Hi,

I built this power amp circuit

http://www.aaroncake.net/Circuits/amp20w.asp

I'm only using one chanel right now, so it's just a 22 watt mono amp. I'm using it with a guitar speaker (not HI FI).

So I tried putting a couple different preamps in front of it. Both from RunOffGroove.com

Tone Mender - http://runoffgroove.com/tonemender.html

Professor Tweed - http://runoffgroove.com/professor.html

Both sound great into my regular amp, but they don't quite turn the 22 watt circuit I made into a real guitar amp. The make a huge improvement over the power amp alone though.

My question is, is there anything I should do to the power amp circuit to make it more like a guitar amp?

Does anyone have any sugestions for pre-amps or a combination of pre-amps?

My goal is to have a 2 chanel (clean & distortion) amp with master volume.

Thanks, Doug

What kind of speaker/cab are you using? In most SS amps the preamp provides all the "tone shaping" and the power amp is as linear (and clean) as possible. However, the frequency response of a guitar speaker in a proper cabinet contributes greatly to the "guitar amp tone" you're after. If you're using HiFi speakers you simply won't get the same sound.

Have you tried piggy-backing both your pedals together? Run the tweed into the tone mender and see how that sounds. I've found that the prof. tweed sometimes doesn't have enough gain to drive a Hi-Fi power amp to full volume. The input impedance of that amp is 30k (per channel). With the professor tweed your output impedance is at least 20K at max volume. That means your signal voltage is nearly cut in half even at max volume on the pedal. I would try a simple buffer on the output of the professor tweed to make sure you're getting good voltage transfer between stages.  A simple source follower configuration with a spare MPF-102 fet should do the trick.

The speaker/cab is my 15 watt vox combo. I just disconnected the speaker from the combo amp and put a 1/4" jack on it to connect to my diy amp. That buffer idea sounds really good. I didn't try piggy backing the two ROG circuits yet because I've only had them assembled on my bread board. First I did the tone mender. It really sounded pretty close to being good, but it was missing somthing.

Then I did the Prof. Tweed. It sounded good at one setting and with the neck pick up. But it wasn't consistet. Maybe I need to try a tonemender into a prof. tweed and a buffer at the end. What do you think?

if you like the combination of both circuits I would just ditch the tone control on the tweed since it's so limited compared with the tone mender.

Hello doug7410,
                     If your searching for a tweed circuit then try the Sansamp GT2 circuit
(I think it's still at "Tonepad") as it's one of the better ones.
It's just the first opamp part you need not hard to miss as it's much like the end of the professor tweed. Should give a big deep notch near 1khZ.
As your tonemender is already opamp powered then you can just tag that extra bit on the end.
But you may not get the edgey distortion of the fet circuit.

I can give you another circuit similar to the *tonemender* but IMO far better.
As you are at the bread board stage then why not experiment a little before you commit,
just a thought.
Cheers, Phil.

Quote from: phatt on May 21, 2009, 09:33:20 AM
Hello doug7410,
                     If your searching for a tweed circuit then try the Sansamp GT2 circuit
(I think it's still at "Tonepad") as it's one of the better ones.
It's just the first opamp part you need not hard to miss as it's much like the end of the professor tweed. Should give a big deep notch near 1khZ.
As your tonemender is already opamp powered then you can just tag that extra bit on the end.
But you may not get the edgey distortion of the fet circuit.

I can give you another circuit similar to the *tonemender* but IMO far better.
As you are at the bread board stage then why not experiment a little before you commit,
just a thought.
Cheers, Phil.

Hey Phil, can I get this circuit "similar to the tone mender" from you?

Thanks,
  Zappacat

Hi guys,
I'm also interested in Phil's offer...
Phil, can you post it, or point-out some link for us ? I'd try it in 2 different scennarios: my Dean GT12, and a TDA2040's amp I'm making. Thanks a lot !
Sergio

Hi chaps,
            Sorry iza been busy,,, but check the Schematic page under(Passive Tone Circuit) all up for you guys to get your breadboards running hot. 8|
I figure that's the right place to put it.

Thanks for the interest,,, Phil.