tube Pre amps ?

Don't forget about transformers - they can also introduce distortion, especially if overdriven with low frequencies. In old valve gear, there are likely to be both input and output transformers to match the high impedance of the valve stages with low impedance sources and destinations. Some circuits even have transformers between stages. One valve in a low-voltage circuit hasn't got a hope of replicating that compex harmonic signature. Even a high-voltage multi-valve circuit may not do "it", if the transformers aren't right.

King Simeon wrote: I looked into this & was told to get that sound is not easy anymore, parts no longer exist.. optical filters not like they used to be. I'm in agreement that it's a lot of effort to not gurentee satisfaction. No harm in testing though, to get what you want.

The VF1 is an interesting bit of kit because the valves in it really do nothing to the signal. They are in circuit wired as cathode followers which means they buffer the signal and add negligible distortion to it. However they are preceded by a classic back to back diode feedback op-amp circuit which is where the overdrive comes from. So everyone who has ever gushed about how valvey and analog a VF1 sounds, haha. Nope, all solid state and quite basic solid state overdrive circuit at that. Very popular with guitar overdrive guitar pedals. You can find the service manual online and follow the circuit yourself to check.

I build a bit of a kit years back for a friend meant to have a bit of VF1 similarity, but I couldn't also resist throwing the kitchen sink in with regard to state variable filters triggered from a selection of intermixable sources. This unit used "proper" valve distortion in that the tubes were wired for gain and actually clipped/rounded the signal themselves before it was reduced and re-mixed back to the source.

Device itself worked ok, needed more refinement but parts of it had potential. I was most happy with the automatic gain control circuit that took the bass output of the valve overdrive and mixed it back with the original signal. Unique circuit in its way as far as I know. Anyway kids etc arrived and time disappeared after the first prototype which as far as I know is still kicking. If the faceplate looks a little scrappy its because I did it all using my cnc mill and it was a learning process (still is tbh).







Anyway the moral of the story is, don't get all excited just because something says it has a valve in it...

i have similar thought patterns...