What kinds of ideas have been used in the past to make so called "hi quality" sounding amplifiers in stereo systems?
I'm thinking of things like the Carver amplifiers of the 80s. Are there any odd ideas that people have tried in the past?
**You're kidding, right? The list is very long. **Carver actually used two separate and equally bad technologies to build his lightweight products. They were:
As for your question, yes. The list of odd ideas is simply enormous.
-- Trevor Wilson www.rageaudio.com.au
Try looking at a copy of Audio Electronics by John Linsley Hood at your local library. The Borbely cascode amp was fairly weird.
-- Eiron I have no spirit to play with you; your dearth of judgment renders you tedious - Ben Jonson.
One of the strangest was called "tubes". Something about electron flow through a vacuum.
In the category of tubes there is a really odd one called "SET" or Single-Ended Triode. Back in the late 1920s it was found that using push-pull output stages provided a large number of worthwhile benefits, but that apparently hasn't stopped some people from trying to roll the clock back to the days of Prohibition.
How about SS amps with no loop feedback? This creates a number of problems including a near-total lack of power supply ripple rejection.
Lots of them. Another oddity involved attempts to implement SET using FETs.
**On the contrary, the system works quite well. Just not the Carver did it. Think about their system. Focus on the transient abilities of the Carver system.
-- Trevor Wilson www.rageaudio.com.au
Like a tube amp of multi-parallel triodes and no OPT?
Or multi-sectional cross-wound transformers?
Or bad ideas like:
The 'ear shaped speaker'... talk about convoluted logic...
The 'reflected Bose' speakers.
There is a long list..
You wanted exotic.
Check out the Zen-lightenment from
Now thats pretty cool1 An amp you can read by!
If you download the circuit diagram and you know a bit about electronics you will scratch your head even more. It's a class A design with bare minimal components, EXTREMELY power hungry and inefficient, has a very high distortion statistic (which is disclosed in a graph but not ever mentioned in the text) but all in all if it gets people into electronics, I like it.
Looks like a lot of hobbyists have made it. Some of the box designs are out of this world. One guy has made two monoblocks. Each as big as a floor standing subwoofer. Due to the inefficient design of the amp, his listening room would be similar to a room with a 2000W electric heater while running them. Not just at full volume, but all the time!!
(snip)
That must be why you see so many Marantz, Yamaha, Hitachi & NAD powered theatre & stadium concert PA rigs, wheras the minnows of the PA world like Crown, QSC, BSS,LabGruppen etc have no problem with rail switching and rail riding technology :-) M
Rail switching is justified by economic considerations. Home audio amps as a rule are too low-powered for rail switching to be cost-justified.
**Utter, banal nonsense. NAD, Marantz, Yamaha, Carver, Hitachi and many others have used rail switchers in home audio products, because it allows them to inflate transient power abilities, at very low cost. The first, highly successful, amp I saw was the NAD 2200 power amp. It was rated at 100 Watts continuous, with 400 Watt transient ability. So successful was it, that it spawned a line of smaller and larger amps from NAD. Of course, it sounded like crap and had a bad reputation for destroying speakers, but it looked great on paper and the reviewers fell over themselves to rave about it. Consequently, customers fell over themselves to buy them. NAD later dispensed with the technology, after losing significant sales to competitive products (which didn't use rail switching technology).
-- Trevor Wilson www.rageaudio.com.au
**Of course. Such amps are rarely used in critical listening situations. Power output, cost and size and the over-riding factors.
-- Trevor Wilson www.rageaudio.com.au
The feedthrough from the rail switching into the audio path is actually minute.
I've designed several rail switching amps for SR use. As Arny says though, there is considerable extra complexity in the bits so I wouldn't use the method much below the 400-500 wpc category.
Graham
there
It makes sense even in smallish amps where heat disposal is an issue, ie in pg 9 of :
**Perhaps. That is not the major part of the problem. Examine the curves of the output devices. Look at the difference in characteristics with different VCE applied. **You may not. All the companies I quoted did use them in lower powered amps. NAD have used rail switchers in amps with continuous power outputs as low as 30 Watts.
