Any suggestions for DIY vacuum tube soft distortion, suitable for Shruthi output?

Can anyone recommend a DIY vacuum tube distortion design (or kit) which would be suitable for use with the output of a Shruthi - either in-line before the mixer or as a pre-fader/pre-EQ effect send (which is essentially the same thing)? I’m interested in soft distortion or just some gentle “warming”, not harsh screaming clipped distortion. Mainly for use with the Dual SVF filter, and maybe the SMR4mk2 - I’d like them to sound more like the ladder filter by TubeOhm when it is gently overdriven, at least sometimes. Vacuum tubes rather because it has to look interesting and ideally, glow enticingly when the lights are dimmed.

I should add that a starved anode design which doesn’t require high voltage is desirable, even though I do have a death wish.

OK, I’ve realised that the outputs of the Shruthi filter boards are hot enough to work OK with Eurorack modules, thus the L-1 Tube VCA is the obvious choice. And the Hexinverter Battery Acid CV module (OK, no valves [vacuum tubes] in that). And the RYO Optodist.

Question answered, by self. That’s the best kind of answer.

To be honest: i’ve never seen any outputs hotter than these.

HI, the problem is the tubes works with high voltage.But there is one solution.
You can take a ECC83 as a preamp . This Tube can work with 30…40 Volt , but than you need an additional OPAMP for the OUTPUT , and , don’t forget, the heater takes 250-300 mA 5V (6,3V).
But it is possible to insert a Tube behind the Shruthi filter.
You need a cascade x8 to make from 5V to 40 V. The heater current you can take from the 7505 but than you need a great cooler.
Or, use simply this one:


ian does a tube dual card its diy and he does psu for this to work

i have been building his tube mixer the tube dual channel cards i use for stereo tracking channels but you can set them up as a line input tube gain stage

all diy documents are on this page

@tubeohm Thanks! The Behringer unit is not DIY but it looks ideal, it has a 20dB pad switch so should cope with Shruthi-level input, gets excellent reviews, and is very cheap. I must not succumb to too much IKEA cognitive bias!

@jhulk Thanks, I’ll look at those designs more carefully, but at a glance they might be overkill for what I want.

Hi , and it is not so expensive. I think build a DIY Tube cost a lot more.
But, it is also possible with DIY . I had build a Tube Preamp in 2009 with 40 V and a ECC 83 .
Maybe and if i had a lot , lot, lot of time , i will do it again with Shruthi. The schematics is very simple and if you have a Tube inside the Shruthi this should look very cool


Starved plate vacuum-tube designs sound like horses***** compared to the real deal, and you will never get that soft, consistent and organic distortion out of such a design.

Go buy a high-voltage tube guitar pre-amp (or get one built) and add some op-amps afterwards to get you up to line-voltage or whatever it is you need.

thats why i pointed out the tla tube card the line level input and output are done by balancing transformers theirs also a section for a passive eq red47 meq5 or the helios eq