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Vintage threads from the first ten years

sub-mini tube effects?

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10/3/1999 3:53 PM
Patrick	sub-mini tube effects? Has anyone ever tried building a distortion pedal using subminiature tubes? Every once in a while I think about looking into it, but I figured if it was feasable somebody would have already done it. Anyone?

10/3/1999 4:05 PM
Mike Burgundy	Thought about it, yes, but the darn things are impossible to find anywhere. Bigger tubes work though, one or two 12ax7´s will still fit in a reasonably sized box, tranny an´all.

10/3/1999 6:31 PM
R.G.	Dead right, Mike. I am a random tube collector, and it wasn't until this spring after several years of looking that I found some of the micro tubes to play with. And then again, where would we find sockets?

10/4/1999 12:17 AM
Don Symes	We talkin' 12-pin 12xx7-size sockets? One of the tube vendors linked here has some.

10/4/1999 1:21 AM

You mean Nuvistors, right? Miniature metal-cased valves for Minuteman guided missiles? The only one commonly (!) available one is the 6CW5, which is a single triode with a mu of about 70. Problem is, they don't have very nice tone. Very flat and dead-sounding. Also RG is right, sockets are hard to find, and when they're gone, they're gone. AES sells Nuvistor sockets and 6CW5s but its easy to build a pedal with a single tube about the size of a Phase 100 (with an ext. power supply.) I have a schem for a tube pedal on my website (under DIY) that fits in a 4"x4"x2" box easily.

Farrow
http://surf.to/pharaohamps

10/4/1999 8:56 PM

The required sockets would look like a multi-pin transistor socket, like for those ICs that came in a TO-5 can. The subminiature tubes are about 3/8" diameter and vary in length from about 1" to 2". They are all-glass, look like a tiny 7-pin or 9-pin tube, but the leads are thin wires, just like on a transistor. Most leads are at least an inch long, so they can be clipped short for socketing or soldered directly into the circuit. These tubes are sometimes referred to as pencil tubes. Sockets are definitely hard to find.

Nuvistors are a different animal. They have a tiny metal housing, and a ceramic base recessed up into the skirt. The skirt has two blades of different width, that locate into perimeter slots on the socket. Some nuvister types are rare and expensive, but you could use the 6CW4 and 6DS4 types as tubes for a stompbox. Sockets are available, like at AES.

10/5/1999 1:02 PM

Hi, folks. A little more on the 6CW4 Nuvistors; they have a pretty high transconductance for a tube, about 15K if I remember correctly. Their original use was for RF amps. They are sometimes used in audio for high gain low noise phono stuff. I now have a phono preamp using Nuvistors and the sound is almost magic.

However, they are very microphonic, every one I have used. Flick one with your fingernail and it will ring like a bell. In audio I have had to add damping to every one to fix the ringing. Never tried one for guitar, though. They also seem to want a DC filament supply for low hum.

Another thing, you can get the 6CW4 in two volt and 13 volt filament versions.

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