DIY Front End 2022

How balanced does the power supply need to be? I built a +/- 27 vdc supply using 3x 9.1 volt zeners and fets and it ended up +0.3 volts higher on the positive side. I think I could change some zeners to get it closer but I don't want to if this is good enough.

Also....What current draw should I expect?
Can you guys tell if I can use this as mic pre for SM7B? I have a tube preamp with 2 channels with phanthom power (REDD .47).
How to commutate theese correctly from preamp XLR with 48V and mic output? What connect where.
On the board I see In+, in-, v+, v-, grnd, out. I plan to use 2 boards in same enclosure for both channels. SK170BL pair on each board.
Thank you

I have just finished my FE2022 and wanted to share some pics, the enclosure was build by one of my friend on this forum. This preamp plays great, thanks a lot Mr Pass 👍
The big 4 pole switch if to select from a gain of 4x or 10x.

IMG_1675.png IMG_1676.png IMG_1677.png IMG_1678.png IMG_1679.png
Last edited:
  • Like
Reactions: 15 users
whatever you want to add, it goes either in front of Black Box, or after Black Box

so, in short - No.

Volume pot goes in front of Black Box
main reason - R1 is defining part of circuit, gain wise and impedance wise; R3 also being important ........... and - in case of resorting to single rail arrangement, there is substantial DC potential across R3

Volume pot is being suggested in front of the Front End.
But it is also mentioned that addition like volume pot could go before or after the Front End board.

If i want to keep the inputs as XLR / balanced until it leaves the Front End, can i put a volume pot (Alps RK27 10k) after the Front End without any adverse effect ?
Idea is to have "XLR/balanced inputs" -> "Front End" -> "Volume Pot" -> "Ship of Theseus" in 1 box.
[But if there are incompatibilities mentionned, that would be "RCA/unbalanced inputs" -> "Front End" -> "Volume Pot" -> "Ship of Theseus" in 1 box]
Official Court Jester
Joined 2003
Paid Member
why placing vol pot after gain stage ?

proper place for volpot is before gain stage, which is also acting as buffer for volpot output impedance

if your goal is to save money, instead of using bal volpot in front of gain stage, so you can use normal stereo volpot after the gain stage, logic is no good, reasons explained above

and also you get gain stage not working in full scream mode, if getting full voltage from sources
@Zen Mod
Thanks for the answer.
I didn't knew balanced vol pot existed...when i searched around for balanced volume control, i mostly found solution based on opamp and integrated circuit. I will search better
And if i don't find, i will then forget XLR/Balanced and go RCA/Balanced -> Vol Pot -> Front End -> Ampl.
(sorry, did a bad copy/paste in the original post. I should have inverted the position of the vol pot...but then you helped with your explaination. thanks for that)