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Old 12th December 2005, 06:59 PM   #1
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Default Carver Magnetic Field Power Amp -whazzit????

I don't know 'what' this gizmo is so I put it here. Can anyone explain what a Bob Carver Magnetic Firled Power Amplifier is? I have wondered about this for long enough. There is a pair on ebay now here. < http://cgi.ebay.com/Pair-Bob-Carver-...QQcmdZViewItem >

With a name like that I have visions of a saturable reactor being used as the amplifying device. Am I correct?
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Old 12th December 2005, 07:35 PM   #2
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Hi There,

I've worked on a few of these and I've observed the following:

1) Magnetic Field Power Amp = a fancy (maybe even copyrited) name just to stand out among other amps and dazzle (baffle) the uninformed consumer.

2) The only thing related to a magetic field is the use of a TRIAC plus additional circuitry to modulate the primary of the power transformer to limit power/secondary voltage. It doesn't appear to be very well regulated and only seems to "stiffen" the AC line under heavy loads. Not real fancy, not real effective, and can be very noisy due to the low frequency AC lines and spikes caused by high voltage switching.

3) All Carvers I've seen run 'Class G' (rail switching) circuitry in their output stage. They run low/med/high Vcc rails with the 'Class A' drivers running on the highest rails and the additional output devices connected to the higher rails by fast recovery diodes. The entire output stage is controlled by a single op-amp through global feedback. This gives the benifit of lower idle power thus the need for smaller heatsinks, along with high peak-power. The best example of this is their famous little cube amp rated at 200WPC with virtually no heatsink.

Like so much in this world, when you hear exotic names and fantastic claims, think marketing and sales hype, not NASA.
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Old 12th December 2005, 08:27 PM   #3
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Hi Rob,
I'm "Mr. Carver" too. My shop was factory Canadian warranty.

Carver amps use a "mag coil" for the input power control. Normally three tiered supplies for the output section. Some class G, some H. It's a very light efficient amplifier that will deliver devastating amounts of power.

If you want to get these, we are semi close and I can help you out with any problems you may run into. There are a couple threads on Carver amps here somewhere.

-Chris

Edit: Think Nasa, it's valid.
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Old 13th December 2005, 12:51 AM   #4
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Thanx for the replies guys! Very deceptive marketing name then. Thanx for the offer Chris but I think I'll stick with my 'vacuum tube transfer function programmed' vacuum tube amplifiers.

'vacuum tube transfer function programmed', That's what the seller claimed as though he was just passing on hype from the Carver literature about the product he is re-selling. Geeze what a bunch of c r a p. It is exactly that sort of thing why I now pronounce Bonus as 'BOGUS'.

I'm not making judgement on the amplifier itself of which I have no experience and which Chris spoke well of, just the marketing of it.
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Old 13th December 2005, 01:30 AM   #5
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Hi Rob,
The marketing hype that went with this stuff drove me crazy! That part is cr*p for sure. I have to admit I was a bit surprised by your interest. They are good amps for what they were designed for. Tube amps they ain't.

TFM=Tube transfer Function Modified. There is an added resistance to reduce the damping factor. I don't know of any other changes that may or may not be present.

-Chris
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Old 13th December 2005, 06:13 AM   #6
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Quote:
Originally posted by anatech
Hi Rob,
I have to admit I was a bit surprised by your interest. They are good amps for what they were designed for. Tube amps they ain't.

-Chris

I had no intention of buying, I love my tube amps and highly efficient, very low distortion full range speakers.. The latest Carver auction I spotted just reminded me that I was curious about what they were as I had thought about it ever since I'd heard the hype (it turns out) name and really did think it was some clever applicatiion of a saturable reactor as a audio power amp. I mean with a name like that, what else could it be right?
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Old 13th December 2005, 06:16 AM   #7
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This amp is horrible s...
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Old 13th December 2005, 11:58 AM   #8
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Hi Upupa Epops,
You were going to say sand, right?

Bob Carver always had a way with advertising. I won't defend that because I found it embarrassing (being the national service center and all). But his engineering was good. He set out to prove a concept and did. The silly TFM came from those famous tests with that magazine.

Having said that, his later amps didn't sound bad, not like the M1.0t. Still there were all those op amps!! Somehow, though all of that, there were much worse sounding amplifiers on the market. His delivered silly power and seldom damaged a speaker when they failed. Now that's an engineering feat!

Would I own one long term - no. Although the Lightstar wasn't bad.

The transformer wasn't a saturable reactor per se, it wasn't used that way. There was no capacitor involved. I've never bothered to sit down and figure out exactly what it was. That was yet another terminology fight. Didn't need or want that.

-Chris
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Old 13th December 2005, 12:34 PM   #9
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Chris, BC is probably good engineer, but much more better bussinesman... His machines are tailed-made for american market...No glory parametres, but giant power...Look at measured parametres and somewhere listen it ...You wil know, whatabout I'm talking
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Old 13th December 2005, 12:52 PM   #10
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Hi Upupa,
Yes, I agree. That's basically what I said. I listened to them for years. They got better, but not good to my standards. I listen to a Marantz 300DC and an Eico HF-87a. I am looking forward to building the SymAsym when I can get the boards made.

I've been very lucky to have been able to take home almost every decent amplifier made over the course of 20 years or so. However, in Europe you have an advantage over us in North America. Your industry is rich in two channel audio. Ours is an underground secretive kind of thing. Only a few two channel brands. Tube is even more a rare thing. Most of our good older tube product has been bought and taken to the Orient.

Curious, Upupa, have you listened to the Cyrus product and if so, what do you think? I am referring to the new Cyrus Power.

-Chris
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