| Author | Message | ||
| Chris Metcalfe (chris_m) Username: chris_m Registered: 10-2006 |
I have always liked the cosmetics, bomb-proof build, size and weight of the RD50, but I recently got to the end of the line changing parts in a ( probably futile) attempt to get rid of that horrible crossover distortion on 'clean' - which is probably inherent in the high voltage-low current design anyway. So, just for fun, I completely stripped out my RD50 and rebuilt it with a tweaked deluxe tube front end. This proved surprisingly fulfilling. I stripped all the traces from the board, and it became an excellent turret board for drilling. Clearly the B+ had to be reworked, so I wired it for a bridge rectifier at 200 odd volts ac and twice the original current, and added ( in series, in phase - thanks, Kevin O'Connor)the low voltage secondary winding ( fused @ 400ma) to give another 60vac, making 350 dc on the 6l6 anodes - enough for about 25 watts output. The chassis easily accomodated two more 12ax7 sockets, placed where the coax sockets were. This power supply works great under full signal load, barely getting warm, which is a REAL tribute to MM transformer overbuilding!! The end result really does sound good, as the lower B+ allows an idle current of 35ma per side, and no crossover distortion at all. I know some of you who read this may regard it as a heresy to give up on the classic MM circuits, but for any other potential heretics out there, it's a very easy rebuild, as the MM hardware and chassis build quality make rebuilding a breeze, using the original board, wire and some of the pots. Is it still a MM?? I don't know, but I'm not taking the badge off the front.I guess I'll have to see if I get fired from this forum..... | ||
| Steve Kennedy (admin) Username: admin Registered: 03-2002 |
That's pretty neat! Good tone is where you find it (or what you make of it)! It is your amp and making a project of it certainly doesn't bother me, it sounds like a fun project! Check this out... I received this message from a guy in Chile who bought an amp he THOUGHT was a Music Man but became suspicious because it was so clean: ____________________________________________________ From: Rodrigo Stambuk Sent: Saturday, January 06, 2007 3:30 PM Subject: sixty five in chile..photos... Here come the photos you request . Hope It helps. This amp came with Line out jack? You can see in the photos there?s no serial number Can you note the impecale and new state of the case (the place where tubes are set) And in the rear, it?s look somebody just stick the information panel.(where the chassis info are or ohms info, looks like a sticker) Rodrigo.   ________________________________________________________ My reply: Most interesting.... you have a Music Man cabinet and front/back panels and logo plates but the chassis appears to be a newly manufactured chassis made to fit into the cabinets and use the Music Man plates! Music Man didn't use pop-rivets (which are everywhere on your amp), they used regular screws, washers and nuts. Music Man also didn't have tube preamps which your amp obviously does! Your amp may very well sound great, but it certainly isn't a Music Man design! I also note that the line cord exits in a different place (I can see it was drilled, not punched), there is an unknown toggle switch next to the line cord ("hum cancel" switch?) and the chassis appears to be aluminum, not the welded and stamped steel chassis of the original Music Man. Also, the grill cloth is mounted 90 degrees away from the proper orientation (the black stripes go side-to-side, not up & down), the Tolex covering of the cabinet is not original and the cabinet hardware is black, not nickel plated. The knobs are Music Man knobs, though. Can you send me a good photo of the entire rear showing the whole chassis? How about a good clear photo of the interior of the amp? I'd like to post it on the web site! Steve www.musicmanamps.com | ||
| Chris Metcalfe (chris_m) Username: chris_m Registered: 10-2006 |
That's very interesting indeed - must have cost a lot more than the original amp. In a way, that's a tribute to someone's view of what an MM amp should be worth. It's certainly true that the build quality of these amps makes them the best platforms for rebuilding - I saw somewhere that a well-known tech actually offers tube rebuilds of MMs. Personally, I only did this through sheer frustration at not being able to get a clean sound; otherwise I would have left it alone. But you're right, Steve, it was a really fun project and a fast build, which compares well with the many hours I have spent trying to fix the amp's original circuit. I wonder if MM would still have taken the hybrid direction if they had been able to read the future - in some ways they are what fenders could have evolved to, but history has judged the hybrid route a dead end ( probably through the resurgence of tube manufacture!!. No way MM could have known that at the time, of course. My feeling is that they should have stuck to getting the original 65 circuit PI }right, and avoided the switch to cathode driver topology. After all, other manufacturers have managed to make tube PIs work well in high B+ amps....I loved my 12-65, in the 70's - brilliant amp. |
Tue, 03/25/2014 - 09:30
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