"New" 102 ish FET options ...

[Deric]

Started a 102-ish build back in 2018. Populated boards, installed most hardware, wired the OT and a few other things. Then it sat... Finally got back at it a couple weeks ago. Had a couple minor issues when I fired t up - had installed a 100r pot for the bias instead of 10k and a 220k dropping resistor in the power supply in place of the 22k. Sorted those quickly and all was good. Spent some time dialing in the OD trimmer and the PI trimmer. Added a treble bleed to the OD (.001uf/120k). Currently running Tung Sol 6l6GC STR and JJ 12ax7 in the preamp.

My original plan was to add footswitchable FET with a push/pull pot on the front panel. I remember reading over the years talk about subbing other circuits. MXR Micro Amp, RC Booster, etc.

Anyone tried this? Results?

Thanks!

[martin manning]

Member Beasleybodyshop replaced the FET circuit with Echoplex EP3 preamp, and was quite happy with the result.
https://ampgarage.com/forum/viewtopic.p ... 20#p458420

[JD0x0]

I did a high voltage LND150 setup that worked well. I intentionally gave it an EQ curve you'd expect from an OD pedal (shave some highs and lows) rather than a flat response. It works well in place of a pedal in front of the amp, which is a very common setup.

[Deric]

Thanks for the replies!! The EP-3 is one that I remember seeing.

JD0x0 - The LND150 idea is intriguing. Any chance you have a schematic?

[Matt J]

I'm planning on my own #102 build shortly and am curious about that treble bleed you've added to the OD. What are your thoughts on it? I know some ODS builds, like #94, have and adjustable one installed.
It's something I'm considering adding to the one I am going to build.
Thanks!
Matt J.

[Deric]

I really like the treble bleed. It helps balance the clean and OD tones. I usually build the amp without then use a pot and a .001uf cap to dial in to taste. I've always ended up between 100k and 150k. When building a board from scratch I add eyelets for the extra resistor and cap. On this build I used Amplified Nation's boards so had to squeeze (plenty of room) it in.

[Colossal]

I really like the treble bleed. It helps balance the clean and OD tones. I usually build the amp without then use a pot and a .001uf cap to dial in to taste. I've always ended up between 100k and 150k. When building a board from scratch I add eyelets for the extra resistor and cap. On this build I used Amplified Nation's boards so had to squeeze (plenty of room) it in.

Thanks for this tip. I see where you snuck it in. Very nice looking build!

[martin manning]

I see where you snuck it in.

That's one of two options. The other is hanging it from the OD2 plate.

[Colossal]

I see where you snuck it in.

That's one of two options. The other is hanging it from the OD2 plate.

I like that idea too, Martin.

[Reeltarded]

It looks fantastic!

[Deric]

Been reading up on different approaches for this and have come across a few instances of damaged FETs and transistors most likely from over-voltage. Anyone here ever add over-voltage protection tho the FET circuit?

[martin manning]

Seems like it would be difficult to get a lot of voltage on the FET. Wort case would be powered up with no tubes installed. You could put a Zener across the lower part of the divider coming off of B+5 if you wanted to be sure it wouldn't rise above some maximum.

[Deric]

Wort case would be powered up with no tubes installed.

That was my thought as well. Thanks for the tip on the zener.