Diy Amp

[vaustin89]

hello, i need an opinion about this, i have started to build both a guitar and bass amp, well i have finished the preamp section for both, my problem now is the power amp, my guitar amp should be around 50-75w and my bass could be 100-150w.
would the power amp section of this design be good for bass,  http://sound.westhost.com/project27.htm, i have heard good feed backs on this project for guitar, not sure about the bass.... i'm more concerned on the power-amp section..
and can someone explain the difference between the speakers used in guitar amps and bass amps? :duh
thanks for any input in advance. :tu:

[joecool85]

I would forgo that poweramp, make it easy on yourself and build a chipamp.  I'd use a LM3886 based circuit for the guitar and a bridged LM3886 or LM4780 (I think that's the right number) which is a bridged LM3886 setup in one chip.

[J M Fahey]

Agree. The P27 is an excellent amp, but you will need to design and build your own PCB, too much work for just one or two.
Even more important in the Musical Instrument world, it has no short circuit protection.
Good enough for a combo, dangerous in a head which gets connected and disconnected often, specially considering plugs are the worst connector in the Universe.
Too bad they are the standard connector for us.
All of that is pre-solved in the chipamp.
It's also easier to mount: just 1 hole through any flat aluminum surface, be it a heatsink or simply a piece of 2 mm aluminum sheet.
As of the speakers, guitar ones need to be specific for them, check Jensen, MOD, Eminence, Celestion, or WGS ... o EBay, where many guys upgrade their original speakers and sell Fender/Peavey/Crate/etc. labelled ones for peanuts.
They are usually good Eminences.
For Bass you can check the above manufacturers or in that case, you *may* use an audio or PA type woofer , *never* subwoofers or even worse, Car type speakers.

[vaustin89]

  thanks for the help, i can manage building complex circuits i kinda' like designing PCB's.. does different design on power amp change the amps sound dramatically or just a subtle change can occur on sound.. if it does change the sound, i think i'll build 2 different power amplifiers..

[joecool85]

thanks for the help, i can manage building complex circuits i kinda' like designing PCB's.. does different design on power amp change the amps sound dramatically or just a subtle change can occur on sound.. if it does change the sound, i think i'll build 2 different power amplifiers..

In solid state gear a power amp is a power amp.  Or at least with good ones this is true.  Solid state gear get's it's sound from the preamp devices rather than a combination of pre and power amp distortions like tube gear uses.

[vaustin89]

thanks for that information, so therefore power amps in SS amps is basically a power amp, while in tube amps, they can add color to the amps sound.. now i can push through with my work.. thanks for the help..  :tu:

[teemuk]

I can't say I share this view.

In about 90% of modern solid-state guitar amps the power amp is designed to at least adds some colour by having a somewhat non-linear frequency response.

Then you have amps like the Valvetronix series from Vox, TransTube series from Peavey, MOSValves, Pritchard Amps, and a great deal of other random SS amps with soft clipping or tube emulations designed into the power amp just for the sake of getting good cranked up distorted tones from them. Heck, even most Randall amps without such schemes still love being cranked to power amp distortion.

[Alexius II]

This was true even with my first ever electrical project: ruby amp... "pure" power amp distortion 

[J M Fahey]

Well, some pedals use an overdriven LM386 (a power amp) as a distortion generator, with good results.

[teemuk]

And tone of that little Pignose is heard on a few mighty famous albums...

I think it's just just a matter of designing graceful clipping and clipping recovery; without odd and nasty-sounding behaviour like rail clamping, hysteresis or ringing.

For example, there are bunch of classic and quite good sounding designs out there based on overdriving OpAmps (e.g. Marshall Lead 12 or SansAmp) and that's also one of those things that's commonly claimed to be a strict no no - but it still works and can actually sound pretty good if the design is executed properly. If you think about that a generic solid-state power amp is basically just a high power OpAmp...

[vaustin89]

thanks for the help.. 8|.. About cabinet construction, what are the dimensions of an upright 2x12 stack? can anyone give a generic dimension? what is the best material for enclosing the circuits? can a GI sheet be used? what are the pros and cons of each material used in amp head enclosure..thanks for the help in advance.

[J M Fahey]

Just as a guide, anybody has his own preferences, my basic 2x12" cabinet is 50cmx70cmx25 to 30 cm ; about the classic size for most 2x12" combos.
Of course you can use it horizontal or vertical.
Don't know what a GI sheet is.
If the chassis is self built, I much prefer aluminum sheet, 1.25 to 1.5 mm thick (1/16") , because it can be worked with simpler tools, and does not rust all by itself.
The cabinet may be made out of plywood (best), chipboard(cheap) or MDF(heavy).
You needn't worry too much about finishing or covering, just sanding it and some edge rounding , followed by flat black painting looks reasonably good on stage, if the club has dim lighting and the general public has had a couple beers or whatever.