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RM-9 Mods - FREDs, VTV Caps...

12.7.142.67

Posted by Rob Thomas on June 23, 2001 at 15:20:17

In Reply to: electrolytic caps vs. paper in oil caps posted by mark maloof on June 23, 2001 at 03:27:03:

I've got two sets of Ixyss FRED's, (cheap from Digikey.com), awaiting installation in my RM-9.

I'm going to replace the diodes in the rectifier bridge with the FREDs. Of the common mods, this allegedly provides the greatest improvement in sound.
(Anyone up on bypassing the FREDs with caps for smoother operation?)

I'm also close to ordering the Vacuum Tube Valley Ultra-Tone Silver alloy foil paper in oil caps to upgrade the coupling capacitors in the RM-9. This requires lowering the bottom cover of the amp about a half inch with spacers, and may look kinda amateurish, but will improve air circulation in the amp. (Of the Jensen, Audio Note, and Angela Paper in Oil, the VTV appear to offer the best price/performance ratio.) Still, it's $88 bucks or so for just the four capacitors.

I'll probably upgrade the power cord while I'm at it, this allegedly helps a bit too. I doubt I'll bother with upgrading the internal wiring, rca jacks or binding posts.

I feel a little reticent to mod a classic amp such as this though, I am reverent of the little quality check stickers in the unit initialed "R.M."...

I'm curious about the Triode zero feedback mod and how it is implemented. I understand a single resistor converts a pentode to triode operation...

• VTV Caps web page

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