Box 66 transistors

[Kroars]

A little while back I built a box 66 with two MP21a’s both with around 125 mA leakage, Q1 low 70’s and Q2 mid 80’s (I believe). While I liked the sound of the circuit, I recently had a buddy ask me to build him one so he could retire his original from touring. When we placed mine next to his original we noticed the one I built was quite a bit darker -just lacked the higher end trebly fuzz.

Wondering if I got the formula right for transistors and if anyone has any suggestions on which ones work best in the circuit. I’ve got MP16’s, MP20a & b, MP21a & b.

Looked around for OC75’s/76’s as well as AC125’s and can only find a few on eBay, not sellers I’ve used and trust.

Thanks!!

 

[Kroars]

2N167A Germanium Transistor NPN Flat-Hat GE

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smallbear-electronics.mybigcommerce.com

Get some before they go.

On the other hand, have you thought about tweaking the frequency shaping components to brighten it up?:

C2 - 470p is pretty large. This will clamp down on noise but also high end. D*A*M* may have used this because of hiss inherent in the OC-xx series
C4 - You could leave C2 as is and tweak C4. Something in the 2.2 uf to 15 uf range might help
C1 - This is already pretty small so I can't see this helping much

My opinion? Use what you have and tweak C2 and C4.

As a side note, I prefer 1kC pots for Attack/Fuzz in Benders and Fuzz Faces.

Thanks! I believe the 66 requires PNP trannies, but I may grab a few of these to hang onto thanks for the heads up! Good thinking tweaking C2 & C4, I’m still learning how to read/understand schematics properly -so that helps a lot!

 

[Kroars]

You can use NPN on that board. You just need to flip all the polarized components and the power feed.

I see. Thanks for the clarification. Are there any upsides of using NPN over PNP in this circuit other than giving you more option to find the “right pair”?

 

[fig]

Those Flat Hats from Small Bear are awesome (everything from Small Bear is awesome). I was able to get a couple awhile back, and this past week when they were made available. I've also had some pretty good luck with a few eBay sellers in Bulgaria with some PNPs and a few NPNs. If you need a certain gain or leakage, hit me up, I may have it.

 

[Kroars]

Those Flat Hats from Small Bear are awesome (everything from Small Bear is awesome). I was able to get a couple awhile back, and this past week when they were made available. I've also had some pretty good luck with a few eBay sellers in Bulgaria with some PNPs and a few NPNs. If you need a certain gain or leakage, hit me up, I may have it.

I do appreciate it good sir. I’ve actually had some good luck with a few Russian sellers and have amassed quite the pile of the MPxx’s, I just have to go through them. Thanks again for the offer though