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Dr Bunsen Honeydew
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Ask a designer

Unread post by Dr Bunsen Honeydew »

Recent events have shown that perhaps I expect hi-fi enthusiasts to have more knowledge or even common sense than I give them credit for.

So any questions to do with specs, amp design, cable design, speaker design, hi-fi myths or hi-fi usage or anything else industry related and I will answer in the simplest terms I can.

Though you will get *my opinion* on things subjective, but factual on things of an objective nature.

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slinger
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EUROPEAN_UNION

Re: Ask a designer

Unread post by slinger »

I suppose some sort of reasonable analogy would be that if I sold you a car I'd expect you to know how to put petrol (or diesel) in it, but maybe wouldn't expect you to know how to change the head gasket, or even a fuse, without consulting a manual?
Amps - NVA P50, AP30, A40, Stanislav Palo Tube Headphone Amp BB 85
Speakers - Monitor Audio Silver RX2
Cables - NVA LS1+LS3, SSC, Gotham S/PDIF, IBRA Optical
Digital - NAD C516BEE, SONY ST-SDB900 DAB TUNER, TEAC UD-H01 DAC
Analogue - Pro-Ject Debut Carbon Esprit SB, Graham Slee Gram Amp 2 Phono
Cans - Grado SR80, ATH-M50X

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howardc1951
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Re: Ask a designer

Unread post by howardc1951 »

As a matter of interest can you describe the symptoms of instability and also what damage it causes to the amp when it happens please? And also what else can cause it other than increasing the capacitance of the speaker cables.
Thanks

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Re: Ask a designer

Unread post by Dr Bunsen Honeydew »

Instability is ringing http://en.wikipedia.org/wiki/Ringing_(signal) and http://en.wikipedia.org/wiki/Ringing_artifacts

It occures at high frequencies when the amplifier is required to drive a reactive load, it shows up on musical notes with a strong percussive element and very high frequencies such as a piano key being struck. It sound like a halo of distortion around the note. Two ways to cure it, 1/ fit a zobel network (filter) http://en.wikipedia.org/wiki/Zobel_network in the output stage of the amplifier. 2/ remove the reactive element from the load which is normally unusual load loudspeaker cable.

Normally it just ruins the music but when it is gross as in Litz or Goertz cable it can cause the amplifier to overheat and self destruct. A zobel network being a filter ruins the music as well so should be avoided if possible. My decision was not to have it and insist on cable that didn't cause the problem.

Go to http://www.nene-valley-audio.com/ link to interview and the first page has the explanation.

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Re: Ask a designer

Unread post by Dr Bunsen Honeydew »

Does that answer it Howard or have you a follow up.

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Re: Ask a designer

Unread post by howardc1951 »

Thanks a lot Richard. Just been reading the interview (now that I've actually been able to get on the computer). Very interesting read. Years ago I experimented with making up some speaker cables including some that were plaited. On initial listening they were very clear on vocals until someone who was listening pointed out that the bass frequencies had disappeared.

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Re: Ask a designer

Unread post by Dr Bunsen Honeydew »

Interview - 1994 I think, it was in Taiwan. I loved Taiwan fabulous tea and local food (night markets mmmm). Nice people, we think all Chinese are Chinese. Far from it, Cantonese are mad, Beijing are snobs and rude, Shanghai is just business. Taiwan they have time to be friends and they are not just after your money - real traditional China, not that Mao destroyed apology across the straights.

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Re: Ask a designer

Unread post by Dr Bunsen Honeydew »

Come on take advantage. If I can avoid idiocy like that involved with r100 then it is well worth it.

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Re: Ask a designer

Unread post by Andrew »

Funnily enough, you already answered my next question about interconnects and speaker cable lengths.

On a (slightly) related note, I've always been interested in balanced operation. I have often hankered after amps that offer this but was put off when I read comments about the balanced version of the KSA80. A techie said you had to design an amp from scratch to benefit from balanced operation and Krell had offered it as a marketing gimmick to satisfy the hype stirred up by reviewers.

My interest in balanced operation comes largely from a desire to get the power amp(s) between the speakers in order to shorten speaker leads. I've heard that balanced pre/powers don't suffer as much signal loss with long cable lengths. I've no idea about the truth of any of this, so any light you can shed will be great thanks.

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Re: Ask a designer

Unread post by Dr Bunsen Honeydew »

It is a perfect case of hi-fi bullshit. The marketing men are always looking for angles and they often go off to the pro industry to find something they can spin some sort of yarn around. Well the two most prominent of these are active speakers and balanced line / operation.

Balanced line advantage - 1/ in a PA system you can run hundreds of yards of cable between desks and stacks without noise pick-up 2/ in a studio or club where there is loads of gear and effects all in close proximity it again removes hum and RF pick-up.

Balanced line disadvantage - apart from a phono cartridge nothing is naturally balanced, it is all single ended, So in order to be balanced you have to do something, superimpose something in the way of the music. This is either an active balancing circuit based on op-amps, or a balun (balancing transformer). And you have to have this at both ends as speakers are single ended. All of this gumf gets in the way of the music.

Quite simply it is marketing bullshit. If you have enormous US style living rooms with 30 ft long interconnects then you could make a case, but the case is marginal. In normal domestic situations it is both unnecessary and musically damaging. It is the usual exploits of rip-off marketing people looking for new ways to get your money - full stop!
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