Bewitch or kit valve amp? - AVS Forum
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post #1 of 18 Old 04-17-2012, 04:12 AM - Thread Starter
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I have been listening to good hi fi for 30 or more years now, and had my pair of Quad 57s for most of that time. I have had various amps culminating in a Marantz PM4 which is fantastic. I have just refurbished the speakers and they sound so much better. CD player is a Marantz 63 Mk2 Signature. I listen to blues and prog rock almost exclusively.

So, I know the amp is good, but am I being stupid looking for a valve amp? I can't help but look at the Bewitch range. They seem to offering so much on the valve front, but I can't help thinking that the price is kept that low by using cheaper transformers and components. Bearing in mind that I am very adept at building electronics, is my money better spent on one of the current kits? Even then, the finished job would still cost more than the equivalent Bewitch.

Can anyone give me guidance? If I did go for a Bewitch, what level in their range would be right for me? I haven't found anywhere in the UK where I could audition them.
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post #2 of 18 Old 04-17-2012, 07:11 AM
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Quote:
Originally Posted by Ed Howarth View Post

I have been listening to good hi fi for 30 or more years now, and had my pair of Quad 57s for most of that time. I have had various amps culminating in a Marantz PM4 which is fantastic. I have just refurbished the speakers and they sound so much better. CD player is a Marantz 63 Mk2 Signature. I listen to blues and prog rock almost exclusively.

So, I know the amp is good, but am I being stupid looking for a valve amp?

IMO, yes.

Quote:


I can't help but look at the Bewitch range. They seem to offering so much on the valve front, but I can't help thinking that the price is kept that low by using cheaper transformers and components.

Valves when audibly different are non-user-adjustable audible distortion and
noise generators with relatively strongly time-varying performance (degradation due to tubes loosing emission and often shorting out in actual use).

Why would anybody voluntarily subject themselves to this kind of abuse if they are primarily motivated by a desire for the best possible sound quality?

Bearing in mind that I am very adept at building electronics, is my money better spent on one of the current kits? Even then, the finished job would still cost more than the equivalent Bewitch.

Quote:


Can anyone give me guidance? If I did go for a Bewitch, what level in their range would be right for me? I haven't found anywhere in the UK where I could audition them.

If you want to make audible changes in the sound quality of your system, why not just get a good parametric equalizer? On the worst day of your life you can just randomly adjust the knobs and have the different sound de jour that you apparently lust after, with no additional out-of-pocket cost. ;-)
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post #3 of 18 Old 04-17-2012, 09:08 AM
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Personally, I don't think tube amps are the best selection for ESL speakers known for both high capacitance and difficult load.

Additionally, I'd be concerned about the reliability of the kit.
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post #4 of 18 Old 04-17-2012, 05:25 PM
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Quote:
Originally Posted by Swampfox View Post

Personally, I don't think tube amps are the best selection for ESL speakers known for both high capacitance and difficult load.

Additionally, I'd be concerned about the reliability of the kit.

Quad 57's are from the tube era, bro.

http://www.quadesl.org/Amplifiers/AmpList/amplist.html

Have only read one review of a Bewitch amp, the guy liked it but had to mod it right away and felt it was short on bass. That makes me wonder if the Chinese manufacturer skimped on the iron...

I'd pass on it and keep looking, lots of tube goodness out there.
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post #5 of 18 Old 04-17-2012, 08:38 PM
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Quote:
Originally Posted by rntlee View Post

Quad 57's are from the tube era, bro.

http://www.quadesl.org/Amplifiers/AmpList/amplist.html

Have only read one review of a Bewitch amp, the guy liked it but had to mod it right away and felt it was short on bass. That makes me wonder if the Chinese manufacturer skimped on the iron...

I'd pass on it and keep looking, lots of tube goodness out there.

