MusicMan RD-50 to CLone project

[heisthl]

This is one of my current projects and I thought some of you might have one of these in you donor amp pile. Its a really nice size to carry around and should make an excellent clone. So far I have gutted the chassis and done the front panel layout. The base build will be NON-HRM with the recommended values from this discussion board. I will post layouts and progress pics as the build progresses.

[BobW]

heisthl,
I posted a mod to the RD-50 over on the music electronics forum. The mod changes the limiter channel gain stages to an OD. I was initially wanting to do the same as you, ie gut the RD-50 and install a Hybrid REVA layout, but after the mod changes, I decided to keep the MM, and sacrifice another amp, my silverface bassman. My layouts are in the files section. good luck w/your layout.

[heisthl]

Borrowing heavily from the #124 files I have a layout - not perfect but good enough to build from. Note the wierd PS layout necessitated by the Music Man transformer. Basicaly a doubler design which puts out 590 volts. I'm sure I'll have to play with the dropping string values for proper preamp voltages(200 on V1&2). On the plus side, the solid state taps were good for both bias and relay power. I had to use XICON filter caps to have enough room.

EDIT: OUT OF DATE LAYOUT REMOVED

[BobW]

heisthl,

Your layout is looking great. The colored layouts of yours, Normster and Bob_I, really bring out the detail and are easier to view than my plain B/W layouts Keep us posted on your progress. Am now having second thoughts about my RD-50.

[heisthl]

Well Bob if you decide to jump here is the drilling layout and I should have an extra vinyl front panel graphic depending on what kinkos gives me. I can give you these in Visio or some other format if it's easier for you...

EDIT: OUT OF DATE TEMPLATE REMOVED

[BobW]

Well Bob if you decide to jump here is the drilling layout and I should have an extra vinyl front panel graphic depending on what kinkos gives me. I can give you these in Visio or some other format if it's easier for you...

Thanks for the generous offer. sorry for the late reply.

[heisthl]

When/If you decide to go for it PM me and I'll send you the latest - the build is almost done and I'm sure there will be some tweaks required for P/S voltages and tonality matching to the MMan Iron. The attached picture was taken a few days ago and I'm actually quite a bit farther along...

[Bob-I]

... the solid state taps were good for both bias and relay power.

I'd caution you on using the same taps for bias and relays. Relays are noisy and the bias goes directly into the grids of the power tubes so noise gets transmitted easily.

[heisthl]

I'm thinking the 12V regulator will isolate the noise - if not I'll use a small seperate xformer for relay power. I should be testing this in the next couple of days.

[BobW]

heistl, Have you measured your B+? As you know the stock RD-50 was way up there at 585VDC, although they did use NPN cathode drivers. Was the reverb eliminated or is it controlled on the back panel? Your board layout looks great!

[heisthl]

No reverb - this is a straight non-HRM - Yeah the voltages are too high so I'm using an old transformer trick and put half of the solid state tap in series and out of phase with the main secondary winding, the doubled B+ is now around 480v which is useable. I redesigned the bias supply using a .05 off of one of the B+ diodes to the existing bias feed and with an additional resistor and 1 value change it is yeilding around -39 to -59 with minimal board rework. I gutted a 15VAC wall wart and have mounted it in the chassis for the relay power. Still have some work to do before I can actually hear what this one is going to sound like. Pictures and new documentation soon.

[heisthl]

Ready for the "smoke test" and tweakings.

[skyboltone]

Hummmph;
You got a hole in the table for the iron. Works good?

[heisthl]

optical illusion - no hole in the bench - The MusicMan transformers are the same height.

[heisthl]

Amp is up and running - voltages are near perfect, noise floor is good, relays are silent and the clean tones are amazing. Still working on OD tone - seems to have a little of the solid state sound in the overdrive tone so I'm experimenting with value tweaks and tube selection. I'll post the layouts and schematic when I'm more satisfied with the OD tonality.