Anyone have Q-tron schematic?

[Nick123]

I guess it is just an slight upgrade of a Mutron, but want to
see how they solved LOOP and notch function.
Need schematic just for educational purpose, of course ;-)

[Mark Hammer]

I don't have a schematic, but the loop function is simply a pair of jacks between the signal from the input stage and the input to the filter.  The notch function is simly the combination of the lowpass and highpass.  Anderton had this in his EPFM "Super Tone Control" a quarter century ago.

Take a look at the Mutron schem and especially the breakdown of the elements in my Technology of Autowahs article, either at my page or geofex, and you should be able to figure it out.  The key thing to the loop is the ability to tap the input signal for envelope detection BEFORE any additional processing.  The Q-Tron itself may well have some additoonal buffering to improve the process, but you can accomplish easily enough within the context of a plain old Mutron, which most of us have a schematic for.

[moogatroid2000]

Mark is correct. The loop is easily dropped into the MutronIII design. Thanks to Mark's article I have done this myself. What I did was build a buffer, split the signal, built replication of the mutrons first gain stage. The original gain stage would drive the envelope detector always. There is a switch to choose either gain stage as going into the filter.
I found that you need to get both gain stages balanced to give the best results. I was hopeful that I could crank the gain going into the filter and have a small envelope, or low gain with a huge envelope. Didn't seem to work that way for me. I may have made the whole thing too complex.
Anyway, an octave divider in the loop sounds very different and much cleaner in the loop than before the tron. It was a cool addition.
While I do not have the schematic of it I can say that of the 3 units I have peeked at the Q-tron, Q-tron+, and Mini Q-tron. The Mini Q-tron is closest in design to the original mutron. Not sure how the power needs are different than the original, but component and value wise it is super close.
I did not have time to compare the tone of each to see which I thought was closest to the Mutron though.
Good luck with it. One of the coolest effects ever!!!

[STOMPmole]

FWIW, I've tried out the Q-Tron on a couple of different occasions and I'm not sure I'd refer to it as an "upgrade".  To my ears my Neutron sounds MUCH MUCH better.

[StephenGiles]

But they all suffer with ripple in the sweep generator. Until that problem is solved it really makes no difference which one you use/clone. I havn't tried the Harry Bissell solution because I couldn't get it to work, but Mark (probably asleep as I type this at 11.25am GMT) has heard a demo and was impressed.
Stephen