Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => AmpTools/Tech Tips => Topic started by: PRR on June 27, 2010, 12:24:04 am

Title: R.G.'s "A fake guitar for your test bench"
Post by: PRR on June 27, 2010, 12:24:04 am

Quote from: R.G.

I had the need for a test oscillator when I was away from my signal generator, so I trotted out the Q&D oscillator, which had been broken by its storage.

So while tinkering, I did some things to it I'd intended to do for a while. I made it fake a repeated string pluck by adding an adjustment to make the oscillation decay to zero over a second or so, and a "plucker" to fire off repeated notes.

http://geofex.com/FX_images/Fake Guitar Oscillator.pdf (http://geofex.com/FX_images/Fake Guitar Oscillator.pdf)

You can flip it to a constant tone, too. I think this constitutes the world's most accurate, if boring, assistant guitarist.

One dual opamp and a few other parts.

http://www.diystompboxes.com/smfforum/index.php?topic=85408.0

Looks very useful.

Title: Re: R.G.'s "A fake guitar for your test bench"
Post by: Fresh_Start on July 04, 2010, 09:03:04 am

Very cool concept.  I think this would be great for fine tuning preamp stages.  Use it like the "listening amp" in reverse.  IOW injecting the signal at different points to see - and hear - what the effect of each specific stage is. 

I wonder how difficult it would be to add a frequency adjustment.  Not calibrated, just a way to go from say 80Hz to 1,000Hz.

Thanks,

Chip

Title: Re: R.G.'s "A fake guitar for your test bench"
Post by: jjasilli on July 06, 2010, 08:23:19 am

How about running a signal generator through a normally-off momentary SW?  Not automatic though.