100W amp

[Mihkel]

Has anyone here built this amp? Is it any good?
Does anyone have a layout for it or is someone willing to make one?

[zeta55]

Hi.
I've built the preampsection, the new version. I'm using it with a 50W amplifier I had around.
Sounds good, great tone control, nice sound both clean and distorted.
I just might have the layout i did, Pm me if you want it.
I recomend the new version of the preamp, don't know about the amplifier though.

[littlegreiger]

I was thinking about building that amp.  If you do build it you should definitely write a build report because I want to know if its any good or how hard it is to build.

[Peter Snowberg]

I used to have a marshall practice amp that was built arount a VERY similar output stage, but with only one pair of 3055/2955 and a lower supply voltage. I thought it sounded pretty good.

[Rich G.]

To simplify the power amp section, maybe use a TDA7293.

I just worked on a Marshall AVT150 that used two of these in the power section.  The good thing is they're only about $4 from Mouser.

[Steben]

It looks like the clipping section (diodes to ground) come after the tone control, which is more classical sounding. This way you can voice your distortion with the tone knobs(like treble boost etc...).
Yet I would change for each polarity 1 diode by a LED though.

I think it's quite nice as an easy build "big amp" project (in comparison to tube amps anyway).
Yet I think it would be even amazingly better to think about a MOSfet or Jfet booster pedal in front of it, or something like that, to get a more tube tone into it, even when "clean". The booster level should be set on low then, in order not to distort the first ss chip in the amp.

[smoguzbenjamin]

Looks like a fun build! If I could gather the cash and manage to find a speaker cab that I can afford I would probably try to build this baby... You can always play with tone control later on.

[Mihkel]

I have a 42 volt DC adapter lying around and I'd like to use it for this amp. Can I do that or does this thing need more current?

[mugan]

Anyone know what transformer would be suitable for this project? i mean the pimary secondary parameters?

[lightningfingers]

If I had the cash, I would use a Hammond transformer. They really are unbelievably quiet, Its just a shame that the price tag is kind of huge...

[Mihkel]

Yet I think it would be even amazingly better to think about a MOSfet or Jfet booster pedal in front of it, or something like that, to get a more tube tone into it, even when "clean". The booster level should be set on low then, in order not to distort the first ss chip in the amp.

So, I can only use a distortion pedal via the In and Out of the power amp?
Not guitar- pedal- preamp input?

[Michael Allen]

I think what he meant, was that the output of the booster should be set low so that it does not completely obliterate the solid state input stage. Solid state does not respond very well to being driven very hard. You can use the booster on the guitar in, it's just that you need to adjust the level in order to not push the opamp too far.

[Mihkel]

To simplify the power amp section, maybe use a TDA7293.

I just worked on a Marshall AVT150 that used two of these in the power section.  The good thing is they're only about $4 from Mouser.

Could someone clear this up for me? How could I use it in the circuit?

Thanks a lot

[sir_modulus]

That's simple !?!?!? I think a tube amp is a lot simpler than making a layout for that. I'd just be more expensive. (well not by too much).

Nish

[brett]

Hi.  I'd be a little wary of the TDA7293 if you want to drive it hard.  What are you gonna do when it decides to go into thermal shutdown?  Bridging 2 or even 4 of them for a more "conservative" power rating and using a conservative fuse might help.

Myself, I use the old fashioned approach of lots of rugged, bulky transistors (4 x 2N2955 and 4 x2N3055s) and a dirty big heatsink.

cheers

[Boofhead]

There's nothing wrong with the ESP design.  The BC559's are pushed too close to the wind on the MKII - I suspect the BC556 on the MKI is the correct part.

I use the old fashioned approach of lots of rugged, bulky transistors

Modern flat packs are often better than a lot of those old transistor designs. Mounting flatpacks is much easier- especially on a PCB.  The MJE2955/MJE3055 parts definitely aren't modern though (but not bad).

[brett]

Fair comments about TO-3s being awful to mount.  But you can run 2955s and 3055s hot and use them as coffee makers. :wink:

[R.G.]

It's simpler to use two LM3886 ($5.00, Digikey) for 50W each.

48Vct transformer, 3A powers it, $22.80 from parts express.

This approach is much more forgiving for a beginner than making their own amp. Perfboarding even works, as it's essentially a heat sinked opamp.

[The Tone God]

I would use some bridged LM3886s. You might even be able to get the price down by getting some as free samples. :wink: Very simple to get going and good sound. Hard to beat the price and simplicity.

Andrew

[Mihkel]

The bridged LM3886 with the preamp? I'd really like some tone controls also.