Gus OD?

[Arn C.]

Does R7 or R8 contol the volume in Gus OD?  I was wondering how to put a vol control or trimpot.  I find it just a Little bit too loud.
Thanks!
Arn C.

ps  by the way, this is a great sounding boost!

http://www.diystompboxes.com/pedals/gusOverdrive.gif

[petemoore]

  Make R8 a pot instead of a resistor. wired like basic volume pot.

[Arn C.]

Thanks Pete!

Arn C.

[Jered]

Does R7 or R8 contol the volume in Gus OD?  I was wondering how to put a vol control or trimpot.  I find it just a Little bit too loud.
Thanks!
Arn C.

ps  by the way, this is a great sounding boost!

http://www.diystompboxes.com/pedals/gusOverdrive.gif

  Most, if not all of Gus' boost circuits sound great. He does the math, and it shows. If you haven't tried the NPN Boost, you should. Still my favorite BJT boost pedal. Say goodbye to your LPB.

[Mark Hammer]

Does R7 or R8 contol the volume in Gus OD?  I was wondering how to put a vol control or trimpot.  I find it just a Little bit too loud.

Both R7 and R8 create the specific volume level, actually.  Take C5 out of there, and you soon realize that R7/R8 form a voltage divider pair that drops the output level down a smidgen.  The addition of C5 lets the R7-R8 pair also provide some treble-taming (though nothing you'd really notice).  If you made R7 a bit bigger, like 22k, the output level would drop more and you'd cut more treble from the output.

[Arn C.]

Thanks Jered for the recommendation, I will have to try the BJT Boost Pedal! Did you use the simple version or the one with the tone and buffer?

Thanks Mark for the info.  I really like the sound that I get from this as is, just need to drop the volume a smidgen.  I was planning on putting a 3 turn pot in so I can dial it in just where I want it.  Again thanks for the explanation.

Arn C.

[Mark Hammer]

Thanks Mark for the info.  I really like the sound that I get from this as is, just need to drop the volume a smidgen. 

You're welcome.  From what you said, I think you may find what you seek by merely changing the 10k output resistor to 12k or 15k.

[Gus]

"(though nothing you'd really notice)"

Are you sure about R6,R7,C5 and R8 lowpass as drawn

[Mark Hammer]

"(though nothing you'd really notice)"

Are you sure about R6,R7,C5 and R8 lowpass as drawn

My calculations tell me that R7 and C5 start rolling off highs around 15khz, well above what might be expected to be audible from HBs going into a 12" speaker.

At the same time, I've learned these last few years that many of my assumptions/calculations of components in isolation were incorrect when the entire context was considered.

I'm open to correction.  What am I missing here, or are we simply disagreeing about whether attenuation at 15khz makes an audible difference or not?

[Gus]

Need to add R6(output resistance) collector resistor to R7, the roll off is a bit lower: however even a 15Khz low pass can take some "edge" off.

Output R is Rc with this type circuit
http://en.wikipedia.org/wiki/Common_emitter

FWIW Duncans has a source R correction for when people model tone stacks in the program.

[DougH]

FWIW Duncans has a source R correction for when people model tone stacks in the program.

Yeah, and most people miss that when they start wanting to mix & match tone stacks in different circuits.

It makes a HUGE difference...

[Arn C.]

Update:  I put a 50Kpot in place of the 10K resistor(R7) as a variable resistor, used center leg and one outer leg.  It works fine, but still not low enough output, yet plenty high output.  Should I try a 100K pot there instead?

Thanks!
Arn C.

[Jered]

FWIW Duncans has a source R correction for when people model tone stacks in the program.

Yeah, and most people miss that when they start wanting to mix & match tone stacks in different circuits.

It makes a HUGE difference...

  In the tone stack calculator? I missed it.

[DougH]

Hey Jered,

Yeah, it's on the left side. Click on "Zsrc" and you can change the value.

Doug

[Arn C.]

I decided to tack on a 10K resistor in series with the pot, I will try it out tonight.

Arn C.

[Jered]

Hey Jered,

Yeah, it's on the left side. Click on "Zsrc" and you can change the value.

Doug

  Well I'll be damned. Sure enough. It does make quite a difference. I'm so glad you pointed this out. I was often a bit confused because, what I would see on the TSC sim and what I would hear on the breadboard didn't seem to equate. This is great, thanks.
  Jered