Tone Bender MK III & EQD Tone Reaper - how similar do they sound?

[Chuck D. Bones]

Hi, I'm fairly new here, been lurking for a year or so.
I've got the itch to build a Tone Bender MK III, and in the process ran across the EQD Tone Reaper, clearly a derivative.  My questions are...
1) Do they sound similar?
2) How important (to the sound) is it for the 1st stage to be Germanium?

Looks like the main differences are the Si front-end, stabilized bias in the 2nd stage and retuned tone network.  That Si 1st stage has got to be much quieter.  I plan on tweaking the tone network.

Thanks,

- Chuck

[soggybag]

Looks like the tone reaper is NPN. Where the tone Bender was PNP. The Tone Bender had an extra transistor to get more gain on the input. I can't recall if the MPSA18 is a darlington. It is high gain.

Looks like they replaced the tone section with a BMP tone control.

[willienillie]

I can't recall if the MPSA18 is a darlington. It is high gain.

Nope.  Yep.

[Chuck D. Bones]

Makes sense that the Tone Bender was PNP because back in the day, the PNP Germanium transistors tended to be less leaky than the NPNs.  The Tone Bender has a Darlington 1st stage because even the good Germaniums had fair to middling hfe.  The MPSA18 is not a Darlington, but it has more than enough current gain.  I have some PNP Germaniums, GT402B and 2N1309, so whichever one I build, it will be with PNP devices and a charge pump to make -9V.

[soggybag]

Looking at the schematic for the TB mkIII and Reaper they the both use a diode on the base of Q3. I thought this was used to bias Q3. Is that right? I thought on the TB the ge diode leakage was enough to bias Q3. The Reaper shows si diode which wouldn't seem to work?

Obviously I'm I'm not getting the purpose of this diode.

[Steben]

Looking at the schematic for the TB mkIII and Reaper they the both use a diode on the base of Q3. I thought this was used to bias Q3. Is that right? I thought on the TB the ge diode leakage was enough to bias Q3. The Reaper shows si diode which wouldn't seem to work?

Obviously I'm I'm not getting the purpose of this diode.

The diode works with the cap as a clamper. A clamper holds bias as the cap gets loaded more on one polarity than on the other. In a way you can call it a simple noise gate. The distortion comes mostly from the transistor.

[nocentelli]

The D*A*M Greasebox '83 is another MKIII derivative, but it uses Si transistors for both Q1+2. I really like it, although I modified the schematic a bit by changing the gain pot to be a fuzzface-style fuzz pot on Q1' s emitter, and added a Rat-style filter pot at the end (GB83 has no tone control). Well worth trying out, and no Ge transistors required.

[Steben]

The first two transistors don't add too much to the tone as they are roughly serving as a gain source. Years ago I saw an mkIII derivative with an opamp in front instead of the two transistor stage, I think Aron here designed it? Or not? Or was it me myself and I?  God, aging.....

[Chuck D. Bones]

Looking at the schematic for the TB mkIII and Reaper they the both use a diode on the base of Q3. I thought this was used to bias Q3. Is that right? I thought on the TB the ge diode leakage was enough to bias Q3. The Reaper shows si diode which wouldn't seem to work?

Obviously I'm I'm not getting the purpose of this diode.

The diode works with the cap as a clamper. A clamper holds bias as the cap gets loaded more on one polarity than on the other. In a way you can call it a simple noise gate. The distortion comes mostly from the transistor.

The diode and Q2's base-emitter junction form a back-to-back parallel set of diodes.  Each one acts as a clamp.  Without the diode, current would flow only one way, through Q2's B-E junction, the coupling cap would accumulate charge and drive the transistor into cutoff.  The Tone Reaper uses a silicon diode instead of germanium to set a higher clamp level.

I've got my Tone Reaper built, but not boxed yet.  Bench testing with a scope & funky gen are informative.  I've tried a few different transistors for Q2.  The GT402B leaks the most and biases itself at around -4.5V on the collector.  The 2N1305 & 1307 are much less leaky and bias closer to -8V.  This weekend it goes into the box and gets a guitar plugged into it.

[Chuck D. Bones]

My Stoned Reaper PNP Tone Reaper is one nasty-ass fuzz.  Tried it first with a 2N1309 for Q2.  The leakage of this transistor is very low and resulted in very gated sound.  Too sputtery for me, even at high Fuzz settings.  Then the Russian GT402B went in.  Much better tone, pretty gritty even with Fuzz set to 0.  Responds well to touch and the guitar's volume & tone controls.  Besides reversing the transistor polarities, I made two other tweaks to the Tone Reaper design: Increased the treble roll-off cap on the Tone control from 470pF to 2.2nF and added a 4th pot, a Voice control.  The 10uF cap that bypasses Q1's emitter resistor is replaced with two caps: 22uF and 2.2uF.  Each cap goes to one end of a B2K pot with the wiper connected to ground.  When the Voice pot is at zero, the 2.2uF cap is connected to ground and the 22uF cap has 2K in series to ground.  When Voice is at 10, the 22uF cap is connected to ground and the 2.2uF has 2K in series.  When Voice is at 5, both caps have 1K in series to ground.  Voice does two things: at the ends it controls how much low-mid and bass gets through and in the middle it reduces Q1's gain, up to 9dB.  The output is very strong; I have to set the level between 2 & 3 to obtain something close to unity.  I'll probably end up inserting a 220K resistor between the Tone & Level controls.  If anyone's interested, I'll post a schematic.