DIY Custom PCBs

Set1: Stereo LDR Pre MkII kit: 60 eur


  1. Main PCB

  2. Upgraded Nano Clone with Atmega328PB and latest firmware

  3. Packaging and postage to Europe (add 5 eur for destinations outside Europe)

Features: 4 stereo inputs and 2 outputs, LDR volume control. Can be remotely operated by Apple compatible remote or rotary encoder with push button. Runs on 7.5-9V (I>300mA) switching power supply adapter (not included). For BOM see link below.

See forum link for more details:

Set3: Compact PCBs for one full channel of RMI-FC100 (with LM317 as front end PSU voltage regulator): 20 eur. Includes:

  1. Custom compact main amplifier PCB

  2. Back-end PSU PCB

  3. Front-end PSU PCB (LM317 based)

  4. Packaging and postage to Europe (add 5 eur for destinations outside Europe)

If you want to build stereo power amp, you need two sets (one for each channel).

Set4: Fully Completed LDR Pre MkII SE Kit: 260 eur


  1. Fully built and tested main controller PCB with latest firmware

  2. 2.42" graphical OLED

  3. IR sensor

  4. Rotary encoder

  5. Interconnecting cables and connectors

  6. Packaging and postage to Europe (add 10 eur for destinations outside Europe)

All you need to add is remote, RCA connectors and enclosure of your choice!

You can find cheap compatible remote here:

or buy original A1294 Apple remote:

RMI-FC100 fully assembled and tested power amplifier kit

RMI-FC100 is a reference, single stage power amplifier designed by Mihai Rauta and generously shared with DIY community. You would be hard pressed to find a better sounding (commercial or DIY) amplifier under 10K. It delivers 2W pure class A and 90W class B into 8ohm. The amp was silently used as a reference amplifier for testing other hifi gear by a german magazine here: hifitest .The only problem with this amp is that you cannot buy it anywhere - you need to build one yourself. For more details see this forum link: RMI-FC100.

Now it's possible to order already soldered and tested boards, to save a lot of effort and time that requires building this amp. Please note though that it might take up to 2 weeks to build one channel, due to complexity of this project. However, the sound delivered is well worth both the cost and the effort. Kit is fully built in and shipped from Belgium, no cheap labour or parts from abroad involved.

Included in the kit:

  • Main amplifier board with ONSEMI ThermalTrak NJL0302D and NJL0281D matched transistor pairs

  • Back end PSU PCB with four Kemet ALC10S1103DH audio grade slit foil 10000uF capacitors and 8xMUR860 diodes as rectifiers.

  • Complete front end PSU with 230V 2x30V transformer

Not included in the kit:

  • Main power transformer(s) 2x25V, 400-500VA (or 2x200/250VA)

  • Soft start circuit

  • RCA connectors

  • Chassis and heatsinks

  • Switches, cables, etc.


It can be used as standalone power and softstart circuit, controlled by DPDT low voltage switch. With some modification, it can also be used with LDR Pre MkII board to control power amp with remote , and power up one or two toroidal transformers.

LDR Pre MkII BOM with Mouser and Digikey ref
LDR Pre MkII User Manual

Questions? Send an email to

24bit/192KHz High End USB DAC - XR+ DAC ... read more

LDR Pre MkII BOM and firmware: