Hey there people! Here’s a sneak preview of some new circuit boards that just arrived, in preparation for my web store grand opening. All but two of the boards shown will be available for purchase by DIY’ers. (Along with existing boards like the GFA-555 soft-start power supply and GFA-565 input boards.)
- GFA-535 MKI power supply, now using WAGO Cage-Clamp terminal blocks for ease of assembly and service.
- GFA-535 MKII power supply, with a completely new layout that leaves more room for large aftermarket binding posts. (Via square cut-outs in the corners.) Also, now with WAGO Cage-Clamp terminals.
- GFA-545 MKI or MKII power supply. Same features as above.
- Universal amplifier soft-start. For the DIY amplifier builder who wants a high quality soft-start circuit.
There are lots of cheap soft-start boards available on Ebay. Besides being sort of crappy, I noticed that none of them provide connections for power transformer AC primary coils. They all just switch the incoming AC, and you must subsequently break out to a separate terminal block for the primary connections. This board provides WAGO Cage-Clamp terminals for one to four 120VAC primary coils, or two 240VAC coils, for transformers totaling up to 2000VA. The soft-start circuit utilizes an NTC thermistor as a resistive element on initial start-up, which is bypassed after 300ms by a 30A relay. The thermistor is an Ametherm Mega-Surge 32, a comically oversized part, and absurd levels of over-kill in terms of power handling. (I’m paranoid.) The relay driver circuit has it’s own regulated power supply, which gives extra protection from relay chattering in case of brown-outs. It will operate correctly with no change in delay time, with as low as 75VAC input.
- Unbalanced line driver and distribution amp. One pair of stereo line-level inputs, to five pairs of buffered stereo outputs. Extremely low noise and distortion. Designed to drive long cables with minimal loss. Useful to break a tape output into 5 sets of buffered outputs, or to drive systems in other rooms by long patch cables. (Though balanced would really be better.) Can be used to split a preamp output as well. Compact design allows installation into existing equipment; for example, to add buffered tape outputs to a preamp or receiver.
- A “Cap Topper“, that makes working with chassis-mount power supply capacitors easier. The board mounts to the screw terminals on top of the capacitor, and provides connections for the bypass capacitors, drain resistors, and supply wires up to 14ga. This is similar to the stock arrangement on a GFA-555 and other amps. I originally made these to save myself the bother of modifying the existing boards, while providing a better result.
- A GFA-565 bias delay board for a personal project; a four-channel version of the GFA-565. Not for sale.
- DIYAUDIO.COM transistor matching board. Not for sale; it’s a collaborative project at diyaudio.com. This is just my version of the PCB. Circuit is by the user/moderator Anatech, and the original board design, which I have modified, is by Cogeniac. Boards will be available in the future, probably as a group buy. This will probably become an open-source project, as it has broad appeal to many fields of electronics. Read all about matching transistors here. It’s quite an involved topic! This is what I use to match the input transistors for the amps I refurbish.
Thanks for reading!