Using FREDs in Power Supply???

[Allen]

Hi everyone-

I'm an occasional lurker. Really enjoy reading the posts on the vintage Marks.

Just a quick history about my amp:

I've got a late '83 Mk II C (ser # 12009) that was given the free C+ upgrade by Mike and the gang back in early '84. When I knew I wanted a Boogie, I came up to Petaluma and spent the day with Doug West and test drove several floor models/configurations and then settled on the Simul IIC EV12L combo with reverb and graphic in Bubinga. They went to work and built me one. The old girl has been well cared for and never had any major trouble. I'm a bench tech and a couple years back rebuilt the power supply board with the standard value caps and upgraded the silicon diodes from IN4006's to UF4007's which seemed to smooth out the leading edge somewhat... very subtle: mostly noticeable when using the rhythm channel.

I build an amp now and again, for myself or a friend, and have been looking into using FREDs (fast reacting epitaxial diodes) in my power supplies. The word is that they don't have as much of the brittle leading transient distortion or harshness that standard silicon diodes can have. (If you have an old Fender set up to run on 110-117 VAC and your wall power is 125 or so, you've probably heard this brittle harshness). So, I got to wondering if Mike or anyone else has tried retro-fitting some FREDs into their Marks? If so, was there any perceivable difference? I'm not at all dissatisfied with the sound of the amp, but just curious if there's a relatively simple improvement to be had.

Thanks for any info and see ya around the board!

Allen

 

[Mr. Kite]

Back from the dead. I'm interested as well.

 

[>Photi G<]

Back from the dead. I'm interested as well.

I sincerely thank you for this necropost. I am also interested, as I too experience the "Brittle Harshness" described.

 

[Restless Rocks]

I've read much debate on the use of FRED's in a guitar amp. Particularly when most of the fellows these days are using so much gain and preamp saturation buried in effects, it is thought by many that any benefit of reduced high freq. intermodulation distortion would really be unnoticable. Here's a quote on the subject from another forum:

Well, in the world of tone since the beginnings of electric guitar music, I’m sure FRED is going to have little impact on the listening public. In other words, are they going to be saying, "Holy ****! That guitar player has Great FREDS"! Then, by the current application of the high tech effects that ar slapped on tube amps in general, and effected difference a FRED could give, is rendered null and void in the end result. Not to mention, in the mix of the band, anyone who can detect the amp with the FREDS in it, is a typical musician who has lost their way, and has fallen victim to the polished turd salesman. A new set of strings on your guitar will yield far greater improvement in the tone of the instrument, than any FRED will. BTW, most FREDS end up on the end of the train anyway. Same thing in the amplifier game. It’s just another gearhead thing, for gearheads to debate, and waste good money on. Regards, Rich Koerner, Time Electronics. http://www.timeelect.com Specialists in Live Sound FOH Engineering, Music & Studio Production, Vintage Instruments, and Tube Amplifiers

I personnally, as a tech myself, am intriqued by the possibilities particularly in the use of FRED's in my stereo HiFi amps and in guitar amps intended for use by Jazz or Country purist types and especially the Steel guitar amplifier.

 

[X-1]

Check out the latest issue of Vintage Guitar Magazine (July 2010??) for an article in which the author modded an older tube amp and ran it with standard diodes, FRED's & also a tube rectifier.