daveyu

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158 posts in this topic

Dammit - Cloffo's hacked big Jack's account! :x

Where's me banhammer?

Don't you mean "Sodbury is looking for his banhammer"? :cafe:

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Cyclopse says he is going to have to travel upto Scalford next year with his reference vinyl system. Vistors can get a taste of what they are missing. Now back to the music Jive Bunny tonight I think.

Regards

Cyclopse

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Of all the subjects raised around hifi, only cables are surrounded by more mythology and misunderstanding than mains power.

A big part of the reason for this is there are so many variables...

A common misunderstanding lies in what constitutes mains perturbances:

For a start, no-one seems to know for sure what UK domestic voltage should actually be thanks to deliberate obfuscation by power suppliers. Nominally we're Euro-harmonised at 230VAC @50Hz, but that voltage figure is +10% / -6% allowing them to go right on generating at the 240VAC they always have. This can and does fluctuate considerably, although the core frequency is remarkably stable.

Nonetheless, due to local and regional demand, inclement weather, grid switching, faults etc. you may experience undervoltages ("sag" or "brown-out" - lights dim/flicker) or overvoltages ("surge" - lights brighten, sensitive electronics keel-over or experience reduced service life), either can be transient (uS, mS) or sustained (S).

From generation to your fuse box the supply cabling is picking-up waveform distortions throughout the frequency range.

Some of this is just passive pickup of high-frequency noise, both conducted and radiated, some of it is much lower frequency, usually due to badly designed or unsuppressed electrical installations in homes, factories, shops etc. On top of this is growing use of power lines for data and even voice signal transmission, which started with the power companies using the lines to control their own equipment remotely and has grown to include anything from encrypted data to in-home baby monitors.

Mains pollution doesn't stop at the fuse box though. The commonest complaint is of pops, clicks and data-lock losses due to thermostats, rheostats and unsuppressed switching within the household.

An increasing if less immediately obvious problem are switchmode power supplies - chiefly wall warts and the internal PSUs in many smaller digital devices. SMPS tend to produce switching noise at high frequencies, this can be suppressed, or more commonly the SMPS is designed to produce its noise at frequencies outside the operating range of the device it's intended to power... Fine for that device, but potentially bad news for your hifi.

There are countless sources of hi frequency noise, but lower frequency interference can manifest strongly too.

The commonest is so-called DC offset, which is a severe AC waveform clipping caused by asymmetrically switching devices like certain crude thermostats and some devices utilising thyristors. The effective DC voltage is low, usually mVDC range, but this is plenty enough to saturate marginally specified transformers, especially toroidal ones, causing mechanical noise and a great reduction in efficiency.

The most often overlooked source of mains perturbance is your own hifi. Rabski touches on this, but it's doubly significant because it is right at the heart of your system. Digital kit can produce a lot of out-of-band interference, both radiated and conducted, while so-called digital amps (usually varieties of switchmode) may produce extremely low output distortion yet feedback masses of noise via their PSU, and of course, SMPS are ever more common for all kinds of non-amp functions, especially with the rise to dominance of computer audio.

With all of this being well-known and universal, it is most definitely odd that so few manufacturers take steps to protect their kit with built-in filtration, indeed aside from manufacturers of digital amps who are compelled to, the only one I know who really do things properly are Bryston, who build-in common-mode, differential and DC fliters into their amps. Seems it takes a pro audio company to do it right - which is amusing when some pro-oriented hifi pundits rubbish the need for mains filters at-all!

Still, there are filters and filters - indeed I had to design my own to overcome the issues - but the fact is many act as a bottleneck. They may prevent ingress of external noise, true, but they also actually couple self-generated noise in a system more efficiently by providing too high an impedence at various points. The BT isolation transformers mentioned earlier are good example (hence why they're sold-off so cheaply...), and in common with all isolation transformers have their own problems, as they very readily saturate if any DC offset is present - vibrating and buzzing like a bastard and strangling system dynamics. Most are in any case underspecified to cope well with dynamic transients.

Mains is a minefield, and spurs just one trip hazard along the way, but they really are only useful if you don't have enough sockets or the rest of your house-wiring is an obsolete, high-impedence rats' nest.

churz, sod

Erudite, detailed and accurate.

However, it misses slightly my basic point.

If we are spending massively over the odds (and we are) on 'serious' hi-fi products, why the fuck are we putting up with design and build that is incapable of dealing with mains-borne interference and voltage shifts that are inherent in virtually every mains supply in the land?

If I can buy an amp for £100 to run my guitar through for gigging, and it shoves out a decent 500Wrms and suffers NO effects from mains interference, then why should I accept that a £5000 hi-fi power amp should need me to spend a further couple of thousand pounds on power conditioning in order to be usable in normal domestic situations.

No fucking wonder the domestic audio market is in such a mess. 'Fitness for purpose' comes to mind...

