Aquataur -- excellent DIY circuit mods & improvements

[midwayfair]

Bookmark this guy.

http://user.eduhi.at/aquataur/aquataur/musicstuff/musicstuff.html

It took me FOREVER to find him again.

His "Queen of Tone" article is gold on its own, and the new Umble improvements are certainly worth a really close look (considering he managed to get something far better out of one of ROG's least successful designs).

[atreidesheir]

Helmut is a good guy and his work is always top notch.  He has done good work with fuzzes and is never boring.

[ch1naski]

Thanks for the link Jon!

[Cortexturizer]

Yeah somebody once told me about this site but I forgot about it in the meantime. Thank you John!

[ChrisM]

I couldn't find his Umble modified schematic.

[midwayfair]

I couldn't find his Umble modified schematic.

I don't think he posted a modified schematic for the whole pedal, but here's the umble article.

http://user.eduhi.at/aquataur/aquataur/musicstuff/umble.html

His mods include a compressor/sag circuit that involves like three parts, so of course I had to ask him about it:

I'm intrigued by your little compression setup, and I had a couple
questions. First, it looks like it's half-wave rectification, so would a
second diode on the hold cap/resistor side provide full peak-to-peak
rectification? Second, could you take a guess as to the /attack/ time (it looks nearly instantaneous?) and the ratio?

Yes it is half wave, but allegedly some state-of-the-art circuits use nothing more. According to the author of the series of books I am citing (Kevin O´Connor, whom I have mixed experience with personally...) it does not make much difference.

Using a second diode would kill the circuit stone dead because it would introduce a positive voltage rather than a negative. A much more elaborate circuit (with a precision rectifier) would be in order, which would probably gain nothing. This is, if I understand right what you suggest. On a scope you can clearly see the compressor kicking in.

The attack time is determined by the series 100k and the 1uF, resulting in 100ms attack/decay time. Although there is no exact number to be determined for the r/c time constants that produce sag when the tube power stage draws current (they all seem different...) 100ms seems a good starting value. If you make the envelope flatter (bigger attack time) you start to lose treble and change the tonality. But fiddle with the cap - by all means.

This primitive circuit seems to work well, I like it much for slide because it takes away some of the "ping" of a brass slide while retaining the raunch. Sounds much better than without. Unfortunately, those things are hard to convey on seconds-long demo files replayed on pc loudspeakers.

Let me know about your findings,

sincerely,

-helmut

[ChrisM]

Thanks Jon, I'm going to give that little circuit a try.