What is the Just the Fuzz section on Roger Mayer Octavia?

[pete_g]

The newest Band Of Gypsys chrome  fuzz face is based on the RM octavio without the upper octave section of schematic and is apparently the one Hendrix used with The Band of gypsys.

Can someone please upload the schematic with the section that is not used?
Thank you and merry Xmas to all.
image upload no size limit

[nocentelli]

Q1 and 2 produce the fuzz, Q3 does the octave, and Q4 buffers the output. You could try snipping out everything to the right of the 0.01u output cap from Q2's collector up to and including the 0.01u cap coming from the diodes, then connect the volume pot lug 3 and everything to the right of that to the free end of the Q2 collector output cap.

[pete_g]

Is this what you meant?
Please alter the schematic and show by a picture what you mean.Thanks.



screen shot pc

[anotherjim]

That's what I'd do. You could design the buffer Q4 out, but I think it's worth keeping.

[Mark Hammer]

If you simply lift the connection to the lower diode, you will cancel the octave effect, in exactly the same manner as the Foxx Tone Machine.  However, the remaining diode inserts crossover distortion, which is good for some things and not for others. 

What I would suggest is the following, which works well for the FTM.  Get a 3-position SPDT on-off-on toggle.  The common goes to the junction of the lower diode and 100k.  One of the outside lugs goes to the junction of the upper diode, 2M2, and 22uf.  The other outside lug goes to the lifted end of the lower diode that would normall be connected to the 100k.

The middle position leaves the lower diode disconnected, eliminating the octaving.  One of the side positions connects the diode to restore octaving, and the other side position disconnects  the lower diode but also bridges the upper diode to effectively remove its impact on the circuit, giving a less "reedy" distortion.

[Electric Warrior]

[Cozybuilder]

Mark- That is a brilliant solution! Thanks for sharing.

[Mark Hammer]

Mark- That is a brilliant solution! Thanks for sharing.

Thanksfor the nod but not that brilliant at all.  It comes from about 6 or 7 years ago.  We knew this was how the FTM engaged/cancelled octaving, but some members found the resulting non-octave fuzz a little annoying.  Looking at the schematic I realized the signal still had to pass through  a diode, chopping off a half-cycle.  I gave a listen to one I made, bypassing the diode, and thought it sounded better.  Then I realized one could get all three modes with one switch.  The original design made it easy.

[antonis]

If you simply lift the connection to the lower diode, you will cancel the octave effect, in exactly the same manner as the Foxx Tone Machine.  However, the remaining diode inserts crossover distortion, which is good for some things and not for others.

+++++++

I've made this by mistake (left the diode anode unconnected during replacing it in a Fender Blender.. ) and obtained an interesting "bluesy" sound with low gain setting..

[pete_g]

I looked closely at this and it's not the same as chopping off the last section of the octavia. Thanks anyway.

[pete_g]

If you simply lift the connection to the lower diode, you will cancel the octave effect, in exactly the same manner as the Foxx Tone Machine.  However, the remaining diode inserts crossover distortion, which is good for some things and not for others. 

What I would suggest is the following, which works well for the FTM.  Get a 3-position SPDT on-off-on toggle.  The common goes to the junction of the lower diode and 100k.  One of the outside lugs goes to the junction of the upper diode, 2M2, and 22uf.  The other outside lug goes to the lifted end of the lower diode that would normall be connected to the 100k.

The middle position leaves the lower diode disconnected, eliminating the octaving.  One of the side positions connects the diode to restore octaving, and the other side position disconnects  the lower diode but also bridges the upper diode to effectively remove its impact on the circuit, giving a less "reedy" distortion.

How many other components are not part of the fuzz circuit?
The Axis fuzz seems close to the octavia but clearly has different resistors than the octavia.
I tried to draw up a new schematic of an Axis fuzz with the octavia's values but got stuck around the Volume and drive sections.

would be great if someone had the time to redraw up a schematic of the octavia's fuzz section only, otherwise I'll have to try and assemble your ideas.
Thanks.

[pete_g]

Is this what you meant?
Please alter the schematic and show by a picture what you mean.Thanks.



screen shot pc

Is this re-draw of the octavia schem wrong?
Nobody pointed anything out.

[anotherjim]

Should be fine.
...but you can see in the Axis Fuzz how that 39k collector resistor on Q2 has been split(ish) into 22k+10k and the volume control tapped off the middle? Should you wish to delete Q4, that would be the way to go I think -  although I'd breadboard first!

[nocentelli]

The value of the Q2 emitter cap (0.1u) has been trimmed, but the schematic looks OK and works on the breadboard

[pete_g]

Should be fine.
...but you can see in the Axis Fuzz how that 39k collector resistor on Q2 has been split(ish) into 22k+10k and the volume control tapped off the middle? Should you wish to delete Q4, that would be the way to go I think -  although I'd breadboard first!

Yeah I noticed those 2 resistors together to form 32k and cut the end off it.
So the volume should go from lug 2 and go straight to the output, bypassing all the Q4 section in the above schematic?

I put this together and added the 2.2 uf cap on the vol pot (instead of the .01uf output cap) and a 22uf (instead of .1 uf) on Q2's Emitter (near the 39K resistor) as the axis fuzz has it. Not sure if it needs these parts. Any more help would be great.
Are the fuzz and vol pot values correct?
It's almost identical to the Axis Fuzz when those values are added.
I'll have to try the 32K , .01uf input cap (maybe the .01 output cap) 22uf instead of .1uf (on Q2's Emitter) and MPSA13 for Q2 and see if it's the BOG sound. Alternating these is the key I guess.


picture uploader