EP Boost clone questions

[fuzz guy]

I've just completed building a Fuzz Dog Ep Boost clone. It's a nice sounding circuit, but even with the gain knob all the way down it seems to be boosting the signal a bit. Is there a simple way to get it down to unity gain? Here's the schematic from the Fuzz Dog online build doc.




Also, what components would I tweak to take a bit of bass out of the circuit?

[duck_arse]

both C3 and C4 control how low the boost goes, so reduce the 10uF to 1uF or less, change the 100uF to 10uF, see where that gets you. C5 at 47uF is quite large, lets lots'o'bass thru, knock some uF's off that to restrict the bass. knob all the way down will still boost by ~R5:R4.

[alexradium]

that's the nature of the beast,the original pedal is like that,it has 3dB at low gain,the second version they added a resistor in the output to cut the volume and make it flat

[antonis]

what components would I tweak to take a bit of bass out of the circuit?

What Stephen said..

In case you don't wish to alter gain stage tonal, raise C2 value..
(more bass will leak out of Q2 Base..)

[PRR]

> even with the gain knob all the way down it seems to be boosting

That's not a bug. It is a Feature. It's a booster. It boosts.

If you truly want *roughly* unity gain, change R5 to about 3.3k or 3.9k. Maximum (distorting) output will be lower however.

[fuzz guy]

> even with the gain knob all the way down it seems to be boosting

That's not a bug. It is a Feature. It's a booster. It boosts.

If you truly want *roughly* unity gain, change R5 to about 3.3k or 3.9k. Maximum (distorting) output will be lower however.

Fair enough, but it's the first boost I've ever used that couldn't be set at unity or even less. One of the things that led me to build this circuit were all the reviews about it being a great always on sort of tone enhancer without adding any boost.

Thanks for all the replies, I really appreciate the help!

To sum up, if I want to get less boost I can reduce the value of C3 and 4, add a resistor at the output or change R5 to 3.3 - 3.9k. To trim some bass I can reduce C5 or increase C2. Is all of that correct?

I realized I could run this thing up to 18v, so I tried today and I like it a bit better. There is a bit of a high pitch whine and an intermittent rumbling sort of sound that wasn't there at 9 or even 12v. Any ideas what might cause that?

[antonis]

After all, you shouldn't wish to own a disgraced Fuzz Dog used as a unity gain buffer, should you..?? 

[antonis]

To sum up, if I want to get less boost I can reduce the value of C3 and 4, add a resistor at the output or change R5 to 3.3 - 3.9k. To trim some bass I can reduce C5 or increase C2. Is all of that correct?

Almost correct.. 

Reducing C3 & C4 values result in reducing LOW freqs boost..(you offset HPF cut-off point..)
To change R5 to lower than 8k2 value you have to place a 6k8-5k6 resistor IN PARALLEL (may by a SPST switch).
Inverse trimming of C5 or C2 is correct.

[fuzz guy]

It looks like later versions of the Xotic ones got rid of the bass boost switch (which does very little) and replaced it with a -3dB switch to allow it to run without any boost. I've looked around and can't seem to find a schematic for this newer version though.

Running my pedal at 12v is working pretty well. I think I might use it as is for awhile before deciding whether to make any mods.

Thanks for all the help.

[antonis]

It looks like later versions of the Xotic ones got rid of the bass boost switch (which does very little) and replaced it with a -3dB switch to allow it to run without any boost.

Can't visualize that circuit, but -3dB attenuation should make no audible difference..
That's exactly the half power point (0.707 V_out/V_in) which is hardly - in not at all - perceived by human ear..)

[fuzz guy]

Apparently the original circuit is still boosting the signal 3dB when the boost knob is all the way down, so the switch on the newer version allows it to get to unity. I'm certain I could hear a 3dB difference, especially when A/B'd against each other.

[antonis]

I'm certain I could hear a 3dB difference,

Have you ever thought to become an ear donor to physical science..?? 

[fuzz guy]

I'm certain I could hear a 3dB difference,

Have you ever thought to become an ear donor to physical science..?? 

Why, do you need new ears? 

Everything I've ever read has said that the lowest change humans can detect is 1 dB, and an increase of 10dB sounds twice as loud. So I would confidently say that a 3dB change isn't hard to hear, especially when clicking on a boost pedal that is driving the front end of an amp.

If you have a graphic EQ set the level to +3dB and play a chord without the EQ engaged and then click it on and I'm sure you'll hear an increase.

If not, you may need those new donor ears. 

[PRR]

Mid-band, on *tone*, I could consistently hear 1dB change in an A/B test; sometimes 0.8dB in certain zones.

We had a mixer with 2dB steps. On *music* it was fairly hard to hear the steps even when you knew you were doing it.

In un-controlled "blind A/B" tests of hi-fis playing music, it often turns out that a 1dB-2dB difference of level overwhelms all other factors-- the louder one sounds "better".