Phono 3 noise issues

[John Caswell]

Bulk Foil resistors are very good for low noise areas in valve stages but you need to be careful to use them within their ratings.
I think, without checking, they are mostly rated at 600mW so should be fine for phono stages, but obviously calculate the rating required, and also take out a new mortgage to fund them.
Just checked on Farnell/RS, they are rated at 600/400mW so care is required, and they are not standard E12/E24 series so you may have to series/parallel them, yet more expense!

John

[bikerhifinut]

You weren't kidding John!
I think I will have a look at everything else before even thinking about shelling out for bulk foils.

Andy.

[bob orbell]

A bit of an eye opener Andy . Bob

[Damien]

Hi Andy

Thanks for the offer but the difference in design is so small there seems little point building a III.

Glad to hear you’ve been inspired to do another yourself though

The latest is that the 150uF caps arrived & fitted in the PSU & phono power input.

As they were sold in pairs I also fitted the spare in C3 position having shorted R4.

Slight reduction in the mains hum but as I said before it wasn’t audible at anything like sensible listening levels.

I,ll try & stop fiddling & enjoy listening for now but wil no doubt come back to John’s resistor suggestions & the phono III RIAA tweak later.

Thanks for everyone’s suggestions.

Damien

[bob orbell]

OK John, following on from your post about Z-Foils, I think I may have a bash, my Phono at the moment is very good but would like to try these resistors, are we looking at R5/6 15/16 7/8 and 17/18 that's about £100, any more ? Bob

[John Caswell]

Hi Bob et al,
Well it is cough and hold your wallet time!!!
Resistors that will benefit changing to Bulk Foil type are
R1/2 - 1K, R3/4 47K (50K is fine), R5/6 100K, R7/8 1K2 ( This may have to be made up from a 1K and a 220R) but not changing it won't affect noise really.
I have battery bias so R7/8 are not in circuit. All the rest of my resistors are standard MRS25 1%. fixed filtering on C3/4 etc, 3.18µS variable C etc
Noise level at normal levels is inaudible.
I have arranged the inputs to be relay switched MM/MC with Sowter 8055 MC SUT 10:1 with balanced input from an Ortofon Jubilee cartridge in an SME 309 arm.
For those that wish to try balanced MC input this is fairly easy to do with the standard SME cable. MM is a little more difficult as often the right channel earth is fixed at the cartridge end.
My PSU is valve rectified choke filtered bog standard design

Hope this gives people some ideas.

John

[bob orbell]

Thank you for the feed back John, for your information I use a Ortofon Cadeza bronze in a SME 309 fitted to LP12, in Phono I too have the relay board and Lundall SET's that you gave to Richard, they sit on a dedicated PCB, but the primary earth connection has been removed, this reduced noise considerably. I will shop around for the Z-Foils you suggest. Bob

[bob orbell]

I have now ordered 8 Charcroft Z-Foils for the Phono as John has recommended from Nick Lucas, just over £120.00 they should be with me next week and I will report back after fitting, John, your reputation hags in the balance . Bob

[Chris]

Bob, don't forget to give them a few days to settle in before making any critical listening.

Chris.

[John Caswell]

Ha! "Chacun a son goût" as they say, or even a Bronx cheer.

John