Print Page - Op Amps for SansAmp GT-2

Title: Op Amps for SansAmp GT-2
Post by: Manolo Dudes on December 01, 2003, 09:03:10 AM

I tried a couple of TLC2262CP for IC2 and IC3 in my Sans Amp GT-2 clone (http://www.pisotones.com/GT2/GT2.htm) (using Tonepad (http://www.tonepad.com)'s layout) and a/b'd it with the original GT-2. It was amazingly similar in tone to the genuine... which really didn't happen with the proposed TL072, but it was not until I put another TLC2262CP as the fourth IC that they sounded exactly the same... go figure!

It seems that you need CMOS rail-to-rail op amps in this circuit to achieve such high gains without op-amp distortion.

IC-1 is still a TL072 as in the original.

Title: Op Amps for SansAmp GT-2
Post by: Arno van der Heijden on December 01, 2003, 11:11:09 AM

Does the substitution of the 4th IC really make that much of a difference? I didn't expect that because I thought that stage is only there for toneshaping purposes, and works in its lineair region anyway. Maybe because of better headroom?

Does it clean up better with the new IC's, in particular the fender mode?

Damn, I really need to get hold of some TLC2262's for my GT-2... :mrgreen:

Title: Op Amps for SansAmp GT-2
Post by: Manolo Dudes on December 02, 2003, 03:31:56 AM

Yes and yes... I heard an improvement with IC4 as TLC2262CP though not "that much" as you ask and I too think it's mostly because there is grater headroom.

Both Marshall and Mesa modes seem to me more "defined" i.e. less grungy and the Fender mode (the best IMO) sounds more "open".

I definitely recommend those chips. I also tried three TLC2272CP but heard no difference. Switched back to 62s because of lower power requirements.

Title: Op Amps for SansAmp GT-2
Post by: Vasiliok on December 02, 2003, 06:20:00 AM

Hehehe! Guys I told you!
Only TLC ICs will make your copy of SansAmp GT2 sound exactly like original pedal!!!!

Manolo Dudes,
thanks for posting results of your test! :wink:

Title: Op Amps for SansAmp GT-2
Post by: Manolo Dudes on December 02, 2003, 06:41:06 AM

Vasiliok, I got the idea from your web. Look here (http://diystompboxes.com/sboxforum/viewtopic.php?p=89709#89709)

But it wasn't until I could get an original GT-2 that I noticed that your schematic was based on a previous version of the GT-2. Yours is version GT-2_12 and tonepad's is version GT2B_2, the same version of the one I dismantled. In your drawing you link pins 2 and 5 of IC1 (TL072 BTW) and in version GT2B_2 it's definitely 3 and 5, that is both non-inverting inputs. I tried both ways and I positively think that 3+5 is the way to go. It sounds better to me.

IC4 has the reference "sanded out" and IC1 is not. It clearly displays a TL072 reference... hum... I think it's a trick to make us believe all ICs are not rail-to-rail :wink:

Title: Op Amps for SansAmp GT-2
Post by: Vasiliok on December 02, 2003, 07:16:30 AM

Manolo Dudes,

it's really cool you posted the results!
I think people must know the truth (talking 'bout ICs).

I hope a guy from tonepad will read this topic and put some notes about ICs on his great site!!!

Woohhoo!
Now we have a chance to make ourselfs 100% copy of original SansAmp GT2.

Cheers. :wink:

Title: Op Amps for SansAmp GT-2
Post by: Manolo Dudes on January 16, 2004, 11:00:41 AM

Quote from: Manolo DudesIC4 has the reference "sanded out" and IC1 is not. It clearly displays a TL072 reference... hum... I think it's a trick to make us believe all ICs are not rail-to-rail :wink:

Verbi gratia:

(http://www.pisotones.com/GT2/imgs/GT2_B2.jpg)

That's the board of version "GT2_B2" as in Tonepad's. Look now at a zoom to IC1 (TL072) and IC4 (sanded out):

(http://www.pisotones.com/GT2/imgs/Ambos2.jpg)

I swear by jove that IC4 sounds better to my ears with a TLC2262CP too. IC2 & IC3 are in the form of a 14 pin TLC2264 under the rectangular black hider as seen in Axiomdrift (http://www.axiomdrift.com/schematics/GT-2%20board.jpg).

Believe me!... do yourself a favour and go and get 3 TLC2262CP chips for yout GT2 clone :wink:

Thanks a lot to Valsiliok (http://www.sugardas.lt/~igoramps/sagt2.htm) for pointing us to all this.

P.S. Hehe!.. My web pisotones.com (http://www.pisotones.com) is up and running again! 8)

Title: Link to datasheet
Post by: The Red Rooster on January 16, 2004, 01:10:14 PM

For those interested. :wink:

http://www.chipdocs.com/pndecoder/datasheets/TI/TLC2262CP.html

Regards

Kurt

Title: woops - datasheet NOT for free - sorry
Post by: The Red Rooster on January 16, 2004, 01:12:13 PM

I guess I was to fast hitting my 102 button-thingy

sorry

Regards

Kurt

Title: This one is for free - and works
Post by: The Red Rooster on January 16, 2004, 01:14:48 PM

http://www.hardware.dibe.unige.it/DataSheets/TLC226x.pdf

Regards

Kurt

Title: can smallbear stock these?
Post by: dubs on January 18, 2004, 08:37:24 AM

Hey Steve Daniels,
Can you stock the TLC2262? Can't get em in australia and rather order from one place.n

Cheers
Daz

Title: Op Amps for SansAmp GT-2
Post by: WGTP on January 18, 2004, 01:27:41 PM

FWIW, the TLC2272 has a little more gain.

Title: Op Amps for SansAmp GT-2
Post by: dubs on January 18, 2004, 05:40:20 PM

Hey does anyone out of their kind heart be able to sell & send me some TLC2262 to Australia? I can pay by paypal...

Title: Op Amps for SansAmp GT-2
Post by: Manolo Dudes on January 20, 2004, 09:28:05 AM

Hint:

Go to www.ti.com, register and ask for TLC2262CP free samples. You can request 3 samples... in fact that's exactly what you need for a GT2 :wink:

I did it! :P

DIYstompboxes.com

DIY Stompboxes => Building your own stompbox => Topic started by: Manolo Dudes on December 01, 2003, 09:03:10 AM