Maestro FZ-1S clone - sustain sorted

[yeeshkul]

I was tweeking my FZ-1S clone, because i was not happy with the sustain. It wasn't smooth at all - the sound was dying abruptly in the middle of a tone.
Correct me if i am wrong but i suspected Q4 (GGG schemo, the switching tranny) to be in charge of that. I put all the trannies in sockets and started experimenting. Well, it was Q4. After checking out about 20 different pieces i found the "magical" one. Sound is the same as before but the sustain is smooth. Ill provide you with some soundsamples soon.

[gigimarga]

Woow...which are the characteristics of Q4 that makes this magic?

[yeeshkul]

The buffered Q1 signal goes through the gain stage Q3 to have enough power to turn on/off the Q4 switch that produces squares(on/off/on/off ...). I guess the troubles with sustain are caused by Q4 as it is prematurely turned off by dying guitar->Q3 signal (note that Q4 is DC biased to be off). The strange thing is that even two Q4 trannies of the same kind and similar Hfe do not behave the same. I have secceded with BC108B(Hfe 373) but another BC108B failed (not completely, but the other one did much better job). It must be something with their B-E junction behaviour. Just use a socket and try a few pieces. You can even try to reverse such a tested transistor (E->C/C->E) - the small reverse Hfe is often enough to controll the Q4 switching(this has influence on the sound though - the fuzz is then a bit milder).

[yeeshkul]

Here is the soundsample. Hard notes help sustain a lot as well as humbucker pick ups (for the above reason). The beast doesn't like soft picking at all!

http://www.hoho.cz/public/MFZ1S.mp3

After all of that struggle i like the sound more than i expected . It can sing really fine.

[gigimarga]

Thx a lot...i will try what you said!

[yeeshkul]

just one more sample , Dr. Who fans forgive me ... (neovibe and wah engaged)

http://www.hoho.cz/public/FZ1S-who.mp3