The Audiophoolery Thread.

[Craig Sawyers]

I use Self's Devinyiser. I actually integrated it into my active LX521.4 crossover, largely to get rid of excess cone movement. It is switched, so I can remove it for non-record listening.

But you know, I just leave it connected. Its presence is undetectable regardless of source

Regarding D'Agostino's admission that his meter is designed to fib, because it it runs to 1500W, and most listening is done at 1 - 2W. So why did he not make the scale non-linear? Then it would twitch merrily at low power.

Craig

PS I just bought the Devinyliser board http://www.signaltransfer.freeuk.com/devinyl.htm and populated it myself.

[vinrads]

Originally Posted by David G4EBT

Oh well, it's good to have a laugh in a troubled world!

Pebbles indeed!

There are lots more stupid things in the world in which people have the utmost faith.

(The definition of 'faith' is 'a strong and unshakeable belief in something without proof or evidence').

Thought for the day:

"Never attribute to malice that which is adequately explained by stupidity."

Wonderful stuff David I couldn't agree more , Mick.

[slidertogrid]

Originally Posted by vidjoman

Looking at the circuit boards on the photos in post 2097 it looks like the transistors around the centre of the board run hot as the board is discoloured. As it is mounted upside down the heat will rise and cook the board and in time will make the solder joints fail. Leaving on all the time will help it to fail even quicker. There are many noticeable poor solder joints visible in those photos, but then maybe wrapping one wire around another to make a good mechanical connection before soldering might cause unwanted sound effects.

Yes I thought exactly the same thing and as the board is fiberglass I thought they must be getting really hot to scorch that.... However on closer inspection the PCB is just coloured red on the reverse which looks like scorching. Its a triangular pattern . That said those tiny little transistors do run hot!
Another strange thing is that some of the electrolytics are wrapped in insulation tape others are not....

[Craig Sawyers]

I think what looks like a scorched area is just a dob of adhesive holding the board in place, seen though the board material.

Craig

HFN&RR spoke to the designer about that meter.

It could be made logarithmic (pick your own exponent).

and is justifying the use of a cheap movement from Shenzhen...

Those movements do what is said "on the tin" a bit of electronics behind and they can behave like a posh one. These days it is easier and cheaper to do the human interface with a micro. One wonders.

[knobtwiddler]

>a bit of electronics behind and they can behave like a posh one

They can indeed when they are new...

...for a few days...

...whereupon the bearings in the cheap one become so loose that stereo usage becomes impossible, as the ballistics between L/R become completely out of kilter as they don't wear at the same rate.

As you will probably have seen, the good ones from Simpson and the like use pivot jewel bearings. If you put the Alibaba one on the table next to the Simpson the difference is striking. Aside from bearings, the lams are about 10x the size, with a corresponding increase in weight and size of motor.

Having said the above, if the customer isn't bothered by something meaningless, that flaps and bounces in a way that pleases them, why do I worry...

[Radio Wrangler]

Originally Posted by merlinmaxwell

It could be made logarithmic (pick your own exponent).

The big ATU i built has logarithmic power detectors (Analog devices chips circa 1993) So the forwards power meter and reverse power meter have calibrations at 10mW, 100mW, 1W, 10W, 100W, 1kW. There's a PEP function for SSB, and with CW you can select the reflected meter to read computed return loss (SWR by another name)

And for kicks, I put in a phase meter.

Now for the admission.... building an SPC transmatch was completely a daft thing to do as al my HF antennae have been balanced. Trying to run a balun between an ATU and an antenna is just plain stupid. Oh, well, I found out the hard way. Lovely bit of construction, though. but completely the wrong thing.

David

[Beobloke]

Originally Posted by Radio Wrangler

HFN&RR spoke to the designer about that meter. Seemingly his previous model had a reasonably accurate meter, but he got complaints that it didn't move much and people thought the amplifier might be faulty (obviously not trusting the evidence of their ears ) So in this model he dispensed with any pretense of accurate measurement and just made it bounce around a lot as an entertainment. An insight into what for all of us is an unaffordable world.

David

And what's the problem with this? Everyone knows that moving coil meters make stuff sound better, and the more enthusiastically they move, the better the sound.

That's a fact, that is...

[stevehertz]

Certain vintage hi-fi amps used to have a divide by ten switch for the power meters. What's wrong with that? You could have two or three positions even.

[Radio Wrangler]

Originally Posted by Beobloke

Everyone knows that moving coil meters make stuff sound better, and the more enthusiastically they move, the better the sound.

That's a fact, that is...

I thought measurements were anathema, and that when a really high end system was delivered, the purchaser got a signed and sealed certificate that none of the equipment had ever been measured in any way. Such an action would have irretrievably polluted it.

