Gyrator PCB


Step 7 - C1 option 2After 5 years of working with the gyrator load circuit in DHT preamps and valve amp driver stages, a friend of mine suggested in building this PCB for the DIY audio community. The result of many years of experience and testing plus some refinement of the PCB design made by Tom Browne from Sonic Illusions, is this flexible PCB.

If you don’t know what I’m talking about, however someone told you about this board, then I suggest you pay a visit to some of the following articles and blog entries on my website:

01a DHT Pre-amplifier (Gen2)

Gyrator boards

PCB Features

  1. Gyrator load (or voltage-controlled CCS) to build a “hybrid” mu-follower stage for either DHT or IHT valve stages:
    1. DHT Preamps (e.g. 4P1L, 01a, 26, 10Y, 3A5, 71a/CX371a)
    2. IHT Preamps (e.g. 27)
    3. DHT output stage drivers (e.g. 4P1L, 300B, 45, 10Y, 211/845, 813, etc.)
    4. Push-pull drivers in LTP configuration
    5. Phono output stages
    6. Parafeed stages
  2. Flexible PCB design to fit multiple capacitors
    1. From a low cost WIMA MKS 100nF / 630Vto
    2. Any boutique cap up to 2.7cm x 6cm
  3. It can be re-wired to build a CCS load instead
  4. Stable voltage reference source provided by a cascoded pair of LND150 FETs
  5. The top MOSFET is located next to the edge of the PCB so you can use the heatsink (if needed) of your choice
  6. Top MOSFET can be either DN2540 or any funky depletion MOSFET like IXYS 01N100D or similar
  7. Various options in the PCB to fit low noise and capacitance JFET like either J309/J310, 2SK170/LSK170 or BF862 / MMBJ310 SMD devices. This will provide a wide range of anode currents with great HF response.
  8. Anode current test point across a 10R resistor
  9. PCB characteristics:
    1. 70x65mm board on a high-quality 1.6mm thick FR4 board
    2. ENIG finish, 2 oz. copper.

SMD pre-soldered boards

You can get your pre-soldered BF862 lower jFET device (suitable for 01a up to 4P1L) with its protection zener diode (between drain and source) if you are not used to do SMD soldering. Here is how I do it:


Each board is tested individually and its wrapped on an individual antistatic bag per board.

Ping me a message for availability. I don’t always have these boards in stock. It takes time to do this neat soldering job!

How to get the boards?

If you want to send me your requests please use the form below:


If you don’t hear from me in a couple of days, just ping me an email to the following address as generally the contact form doesn’t work in WordPress:

contact address