The "Mk1"

[GammaFlex]

This build was a fun one, my take on a Mk1.5 Tonebender.

The enclosure could've been finished better but I'm happy with it. what I'm more happy about is the fact that it worked 100% the first time I plugged it in 

[jkokura]

Pretty nice. I like the guts a lot.

Jacob

[Leevibe]

Great job! The wiring is beautiful. Well done.

[hoodoo]

Great job mate, very tidy all round 

[lincolnic]

If this sounds as good as it looks, then you've got yourself a hell of a pedal there. What transistors are you using?

[midwayfair]

I only see two transistors? 

[GammaFlex]

I only see two transistors? 

You are correct, I meant to write Mk1.5 based, my mistake

[Bret608]

This looks really nice! I am curious, whose layout did you use? I've been wanting to try this circuit out. From what I can see, it's basically a Fuzz Face, but with 1) 4.7u rather than 2.2u on the input; 2) 47k rather than 33K for that position; 3) and 100kA rather than 500kA for the volume pot. Just curious how you're liking the sound.

[GammaFlex]

This looks really nice! I am curious, whose layout did you use? I've been wanting to try this circuit out. From what I can see, it's basically a Fuzz Face, but with 1) 4.7u rather than 2.2u on the input; 2) 47k rather than 33K for that position; 3) and 100kA rather than 500kA for the volume pot. Just curious how you're liking the sound.

I did my own layout for this one. If you want it I can get it to you.

You are correct in that it's a fuzz face but this one had some variances that are different from what you mentioned.  I still used the 2.2uf on the input (it was all I had), the 47k for the biasing resistor on Q1, and I used a 10K Log pot for the volume (all I had but it works well). In the fuzz face schematic there is a resistor that is in series to the power supply that's a 470R. In this case I simply put 2 470R in series which changed the output significantly (for the better in my book).  If you're going to build this I highly highly highly recommend that you use a 10k or 20k trimpot for collector input on Q2 to adjust bias, it will make your life much easier. you can do it for both Q1 and Q2 if you wish.

[midwayfair]

This looks really nice! I am curious, whose layout did you use? I've been wanting to try this circuit out. From what I can see, it's basically a Fuzz Face, but with 1) 4.7u rather than 2.2u on the input; 2) 47k rather than 33K for that position; 3) and 100kA rather than 500kA for the volume pot. Just curious how you're liking the sound.

I did my own layout for this one. If you want it I can get it to you.

You are correct in that it's a fuzz face but this one had some variances that are different from what you mentioned.  I still used the 2.2uf on the input (it was all I had), the 47k for the biasing resistor on Q1, and I used a 10K Log pot for the volume (all I had but it works well). In the fuzz face schematic there is a resistor that is in series to the power supply that's a 470R. In this case I simply put 2 470R in series which changed the output significantly (for the better in my book).  If you're going to build this I highly highly highly recommend that you use a 10k or 20k trimpot for collector input on Q2 to adjust bias, it will make your life much easier. you can do it for both Q1 and Q2 if you wish.

The input cap change doesn't matter (there's nothing extra to let through with a 4.7uF on a guitar anyway), but the if you're going to use the 10K for the volume, increase the output cap by x10. You've raised the output cutoff by an entire decade, from 338Hz to 3.38 THOUSAND Hz. That's a "kind of" severe bass cut (for reference, it's every frequency on the guitar, and even above the range of the higher harmonics ... 2K is where most of the harmonics appear in this sort of circuit), so I'm surprised that you would say that "it works well."

The "470R in series with the power supply" -- it might help you to understand the more proper way to put this: It forms a voltage divider -- volume control -- with the resistor connected to the collector of Q2, as well as setting the bias of Q2 when both are added together. Increasing this leg of the divider also has an effect on the midrange in the circuit, though. It's important to realize that even if you like the change (and I do personally) that it's going to have an effect and doesn't sound like the original. Fixing the volume pot might mean that you don't need to use the 1K instead. The other thing is that if you're going to run the circuit at unity volume, increasing the output by increasing that resistor means that the resistance across the volume pot will change, which changes how the circuit sounds at the same volume setting.

