Marshall 5010 Preamp

[Blackboarcult]

A nice sounding JCM-ish 80s combo. May be a good addition for those who like to toy with small SS amps.
You may need a bipolar voltage converter for this one.

As usual, adapted for wiring with terminal blocks, 5-mm spacing.

I'm pretty unsure about the function of the two diodes at the beginning of the circuit, but since they were on schematic I could not let them out. If anyone can explain why are they here and what do they do, I'd be grateful

Not verified yet, I'll try to breadboard it before building just in case. God, so many time to drool over layouts, so little time to actually build'em...

Schematic here.

Enjoy!

/ZVDW

EDIT ONE: moved a couple of capacitors wrongly placed, and changed value for one of them. Schematic is a bit blurry so I got one value wrong.

[Blackboarcult]

At last, verified. And a nice sounding one indeed.
Great to couple with a presence&resonance circuit and a Class D amp, and currently my go-to gadget to rehearse at home.

[ibanez48]

So did you use a bipolar voltage converter. I breadboarded it first to see if I like it. But I can’t get it to work I’m using a universal power supply it actually for lap tops but I use it on all my pedals. It has different voltage settings on it 15/16/18/19/24volts. I was using it on 16 volts but I think it’s got something to do with the power supply. I can adjust the gain pot and it’s working I can here it going up and down I can tell it’s got a lot of gain. I’ll mess with it some more. I may have to build that bipolar voltage converter.

[HamishR]

I would imagine that the diodes on the power supply inputs are acting as a safeguard kind of rectifier - ie helping prevent negative or positive voltage going where it shouldn't.  Pretty straightforward stuff.

[Blackboarcult]

Yup, wont work properly without the bipolar converter. FWIW my readings give +17'1V, -16'3V, great sound and nice headroom. Havent tried it with lower voltage though..

As for the diodes, yes theyre probably there for circuit protection. The whole thing does not give much more gain than the 3005 preamp, a tad more 80s sounding maybe. But I like it better than the 3005. Put a TS or a Cornish in front of it, and instant classic metal here