-- Trevor Wilson www.rageaudio.com.au
A question, Trevor. If the reviewers praised the product, and customers bought it en masse, how did NAD lose "significant sales to competitive products"? It sounds as though you were the only one who noticed it sounded like crap.
**You need to understand how the retail world operates. In reality, the number of people who actually listen to products, before purchase, is incredibly tiny. Almost all purchase based on the following:
I would estimate that the number of people who actually do a good, hard listen to a product, BEFORE purchase, at around 0.1%. Or less. Bribery in the audio business is pretty much ingrained (though not in Australia, AFAIK). Reviews are bought and sold in the US and the UK. Before you ask: I have dealt with US, UK and Australian reviewers. No Australian reviewer has asked for 'consideration' for a review. SOME US and UK based reviewers have spelt out, in no uncertain terms, how much a good review will cost. I cannot say if that is a function of the publication, or just corrupt reviewers. Either way, I don't trust any of them. Except Scot Markwell. He seemed to be honest and straightforward.
NAD had (justifiably) acquired an excellent reputation for budget, 'high end' sound quality (my favourite was the brilliant 3120). Albeit, with rather dodgy constrution and suspect component choice, thanks to the manufacturing company - Fullet. Sometime around 1984-5 NAD moved production away from Fullet and released the NAD 2200 power amp. As an NAD dealer, at the time, I ordered them for my store. I was immediately struck by three things, when I listened to the amp:
Based on the above, it is easy to see how, with a good review, the NAD 2200 would gather significant sales. After all, few people actually took the time to listen to the thing. The market place is a funny thing. Like most things, there is a time lag, between cause and effect. Yamaha, for instance, built very good amplifiers, back in the 1970s. Quality plummetted in the 1980s, but their sales continued rising, during the 1980s, due to the high quality of their products produced a decade earlier. Marantz is another company which built very good products in the 1960s and pretty decent products during the 1970s. Late in the 1970s, my boss at Marantz called me into the office. He explained that Marantz was about to embark on a new style of constrution called 'value engineering'. This sounded exciting. The reality was somewat different. Products produced by Marantz in the late 1970s were very poorly constructed, using cheaper parts, than the equipment I was accounstmed to. Nevertheless, sales increased. Largely due to the previously excellent reputation and the more contemporary styled front panels. IOW: Outside they looked great, inside was crap.
[ASIDE]: I sold a 2200 to a client who was using a pair of KEF 104.2 speakers. Although I had sold lots of KEF 104.2 speakers, I had only sold one 2200/104.2 combination. Some time later, the customer brought back the KEFs complaing that they had no HF. They didn't. Both (ferro-fluid cooled) tweeters were fried. This was unheard of. The KEF 104.2 tweeters are very tough. I sent them back to the distributors (Fred A Falk) for under warranty repair. They rejected the warranty claim, suggesting that the amplifier was at fault. I replied that the amplifier was an NAD 2200 (which Falk also imported). Silence. "OK, we'll repair them free of charge." Apparently, the NAD 2200 has/had an appalling reputation for destroying tweeters. Here's my theory:Customer turns amplifier up to the point of clipping (400 Watts). Then allows the amp to run for a period of time at high levels. The Power Envelope circuits have a time/energy circuit, which prevent damge (to the amp), which shuts off the high Voltage supply, after a period of time. Thus, instead of mild clipping, the amplifier reverts to massive clipping, thus allowing huge levels of high order harmonics to destroy HF drivers. The listener, whose ears are suffereing from continuous high level audio, cannot hear the massive clipping and the tweeters are destroyed.
It sounds as though you were the only one who
**I very much doubt that. I am pretty certain other people actually listened to the stuff too.-- Trevor Wilson www.rageaudio.com.au
I don't know the situation in Oz, but in Europe, Crown is often found in broadcast and recording studios.
Iain
By pointing out the 400 watt capabilities of these amps, you supported my claim. Thank you very much, Trevor.
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