They may be from the tube era, but that doesn't mean a high current, low output impedance solid state amps wouldn't be a better fit. They are a highly capacitive load and dip down to 2 ohms in the upper octave.
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post #6 of 18 Old 04-17-2012, 09:06 PM
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2 ohms impedance is getting quite close to a short, most solid state amps won't tolerate that small a load...at least not for very long.

From the Quad website:

Quote:


Generally valve amps are not upset by an awkward load as presented by the '57, but many solid-state amplifiers quickly give up in a cloud of smoke. I encountered several "trannies" that immediately blew up - some of these items even damaged the delicate Quad speaker before they died. The biggest crap I ever encountered was the BGW series 200 : I connected it to my Quads as the manufacturer had stated in the manual that model 200 was stable into electrostatic speakers - actually it was not ! Within milliseconds the BGW went into oscillation and killed both treble units. It cost me a fortune to repair both the Quads and the amp.

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post #7 of 18 Old 04-18-2012, 06:04 AM
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Quote:
Originally Posted by rntlee View Post

2 ohms impedance is getting quite close to a short, most solid state amps won't tolerate that small a load...at least not for very long.

From the Quad website:

It would certainly need to be a good amp.

Tube amps clearly interact with the speakers with those type of loads. Additionally, tube amps might not short, they will clip when asked to deliver current to very low impedance speakers.
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post #8 of 18 Old 04-18-2012, 06:20 AM
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Quote:
Originally Posted by rntlee View Post

2 ohms impedance is getting quite close to a short, most solid state amps won't tolerate that small a load...at least not for very long.

Quote:
Originally Posted by Quad website View Post

Generally valve amps are not upset by an awkward load as presented by the '57, but many solid-state amplifiers quickly give up in a cloud of smoke. I encountered several "trannies" that immediately blew up - some of these items even damaged the delicate Quad speaker before they died. The biggest crap I ever encountered was the BGW series 200 : I connected it to my Quads as the manufacturer had stated in the manual that model 200 was stable into electrostatic speakers - actually it was not ! Within milliseconds the BGW went into oscillation and killed both treble units. It cost me a fortune to repair both the Quads and the amp.

I don't doubt the truth of the experiences related above. However, if we give it credence today, we presume that there has been no significant progress in SS amp design and construction since the days of the BGW 200, which I would place as 1980s - now over 20 years ago.

From the BGW web site:

Quote:


In July 1974, BGW Systems was chosen by Universal Studios to supply power amplifiers for use in movie theaters worldwide. These amplifiers were an integral part of Universal's Sensurround´┐Ż sound system featured in "Earthquake", "Midway", and "Rollercoaster". During that period, thousands of BGW Models 750 and 750A's were purchased by Universal. And, most are still being used today in Universal Studios' theme parks.

This is the tip of an iceberg of obsolete facts that bedevil modern audiophilia. In past days, every amplifier did indeed audibly change sound quality, and even the best DACs had audible flaws. That was then and this is now!


The days of SS power amps that won't tolerate 2 ohm loads is long gone, although there are no doubt occasional throw backs.
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post #9 of 18 Old 04-18-2012, 11:41 AM
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Well, you could test it out for us arnyk. Just wire some 4 ohm speakers in parallel and hook them up to your favorite ss amp. I'll do the same with a tube amp I have here and we can start a pool on how long each will operate at moderate power.

You gotta disable the protection circuit though, or it wouldn't be a fair test.

Spoiler: Arnyk will be looking for a new amp soon, if anyone has one for sale...
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post #10 of 18 Old 04-18-2012, 12:12 PM
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Bollocks. There are plenty of SS amps that will drive 2R reliably for extended periods. The 2R load of the Quads is at HF where there is little energy anyway.
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post #11 of 18 Old 04-18-2012, 01:49 PM
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Quote:
Originally Posted by rntlee View Post

Well, you could test it out for us arnyk. Just wire some 4 ohm speakers in parallel and hook them up to your favorite ss amp.

