Simple tube and transistor (solid state) synth modules, effects and line stages/DIs for electronic music. Made to properly match drivers receivers, amplify, attenuate, fix digital artifacts like "sterile sound" (often due to unwanted harmonic distortion spread, phase shifts and such things, have analogue section as good as it can be, etc. Building them, modifying.
I'm a specialist for any kind of mic preamps and other outboard gear, meant mostly for vocals and acoustic instruments, also electronic.
Check very basic uses of tubes here; fig. 2 shows classic tube VCA, while fig. 3 is simple line stage (triode wired EF86, similar to half of 6SN7) that actually needs cathode follower (second half of 6SN7 maybe) to be compatible with modern line inputs. Output transformer after CF or classic anode output helps with bass and sound in general. There is enough data on the net about how to add one to the basic EF86 line stage (about 28dB of gain, depending on settings called bias):
http://www.tube-town.net/cms/?Info/How_To_Use_a_EF86
Another resource having ready made pcb-s with "everything related to synths" is here:
http://www.cgs.synth.net/
A lot of newly found information about tube use for such things was posted online by Eric Barbour; he is authour, tube synth conosieur, ex engineer for tube production at Svetlana plant, founder and owner of Metasonix, etc. I like idea of using strange old tubes like high gain triode and dual diode in one bottle, although it is advisable to use only tubes in production because old stocks might become oboslete. Both links also show simple power supplies for this things:
http://www.cgs.synth.net/tube/index.html
Pretty simple and very effective pentode filterbank produced by Metasonix as TS-22, uses EF86 sharp cutoff tube type too, so there are no exotic parts, except for testing to find matched optocouplers:
http://www.cgs.synth.net/tube/ts22.html
All of this maybe seems complicated, but tubes don't mind even bigger mistakes, etc. I showed pentode wired EF86 pentode because very simple VCA can be made by varying screen grid voltage to give gains up to around 100. Starting with simple SRPP gain stage with 6CG7 (6SN7 with shield)will give about 28dB of gain too, lots of 2nd harmonic, can drive  transformer into 600ohms directly, so it is very simple thing for those who feel their analogue stages aren't that good. My trials show this is so and even simple transistor stage helps, when attached to output transformers things get even better.
Who is interested enough to read until here, check this schematic :)
http://ax84.com/media/ax84_m58.pdf
This tube Fuzz/Wah pedal with LC filter has excellent sound, even as a "drive preamp" without Wah part (variable cap is a bit hard to get, although many will work, original part is still available). Input gain is quite high at 150 for synths, it can be simply lowered by adding higher screen grid resistor, a bit of playing with bias or just adding output attenuator. Yeah, wierdos do exist :)

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