High Voltage, Tube Warmed Repeat, Digital Delay Stompbox...

[liquids]

Just throwin' this idea out there...I'm sure someone could run with it...if this hasn't already been done partially or altogether (Fuchs?)...

With the 'ease' and growing increase in stompboxes with preamp tubes running true high voltages...thought of an idea...

Those with the ability to create and/or program "true" hi-fi digital delays/reverb stuff...ie. not the PT chips....

One could have a digital delay and all the glorious benefits of non-bbd/tape (good digital is my preffered route for echo/reverb), but has that oft-described "sterile" reproduction of the signal at least on the repeats repeats repeats...

But, then, the echoes/delay could be "warmed" with a tube, since tubes (allegedly?) warm everything up and in a way that only tubes can, according to some...
With that...one could either go for all the repeats hitting the tube "once" at the output of any and all echo feedback...or "in the loop" so that every echo regeneration, the signal goes through the tube again-again-again-again....

Heck, one could use a second, or the other half of a dual triode preamp tube, so that you could also dial in a 'blend" of the straight clean tone mixed between "not tube" and "tube" - though of course some simple finagling would have to be done in order to make sure the tube-warmed "straight" signal was of the same gain as the actually straight clean signal to have continuity of gain along the mix between the "tube warmed" and "not tube warmed" straight signal....

And likewise...the sub-miniature tubes have lower plate voltage requirements which could make this easier...

In my experience, which should be understood as expirimenting without isolating all variables, the higher the B+ on the plates of a preamp triode, the more "fidelity" they seem to have...so slightly too low of a voltage here may be an asset and add to the "tube warmth" mojo, even if it does limit input swing (not ususally a problem unless you're cascading gain stages without attenuation when amplifying with preamp tubes)...

The options may be big...but hey...while there may be "nothing else like real tape delay," or "real bucket brigade echo," in the 21st century, why not blend the capabilities of "solid state reproduction of signal" with "digital delay" capabilities with "tube warmth" and see if there is also "nothing else" like combining those three things to taste, all in a little box that may be DIYable for the DSP/pic programmer (etc) who know how to work with tubes and high voltages to good effect?

Hope someone who is capable and likes this idea has fun with it....put my name on your PCB if you go to the stompbox scene with such a product

[R.G.]

In my day job, our single and double delays both use a variable treble cut on the recirculates for de-sterilizing the echo sounds. It's a well known technique.

Using a tube to do the "warming" is OK, and would add a bit of the tube-sweetening even-order distortion. You'd have to be careful with signal levels as the tube adds gain, so you'd need to attenuate it back down to keep the loop gain from delay through recirculate below one.

You might well be able to do something similar by using either a JFET or MOSFET stage, as they do a similar thing when used without feedback, or even a single clipping diode appropriately softened in its clipping.   

[liquids]

I certainly agree that filtering makes plenty of sense...it's sufficient for me...but hey, I have a rack unit for delay reverb, and at least 10 patches for variations in feedback/intensity/filtering/variety in combination of echo& reverb...I'm content for my own needs...

I was still thinking of how people like the mojo of tubes...and for some, it might be the magic (psychological) thing ...though yes, I certain let FETs myself, and easier to work with at low voltages...but less product/design mojo =]

Good point...attenuation of the delayed signal as 'effected' by the amplified component (tube, fet, etc) would cetainly be essential...