what's your opinon on using HexFred diodes in tube amps?

[jvegas]

I was thinking of using some HexFred diodes in the power supply section of my 5150. I heard this gives a positive effect on the sound of the amp ,better bass, less harsh mids and highs and all around better clarity. I like to have some more opinions on this matter.


J.

[Structo]

The only advantage I have read about is less switching noise.
Most can't hear the difference.

[Trout]

On the opposite end of the spectrum, I have often wondered if some of the newer Fast soft recovery rectifier diodes would better emulate a tube rectifier. Fast switching but soft response.

I noticed these a bit back, but have not located a good source for them in smaller quantities.

Rectifier Diode Data (http://radiocomplect.com/nvss/download/476.pdf)

[mooreamps]

Most probably can not hear the difference as using the fast recovery diodes only removes one of the hiss makers in a pre-amp. The thermal noise generated by using carbon resistors in the cathodes of the pre-amp are also hiss makers. As such, I use fixed bias for pre-amp gain stages, instead of self bias, and the fast recovery diodes in my pre-amps to totally abate the hiss noise.

-g

[Trout]

Most probably can not hear the difference as using the fast recovery diodes only removes one of the hiss makers in a pre-amp. The thermal noise generated by using carbon resistors in the cathodes of the pre-amp are also hiss makers. As such, I use fixed bias for pre-amp gain stages, instead of self bias, and the fast recovery diodes in my pre-amps to totally abate the hiss noise.

-g


That is actually a pretty good idea, what percentage of hiss is removed on the average? Did you get any scope readings on this?

Also, any experience with the fast soft recovery rects? I always suspected them to reduce perceived noise as well.

Trout

[donnyjaguar]

This comes up every once in a while. Using Hexfreds, or any "fast recovery" diode in a 50/60Hz application is a total waste of time and money.

[stratman_el84]

This comes up every once in a while. Using Hexfreds, or any "fast recovery" diode in a 50/60Hz application is a total waste of time and money.

I gotta agree with you Donny. I simply can't see the advantage of fast/soft switching diodes in a 50/60Hz rectifier circuit. Normal diodes' switching times are already far far faster than the relatively glacial pace of switching 50/60Hz AC power for rectification in a power supply.

The only really justified use I can see for those diode types in a guitar amp would be for low-level signal path switching.

Cheers!

Strat

[jay42]

You're trying to avoid inter-modulation. Yes, the frequencies of the noise coming of PS diodes are above the guitar amp range, but it can intermodulate.

So Mr. Moore, there are diodes in your pre-amps? Are you talking about generating distortion, keeping the power amp from sagging the pre-amp power supply, or diodes in your fixed bias scheme?