The Audiophoolery Thread.

[knobtwiddler]

I'm pretty sure there are tweakers out there who'll remove your Zobel, for a fee! I recently had a client bring a power amp over, which he claimed had blown some tweeters. Within about 30 seconds of him bringing it in, I simply put a 10K square through it and looked on the scope. The amount of overshoot was quite something. I then noticed that the response started to rise if you swept beyond 20KHz. It was the same on both channels.... It transpires that the owner of said amp had paid someone £1,000 to modify it... I didn't have time to flip the lid and look at what had been done, but I think there's a fair chance of the Zobel being removed. It was oscillating at around 3MHz. Why settle for a flat response to 22KHz, when you can remove the Zobel and go to infinity and beyond! I'd imagine it had all manner of other stability mods removed as well - and they probably changed opamps from 5532 to video-grade!

Self Blameless amps

Yes, a good design, I have the book "Self on Audio" a very well written book that goes into proper detail and reasoning for those amplifiers. Built a pair once, they sound of nothing like any good amplifier. I have a Shaffner mains filter feeding the sockets (left hand radial in the kitchen) for TV/DVD/amplifier/freeview box/chargers etc. the thing it does do is reduce the hash radiating to my amateur radio antennae, I didn't notice (or expected*) any improvement in audio quality. It is a fairly posh one rated for 15A, loads of attenuation and about the size of a house brick, must have cost hundreds new, 'twas a WEEE bin find.

*/ironic mode on/ perhaps I should have done /ironic mode off/

[Craig Sawyers]

Originally Posted by Radio Wrangler

TBecause of where the feedback is picked off the output, this added pole is within the loop when the loop is closed.

The frequency of the capacitance load pole depends on the load capacitance, so high capacitance brings its frequency down and it takes out the phase margin of the loop design and the whole amplifier bursts into ultrasonic/RF oscillation, followed by smoke and pyrotechnics.

I've seen some circuits where the feedback got taken off AFTER the Zobel... which rather neatly spoils the point of it. Oh, well. So much audio stuff gets designed on witch-doctory principles. Maths gets left right out of it.

David

Self in his book on Audio Power Amplifier Design spends an entire chapter (Ch14 in the 6th ed, pages 355-383) on Output Netwrks and Load Effects, that should be required reading for power amplifier designers. And idiot modifiers.

Even the mighty Krell got it wrong. I owned a KSA100 back in the day, which was 100W class A into 8 ohms. It heated the room nicely in the winter from its fan-cooled heat sink chimneys. However, although it had a Zobel across the speaker terminals there was no output inductor, so its stability was a bit marginal (it blew up twice, spectacularly - there were no fuses in the +/- supplies so the full juice of the power supply fuelled the fire).

The Zobel was also underrated, the resistor was too low power, and because the RC pair was in a piece of shrink wrap, the resistor cooked the capacitor.

Apart from those problems it sounded superb, with no crossover distortion.

Craig

[Craig Sawyers]

Originally Posted by merlinmaxwell

Yes, a good design, I have the book "Self on Audio" a very well written book that goes into proper detail and reasoning for those amplifiers. Built a pair once, they sound of nothing like any good amplifier. I have a Shaffner mains filter feeding the sockets (left hand radial in the kitchen) for TV/DVD/amplifier/freeview box/chargers etc. the thing it does do is reduce the hash radiating to my amateur radio antennae, I didn't notice (or expected*) any improvement in audio quality. It is a fairly posh one rated for 15A, loads of attenuation and about the size of a house brick, must have cost hundreds new, 'twas a WEEE bin find.

*/ironic mode on/ perhaps I should have done /ironic mode off/

The only thing to watch with older Shaffner filters is that they used RIFA capacitors of death inside. So occasionally they break loose, an because they are potted and in a sealed metal container, the result can be "spectacular"!

Craig

the result can be "spectacular"!

At least I will know when it goes wrong!

[Radio Wrangler]

They blow a hole in the Schaffner can.

