FURMAN LC-6 MODS.
The Furman LC-6 is a IC controlled "FET" compressor. It uses a 2n7000 fet as a variable resistor to pull down on the audio signal. IC Debalancing input (IC101/201 TL072) and IC Balancing Output (on some models it is mono IC103/203 TL072). This is one of my favorite comps. With the mods done, and a DOA/Tranny output, this thing has tons of MOJO. A great bass/Drums/Vocal comp. Ask Furman for a Schematic.
- Add heatsinks to the regulators.
- Replace c1, and c2 with 2200uf 35v caps (516D228M035QS6AE3)
- Bypass those caps with .1u film caps
- Bypass the V+ and V- with .1u film caps
- Replace chips 101, 102, 103, 201, 202, and 203 with better ic's (NE5532, OPA2134, OPA2132, OPA2107, LT1358, or LME49860NA (My fav))
- Replace c104 and 204 with 220uf 16v bipolar panasonic caps (ECE-A1CN221X)
- Replace c101, 103, 110, 111, 112, 116, 117, 201, 203, 210, 211, 212, 216 and 217 with 22uf 35v bipolar panasonic caps (ECE-A1VN220U)
- Bypass those caps with .22u film caps
- Replace Resistors 101, 102, 103, 104, 105, 108, 118, 201, 202, 203, 204, 205, 208, and 218 with 10k metal film equivalents
- Replace Resistors 121, 124, 221, and 224 with 22k metal film equivalents
- Replace Resistors 122, 123, 125, 126, 222, 223, 225, and 226 with 100r metal film equivalents
- Replace c107 and 207 with a polypro cap of similar or higher value. I used a Wima MKP4 .15uf cap here.
Optional: - Instead, Replace C111, 112, 211, and 212 with 47uf 35v bipolar panasonic caps (ECE-A1VN470U) for better bass response. Bypass instead with .47u film caps.
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) by removing r123, 126, 223, and 226 and soldering the input and output leads there.
Or, jumper the resistors and place transformer between jacks and board. Replace the output jack with a stereo Jack.
BLoak or B7 DOA on the output MoD:
- Take out IC 103/203b, 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. take out and jumper/short c111/211
and wire the output transformer to the end of r122/222 or in between the main boad and output jacks (cut gray wire and wire in line).
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 Dual Supply 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) or a +24/-24 (VPT 48-520) transformer.
- Add in a new power supply filter board (MNATS - HERE
or equivalent board) for your +/- 18v or 24v rails for the DOA's only
- Wire in the input of the board to the main board ac connection. Wire the output +/- to the DOA's v+ and v-
Disclaimer: I encourage people to DIY and I'm here in a informative role.
Here are some images: