Can I safely use IXYS FREDs without a rectifier tube

[wcakey]

For my Simple SE, I am going to use solid state power only -- no rectifier tube. George has recommended against using IXYS FREDs in the SSE, but I am wondering if it is OK to use them if I don't use a rectifier tube in the power supply?

 

[maton00]

Depends a lot of the power supply transformer it can overload the amplifier, a tube rectifier will always develop a voltage drop and using silicon diodes will surge 1.41V the AC input you can run some numbers with the calculator if it is inside of the limits of the design it will be okay if not you will need to drop lots volts with a big resistor, chokes or a combination of both.

regarding FRED diodes it looks like there was change in the manufacturing in some models and some arent as rugged as before so they will pop in certain conditions during turn off.
Simple Simple SE questions

 

[bsy020]

I’m using 2 hexfred bridges 1200v 32a for 15 years now. In the past 5 years I use them to get 900v dc to gm70 plate. Had no issues with them. Regarding sound quality, when I’ve compared the bridge to a gz37 rectifier in a 300bxls amp, the bridge sounded better but I think this is because with the bridge I got 430v compared to 380v with the gz37. So I think it depends on the best operating point for the tube.

 

[wcakey]

Thanks for weighing, bsy020. The FREDs I currently have on hand are Vishay VS-E5TX3012-N3 (1200V, 30A) that I got from DIGI-KEY.



I also ordered three others from Mouser:
VS-E5PH3012L-N3 (1200V, 30A)
VS-E5TX3012-M3 (30A 1200V)
VS-30ETU12-M3 (30A If; 1200V Vr)



Which of these four, if any, do you folks feel would be the best to use in the SSE given that I am only going to use solid state for the power supply?


Thanks for your time.

 

[egellings]

I see no problem with ISYS fast recovery diodes or any other brand at all. Just be sure that the diodes' PIV rating is adequate and that the diodes are rated for the current you will draw. When you replace a rectifier tube with them, you will get a higher rectified voltage, and you lose the soft start inherent in tube rectifiers. The diodes come on immediately.