David

[TonyDuell]

Originally Posted by knobtwiddler

It boggles my mind to think that a well-known OEM would market power amps that are so close to the stability threshold that some types of (admittedly audiophool) cable would take them over the edge.

Given it's Naim, nothing would surprise me! I once was inside a high-end CD player from that company. Or at least it had a high-end price tag. But it used the cheap plastic Philips CDM4 deck. And the normal Philips decoder chipset. The only thing was that Phlips said in their databooks that certain decoupling capacitors had to be SMD parts mounted under the DIL-packaged ICs for minimum track length (and thus inductance). On this machine, they were normal through-hole capacitors about 0.5-1cm from the IC. Maybe it makes no difference, but...

[Craig Sawyers]

Originally Posted by knobtwiddler

It boggles my mind to think that a well-known OEM would market power amps that are so close to the stability threshold that some types of (admittedly audiophool) cable would take them over the edge.

The same OEM makes a power amp with an RRP of £150K. And they don't publish its THD+N spec. Publishing such mundane data is beneath them!

We ought to find someone with one of these amps and pay them a visit with some dummy loads and an AP analyser. We can publish the figure for them!

I know the guy behind these - Steve Sells. When I was CTO of Wharfedale in around 1990, we acquired Cambridge Audio, which had just gone bust (for about the 6th time in its history). They had a student who had worked for them called Steve Sells. He was clearly a real talent so I hired him. We were going to re-launch the Leak brand, and I asked Steve to design the best power amp he possibly could, cost no object. He came up with a pair of monoblocks, with comprehensive protection. They were superb, with (with our kit) immesurably low distortion and rock solid stable into any load we concocted. When I was setting them up at the Heathrow audio show, all I got was a very quiet sound a bit like an old transistor radio. I'd left the shorting plugs in the back of the speaker, and Steve's amps were playing into a short circuit - and the sound was produced by the current in the speaker cables. Turned it off with sweaty palms, took the short off - and the amps worked perfectly.

Anyhow, fast forward to his current position as chief engineer at NAIM. They let him off the leash the same way that I did at Wharfedale - and the Statement pre and power amps was the result.

Now no, they do not publish THD plus noise figures. But I absolutely guarantee that Steve has completely characterised the amps under all possible operating conditions.

If they had published them, would it make any difference to the purchase of a hundred-odd grand's piece of kit? I think not. But I again guarantee that if asked by a potential technically informed purchaser to produce the numbers, I'm sure they would do so.

Craig

[Radio Wrangler]

A long time ago it became possible to design an amplifier to produce the required power into the requited load, with more bandwidth than anyone can hear and with trivial distortion.

The problem is that not every amplifier is designed this way. Not every one is competently designed. Rocket science isn't involved, you don't need special components stolen from a crashed flying saucer. Some amplifiers are disappointing.

It's probably less important to know exact figures than it is to know that the designer is competent and that the bean counters kept their fingers out.

As a result of the no-Zobel whoopsie, Naim was on my don't touch list. If they do such a thing and not see the downside, what else might they do? After Craig's comments, I'm warming to their later products, but I don't suppose I'm likely to ever see one at that sort of price.

David

[stevehertz]

Originally Posted by Craig Sawyers

I know the guy behind these - Steve Sells. When I was CTO of Wharfedale in around 1990, we acquired Cambridge Audio, which had just gone bust (for about the 6th time in its history). They had a student who had worked for them called Steve Sells. He was clearly a real talent so I hired him. We were going to re-launch the Leak brand, and I asked Steve to design the best power amp he possibly could, cost no object. He came up with a pair of monoblocks, with comprehensive protection. They were superb, with (with our kit) immesurably low distortion and rock solid stable into any load we concocted. When I was setting them up at the Heathrow audio show, all I got was a very quiet sound a bit like an old transistor radio. I'd left the shorting plugs in the back of the speaker, and Steve's amps were playing into a short circuit - and the sound was produced by the current in the speaker cables. Turned it off with sweaty palms, took the short off - and the amps worked perfectly.

