Foxx Tone Machine Octave issues.

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jsrfo
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Post by jsrfo »

Just built a Foxx Tone Machine, and am having issues with the octave up being too harsh. It's basically useless other than single note playing

The normal fuzz sounds nice.

This build uses 3904 transistors and 1N34A Ge diodes.

Any suggestions on Q voltages, proper Q hFe, etc, would be appreciated.

Thanks in advance.

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mauman
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Post by mauman »

I've built a lot of the Precision Electronics Clean/Octave Blend version of the Foxx Tone Machine, and have gotten the best octave with:

-Q2, Q3, Q4 = 2N5088 or 5089, Hfe at least 425
-Q1 = BC550B or similar, Hfe right around 325-350 (although some people like this one to be >425 Hfe as well)
-The rectifier diodes don't seem to make a huge difference, I normally used BAT46 which are similar in Vf to your Ge diodes. It does seem to help to have the two diodes Vf-matched with each other as closely as possible.
- I also matched those 100k resistors around Q2 as closely as I could.

(Part numbers above are from the Aion Vulcan PCB schematic, which is a Tone Machine.) That said, this design does work best with single notes and the neck pickup. You will get a ring modulation effect with two or more notes, or if you bend a note.

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andy-h-h
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Post by andy-h-h »

jsrfo wrote: 05 Feb 2023, 16:32
Just built a Foxx Tone Machine, and am having issues with the octave up being too harsh. It's basically useless other than single note playing
I'd say that sounds about normal - to my ears, it's only useful around / above the twelfth with the tone rolled down playing single notes.

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CheapPedalCollector
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Post by CheapPedalCollector »

I've had different experience, 150-250 hfe is best, octave works here regardless of pickup and tone control settings, down to about the 7th fret. I've used 2n3904, 2n3565 and 2n5172. I prefered the 1st two and they sound about the same, 2n5172 seems not to bias correctly with the original values.

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Post by andy-h-h »

CheapPedalCollector wrote: 07 Feb 2023, 16:08 I've had different experience, 150-250 hfe is best, octave works here regardless of pickup and tone control settings, down to about the 7th fret. I've used 2n3904, 2n3565 and 2n5172. I prefered the 1st two and they sound about the same, 2n5172 seems not to bias correctly with the original values.
I used the original gob top 2N3565 and some modern low-gain options as well. The octave works all over the fretboard and on any pick-up setting. My preference is up high with the tone down - which is the same for any octave pedal for me (except for maybe a Univox Superfuzz, but that's a different beast) :wink:

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jsrfo
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Post by jsrfo »

Thanks! I'll socket some transistors and do some experimenting! I appreciate the input.

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