Gromit's music centre...

[Gromit]

Perhaps results are different through a valve phono stage? Since you're thinking about building a valve amp, why not build one with a valve MM phono stage and revisit the transformer thing to see what happens?

I was using a Puresound P10 (valve) phonostage at the time.

The hum problem did seem to be a 'local' issue as we tried the set-up at a friend's house where the problem wasn't as bad.

[Marco]

Interesting, Richard.

Out of curiosity, what transformers did you try? It's a bit of a lottery sometimes getting one that truly is the right match for a specific cartridge. The difference with the A23 is that its design is the result of years of experimenting by an avid 103 fan (Keith Aschenbrenner) trying to find the optimal transformers for the 103, so you know that his SUT is *right* (in terms of electrical matching) from the off. He's also voices things in a way which I feel really bring out the best in the 'old nail', as you put it. Keith is a 103 fanatic (amongst other things)!

You may find this an interesting read...

http://www.6moons.com/audioreviews/a...um23/23_2.html

Here's a taster from page 2:

The Auditorium 23 step-up transformer for the Denon 103 phono cartridge is the product of much research by Keith into the principles that gave the historic audio masterpieces such a high degree of musical realism. Keith became fascinated with the beneficial qualities that transformers brought to those designs. "I came into contact with a lot of historic transformers in my research and was impressed with their benefits. I made it a goal to produce transformers with the abilities and characteristics of their historical forbearers. Transformers are important and very specialized partners for musical realism and because of that, there is no one transformer that is best for all impedances, ratios, cartridges and so on - each transformer has to be optimized for its application."

and:

It's always astonishing to me to hear how important the differences are when using properly implemented transformers in various applications. Because different transformers work best in any given application, I never will say this or that transformer is the best - it completely depends on the context of its application.

What he says is exactly what my experience has told me. It's quite a fascinating article...

When I was round at Dave's the last time he had a P10 and we used it with my A23 SUT and the sound was sublime (though there was some hum) - even Dave remarked that he'd never heard a 103 sound that good

Maybe it's one to revisit sometime? If you decide to build that valve amp, give me a shout and I'll lend you the A23 for as long as you need it

Marco.

[pure sound]

Odd, the P10 makes no hum at all used in mm form & not even with most transformers although how arm earthing is done and how (& if) cables are screened will affect things.
Some unscreened 'audiophile' interconnects are hopeless for handling the low level signals going between a transformer and phono stage or indeed between phono stage and main amp.

[Gromit]

That's very generous of you Marco - thanks.

The step-ups I tried were Guy's (then prototype) step-up with variable impedance which sounded excellent, and Noteworthy's own variety which they designed to match the 103 - this was then swapped for one which matched the Lyra, which then got sold to Ray.

I also got lent a pair of 'very old' (I think they were Partridge?) transformers in a home-made box by an electronics engineer friend of mine but they hummed like there was no tomorrow. He stated that at his home they were pretty much silent in terms of hum break-through. Jeez, we tried everything to shut them up but even he couldn't cure it, thinking in the end that there was some mains interference in our house, or a local transformer upsetting things.

[Marco]

Odd, the P10 makes no hum at all used in mm form & not even with most transformers although how arm earthing is done and how (& if) cables are screened will affect things.
Some unscreened 'audiophile' interconnects are hopeless for handling the low level signals going between a transformer and phono stage or indeed between phono stage and main amp

Guy, that's most interesting. What about the interconnect between the arm itself and the phono stage or SUT? The tonearm cables Dave supplies with the Jelco sound excellent, but perhaps they're unscreened and that's why they're acting like 'aerials' for hum?

When you move them about (whilst connected to the A23) the hum varies from really loud to medium, to a faint hum, depending on how you 'shiggle' the cables.

I'd appreciate your thoughts.

Richard, you're welcome mate - just give me a shout. But have a read at that article from 6 Moons about transformers and their relationship with MC cartridges; it's most enlightening

Marco.

[Gromit]

Odd, the P10 makes no hum at all used in mm form .

Indeed Guy - I found it quiet as a mouse in that state. We reckoned that transformers were just picking something up from either within the house or something local. Some cables seemed quieter than others, but the hum was always present when played at a decent volume. Shame, as sonically the whole rig was superb.

Listening to Ray's set-up (with the N'worthy step-up and P10) at his house there's no hum whatsoever, certainly none audible unless the wick was set to a crazy level.

[Dave Cawley]

No hum at all on my P-10 with a AT-630 transformer, AT-0C9ML/II, Jelco arm (both types) and Jelco/Neglex cable.

Dave

[Marco]

Hi Dave,

Perhaps it's the Neglex cables and their 'relationship' with the A23? Or just the A23 SUT itself? But then I never had a hum problem (using the same SUT and cartridge) before you fitted the Jelco...

It's one we need to sort out, mate. Can you get hold of an alternative tonearm cable to plug into the 750 for when I come down? If we plug a different cable in and the hum goes then we'll know what the problem was!

Other than that, I'm open to suggestions.

Marco.

[Dave Cawley]

I think its a grounding problem, I have dozens out there, none hum.

Dave

[Marco]

Okay, no worries. But I think it's a good idea to have an alternative tonearm cable to hand, just in case that is the problem. The last thing I'd want is to make a 600-odd mile round trip and still not have the problem cured. We need everything necessary at our disposal to ensure that the problem is sorted

Marco.