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If I can buy an amp for £100 to run my guitar through for gigging, and it shoves out a decent 500Wrms and suffers NO effects from mains interference, then why should I accept that a £5000 hi-fi power amp should need me to spend a further couple of thousand pounds on power conditioning in order to be usable in normal domestic situations.

No fucking wonder the domestic audio market is in such a mess. 'Fitness for purpose' comes to mind...

Fascinating question.

About 2 or 3 times a week I go to gigs in either Brighton or London.

The bands use regular B&Q type extension leads to power their kit.

If they're from the good ole US of A they have cheap looking voltage transformers.

The sound is full, powerful and real.

They play into amps and on stage 'speakers which are then miked into the PA.

How come this sounds so exciting? It's not just the volume---although that helps. There's an immediacy and naturalness which the Hi Fi can't reproduce.

Gigs aren't Hi Fi. There's loads of things wrong. The vocals are often indistinct, drums aren't usually miked properly, bass guitar is sometimes over amplified.

But there's a freshness which I've spent years trying to achieve at home.

Ho hum!

Guy

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The same thing can be levelled at DACs...why should we pay hundreds or thousands even for a DAC that doesn't buffer, reclock and/or filter properly. Why should we spend hundred or thousands on amplifiers with high output impedance and high distortion. We should we spend hundreds or thousands on loudspeakers with a frequency response that looks like the cross-section of the alps?

Why have we got ourselves into this situation where we pay premium prices for technically inferior product?

S.

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With all respect Guy, point + missed.

Miking up and mixing a live gig is a bloody nightmare. My point only refers to the ability of very cheap and average PA and gig amps to be totally unaffected by mains interference.

I play bass and keyboards. Both to a level of perfection that would stun you, though only through their total lack of virtuosity.

My 'normal' amps are a Laney and a Peavey, with a combination of home-brew speaker stacks and assorted effects shit. The entire lot put together cost me less than £1000. The Peavey is my normal bass amp. It cost £250 and can manage about 750Wrms of low-frequency grunt. More to the point, I plug it into a common supply with a load of lighting effects stuff and assorted other mayhem, and I NEVER get pops, clicks or any other nasties.

Why? Because it has a power supply that's designed to deal with that sort of shit.

My point again. If a £250 amp can be designed to reject mains-borne interference, why can't a £5000 one?

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That will be in part because I wasn't addressing your point other than to mention its validity in passing while echoing the same question. :P

Otherwise the answer to your question is prosaic - cost, and the fact that electronics engineers live in a hypothetical world where all operational conditions are optimal - this is why all their theoretically optimal, low-distortion equipment sounds like dogshit to our highly subjective and individual ears/expectations, and why they leave out line conditioning, because according to their manuals all mains power is a perfect 230VAC undistorted sine wave. :rofl:

Indeed you weren't and indeed you did and indeed you did. And yes. And yes again. And, I think, yes once more.

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There are two different arguments going on here.

Primarily, I buy, build and modify hi-fi equipment purely on the basis of its ability to reproduce music. That is all I am interested in. As long as it fulfils that basic function well, then how it measures is totally irrelevant.

However, I do expect it to perform consistently. If is is adversely affected by the power supplied to it, then in my humble opinion, it is not fit for purpose.

Anyway. I'm going to listen to some Bach organ pieces on my poorly-measuring system. I expect them to affect me, and not adversely. Therefore, I have achieved my aims.

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Mr abbott would like to know what deck you have?

Cyclopse looked far and wide for a turntable that meets his demanding requirements. When he came across this manufacturer he knew his search was over:-

http://www.prometheusaudio.co.uk/

Regards

Cyclopse

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With all respect Guy, point + missed.

Miking up and mixing a live gig is a bloody nightmare. My point only refers to the ability of very cheap and average PA and gig amps to be totally unaffected by mains interference.

Point not missed, just skidded over, Mr Rabski!

As you said, how come your amp can avoid these mains borne problems when Hi Fi at a much higher cost can't?

A point well made. I simply took the opportunity to whizz off on a hobby horse of mine. Why do live gigs sound so good but, at the same time, sound so "wrong" in a Hi Fi sense.

Bass and keyboards, eh? Not Squarepusher are you?!!

Guy

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Chris says That's a Feckin ace TT:cool::cool::love::love::22::22:

As to Elektwickery ....well shucks Buttercup you would seem to know sweet F.A. as wegards dat:roll:....I'd suggest a cavity search to see if Lars is still up one still causing mayhem as this is clearly causing a cognitive infarction in your case;-)

Wegarrrrds vacdac:D

Cyclopse looked far and wide for a turntable that meets his demanding requirements. When he came across this manufacturer he knew his search was over:-

http://www.prometheusaudio.co.uk/

Regards

Cyclopse

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