Firstly, lets get the terminology right this is a vibrato (pitch
modulation), not a tremolo (amplitude modulation). Tube vibrato is
not an original concept, similar schematics proliferate in vintage
tube amps.
I thought I'd try something similar using two 6111 submini tubes at
12 volts. This allows for only two stages of phase shift, but the
effect is very pleasing and useable. More stages could be added for a
deeper effect. The advantage of using just two tubes is that it keeps
the milliamp requirements down - it's quite logical to run the two
tubes' heaters in series from 12 volts, keeping the current draw down
to just ~300ma (!!). I dare say that the 6111's could be replaced
with 12AU7 without too much trouble, or indeed with 6021 or 7327
subminis.
Here's a soundclip:
http://www.aronnelson.com/DIYFiles/up/Vintage_Vibe.mp3Signal path:
Squier Telecaster Custom (HB) > Vintage Vibe > Roland Bolt 60
watt tube combo > Shure SM58 > Event Echo Gina 24 soundcard >
Wavelab
No other processing. It's a montage of a few different settings.
There are a few crackles because it's a breadboard not a pedal.
http://i210.photobucket.com/albums/bb292/frequencycentral/VintageVibe.jpg
.....if you can't open the jpg by clicking on it, just copy and paste
it......I seem to be having problems!?