ledvedder
Well-known member
Does anyone have information or schematics for the brown eye mods on a JCM800?
Samhain
Banned
Well-known member
I don't but its somewhat Dave's take on a Jose' style gain mod.
Not really top secret or anything.
Some here know alot more than i do.
Not really top secret or anything.
Some here know alot more than i do.
scottosan
Well-known member
Of just the mod? no. There tons of BE100 schematics out there that you can just ignore the clean and HBE portions of.
RedPlated
Well-known member
There are schematics somewhere. 2.7k/ 0.68 on both first two stages, 220 and 100k plate resistors in series on first stage with a 500pf over the 220k. 470k/470k/ 500pf into 3rd stage. 500pf over the 100k on the cathode follower. 820ohm/0.68 on 3rd stage. Traditional 33k/ .022/ .022 tone stack. 1 meg MV with a 1meg resistor to ground, 220k resistor from treble wiper to MV input. It's a non-Jose MV. Then there's a SAT circuit and other various options. The early versions had a 100pf fizz cap on the PI. I think the newer ones are 50pf. 220k bias splitters. Those are just some of the things I can remember off the top of my head.
ZEN Amps
Well-known member
Schematic is easy find via a Google search, you'll find it's a lightly modded 2203.
ledvedder
Well-known member
What's the tone difference between the standard 100k plate resistor vs the 100k/220k/500pf?
I already have 2k7/0.68 on 1st 2 stages. But I have 1k/22uf on the 3rd stage.
psychodave
Well-known member
I’ve never cared for those 500pf snubbers. Just makes the high end weird. I tend to like 47pf.
scottosan
Well-known member
I don’t use any have never had oscillation issues
ZEN Amps
Well-known member
A little more gain with the higher resistors, and the cap rolls off some highs and can help with oscillation. I prefer no cap generally for a brighter, Marshally crunch.
RedPlated
Well-known member
I think he actually uses a 22 or 25uf on 3rd. I just remembered that.
The 320k total resistance adds gain and a lot of compression. The 500pf snubber can reduce oscillation but it also changes the feel. I use a snubber here on my amps but not that high of capacitance. It makes the amp feel more buttery and removes some of the harsh highs. Needs to be sized right for the circuit. Too much can be too much.
