U-1226 is a very strange trem circuit. How did you come upon that? The upside-down voltage doubler supply is odd too... I wonder what they were smoking?
martin manning wrote: ↑Sat Dec 08, 2018 1:47 pm
U-1226 is a very strange trem circuit. How did you come upon that? The upside-down voltage doubler supply is odd too... I wonder what they were smoking?
Ya the univoxes had some weird stuff going on. The amp used to be a univox 305r .It pretty much had the U1226 trem in it even though the schematic showed a bias trem. I like odd stuff and thought it sounded cool so I copied it with a few changes. I've got a bunch of 12 Au 7s sitting around that need used. I have noticed that that only certain 12au7s will work in the circuit. Hooking it up to the mid scoop tone control thing was pretty much a happy accident. Just by trying injecting the trem at different points.
I wonder if it would work similar with a fender optical trem?
Yes that's correct and the caps on that schematic I drew are supposed to be .001 don't no w here I got .22 I lifted that tone control from someone and can't remember where.
Hopefully this will be more clear. I don't know what in the hell that thing I drew yesterday was I was spraying lacquer so probably feeling pretty good when I did it
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TUBEDUDE wrote: ↑Sat Dec 08, 2018 8:36 pm
Wow cbass, sounds good. I didn't realize it was the trem. I thought it was the deepest phaser ever.
Thanks I have it on sitch where I can switch to regular trem it's super choppy. I just checked the bias on this amp and it was super cold I've got it up to about 60% now sounds even better the old 7591s stayed within about 3ma of each other
Well, varying the bias on the back-to-back 12AU7's with the LFO is varying the effective resistance to ground in the T filter (the 12AU7's are paralleled with the 100k resistor). That will change the frequency and phase shift of the notch, which is pretty much how a phaser works. Do both the input and intensity pots have useful effects on the sound?
martin manning wrote: ↑Sat Dec 08, 2018 11:56 pm
Well, varying the bias on the back-to-back 12AU7's with the LFO is varying the effective resistance to ground in the T filter (the 12AU7's are paralleled with the 100k resistor). That will change the frequency and phase shift of the notch, which is pretty much how a phaser works. Do both the input and intensity pots have useful effects on the sound?
Thanks Martin, Guess i can call it a swamp phaser trem thing now. Do you think the T filter thing would work with the fender roach trem?
Yes the intensity and speed controls function as normal but as you turn the tone knob up it decreases the amount of modulation coming through untill there is none when it's all the way up.
I was thinking this bridged t circuit could be a stand alone thing without a pot. And could be switched between normal trem. Ich is what have now but I'm also using it as midscoop tone control
I noticed the voltage going to the inteninsity control makes a big difference on the intensity of the modulation.Onhe schematic I think it shows around -2vdc I'm at about -1.4.
I have to admit I'm not sure what that au7 is doing. Is it hooked up as series diodes?
Last edited by cbass on Sun Dec 09, 2018 8:06 pm, edited 1 time in total.