Sansamp gt-2 oscilation... what can do to minimize it?

[Tiruk]

Hello folks... im new at this forum but i want help of all the members (sorry my poor english  :roll: )

I have build an sansamp gt-2 by tonepad design, but it gave me cool sound on fender simulation, but when toggled to marshall or mesa, it gave me an "piiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii" insuportable... reading some posts here, i think thats is oscilation, right?

then i go start build another, i want to know what i can do if this persists, to get off this *** problem , hehe

i read to use a capacitor to ground in a topic and use blinded cables... what more i can do???

really thanks to all

Tiruk  
(im in brazil, i can find every thing that need, including switches, capacitors and ic's ... thanks...)

[Tiruk]

:oops:

[bwanasonic]

The GT2 can be prone to oscillation, as you have found. Try to keep all off-board wiring (to jacks, switches, pots) as short and direct as possible. Other builders have had problems particularly with the three *mode* switches. If you do a search here, you may find some helpful info:

http://diystompboxes.com/sboxforum/viewtopic.php?t=21614&highlight=gt2+oscillation

http://diystompboxes.com/sboxforum/viewtopic.php?t=11718&highlight=gt2+oscillation

Kerry M

[Tiruk]

plx folks, i really need help...

[Tiruk]

bwanasonic

thx man, i will see all that

[/quote]

[Tiruk]

any1?

[plucky]

I change the ICs, I put new ones, and it stops the oscillation, another thing that you could do is to put a Jfet buffer at the beginning  of the Sansamp...

[Tiruk]

You used what ic's ?? and the Jfet, what is???

thanks :lol:

[Samuel]

My experience was that the "proper" ICs, ie. the 2262s performed much better than tl072s. Don't know if you made any substitutions in that area...I've found that all my oscillation problems in the GT-2 come from the bypass switch wiring - if I remove the bypass switch entirely and just hardwire the in jack to the input and the out jack to the output I get a great deal less oscillation.

For what its worth.

[Tiruk]

thx samuel... but only for test, i dont hook up the circuit on a dpdt , only in jacks (no switching, effect always activated), and the oscillattion is really STRONG, but when i play in guitar, its sudden dissapear for some ms, returning and destroying guitar sustain / tone...

i used 1 tl072 and 3 tlc2262cp

i will try again , this time with 3 tl072 e 1 tlc2262...

and what about the new tl082 , its better for this circuit ?

thx folks

[Tiruk]

up

[plucky]

I used tl072 ICs, And a 2sk30a jfet buffer, any transistor buffer should work...
If you have the oscillation in bypass mode, you should use the millenium bypass plus from www.geofex.com, this one put the output of the circuit to ground in bypass mode, that kills the oscillation...

[Tiruk]

thx plucky,

i dont used dpdt (or anyone type of millenium, maybe is this)

i dont wired anything to ground (except for the DC jack), i direct wire the schematic to jacks (no switch to bypass) for testing purposes, and it have a BIG oscillation...

maybe is this?

i will make other now, i will use millenium, make a clean work, hope its get working soon

bye folks, keep posting plx

[12afael]

I think you can try puting a 80/100ohm R in place of jfets on the original schematic.
it will reduce the amplitude of the signal. exesive gain produce inestability on some systems.

maybe the layout is too small and it produce feedback on some stages.-