Barbershop Sag knob...

[HamishR]

I've built a few Chop Shops for friends and have now built one for myself. I have plenty of through-hole J201s so use those and don't seem to have any trouble getting them to 6.66VDC. But I find that the Sag knob doesn't really do a lot. Yes, it gets a little more saggy as you raise the knob but it's not night-and-day. And I seem to like the sound better with Sag fully CCW anyway. So I guess I could do away with the Sag knob which seems a bit sad.

Has anyone tried a larger value for the Sag knob? I'm wondering if 10K is not enough to really make much difference.

 

[szukalski]

IIRC the Sag is just lowering the voltage getting through to the JFETs. You can always break out the DMM and see if it's working right, or pop a resistor in series to see if you like it better.
FWIW I don't bother with it for my Chop Shop builds.

 

[KR Sound]

There’s a certain way that you need to bias it from what I remember. It works great on the one I built.

 

[SYLV9ST9R]

I've built a few Chop Shops for friends and have now built one for myself. I have plenty of through-hole J201s so use those and don't seem to have any trouble getting them to 6.66VDC. But I find that the Sag knob doesn't really do a lot. Yes, it gets a little more saggy as you raise the knob but it's not night-and-day. And I seem to like the sound better with Sag fully CCW anyway. So I guess I could do away with the Sag knob which seems a bit sad.

Has anyone tried a larger value for the Sag knob? I'm wondering if 10K is not enough to really make much difference.

One I did for a friend, I biased nearer to 6V (as I had read many places that stated 2/3 of supplied voltage) and used a B5K for the Sag knob. The sag was missing a hair, but sounded closer to my Modèle B.

 

[Alan W]

At times I really love what the sag does. It sounds convincingly like an amp that’s struggling to get enough power to me—the bass begins to weaken, the dynamics squash in, there’s a bit of lag sometimes with peaks that feel very organic to me. And that’s with me typically running the pedal at 18v…

 

[geoffrey]

Could the problem with the Sag control be due to the values of the J201's you're using? When I built my first one, I remember reading in one of threads that For Q1, you want a J201 that has an Idss from 600-800 uA. For Q2, you want one with Idss about 400-600uA. It was hard to me to find some that within these ranges, but I did and by my ears my sag control works at it should.

 

[swelchy]

don't you have to have the sag knob dialed in a certain way and then set the bias? I built a few and I think I remeber having to set the knob in a position before measuring the bias

 

[swelchy]

Confirmed... you should have the sag control fully counter clockwise before setting bias trimmers voltage

 

[HamishR]

Well yeah - I had the Sag knob letting the full voltage through before setting bias, otherwise you get some crazy numbers.

FWIW I just remembered that I have compared an early version of one of mine to an actual Fairfield pedal and it sounded basically identical. And I suspect that the reason the latest one sounds so good is because of the amp I'm playing it into. Everything sounds good into this amp. My Broadcast sounds amazing into it, and it used to sound a bit too ragged when breaking up before. The Fairfield I tried behaved much like the ones I have built - D'oh! I had forgotten about that!