FURMAN c128 MODS. The Furman c128 is a ssm2013 VCA compressor. Ask Furman for a Schematic.
- Replace c1, and c2 with 2200uf 35v caps (516D228M035QS6AE3)
- Bypass those caps with .1u film caps
- Bypass c3 and c4 with .1uf film caps
- Take out the resistor/zener diode regulators and put in lm7815 and lm7915 regulators. Add heatsinks.
- Replace the IC's a101, a103, a104 with lt1358, opa2132, opa2134, opa2107, or LME49860NA (My fav)
- Replace c108, c117, and c203 with 22u 35v bipolar panasonic caps (ECE-A1VN220U). Bypass with .22uf film caps
- Replace c120 and c124 with 47u 35v bipolar panasonic caps (ECE-A1VN470U). Bypass with .47 film caps
- Change resistors 101,102,103, and 104 to 10k metal films.
- change r105 to 5.6k mf
- change r108 to 15k mf
- change r118 to 22.1k mf
- change r120 and r124 to 470r mf
Input transformer MoD:
- You could add a input transformer by wiring it in line with the wires coming out of the 1/4 and xlr in to the main board. Cut those. Transformer input to the xlr jack, Transformer output to the mainboard.
A 600/600ohm impeadance transformer for use with older equipment would work here or a 10k:10k transformer for newer equipment (should be no change in volume levels).
Output transformer MoD:
- Add output transformer (Edcor WSM600/600) in line with the output wires coming off the main board to the output connectors.
Or, wire in a DOA on the output
BLoak or B7 DOA on the output MoD:
- Take out A104, and wire in the doa to the underside of the board (+ pin 5, - pin 6, out pin 7, V+ pin 8, v- pin 4 and ground pin 5) with wires out to the space between the main board and output jacks. This is where the DOA will reside.
Note: The reason for the DOA is to drive the transformer. With regular IC's, they don't have enough power to drive a transformer without low end signal loss. In my opinion.
Note: You will only be able to get around +10db output with the 15v rails. You will need to install a new power supply (PSU dual supply MOD) to get 18-24v rails. Wire the DOA v+ and v- to this supply.
PSU Higher Voltage MoD:
- This is needed when you install a DOA on the output to drive a transformer.
- Replace the transformer with a +18/-18v (VPT 36-690).
- Add in a new power supply filter board (MNATS - HERE
or equivalent board) for your +/- 18v rails.
- Wire the new output to c3 (+ side = v+) and c4 (- side = v-)
Disclaimer: I encourage people to DIY and I'm here in a informative role.
Here are some pictures from some mods.
ModDefecation is about making equipment sound better, providing knowledge and support, repairing that awesome piece of gear, and custom builds. Send me you questions or Ideas.