Summary of JFET Moving Coil (MC) Pre-Preamp Kit
The author completed the Boozhound Labs JFET Moving Coil Pre-Preamp Kit to resolve issues with an existing tube MM preamp being over-driven. The kit features a minimalist 2SK170 JFET circuit providing ~30dB gain, utilizing high-quality passive components like Russian capacitors and Nichicon electrolytics. While assembly is quick for experienced DIYers, it requires precision due to small solder pads.
Parts used in the Boozhound Labs JFET Moving Coil Pre-Preamp:
- PCB (Printed Circuit Board)
- Passive components
- Four Stand-offs
- 2SK170 JFET
- Russian K40Y paper-in-oil coupling capacitors
- Nichicon Muse electrolytic filter capacitors
- External 12-24VDC power supply
- Chassis (user provided)
- Connectors (user provided)
I received the Boozhound Labs JFET Moving Coil (MC) Pre-Preamp Kit a while back and I promptly assembled the small circuit board. I’m a sucker for a simple kit and a hot iron. That is where it all stopped. The circuit board remained complete and laying about for a few years. Recently I required another MC stage because the tube moving-magnet (MM) preamp I had just completed did not work all that well with the Jean Hiraga MC stage I had been using for years. It appeared the Hiraga had too much output and was over-driving the tube stage. So I needed another MC stage.
I borrowed a friends Denon MC step-up-transformer (SUT) unit. The system sounded better with the SUT driving the tube MM stage but also sounded a bit dull. This finally pushed me to complete the Boozhound Labs MC Pre-Preamp kit.
The Boozhound Laboratories JFET Moving Coil Pre-preamp kit includes PCB and all passive components to populate the PCB. Four Stand-offs for mounting the PCB are included. You have to provide your own chassis, power supply (12-24VDC), and various connectors. The Boozhound Laboratories JFET Moving Coil Pre-preamp kit features:
- Minimalist circuit using the 2SK170 JFET;
- ~30dB gain;
- Russian K40Y paper-in-oil coupling capacitors;
- Nichicon Muse electrolytic filter capacitors;
- nice quality PCB (made in USA);
- circuit requires external 12-24VDC power supply (batteries work well);
- Assembled dimensions (height with included standoffs): 4 x 2 x 1.625 (inches).
The MC PrePre kit only has a handful of components and for the practiced DIYer the whole soldering chore can be over in less than an hour. Some of the solder pads are quite small so a fine soldering tip and some soldering experience is required. Some solder points I found a challenge and I have been on the cooler end of a soldering iron for over forty years.
For more detail: JFET Moving Coil (MC) Pre-Preamp Kit
- What components are included in the kit?
The kit includes the PCB, all necessary passive components, and four stand-offs for mounting. - Does the circuit require an external power supply?
Yes, the circuit requires an external 12-24VDC power supply, though batteries work well. - What is the gain of this pre-preamp?
The circuit provides approximately 30dB of gain. - How long does assembly take for a practiced DIYer?
The soldering chore can be completed in less than an hour. - Is special equipment needed for soldering?
A fine soldering tip and experience are required because some solder pads are quite small. - What type of JFET does the circuit use?
The minimalist circuit uses the 2SK170 JFET. - What capacitors are used for coupling?
The design uses Russian K40Y paper-in-oil coupling capacitors. - What are the assembled dimensions of the unit?
The height with included stand-offs is 4 x 2 x 1.625 inches.
