Triad TY-250p Ne5534 saturation/balancing circuit

[Jatchley]

I’ve been playing around with the Triad TY-250p. Stuck a 1.5k+1n zobel on it secondaries and hooked it up to the scope and did some messing around with 7vp-p signal from 20HZ to 20KHZ. It was pretty fine and clean. Shoved 600mV of offset into it and just barely started to get some flattening on one side of the waveform. So we ran a Fender Rhodes retrofit preamp into it as an unbalanced OT of sorts and it sounded nice. A lil bit of mid forwardness and a small Low end bump to my ears. That inspired me to whip up a very cost effective line level saturation circuit schematic using 2 of the ty250p and some NE5534s. I’d love any feedback. I was reading all those posts about biasing opamps into class a and thought why the heck not? Still trying to work out

The resistor from V+ to U1 output.

the emphasis circuit ,

the input R,

and both opamps R to 0V at the non inverting inputs.

Also is the trim ok? The resistor to ground makes me think I could play with that for a deeper attenuation.

Should I put a cap before the primary of the OT?

Also wondering if there’s a better opamp for U2? I’d like a buffer that matches or exceeds the slew rate of U1. I guess what’s the point of having U1 at 13v/uS if the output is at 6V/Us?

My use case I guess is to make 4-8 channels of these to use between an unbalanced mixer insert and an A/D converter or to just use it as an analog insert in my daw for some affordable “analog mojo” or to balance and have some drive for a cheap synth. With the TY-250p being 5$ and ne5534s being .36c from TI it’d be cheap to build.

 

[tk@halmi]

I love these saturation effects! Using the Triad transformers it is also really affordable and buildable from through hole components.

With unity gain at the second opamp I don't think you need to worry much about offset. The input is already DC decoupled. However, that offset will depend on your ? resistor.

I would even use an NE5532. Slew rates will make little difference when you are going for the saturation/compression effect.

The one thing I would never use again is biased opamp output stages. I have played with that a lot in the past and to me it is not worth the hassle. Also, when the conditions are right and the output stage straddles modes it is very unpleasant sounding actually.

 

[Jatchley]

Update: gonna try a 2.1khz emphasis and de emphasis with the values of 7.5k/10nf with 1K to 0V (emphasis) and 6.8k with 100n to 0V (de emphasis).

Also forgot to ask what a good value for the series pot from T1s primary to 0V. 100ohm? 500ohm?

Will the 4PDT switch POP without a cap from U1 output to Emphasis input?