KHE's L.A Boutique Screamer build report

[MartyMart]

There's enough controversy surrounding this schem so I wont "link" to it !
It's a tweaked TS circuit with seperate bass/treble controls and supposed to be close to
an "Xotic" device  !
I decided to use a TL072, so ignored the first buffer and ditched the two middle
opamp sections ( toneshaping/slight gain boost ?) to make it a one IC circuit.
Input is just a 1M to ground and a 47n to IC in with 10k from VB.
I adjusted the typical 47n/4k7 to VB to an 82n/2k2 for less bass roll off and higher gain when maxed
diodes are a single 4148 and a single 4001 for assym clipping.
I also adjusted the output BJT to more of a vol recovery from the Eq stage around IC-B ( Muff last stage )
It's quite a clever Eq setup and offers lots of scope for Bass/Treble control - WAY WAY better
than a standard TS tone control 
Keeps the "flavour" of a TS but really makes a wonderful little circuit with a LOT of tones
available.
Gain range with a 1M log pot is superb, clean through mid gain to quite heavy all available....
Keeper 100% !!
Thanks KHE, any "light" shed on the roll of the middle IC would be interesting, works beautifully
without though

MM.

[markm]

OT but, yet another build report that has fallen by the wayside in spite of it being a great circuit.
I feel your pain Marty! 
http://www.diystompboxes.com/smfforum/index.php?topic=54982.0   

[Joep]

Hi MM,

With the 47nF input cap and the 10 to Vr resistor you are rolling off bass from around 340Hz which has significant impact on the sound. Also input impedance will be less than 10K. You might want to consider to increase the 10k to Vr resistor to 100K or bigger.

Joep

[alextheian-alex]

... any "light" shed on the roll of the middle IC would be interesting, works beautifully
without though

MM.

i think I remember that circuit... do you mean the noninverting stage followed by the inverting stage?  If i remember, they are just lopass and hipass filters, but i would have to take another look.

[KerryF]

Nice Marty.  I am planning on trying it out.  Any layouts drawn up that you can post or PM me?  I have a lot of boosts, but this is a boost/TS Overdrive so I will allow myself to try it out 

Thanks
Kerry

[MartyMart]

Hi MM,

With the 47nF input cap and the 10 to Vr resistor you are rolling off bass from around 340Hz which has significant impact on the sound. Also input impedance will be less than 10K. You might want to consider to increase the 10k to Vr resistor to 100K or bigger.

Joep

You're right, larger resistor to Vr would help, maybe even a 470k !
Cheers,
MM

[WGTP]

Marty, I need more of a hint about which one this is.  I found using a single 2N7000 in the feedback to have a nice fat sound, might give it a try.   

[MartyMart]

Just wanted to add that Joep's input impedance/bass content comment was worth working on.
I used a 470k from vref at the + input and had an imediate tonal improvement
Thanks for that.
And just to clear up, this originally used the inverting input, which I swopped to non inverting
like a stock TS uses ( pin 3 rather than pin2 )

MM.