Anyhow, fast forward to his current position as chief engineer at NAIM. They let him off the leash the same way that I did at Wharfedale - and the Statement pre and power amps was the result.

Now no, they do not publish THD plus noise figures. But I absolutely guarantee that Steve has completely characterised the amps under all possible operating conditions.

If they had published them, would it make any difference to the purchase of a hundred-odd grand's piece of kit? I think not. But I again guarantee that if asked by a potential technically informed purchaser to produce the numbers, I'm sure they would do so.

Craig

Well, that only goes to show that the 'new generation' of audiophiles (audiophools?) have a total disregard (a lack of understanding?) for real life, meaningful, technical facts and figures. Personally, I wouldn't buy an amp that didn't provide a technical specification for that very reason. People who buy hifi only or mainly on the basis of subjective, fanciful, whimsical, 'audiophool' style reviews are asking for all that they get. Ironically, the complaints or negative comeback from such purchasers are often few and far between because of their slavish belief in what they are buying. It's audiophool territory, pure and simple. "This piece of kit is the way forwards, it will enhance my listening experience, it will elevate my status in and amongst audiophile groups and it will make me happy (for a while). That's the malady, that's the symptoms. The cure? there isn't one, leave the patient well alone to be happy amongst their million dollar hifi system until the next big improvement beckons.

[Craig Sawyers]

Originally Posted by Radio Wrangler

A long time ago it became possible to design an amplifier to produce the required power into the requited load, with more bandwidth than anyone can hear and with trivial distortion.

The problem is that not every amplifier is designed this way. Not every one is competently designed. Rocket science isn't involved, you don't need special components stolen from a crashed flying saucer. Some amplifiers are disappointing.

It's probably less important to know exact figures than it is to know that the designer is competent and that the bean counters kept their fingers out.

As a result of the no-Zobel whoopsie, Naim was on my don't touch list. If they do such a thing and not see the downside, what else might they do? After Craig's comments, I'm warming to their later products, but I don't suppose I'm likely to ever see one at that sort of price.

David

The Naim oddities were back in the day that Julian Vereker, the NAIM founder, with self-taught electronics, was still at the helm, and hadn't passed the pearly gates, which he did in 2000 at the too-early age of 54. Since then they have moved on to exceptionally solid engineering principles.

They, like all the very few remaining UK owned companies, are surprisingly small, with a turnover of less than £30m and around 150 staff.

At least Cambridge Audio, after many decades of woe and umpteen insolvencies, is still owned in the UK, by Richer Sounds.

Craig

[Craig Sawyers]

Originally Posted by stevehertz

Well, that only goes to show that the 'new generation' of audiophiles (audiophools?) have a total disregard (a lack of understanding?) for real life, meaningful, technical facts and figures. Personally, I wouldn't buy an amp that didn't provide a technical specification for that very reason. People who buy hifi only or mainly on the basis of subjective, fanciful, whimsical, 'audiophool' style reviews are asking for all that they get. Ironically, the complaints or negative comeback from such purchasers are often few and far between because of their slavish belief in what they are buying. It's audiophool territory, pure and simple. "This piece of kit is the way forwards, it will enhance my listening experience, it will elevate my status in and amongst audiophile groups and it will make me happy (for a while). That's the malady, that's the symptoms. The cure? there isn't one, leave the patient well alone to be happy amongst their million dollar hifi system until the next big improvement beckons.

Well that is an exceptionally cynical perspective.

Let's put it this way. If I were to win the Euromillions, I would by Steve Sell's Statement system in a heartbeat. Not for status, not for slavish belief, not for any audiophool reasons, but because I know that Steve has done an exemplary job of excellence of engineering.

Craig

I can still hear no fault in my little TDA whatsit stereo chip amplifier, the chip has specifications, output (20W or so) and distortion (less than 0.1%) that will do me!

[Craig Sawyers]

You can do very well with chip amplifiers. Here is one overall design that is exceptionally well specified and exemplary performance

https://neurochrome.com/products/modulus-686

I do like the "neutrodyne" alignment of the Zobel inductors, not that it would make any real difference. At least someone thought about it and it is a zero cost "improvement". My simple attempt only uses just one of those 15 pin jobs, the transformer cost more than the chip! The recommended Zobel for it is merrily a resistor and capacitor (10ohms 0.1uF), no inductance.

Driving a pair of Tannoy (Chinese now, awfully good) DC4s sounds great, mind you I like radio plays and the stereo image is very clear (important for a play) probably due to the small size of the 'speakers surface area and the concentric nature of them.

I would (and have) rather spend £300 on 'speakers and £30 on the amplifier/cables etc. than the other way round.

Oops, realised I sound like an audio pragmatist rather than a phool, apologies...

[ajgriff]

The Modulus 686 looks really good but is probably a touch too powerful for most people's needs. I do think that so called 'chipamps' or 'gainclones' combined with a decent Linkwitz-Riley crossover make an excellent basis for an active system especially for DIY builders. No audiophoolery necessary.

Alan

[knobtwiddler]

It's not often that Cambridge and Naim get mentioned in the same paragraph. One markets mains cables costing £500+ The other is owned by someone who's made it his life's work to give people bang for their buck, culminating in hiring patron-saint-of-objectivists, Douglas Self.

A problem that Naim might have, were they to publish figures for this £150K+ amp, is that they would be fighting the laws of physics to better the paper spec of the Benchmark AHB2 amp. The AHB2 (at under a fiftieth of the N's cost) can deliver full power at better THD+N than most analysers can measure. This would reduce Naim into having to justify the product exclusively in terms that cannot be quantified. But wait, they do that anyway! 'Plus ca change' as the French (owners of Naim -) might say,

[Craig Sawyers]

There are a few ways of getting vanishingly small harmonic and intermodulation distortion.

The first is to use a mixture of feedback and feedforward. There was a superb series of articles in Linear Audio on that topology and the performance you can get. It uses a lot of active devices (30+) as compared with a Self Blameless (12), and needs someone with their electronic wits about them to get it right and not build an oscillator.

The Benchmark product uses that topology, and achieves the expected exemplary performance of 3ppm over the audio band. The low weight suggests that they are using a switched mode supply, which is perfectly OK.

Another, now alas defunct one that used the same arragement was the Halcro. That went the additional step of two switched mode supplies. A power factor corrected one, feeding a second one to produce several regulated rails. That produced far less than 1ppm (Typically 0.2ppm) distortion over the audio band up to full power, and I think is the first (or only) high power amplifier to pull that stunt.

Finally there is the latest generation of class D. A good example of what is possible is the Hypex NC400 https://www.diyclassd.com/product/nc400/11 . A few ppm distortion across the audio band.

Craig

[stevehertz]

Originally Posted by Craig Sawyers

Well that is an exceptionally cynical perspective.

Let's put it this way. If I were to win the Euromillions, I would by Steve Sell's Statement system in a heartbeat. Not for status, not for slavish belief, not for any audiophool reasons, but because I know that Steve has done an exemplary job of excellence of engineering.

Craig

Undoubtedly, I am very cynical when it comes to the ways in which many hifi manufacturers and retailers now go about their businesses, making and selling components based on the 'new wave' of hifi ethics and beliefs; audiophoolery. Basically, it's stuff that new people drawn into hifi swallow as being true, when more often than not we're talking about totally nebulous items that capitalise on their lack of knowledge to extract money from them. So the audiophool genre grows and it gathers momentum, and we, the 'feet on the ground' objectifiers are seen as the phools - by them! That's not lost on me, though the difference is, my money is used on stuff that is 'real' using tried and tested techniques (not just hifi) whereas the audiophool is spending thousands of pounds on cables and fanciful upgrade widgets that more often than not do nothing to improve their hifi system. It's all in the mind and it's an atrocious rip off. Yes, I'm cynical!