The idea of having a measurement device actually built into an amplifier therefore seems odd. Something with a cheap and wonky movement would not be accurate and would therefore do less damage. The bouncing meter in the 125k monster has a power scale which goes beyond this and into the realm of comedy, so it's free from risk of performing damage, it can even enhance the pleasure. A sort of up-market answer to those Amstrad speakers with built-in disco lights.

Opinions vary, but everyone agrees that anything digital in place of moving coil would be completely unacceptable.

David

[Beobloke]

Originally Posted by Radio Wrangler

Opinions vary, but everyone agrees that anything digital in place of moving coil would be completely unacceptable.

David

Absolutely true. Moving coil meters improve sound quality but LED meters ruin it. Why else do you think cassette decks died out? Oh yes, the powers-that-be will prattle on about hiss, cassette fragility and the arrival of CD, but the fact is that it was the change from moving coil VU meters to digital ones - this ruined the sweet and mellifluous sound of the format and people stopped buying it.

As an aside, this is also why the older 1970s B&O Beocord 2400 cassette deck is so much better than its Beocord 1900 stablemate. Yes, there are tiny insignificant factors like the 2400 being more highly specified and having different circuitry in, but the actual reason for its superiority is simple. The 1900's big, beautiful moving coil meters only work on record - the 2400's work on record and playback.

I am listening to Radio 4 on my Hacker RP38A, it has transistors in it (oops, a bit of foxes paws there), and is working perfectly for speech radio. The elliptical 'speaker helps a lot with its alnico magnet (none of that neodymium rubbish here!).

[Craig Sawyers]

I've just been peering at the internal photograph of the insane d'Agostino Relentless. And I can find no evidence of fuses anywhere. Either on the rear panel, or internally to protect the power lines. I can see no protection features.

Given the size of the reservoir capacitors, and the 128 power devices, if anything breaks loose there is likely to be an internal fire, and something horrible will happen to the speakers.

At one stage I had one of d'Agostino's earlier monsters from the mid 80's - the Krell KSA100, that would chuck out 100W into 8 ohms in class A. Rather a lightweight at only 50kg. Entirely dual mono in one chassis, including two mains transformers.

At least it has a rear panel fuse, and a front rocker switch that incorporated a 10A breaker. And there was speaker protection via a simple circuit and a massive Omron relay. But no fuses between the reservoir caps and the circuit.

It blew up twice. First time it was just the output devices on one channel. The next time all hell broke loose, including two resistors burning clear through the board with clouds of smoke. Each time on turn-on. If I was a betting man I'd say that once it was powered up it was fine - but during power up the thing broke into oscillation for maybe a second with randomly predictable consequences.

But I shudder to think what will happen if something similar happens with the Relentless.

Craig

[Radio Wrangler]

Blew up twice?

Gives a second's worth of oscillation on turn-on?

Clearly, good engineering is undervalued. Circuitry which does not behave properly during turn-on and turn-off is not competently designed. Full stop.

David

[Ted Kendall]

One of Ken Kessler's first features for Hi Fi News was an American tour, in the course of which he visited the Krell factory and was invited to see the first power-up of a prototype. He describes its meticulous construction, so evidently this was no bench lash-up. It cooked almost immediately, and Kessler describes the protoype wireman resignedly commencing dissection to find out what went wrong. And all this was reported as indicative of the company's high-end credentials.

[stevehertz]

But quirkiness and 'this is the price you have to pay for perfection' are all part of the audiophoolery myth. Anything well designed and stable like a top Japanese amp of the late 70s would be considered rubbish. Too many tone controls and switches etc. How bad are they? I mean..

[slidertogrid]

On the subject of a "nothing special" amplifier sounding good and thereby being dressed up and sold for a high price...
Not so long ago I was given an Am$trad tower system with speakers, the whole thing was tatty and rough having been in a shed for years.
I salvaged the cassette deck for parts, The BSR turntable was the cheapest most plastic grotty thing I have ever seen so that went in the bin with the rest of it!
The speaker cabinets were the ones with the flashing LEDs on them and in what I now know to be the best assembly method were of course glued together.
When I broke them apart I found they were fitted with Celestion speakers.

I was very surprised to find that! I expected Alan would have specified the cheapest grot he could have got his hands on!
So maybe that is the secret of good sound - Good speakers and you can get away with murder (to a degree) as far as the amp is concerned... I regret now not testing the thing to see how much that deck rumbled!

[stevehertz]

Originally Posted by slidertogrid

On the subject of a "nothing special" amplifier sounding good and thereby being dressed up and sold for a high price...
Not so long ago I was given an Am$trad tower system with speakers, the whole thing was tatty and rough having been in a shed for years.
I salvaged the cassette deck for parts, The BSR turntable was the cheapest most plastic grotty thing I have ever seen so that went in the bin with the rest of it!
The speaker cabinets were the ones with the flashing LEDs on them and in what I now know to be the best assembly method were of course glued together.
When I broke them apart I found they were fitted with Celestion speakers.

I was very surprised to find that! I expected Alan would have specified the cheapest grot he could have got his hands on!
So maybe that is the secret of good sound - Good speakers and you can get away with murder (to a degree) as far as the amp is concerned... I regret now not testing the thing to see how much that deck rumbled!

Speakers have the largest amount of distortion in the signal chain. Hence, the better the speaker the better the sound. It's always been that way. And yet you can still hear/identify a good amp even though its distortion might be 100 times lower than a pair of speakers. Strange but true. How's that David? Craig? Ted? or maybe you disagree!

[knobtwiddler]

Modern speakers, even fairly modest ones, can have surprisingly low distortion if you're talking about steady tone 1KHz measurements. I don't work in speaker R+D, but I have casually slung test mics in front of decent studio monitors and observed that the highest harmonic when hit with 1K to be around -50 (inc. test mic's THD) relative to the fundamental. Where speakers really distort is at the limit of cone excursion, whereupon what was quite a neat looking FFT plot turns into a many toothed comb of all harmonics. Watching this behaviour on an FFT is quite instructive. It confirms what your ears will have already told you, i..e most speakers typically sound sweetest at modest levels. There is very little warning: the plot looks nice, and you increase the level by only a handful of dB and all hell breaks loose - it comes on brutally. There is also power compression to think about.

As for phono carts, if you know of one that renders the 2nd harmonic (highest one in the vinyl world) at -50, please let me know the model number. Testing carts has an enormous amount of variables. Because of inherent distortion in test records, alignment, generator used to make said test record, tonearm compatibility with DUT - and about a thousand other variables, it's pretty much impossible to give a general THD figure. However, if you have a trusted record and a bunch of different carts, again, the FFT can be highly instructive. The best cart I've measured at 1Khz gave 0.4% THD (an expensive MC cart). With the same record and tonearm, common-or-garden MM carts have given anywhere between 1.2% and 2% THD... I've seen a posh Japanese MC cart start out on the same test track with around 0.5%, and as the weeks go by and it's used more, it winds up looking just as ugly as a DJ cartridge (when new, the harmonics are nearly all 2nd and 3rd, and as it ages, the upper order harmonics grow, as do the lower ones). Again, this doesn't take tracking performance into consideration, so even if 2 carts give identical steady-state THD readings on the same groove, the one with the more agile cantilever and better quality tip will sound far cleaner in actual use.

And if you think vinyl is high in distortion, don't even think about running any form of analogue tape machine through your FFT analyser...particularly cassette...

I write the above with the disclaimer that any measurement of electro-mechanical devices is a 'generalisation' - and others with similar kit will get different values, depending on test media, sample variability etc. I'm also talking about steady-state tone testing at a given level, which is a vastly simplified model compared to real music. However, I think it's fair to say that - with regards to modern speakers - in terms of the ones I've played around with (studio monitors, as I like to hear imperfections such as ground hum and clumsy mute solos - call me weird), they are surprisingly good. As I wrote earlier in the thread, although the conditions of the value might be a little non-specific, I can believe ATC's 0.3% quoted THD figure.

Having said the above, if you define frequency response anomalies as 'distortion', then the speaker is the chief culprit my a mile (in combination with the room). Even high-end recording studios can have peaks and dips that are almost into double figures dB-wise... But the brain compensates very well for this, or the NS10 wouldn't be so ubiquitous, would it?

[Craig Sawyers]

It is an interesting discussion regarding speakers. Yes indeed they are pretty bad, particularly low frequency drivers with a large physical excursion, which can easily get to several percent when approaching xmax.

But in the early days of CD (remember Philips "perfect sound forever"?) they really did not sound good at all. A good friend described it as like having the back of your eyeballs scratched. And even then the distortion components, if you measured them, *should* have been below audibility. They weren't.

I suspect that it is down to the relative order of distortion. Loudspeaker distortions tend to be relatively low order, whereas solid state amplifier distortions can often have components that are higher order - 7th and 9th for example - which are not harmonically related to music and sound objectionable at surprisingly low levels.

Interestingly, the design of pianos specifically incorporates features to suppress high order harmonics because of the fact that they sound awful.

I suspect that is why valved amps - even ones that produce eye-watering distortion like single ended triode - can often be preferred. The distortion is usually just 2nd and 3rd order - so octave and perfect fifth (an octave up), both of which are in all major and minor scales.

Craig