Experience with FREDs in a tube amp PS

I've had a few units that have been upgraded in this fashion.It always seemed to help the amplifiers disappear better,with no drawbacks.Never done it myself,usually done by the manufacturer.

IME in a high-voltage custom full-wave bridge, Cree SiC Schottky surpasses HEXFRED. For low-voltage/high-current filament supply, a ladder of 50V Schottkys sounds better than FRED. In a manufactured 4-pin bridge, IXYS 600V/6.6A SiC Schottky is reportedly good, although expensive.

You will hear across-the-board improvements, but particularly improved dynamics and faster bass.

Transparency and dynamics are what I'm hoping for. I've got a pair of Cary SLM-100s that I'm thinking of tweaking slightly. The B+ right after the rectifier is 488V, and I was thinking of going with an IXYS 1200V bridge to handle turn on surge. I'd love to go with the Schottkys, but- yeah, SALTY! I can get the 600V/6.6A Schottky for about $65.00 ea, which isn't bad. I'm wondering if it would handle the surge though.

To be safe you might try 1200V/10A Cree SiC Schottkys, but depending on power drawn, they might still need heat sinks. Lower voltage/current diodes may be OK if the amp is equipped with a soft-start thermistor on AC. Dennis Had might offer an opinion.

Generally speaking, the safe thing to do is to select replacement diodes that equal or exceed the rated capacity of the stock bridge. Chances are good that this can be done without using heat sinks, unless the original rectifier uses them.

It's definately worth using Schottkys if you can figure it out-- both for B+ and for the low voltage filament supplies.

Those Crees do really look interesting. A bridge of four TO-247's (1.2kV/10A) would take up a bit of space though. The 5A package(TO-220) is only slightly smaller, and I'd really like to have heatsinks on them. This is obviouly going to have to wait until after the holidays($$). I'll be doing the three bridges(600V) in my Hafler TransNova 9505 (woofer amp) too. That's twenty SiC Schottky diodes, and eight of those need to be 25A. HMMM- I wonder if the kids have bought my presents yet?

OH(BTW)- No soft-start. I can tell by what my lights do when I turn the amps on.

FREDs and Schottky diodes will mostly clean up the treble.
If you are looking for more transparency and dynamics, I suggest that you upgrade the amplifier coupling caps.

A few suggestions:
Low cost: Auricaps & Hovland
Medium cost: Mundorf Silver/oil
Expensive but the best IME: V caps TFT by VH Audio.

I've got Aeon polypropylene coupling caps in my mains now which will do for the time being. I'm focusing mainly on power supply upgrades for the woofer and main amps right now. Overall system dynamics and speed are what I'm after.