Tube synth diy

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.mp3

Signal 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!?

sounds great
will try it with 6021s. 
Do I need to consider the on/off resistances of the LDRs and adjust
the 100k resistors to suit?

cheers
Andrew


--- In tubesynthdiy@yahoogroups.com, "frequencycentral"
<frequencycentral@...> wrote:

>
> 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.mp3
> 
> Signal 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!?
>

Hi Andrew,

The LDRs I used:

Typical dark resistance = 1M Typical light resistance = 2K - 4K

The 6K8 resistor in series with the LED and Depth control sets the 
maximum brightness of the LED. You could replace this with a 10K 
trimpot if your LDRs are different to mine. 

As I'm building this as a guitar pedal, there didn't seem much point 
in being able to set the Depth pot to 'no effect' as the effect can 
be bypassed by switch, so at it's minimum there is still a small 
effect. Replacing the 47K pot with a 100K pot would allow you to 
completely 'dial out' the effect.

You shouldn't have to change the 100K cathode resistors at all. These 
are set up (together with the 100K anode resistors) to provide phase 
cancellation (I think/hope!).

If your LDRs have a higher dark resistance than 1M you could just add 
a parallel 1M resistor to limit them.

Have fun and please post your results/improvements!

regards

Rick


--- In tubesynthdiy@yahoogroups.com, "bbluthang" <jumpswine@...> 
wrote:

>
> 
> sounds great
> will try it with 6021s. 
> Do I need to consider the on/off resistances of the LDRs and adjust
> the 100k resistors to suit?
> 
> cheers
> Andrew