Also, I'm not sure what schematic you used, but if you used the Fuzz Central info, then your voltages might not be correct. Q2 isn't biased to 4.5V in any Tone Bender negative feedback circuit. Tone Benders tended to have a much lower Q1 voltage and much higher Q2. The voltages are THE major thing that people building early benders get incorrect.

These notes might be important if you end up build one for someone else ... otherwise it's more useful to call it a modified Fuzz Face than a 1.5.

Bret: This fuzz can be built on pretty any fuzz face board. The circuits are identical with different values.

[GammaFlex]

The input cap change doesn't matter (there's nothing extra to let through with a 4.7uF on a guitar anyway), but the if you're going to use the 10K for the volume, increase the output cap by x10. You've raised the output cutoff by an entire decade, from 338Hz to 3.38 THOUSAND Hz. That's a "kind of" severe bass cut (for reference, it's every frequency on the guitar, and even above the range of the higher harmonics ... 2K is where most of the harmonics appear in this sort of circuit), so I'm surprised that you would say that "it works well."

The "470R in series with the power supply" -- it might help you to understand the more proper way to put this: It forms a voltage divider -- volume control -- with the resistor connected to the collector of Q2, as well as setting the bias of Q2 when both are added together. Increasing this leg of the divider also has an effect on the midrange in the circuit, though. It's important to realize that even if you like the change (and I do personally) that it's going to have an effect and doesn't sound like the original. Fixing the volume pot might mean that you don't need to use the 1K instead. The other thing is that if you're going to run the circuit at unity volume, increasing the output by increasing that resistor means that the resistance across the volume pot will change, which changes how the circuit sounds at the same volume setting.

Also, I'm not sure what schematic you used, but if you used the Fuzz Central info, then your voltages might not be correct. Q2 isn't biased to 4.5V in any Tone Bender negative feedback circuit. Tone Benders tended to have a much lower Q1 voltage and much higher Q2. The voltages are THE major thing that people building early benders get incorrect.

These notes might be important if you end up build one for someone else ... otherwise it's more useful to call it a modified Fuzz Face than a 1.5.

Bret: This fuzz can be built on pretty any fuzz face board. The circuits are identical with different values.

Thanks jon, the more you know!

I ended up changing the volume pot out for a 250K I had laying around, it did change the sound for the better. thanks for the explanations

[Bret608]

Thanks, Jon--this is helpful to me as well. Out of the whole Tonebender family, I think the Mk 1.5 and Mk III are the ones I like best. Nice to know I can just use a FF board for the 1.5.

That makes sense about the input cap. What about that 100kA volume pot though? The output cap on the 1.5 looks to be the same value as a FF. Would these values in concert equal some measure of bass cut in comparison to a FF's wooliness?

[midwayfair]

That makes sense about the input cap. What about that 100kA volume pot though? The output cap on the 1.5 looks to be the same value as a FF. Would these values in concert equal some measure of bass cut in comparison to a FF's wooliness?

Plug in the FF and 1.5 values here, see what happens: http://sim.okawa-denshi.jp/en/CRhikeisan.htm

[Bret608]

Wow, I could play with this thing all day! A very useful tool.

The curve looks really similar. If I'm even remotely close to reading this correctly, I think the 100k in concert with the .01uf cuts a tad of bass and has a bit more upper-mid emphasis than if 500k is the volume pot.

[midwayfair]

The curve looks really similar.

The "curve" is identical. It's a single pole filter (6dB/octave). What you're looking for is the cutoff frequency. Merlin has a useful chart for where cutoff frequencies appear on the guitar: http://www.valvewizard.co.uk/FretFreq.jpg