Tech21 - Sansamp GT2

invictus · Post by **invictus** » 16 Aug 2007, 03:45

.

gut shot:

http://www.axiomdrift.com/schematics/GT-2%20board.jpg

schematic:

http://www.axiomdrift.com/schematics/GT-2pn.gif

.

Goop_buster · Post by **Goop_buster** » 16 Aug 2007, 05:51

invictus wrote:.

gut shot:

http://www.axiomdrift.com/schematics/GT-2%20board.jpg

schematic:

http://www.axiomdrift.com/schematics/GT-2pn.gif

.

I think there is a working PCB-layout for it at tonepad.com.

bajaman · Post by **bajaman** » 16 Aug 2007, 07:05

C17 and C23 are shown as the same value - I am sure this is wrong - I change one of them to 47n and left the other at 4n7, but i cannot remember which one it was I changed - otherwise the mic off axis does not work correctly - I pointed this out to francisco pena on his Tonepad site, but do not know if he has changed it - incidentally the Behringer GDI21 clone of the GT2 has the same error on there factory schematic too

bajaman

JHS · Post by **JHS** » 16 Aug 2007, 08:42

Over the years Tech21 has made some revisions to the GT2 which have influence on the overall-sound.

The Axiomfrift-schem shows only one version, so check the web for the other version, breadboard it and then build the version that sounds best to you.

JHS

jt · Post by jt » 16 Aug 2007, 17:52

Could you give us a link for the other version JHS?
Searching with google i found many sites but all with the Axiomdrift schem.
Dimitris

JHS · Post by **JHS** » 16 Aug 2007, 19:20

I stumbled month ago over the GT-2 history on a DIY-site from Russia.

I don't need a GT-2 and have no intension to build a clone, hence that's the reason while I don't saved those schems.

JHS

analogguru · Post by **analogguru** » 16 Aug 2007, 19:57

"Dark Angel" made in oktober 2003 some minor changes to the tonepad schematic. The discussion about that should be possible to be found in the archives of that other forum.

analogguru

Goop_buster · Post by **Goop_buster** » 16 Aug 2007, 20:08

analogguru wrote:"Dark Angel" made in oktober 2003 some minor changes to the tonepad schematic. The discussion about that should be possible to be found in the archives of that other forum.

analogguru

Found it

https://www.diystompboxes.com/smfforum/ ... pic=1057.0

The "other" schematic

http://www.sugardas.lt/~igoramps/sagt2.gif

Also, there seem to be some nice info here also

http://www.pisotones.com/GT2/GT2.htm

jt · Post by jt » 16 Aug 2007, 22:44

Thanks guys.

estragon · Post by **estragon** » 16 Aug 2007, 22:56

Wow, that 10n cap change (instead of 47n) in the second opamp stage really makes sense to me. My GT-2 clone always had a farty character when playing Marshall style, like too much low frequency intermodulation, even when playing fifths. Surely this would cure it as it raises the low frequency corner from 160 to 720 Hz (TS-like).

kurotenshi · Post by **kurotenshi** » 03 May 2009, 04:17

Post resurrection.

I'm thinking of building a GT-2 and was going follow tonepad's project but now i'm a bit confused. You are saying that the schematic presented by tonepad is wrong (as in sounds/works bad) or that is a newer version of the pedal?

Another thing, will the change in opamp's (tonepad has all TL072 and the older one has other stuff) largely affect the sound (like making me be cloning a GDI-21 instead of a sansamp)?

BAJA, if it's not asking too much, can you explain to me (since the schematics have no component numbers) wich are the caps you said are wrong?

Dr Tony Balls · Post by **Dr Tony Balls** » 22 Mar 2010, 16:07

For what its worth, I built the tonepad layout yesterday and it sounds pretty okay to me. sooo much wiring, though:

oliboy_48 · Post by **oliboy_48** » 25 Aug 2010, 13:46

do anyone have a schematic,pic or simple drawing for the wiring of the switches and what kind of switch to use...pls. send me a link or an email...oliboy_48@yahoo.com...thanks....

Dirk_Hendrik · Post by **Dirk_Hendrik** » 25 Aug 2010, 14:58

oliboy_48 wrote:do anyone have a schematic,pic or simple drawing for the wiring of the switches and what kind of switch to use...pls. send me a link or an email...oliboy_48@yahoo.com...thanks....

Dr Tony Balls wrote: I built the tonepad layout

How hard can it be?

marin · Post by **marin** » 30 Aug 2010, 23:43

oliboy_48 wrote:what kind of switch to use...

either of these:
rotary switch 6x2, or
slide switch Double Pole On/On/On

bluetube · Post by **bluetube** » 16 Nov 2011, 11:46

bajaman wrote:C17 and C23 are shown as the same value - I am sure this is wrong - I change one of them to 47n and left the other at 4n7, but i cannot remember which one it was I changed - otherwise the mic off axis does not work correctly - I pointed this out to francisco pena on his Tonepad site, but do not know if he has changed it - incidentally the Behringer GDI21 clone of the GT2 has the same error on there factory schematic too
bajaman

myth confirmed.

with stock values, toggling s1b at positions 1 and 2, you can hardly hear a difference. then i changed .0047 to .047 cap at s1b2 side. now you can hear differences at all three positions. works for me.

thanks bajaman.

bluetube · Post by **bluetube** » 07 Jun 2012, 08:59

askwho69 wrote:
bluetube wrote:
bajaman wrote:C17 and C23 are shown as the same value - I am sure this is wrong - I change one of them to 47n and left the other at 4n7, but i cannot remember which one it was I changed - otherwise the mic off axis does not work correctly - I pointed this out to francisco pena on his Tonepad site, but do not know if he has changed it - incidentally the Behringer GDI21 clone of the GT2 has the same error on there factory schematic too
bajaman
myth confirmed. with stock values, toggling s1b at positions 1 and 2, you can hardly hear a difference. then i changed .0047 to .047 cap at s1b2 side. now you can hear differences at all three positions. works for me. thanks bajaman.
did you changed the center mic? its too thin for my ear the value 4.7n in mic center

Apologies for the late reply. Yup I changed a cap at s12b from 4.7n to 47n. But I reverted it to 4.7n because the center mic became piercing for my taste when I experimented on it.

CCR · Post by **CCR** » 03 Sep 2015, 19:16

invictus wrote:.
gut shot:
http://www.axiomdrift.com/schematics/GT-2%20board.jpg

schematic:
http://www.axiomdrift.com/schematics/GT-2pn.gif

Hi all. Why there is no R52 (bottom right corner) and C35 (left side of a on/off button) on this scheme? My Sansamp (GT-2, same as at picture above) does not work (no sound, no LED power light) and R52 is VERY hot when 9V adaptor is plugin. It's strange because it's a ground trace. (R52 is 100 Ohm.) It looks like a short circuit between the + and ground but why? What may be the reason?

Intripped · Post by **Intripped** » 03 Sep 2015, 19:30

check polarity of 9V adaptor

CCR · Post by **CCR** » 03 Sep 2015, 22:12

I checked it out first. Center is negative. What is the normal voltage on C28 and C29? I have 0.25 V and 0.11 V. I think it's too low.

Tech21 - Sansamp GT2 [traced]