of their legacy amps used transistors instead of ICs.

http://www.deanmarkley.com/Info/LegacyAmps/Docs.shtml

Like the K-20B (uses an IC for the preamp, but you could change that to something else): http://www.deanmarkley.com/Info/LegacyAmps/Schematics/D1513.pdf

The K-20B is technically a bass amp, but its a great little amp.  If you built something else for a preamp and just used the K-20B poweramp circuit, you'd be good to go for guitar.
Life is what you make it.
Still rockin' the Dean Markley K-20X
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teemuk

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Re: Want a PCB please!
« Reply #4 on: December 18, 2006, 07:36:17 AM »
For some reason people are more keen on sharing schematics than layouts. I don't know if you want to build a discrete amplifier or just make a 10 - 20 watt amplifier rather quickly. In later case I guess the fastest way is to browse through some chip power amplifier datasheets - like TDAxxxx series. They usually present an example circuit accompanied with a PCB layout. You say you want quality: Most of them are excellent quality for that power range and come equipped with short circuit/thermal protection and top quality constant current loads etc. I bet you couldn't build a better one from discrete components aside make as tight layout with equal thermal coupling characteristics. If part of your project is to explain how the circuit works you could do that with a chip amp too; the datasheet usually has a simplified schematic of the circuit.

If you want to build a discrete amplifier I suggest you do the layout yourself. It's a great way to learn why the layout is pretty important part of the whole circuit. It's pretty easy to come up with a schematic that runs ideally on paper. When you build it, it will have all sorts of interference since real-life components and wiring are never that ideal. Besides, you learn a lot more by making mistakes and trying to correct them. Making a PC board layout shouldn't be that time consuming once you get to it and know what you are doing.

By the way, I don't know if you really searched or just expected someone to do it for you. When I typed "amplifier PCB" to google I instantly found several pages that might have a suitable circuit.

http://members.hometown.aol.com/_ht_a/lmdmkm/25w/25wamp.htm
http://www.audiodesignguide.com/Headphone_amp/headphoneamp.html
http://hepso.dna.fi/misc/lm3875/LM3875_amplifier.html
http://www.digisound80.co.uk/digisound/modules/80-14/80-14.htm
http://www.tcaas.btinternet.co.uk/jlhesl.htm

Besides these you could check out the pages of hifi amplifier projects like "Leach" or designs by Nelson Pass to name a few sources. Guitar power amplifiers are still plain power amplifiers and if you concentrate your focus only on guitar amps you miss a lot of information.


Edit:
The Joe Davidson's amp is basically a variation of very old "Leak" circuit; the first commercial solid state amp without output and interstage transformer.
http://home.vicnet.net.au/~vic3d/audio/leak/cctStereo70.gif
http://home.vicnet.net.au/~vic3d/audio/leak/cctStereo30.gif
I don't know who's responsible for the initial design of this topology, Hung Lin perhaps? You can vary this circuit endlessly, here's one example of what you should avoid (extremely bad design as is): http://www.redcircuits.com/Page65.htm
It doesn't have the all important two gain stages - structure so it's an inverting amplifier and the result is very bad: Noisy, low input impedance, narrow bandwidth. If you look at that volume potentiometer configuration and understand how the gain is set in such a circuit you'll see that something is terribly wrong. The "Leak" idea is much better since it separates the feedback from the input signal. It is non-inverting which is superior than inverting.

I've seen the Leak topology used in countless amps (with different component values of course), for example this one: http://www.ssguitar.com/index.php?action=dlattach;topic=195.0;attach=14;image
The other week I traced out the power amp of my old Sansui and it has one too. I bet that if I could get my hands on old RCA manuals with transistor stuff they'd be full of these as well. This topology is pretty difficult to tweak and doesn't work with dual supply. I built one similar amp last summer (it still needs a preamp) and I wouldn't build anything with this topology again; the circuits with current feedback or long tailed pair input stages are usually so much better.
« Last Edit: December 18, 2006, 08:17:28 AM by teemuk »

yatinejkc

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Re: Want a PCB please!
« Reply #5 on: December 21, 2006, 07:59:53 AM »
 Ya man,
                i have been looking for the perfect amp for three weeks(not exaggerating) on google gut i did not get the perfect amp, so thats why i was askin if any professional guitarist would give me a good suggestion. Teemuk, thank you a lot!!!  I have found at last a good amp which is easy but seems to be of good quality. And thanks joe kool, you are doin a great job man!!! Keep it up guys!

                                                                 :tu: