Squeezebox Touch Question for Audiophiles

[adamdea]

The PSU transformer for my DAC+Buffer amp has 4 seperate secondary windings...

I've just snubbed two of them (330ohm+0.02uF polyprops)
Will try comparative listening later...

Good idea. Mind you, an xpsu tweak is all I need. Just when I thought my audiophilia nervosa was easing. If you so much as think about veils lifting...

[Waldo Pepper]

Do NOT try this for signal carrying transformers. They have resonances too, but dealing with them in such a way as to not muck up the audio signal is not trivial. Most good audio designers will have already dealt with the resonances in an audio transformer, its just power transformers that seem to have been neglected.

John S.

Sorry John but this is misleading. Why, with none valve amps would you ever need signal transformers from pre-amps to power amp stages wrt to audio?

Valve amps along with their output transformers introduce second harmonic distortion and are more "classy" in looks than practical as MOSFET amps are far more linear.

Transformers in a signal path are for impedance matching. Ideal for RF circuits when other factors are predominant and as these signals are often on a RF "carrier", sub carrier resonances are not an issue, but with audio...reserved for amplifiers with high output impedance commonly associated with output stages of germainium transistors and valves to drive low impedance speakers

With modern electronics they have no place. Input amps with KOhms of impedance and MOSFET/silicon transistor output stages with near zero output impedance have no need for transformers.

I have never seen a modern amp with signal transformers in their audio path.

[Waldo Pepper]

The PSU transformer for my DAC+Buffer amp has 4 seperate secondary windings...

I've just snubbed two of them (330ohm+0.02uF polyprops)
Will try comparative listening later...

Stereo means the buffer amps and DACs run on seperate turns of the transformer. Nice on paper but as the whole circuits draw such little power - four simple linear regs would do the same off a single turn. Nice marketing!

Power amps however do need separate circuits to achieve total isolation and that's questionable.

[Phil Leigh]

Stereo means the buffer amps and DACs run on seperate turns of the transformer. Nice on paper but as the whole circuits draw such little power - four simple linear regs would do the same off a single turn. Nice marketing!

Power amps however do need separate circuits to achieve total isolation and that's questionable.

No that isn't it at all.
The PSU is basically a toroid with 4 seperate 15-0-15 secondaries, designed to drive up to 4 discrete devices, including DAC's, Headphone amps, MC head amps etc. Each device comes with a cheap & cheerful wall-wart style PSU.
The x-PSU is an optional upgrade that replaces up to 4 wall-warts. I only use 2 of the outputs.

The AC is rectified/regulated inside the devices. The cooking linear regs have been replaced by super-regs in my units.

Using discrete PSU's means that common-mode + ground plane noise is kept to a minimum.

[Phil Leigh]

Good idea. Mind you, an xpsu tweak is all I need. Just when I thought my audiophilia nervosa was easing. If you so much as think about veils lifting...

I don't know about veils lifting... but it does sound good. Must do an AudioDiff test @ the weekend. Can't trust the olde ears/brain. An A/B shows a definite difference at the top end of vocals and cymbals - seems to take away a slight "tizziness". Of course it might just be rolling-off the top-end. It does sound very "smooth" now.

I've plenty of resistors and caps if you want some...

[adamdea]

I don't know about veils lifting... but it does sound good. Must do an AudioDiff test @ the weekend. Can't trust the olde ears/brain. An A/B shows a definite difference at the top end of vocals and cymbals - seems to take away a slight "tizziness". Of course it might just be rolling-off the top-end. It does sound very "smooth" now.

I've plenty of resistors and caps if you want some...

Very kind of you, thanks, but I will pass for now. I have just got my Touch back after audioupgrades fitted the second clock (and connected the first clock which they had actually not connected- the 44.1/88.2 was still coming from the stock oscillator.) I am not touching anything until that has had a little while to settle in (or my ears have had the chance to adjust to it if you prefer.)

I agree with you about the ears/brain: once you get beyond really obvious upgrades I find it very difficult to tell. Frankly every time I listen to music I find it slightly different. I am however coming round to a rather startling conclusion which is that the modification of my X-DAC has had as much of a difference on MP3s as on hi rez FLAC.

While my touch was away I played CDs through my Xray v3 cd player (I really did buy into the X series) and I felt quite strongly that it was not as good a transport as the touch. This is quite significant because when it came out the X ray v3 was reviewed by Hi Fi News and praised specifically as a transport.

[Phil Leigh]

Very kind of you, thanks, but I will pass for now. I have just got my Touch back after audioupgrades fitted the second clock (and connected the first clock which they had actually not connected- the 44.1/88.2 was still coming from the stock oscillator.) I am not touching anything until that has had a little while to settle in (or my ears have had the chance to adjust to it if you prefer.)

