Pimping a PSU3?

[johnm]

Hi folks!

Haven’t visited here in a loooong time so re-registered. So hello!

I finished a Phono 3 stage earlier this week (MM only), and have just taken delivery of the PSU3. Reading through threads here it seems many have pimped the psu3 with slightly better parts, and I want to do the same to avoid faffing around with upgrades later. Just want to build once and do it right.

I’d appreciate if anyone could confirm the following parts are still considered good upgrades:

PCB = V3.2

D1/2/3/4 Supplied with UF5408. Substituting with:

https://uk.rs-online.com/web/p/recti...iodes/7027462/

D5/6/7/8 Supplied with 1N5822. Keeping those as-is.

Rectifier LM1084 IT-ADJ. keeping as-is.

C1/2 Panasonic ED 100uF / 450V. Adding C3/4 and changing all to:

https://uk.rs-online.com/web/p/alumi...itors/4340964/

C5/7 Changing the supplied 100uF caps (LL brand I think? Diamond logo) to Panasonic NHGs. Is there a better choice here? C7 is right after a regulator so does that mean an ultra low ESR cap is out i.e. Panny FC?

Does the above look like an effective route to improving PSU3 a little with going full audio-foo on it?

Cheers,

John.

[bob orbell]

Hi John, most would advise building as is and then upgrading, but, I see no reason why you should not replace the HT diodes with Schottky type although, you do not need and it is not good advice to use 2 amp diodes, smaller current rated diodes would suit better, to that end I think that Matthew has some in stock, HT capacitors, low ESR are the ones to go for and although you can fill all four places, if you are only going to run the Phono it is money wasted as one of them will do nothing, as for the heater diodes and capacitors, I doubt you will hear any difference from the supplied components, regulator is good and the PCB should be the latest incarnation. Bob

[johnm]

Originally Posted by bob orbell

Hi John, most would advise building as is and then upgrading, but, I see no reason why you should not replace the HT diodes with Schottky type although, you do not need and it is not good advice to use 2 amp diodes, smaller current rated diodes would suit better, to that end I think that Matthew has some in stock, HT capacitors, low ESR are the ones to go for and although you can fill all four places, if you are only going to run the Phono it is money wasted as one of them will do nothing, as for the heater diodes and capacitors, I doubt you will hear any difference from the supplied components, regulator is good and the PCB should be the latest incarnation. Bob

Thanks for your thoughts Bob, much appreciated. Looking forward to getting Phono3 up and running, perhaps this weekend.

Cheers.

[MrKettle]

Has there been any change to the spec of the choke? That was the standard first step, putting in something like a Hammond 126C took the hum level down usefully.

[bob orbell]

This Hammond mod I did to one of my power supply's, it did nothing, there was no hum in the first place, the best course of action is low ESR capacitors and a HT regulator,
both my power supply's leave no trace of AC on the scope. Bob

[Greg.]

In contrast, I did the choke mod in my PSU ll and it made a noticeable improvement to the sound overall. IIRC, some found benefit from the mod and others didn’t.

[MrKettle]

It may well depend on whether the PSU is running one or two components, given the effect of draw on ripple. With a Pre3 and Phono 3 putting in two Hammond chokes with an addition LC killed off a slight background hum and even with a different stage with a cascode first stage with zero PSRR there is no hum. For just a Phono 2/3 the standard setup may well be fine.

[colin.hepburn]

Hi John/All
|Yes it was me who came up with the Hammond Choke mod the choke is the 157G/30H @ 40ma/595ohms can be got from here http://www.bluebellaudio.com/

As Greg has said some liked the mod some did not hear a difference But I would say like Bob has said Build it as is first and get an ear for the sound first and then try the choke upgrade

On my system the change to the sound was clear in that there was more body and depth and imaging was is much wider. Now Pleas bear in mind I bid this mod to the PSU 2 version only so cannot speak for the new PSU3

I also suggested the oscon Cap for the phono 2 on the 5751 cathode which was also tested out by Richard who confirmed the same as me that treble was more refined

The modes you refer to in your first post I did on the phono 2 from the off but only because I did not have the kit I only had the PCB board but yes build it standard first if you have got the full kit

The other thing to note About the above modes for me anyway was that my system is singe ended Amp and Frugal Back loaded horns with fostex 126E drivers and Bass helpers So this is likely why I noted the bigger differences with the choke mod
Hope is helps
Colin