Big Daddy + tone stack. Will this work?

[grrrunge]

Is there any obvious mistakes in this?

http://schematics.graudal.dk/bigdaddy_tonestack_buffered.pdf

The drive is Big Daddy from Runoffgroove.
Tone stack is from ENGL E530, all resistors are scaled down by 10, all caps up by 10.
Output buffer is a snippet i found somewhere. I don't remember if it's from geofex, beavisaudio or somewhere else.

[Mark Hammer]

Looks fine.  I don't know how to calculate actual gain of transistor stages, so I can't say whether the recovery stage packs sufficient oomph to compensate for what gets lost/bled-off in the tonestack.  But that may simply be the difference between a pedal that is clearly usable, and one that can deliver enough output at minimal gain settings to still push the amp into overdrive.

I guess you'll find out when you get there, eh?

[grrrunge]

Looks fine.  I don't know how to calculate actual gain of transistor stages, so I can't say whether the recovery stage packs sufficient oomph to compensate for what gets lost/bled-off in the tonestack.  But that may simply be the difference between a pedal that is clearly usable, and one that can deliver enough output at minimal gain settings to still push the amp into overdrive.

I guess you'll find out when you get there, eh?

Great Noob question then - how do i change the gain of the output buffer stage?

[grrrunge]

Oh - by the way: the buffer circuit is from Jack Ormans website - thanks Jack!

[Phorhas]

If you'll take the output from the Drain instead of the Source - you'll get an amplified signal. As it is shown in the schematic above - it is configured as a follower with a max gain of around 0.9~

Taking the output from the junction of the JFET and the 25k trimmer will give you some boost all by itself. If you want more - you could also add a bypass cap paralleled to the 3k3 resistor and that shall give you additional boostage

Experiment with the values of this cap - bigger values will allow more bass to amplified

[Earthscum]

To make it a true amp (recovery gain) stage, pull the 1M from the Drain/Gate, change the source resistor to a 1.5k, and take the output from the drain/trimpot. You can add a Source bypass cap to boost the top if you want. My personal preference is to bias the drain at 4.5V (1/2 VDD), measure the Gate-Source voltage, then rebias to 1/2 VDD + (1/2 VGS). Otherwise you can just tune it to sound the best to you.

Here's a neat trick, as well... you can get a "tube-like" sound from the jfet if you do as I mentioned above, but instead of pulling the 1M from the Drain/Gate, replace it with a 10M. This has a similar action to what the diode does in Joe Davisson's diode compression tricks. I haven't tried it yet, but I thought about the Millennium Bypass situation and what R.G. said about diode leakage. You may be able to just use a 1N4148/914 reversed like in the Mill, but I think it will work a bit differently... should act more like a (constant current source?). The 10M definitely works, though. Works better in a setup like yours than being directly driven... it nearly smoothed out a Bazz Fuss stage, but when I used a volume between, about 1/10th it got a decent amount of harmonics back in the mix. If you get that effect, try lowering the 1M gate pulldown resistor to something smaller, or use a 1M pot and take your volume before the recovery stage. It works pretty good, and your output impedance can remain lower and unchanging.

[PRR]

> Is there any obvious mistakes in this?

"Output buffer" has to be mis-copied from something.

If TRIM is set to zero, it will work as a unity gain buffer. (So why have a TRIM?)

However the tone-stack impedances are so low that you can drive any guitar-chain input withOUT the buffer.

Alternatively remove R5 (seems to be for a MOSFET?) and take output from Q2 Drain. However this gives overall gain of YOWSA!! (=~~ 2,000), and if you put that much gain in a small box it will probably oscillate/howl.

[grrrunge]

> Is there any obvious mistakes in this?

"Output buffer" has to be mis-copied from something.

If TRIM is set to zero, it will work as a unity gain buffer. (So why have a TRIM?)

That was actually me thinking that if Q1 needed it, Q2 might as well. Jacks schematic doesn't have it. Thanks for that!

However the tone-stack impedances are so low that you can drive any guitar-chain input withOUT the buffer.

I would be very happy if someone could tell me how to calculate or measure the impedance of a tone-stack then.
One guy over at FSB advised me to always put a buffer after the tone stack, just to keep things seperated.

Alternatively remove R5 (seems to be for a MOSFET?) and take output from Q2 Drain. However this gives overall gain of YOWSA!! (=~~ 2,000), and if you put that much gain in a small box it will probably oscillate/howl.

So if i remove R5 and take the output from the drain of Q2, how do i regulate the gain to something useful?

Thanks
// grrrunge

[soggybag]

Look a lot like the Smash Drive with an added output buffer.

[grrrunge]

Look a lot like the Smash Drive with an added output buffer.

If you look at the Grace/Big Daddy project at runoffgroove, they write that the Grace/Big Daddy are based off the smash drive. I just stumbled on Big Daddy one first, heard the clips and liked it enough to order parts right away...

I'm building the various "blocks" on separate protoboards for easy swapping, and plan on trying out the smash drive as well as several other tone stacks, just to see what i like the best