I agree with you about the ears/brain: once you get beyond really obvious upgrades I find it very difficult to tell. Frankly every time I listen to music I find it slightly different. I am however coming round to a rather startling conclusion which is that the modification of my X-DAC has had as much of a difference on MP3s as on hi rez FLAC.

While my touch was away I played CDs through my Xray v3 cd player (I really did buy into the X series) and I felt quite strongly that it was not as good a transport as the touch. This is quite significant because when it came out the X ray v3 was reviewed by Hi Fi News and praised specifically as a transport.

Agree with all of that. Having owned a Linn CD12 (gulp) I feel reasonably well placed to conclude that the Touch can outperform ANY cd-spinner as a pure transport.
And that's without spending thousands on machines to grind the edge of the discs, zap them with ultraviolet or any other lunatic scheme to "improve" the wretched discs... :-)

The X-series were genuine bargains, slightly let down by some rather mundane component choices.

The Audiocom full-blown mods elevate the X-DACv3 and X-10 into a different league.
The X-PSU is just icing on the cake really - maybe 1-2% of the overall sound?

As for modding the Touch... Personally I think the basic stock circuit is pretty good. Not sure there is too much mileage there (especially in my setup with the TACT ASRC) - but I'd be interested to hear your opinions.

[JohnSwenson]

I have never seen a modern amp with signal transformers in their audio path.

The original question was about a TVC - a Transformer Volume Control. Its a transformer with multiple taps and a switch used to select the appropriate tap. Some people like to use these as volume controls. They do exist and quite a few people buy them.

My injunction was NOT to try and change anything about signal carrying transformer, I don't see how that is a bad thing. Such transformer DO exist, yes in tube amps (people still buy and build them) as inputs for balanced lines and even in DACs.

John S.

[soundcheck]

The original question was about a TVC - a Transformer Volume Control. Its a transformer with multiple taps and a switch used to select the appropriate tap. Some people like to use these as volume controls. They do exist and quite a few people buy them.

My injunction was NOT to try and change anything about signal carrying transformer, I don't see how that is a bad thing. Such transformer DO exist, yes in tube amps (people still buy and build them) as inputs for balanced lines and even in DACs.

John S.

Hi there.

I own a Stevens&Billington TX102 TVC.

It's from experience better then any pre-amp or other passive approach I had at home ( I got an old Jeff Rowland pre-amp sitting idle side by side with the TX102).


However. IMO only very few solutions come close to direct DAC-Amp coupling. (One of those could be passive I/V with a voltage divider on the DAC output replacing a fixed I/V resistor - I think Lessloss is doing that.)


Regarding cabling in general:

They do make a difference.

* Cables are LC elements (filters and/or antennas). -- Different cables
must be considered different filters. That's physics.
* Cables connectors do make a difference too. Even the condition of the
connector surface makes a difference ( Just clean them with contact
cleaner). Again - that's physics.
* Cable/wire isolation and damping makes a difference. Again - that's physics.

Regarding transformers: I dampened them with a car supply sound deadening paste.
The biggest effect I experienced by dampening the output coils of one of my digital amps.

See also: microphonic effects on coils
(I used those foil coils instead of air coils on a Tripath amp with pretty good results)

Cheers

[adamdea]

Agree with all of that. Having owned a Linn CD12 (gulp) I feel reasonably well placed to conclude that the Touch can outperform ANY cd-spinner as a pure transport.
And that's without spending thousands on machines to grind the edge of the discs, zap them with ultraviolet or any other lunatic scheme to "improve" the wretched discs... :-)

The X-series were genuine bargains, slightly let down by some rather mundane component choices.

The Audiocom full-blown mods elevate the X-DACv3 and X-10 into a different league.
The X-PSU is just icing on the cake really - maybe 1-2% of the overall sound?

As for modding the Touch... Personally I think the basic stock circuit is pretty good. Not sure there is too much mileage there (especially in my setup with the TACT ASRC) - but I'd be interested to hear your opinions.

I haven't tried out the modded audiocom XDAC without the XPSU but am tempted to experiment now. I have always found it as bit odd that it only steps down 240VAC to 24 VAC, as I would have assumed that the point of an external PSU would be to keep to AC/DC conversion outboard. It made me wonder whether it really made that much difference. I did pay for a full mod of sorts, but I was told that an ealier modding attempt had made it impossible to fit their normal regulators. They used something else which may or may not have been quite as good.
As a matter of interest did they do anyhtign to your X 10D/ Perhaps i should send them theat, although it occurred to me that the better the op amps in the DAC the more doubtful the X10D would become.
I am very interests in the Digital room corection, and I suspect that my next step might be to try out inguz. I don't know how good that is relative to the TacT system, but i can see the sense in dealing with the whole thing in software before sending it to the DAC. At the moment though I am using a QNAP NAS which runs squeezeserver fine but would not have the horsepower for DRC.
Have you read the stereophile Oct review of the touch yet. I think the measurements are interesting. I may start a separate post on this invting more technical sorts to comment on what conclusions we can draw.