I do it all the time, and it is a common procedure in professional audio.

Quote:


I'll do the same with a tube amp I have here and we can start a pool on how long each will operate at moderate power.

The tubes in the tubed amp burning out will end the test.

Quote:


You gotta disable the protection circuit though, or it wouldn't be a fair test.

Nonsense.

Quote:


Spoiler: Arnyk will be looking for a new amp soon, if anyone has one for sale...

nonsense.

The reason why: The one thing that every manufacturer fears the most is returned product. If hooking up a too-low impedance load to an amp damaged it, the product's warranty expenses would put the manufacturer out of speaker.
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post #12 of 18 Old 04-18-2012, 03:16 PM
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I don't have an issue with tubes, per se, if the OP really wants tubes for whatever reason. It's his choice and he can look into kits or whatever manufacturer he wants. Tube amps are expensive to buy, expensive to maintain, and unreliable.
Yet, for others to advice him that SS amps are not suited to the task because they go into oscillation and burn out the amps and speakers based experience from 25 or 30 years ago is a bit of a stretch. Most modern high current designs can handle electrostatics and are no longer prone to oscillation or problems with reflected power. You can email or call the manufacturer if you have concerns.

You can even read what Roger Sanders
says about amps and ESL speakers. He has quite a bit of audiophile embellishment, and he does sell amps, but he does not recommend tube amps for his speakers and articulates why.
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post #13 of 18 Old 04-18-2012, 03:40 PM
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Originally Posted by A9X-308 View Post

Bollocks. There are plenty of SS amps that will drive 2R reliably for extended periods.

Of course there are...that's why you guys have named so many off.
Btw, I said MOST SS AMPS!

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The 2R load of the Quads is at HF where there is little energy anyway.


It has nothing to do with the amount of energy and everything to do with oscillation, bro.
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post #14 of 18 Old 04-18-2012, 03:44 PM
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Quote:
Originally Posted by arnyk View Post

I do it all the time, and it is a common procedure in professional audio.

I'm calling shens here. You do it all the time? Heh


Quote:
Originally Posted by arnyk View Post

The tubes in the tubed amp burning out will end the test.

That right there tells me that I'm done here, I don't waste my time bickering on forums with the resident psuedo-experts.
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post #15 of 18 Old 04-18-2012, 04:17 PM
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Quote:
Originally Posted by rntlee View Post

Of course there are...that's why you guys have named so many off.
Btw, I said MOST SS AMPS!

You're the guy making adverse claims, why not back them up with some makes and models?

My problem is that I can't think of any modern SS amps that do as you say.

Example of amps that don't fry on the spot just because they are seeing a 2 ohm load?

Anything made by Bryston, Crown, Parasound in the past 25 years, just to name a few.
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post #16 of 18 Old 04-18-2012, 08:05 PM
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Quote:
Originally Posted by arnyk View Post

You're the guy making adverse claims, why not back them up with some makes and models?

My problem is that I can't think of any modern SS amps that do as you say.

Example of amps that don't fry on the spot just because they are seeing a 2 ohm load?

Anything made by Bryston, Crown, Parasound in the past 25 years, just to name a few.

Bryston is known to be able to drive Quads.
Anything by Parasound designed by John Curl should be able to power Quads, he's been designing high power amps for esoteric speakers forever and knows the issues.
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post #17 of 18 Old 04-19-2012, 01:48 AM
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Quote:
Originally Posted by rntlee View Post

It has nothing to do with the amount of energy and everything to do with oscillation, bro.

Instability into Quads is not a given - I even drove mine (I had 2 pairs at one stage) with NAP160, hardly the most stable design ever.

Otherwise ditto SF's post a few back.
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post #18 of 18 Old 04-19-2012, 05:04 AM
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That right there tells me that I'm done here,

So much for what lawyers call "An unfortunate sequence of statements"

Why is it that some tube advocates have to resort to fictional claims?
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