jawari transformer question

[zeppelinchld]

on the jawari it uses the 42TM018 10k:10k transformer and i was wondering what to do w/ the middle leg of the primary side? do i just ignore it because the schematic only has two legs on the primary side?

[ambulancevoice]

yeah, just cut it off or dont connect anything to it
i have a question about the transformer too
does it have to be 10k : 10k
can it be something like 3k : 3k or something (as long as there the same)

[zeppelinchld]

i dont know about transformers but i believe that since its a 10k:10k thats basically just a 1:1 soi think that any transformer with the same input as output should work. i read somewhere that someone used a 2 10k:30k(i dont remeber exactly what kind) and had them set up so that it went 10k:30k 30k:10k which i guess works

[exiledarchangel]

Hello people, newbie here!

i dont know about transformers but i believe that since its a 10k:10k thats basically just a 1:1 soi think that any transformer with the same input as output should work. i read somewhere that someone used a 2 10k:30k(i dont remeber exactly what kind) and had them set up so that it went 10k:30k 30k:10k which i guess works

Can that be done? I was thinking of building a jawari, but I don't have a tm018, I have instead two tm011 (primary 1,5k secondary 500k). Can I use them just like that:

        ______                ______
-----|         |----------|          |-----
-----|P    S |----------|S    P |-----
-----|_____|----------|______|-----
       

[earthtonesaudio]

Any transformer will do but notice that it's also providing the drain load for the JFET, so a higher resistance value will give higher gains.  I think the text accompanying that circuit says it's supposed to be low gain, so a 3k:3k might actually be better.

[exiledarchangel]

Thank you for the info! Actually this two transformers combined would make a 1,5:1,5 transformer, so it would be even better! If I use the secondary windings on the outside it would be a 0,5:0,5 do you think that would be even better?

[exiledarchangel]

Well I build this using 2 TM011 transformers, but the gain is TOO low, I have to REALLY crank my amp's dirty channel to get some sound.
I guess I must find a TM018 to test...

edit: by reading this

Any transformer will do but notice that it's also providing the drain load for the JFET, so a higher resistance value will give higher gains.  I think the text accompanying that circuit says it's supposed to be low gain, so a 3k:3k might actually be better.

I thought that if I solder a 10k resistor between the drain of the trannsistor and the transformer, wouldn't that raise the gain? Or it isn't so simple?

[PRR]

> if I solder a 10k resistor between the drain of the trannsistor and the transformer, wouldn't that raise the gain? Or it isn't so simple?

You'd get more signal across the resistor (useless); less signal across the transformer.

> thats basically just a 1:1 soi think that any transformer with the same input as output should work.

"Within reason". A 600:600 transformer would be too low. The impedance is really a function of frequency. The "600" winding will rise to higher impedance... but maybe not until 800Hz. All your bass and "body" is lost. OTOH, a 500K winding where you want 10K gives different losses.

5K or 30K would be reasonable subs for 10K, and 2:1 or 1:2 ratio will often "work" where a 1:1 is called for. But they make that w-i-d-e range of transformer impedances for a -reason-: you need to be reasonably close to get good results.

Ah, I just figured out what a "jawari" is. Clever. Simple. Not too tolerant of wild part substitution. It might pull 10K:30KCT, and maybe 5K:10KCT with a tail-wind, but get too far-out and the poor JFET can't lever the diodes and output through the transformer. If the '018 iron is known to work, use it.

[exiledarchangel]

Thank you very much for your answer! I am a newbie in electronics, thats why the silly questions!
The only reason I didn't build it with an tm018 is that I didn't have one handy, so I replaced it with two tm011 back-to-back. I thought 3k impedance would be ok, but now I see I was wrong.