FREDs on PSU

[M Gregg]

Originally Posted by simon2a3

How might you do this M? A couple of small caps across the rails separated by a couple of resistors?

A simple solution is a MOV across the Power Tx primary, however this will only remove Transient Peak's. You need to remove RFI and transients.

This is a bit more complicated than just using a few caps and resistors. Some mains filters seem to work others don't. You are trying to target a wide spectrum of frequencies, However you can make this as simple or as complex as you want.

Here is an example of an external DIY link:

Audio Mains Filter DIY | DMS Audio

You can use mains filter modules and MOV suppression if you want to remove transients. Most people fit a mains filter socket to the back of the amp. This is O.K. however you will probably not notice a major difference.
This is because it does not remove the RFI component. For this you need in line dual chokes or Tx as explained in the link!

Hope this helps!
Regards
M.Gregg

[simon2a3]

Ah, I see. Thanks for the link - is this Swampy's new website? I actually built one of the simple filters a few years ago but didn't notice much difference, perhaps the rest of my system wasn't up to it. I should dig it out and try it again.

[M Gregg]

Originally Posted by simon2a3

Ah, I see. Thanks for the link - is this Swampy's new website? I actually built one of the simple filters a few years ago but didn't notice much difference, perhaps the rest of my system wasn't up to it. I should dig it out and try it again.

Some work some don't.

This is a bit off topic,
On the DC HT supply.

It is interesting to try putting a 0.1uF 1000V polyprop cap across a choke if you have one already in circuit and see what you think!

Just for fun!

Regards
M. Gregg

[CLS]

Originally Posted by M Gregg

...

You may find if you change the diodes to BYV96E (soft recovery) you may miss the brighter sound of UF diodes.

Remember as you "improve the noise floor" of the amp it will make any other weaknesses in your system and recordings show!

Ah, yes, brighter sound, indeed!

Full UF4007 bridge is obvious brighter than the previous GZ37 + FR157 hybrid bridge. The damper diode tube can't 'stop' it, too. Oh, there's no surplus hole. The socket for GZ37 previously is now plugged by damper diode 6AU4.

And I did find the bright sound isn't HF rubbish splashing. In good recordings, the HF is very clean with loads of details. I dug out various violin solos for appreciate that. Just amazing.

However not every recording is in the same good quality, so I turned down the HF several dB on my digital EQ for them. I found it easier for my hearing for extended listening.

From the experiences, I tend to like softer and gentler HF for prolonged listening, so maybe I'll like those BYV's OTOH I'll still give some more time to UF's, too. (I did too many changes these days.)

As to the mains, there are an isolation transformer and a Tripplite line conditioner (in which there're another transformer and EMI filter, surge protector... etc.). I think that's already too much. The isolation trafo was added recently for blocking the power line noise from the air conditioners. The AC frequency converters in them are VERY noisy.

Thanks again, Gregg, you've been so helpful.

Edit: Here is the photo of the amp:
2A3 Spud