PCBs

Here are some boards I designed that you can buy for your projects. Boards are £5 each plus £1.50 P&P for uk postage.

email parenthetical at this domain to get more info and arrange payment

Documentation and photos are in progress, but will take some time to finish as there's a lot to do

Most of the pcbs here so far are for mics, but there are also a buffered balanced volume control, a headphone amp, and some mic preamps.

CAUTION Page is being reconfigured, there may be errors, missing links, and messy formatting until I get it all converted to the new system.

Click on the code for full page on each board.

Microphone PCBs

Code	Description	circuit	body	transformer
OPA1	A simple opamp mic circuit	single opamp	BM700/800	No
OPAD	A dual opamp mic circuit	dual opamp both pins driven	BM700/800	No
OPATX	An opamp mic with transformer	single opamp & tx	BM700/800	Yes

Microphone Preamp PCBs

Code	Description	circuit	transformer
RMP	Ricardo's 70s mic amp	discrete BJT	Yes
THMP	THAT 1512 & 1646 with DC servo	very clean chip mic pre	No

Misc other PCBs

Code	Description	circuit
VOL	Buffered balanced volume control	THAT1200 & 1646
HDA	Headphone amp	parallel opamps eg NE5532

THAT 1512/1646 mic preamp

This board is for a mic preamp using the THAT corp chips 1512 (or 1510) mic amp and 1646 line driver.

The implementation is straight from the THAT datasheet, but with the addition of an optional DC servo to allow DC coupling of the audio path between the two chips.

Headamp for BM700/800

This board has a schoeps style circuit on a board designed to fit cheap donor mics the BM700 and BM800.

Polarisation voltage generator for BM700/800

This board has a dual polarisation voltage generator on a board designed for cheap donor mics the BM700 and BM800.

Designed to generate +/-60v although the voltage can be varied somewhat.

Dip switches allow pattern selection for dual diaphragm capsules.

Hybrid board for tapered mic bodies

This board is designed for tapered mic bodies such as those sold as a "mini U87"

There are 3 or maybe 4 distinct different circuits that can be built using this board, with or without a transformer, if you don't mind departing from the outlines on the silkscreen

A matching polarisation generator board is also available

Dual opamp headamp for BM700/BM800

This board has two entirely separate opamp driven circuits on a board designed for cheap donor mics the BM700 and BM800.

This is my single opamp-per-channel redesign of DJJules' dual opamp pcb here: True-Condenser-OPA-Mics

Designed for use with a 5 pin XLR to give dual outputs for dual diaphragm capsules. But can be easily used as a single headamp by only populating one side of the board.

Board for classic transformer fet circuit

This board is designed for long cylindrical mic bodies

It is designed to make a classic Neumann-style circuit with a single fet and a OEP or Vigortronix 6.45:1 transformer

Board for AKG C460/480

This board has a Schoeps style circuit, and a bias generator, on a board designed to fit an AKG C460 or 480 body.

I made these because i had a pair of C460s that werent working right any more.

They don't sound the same as the original. But they do sound good. Not necessarily better or worse, just different.

Pair of boards for AKG C414B-ULS

Should also fit TLS and other C414s from that era. I would not expect it to fit the current model XLS.

2 boards: a Schoeps circuit, and a polarisation voltage generator

I made these because i had a C414 that wasn't working right any more.

My build of these sounds slightly livelier than the original, which is rather restrained and almost dark, but this has a little less heft in the lows.