[-Richard-]

I am new to this area on Audiocircle... but I wonder if I can ask the SS community for help finding the names and information for a new breed of SS amplifiers from England and Japan that use just one transistor per channel. What I have heard is that they have a lovely mid-range... very much like tubes... but the extension and control that is unique to SS amplifier designs.

Has anywhere any information about them?

Thank you for your kind attention. With Warmest Regards ~ Richard

[lonewolfny42]

Here you go Richard.... (Denmark)

http://www.gamutaudio.com/products/details.asp?id=41

The GamuT Solution
To achieve the purity and clarity that our clients demand, we have come up with a very simple and very effective solution. We only use one transistor per channel, but a very large one indeed. Using a single massive transistor allows us to tune them to sonic perfection and lay out a much simpler signal path. The transistors we use are massively expensive, but we think it's worth it, and you might agree when you hear our amplifiers perform.
   

[-Richard-]

Hi lonewolfny ~

It seems as if it has been years since we shared information with each other lonewolfny... much too long. You have always been a remarkably supportive friend for everyone who needs encouragement and information in our Audiocircle community... for all of your help over the years... and for this information as well... thanks so much!!!!!

I am in touch with a speaker designer that likes these amps for his speakers very much. I hope to have much more to write about him and his wonderful designs very soon. Meanwhile I am most interested in this relatively new approach that seems promising.

Again, thanks lonewolfny... I deeply appreciate your help.

With Warmest Regards ~ Richard

[srb]

Here you go Richard.... (Denmark)

http://www.gamutaudio.com/products/details.asp?id=41

And the RS380M monoblocks are only $140,000 a pair!
 
Steve

[-Richard-]

Yes Steve, I just picked that up... $140,000! We need designers who are willing to apply this technology on the cheap. Thanks for sharing that information. My understanding is that there are several designers in Japan and England just getting started with this approach... but so far I have not been able to find out much.

Warmest Regards ~ Richard

[JohnR]

They use the phrase "single Mos-Fet output stage" - it seems it's only the output stage that uses a single transistor, so still a voltage amplification and driver stages needed, surely. Perhaps someone more familiar with the details of solid state power amplifier design could comment.

[Niteshade]

Power FET's typically have low gain. A driver stage which can increase the gain is necessary.

Note: 300B's are low gain as well and require a good driver circuit to help them along.

A better design would be to parallel at least three or four FET's together to increase gain, lower output impedance and allow for a more efficient driver stage.

[Johnny2Bad]

An amplifier stage that uses just one device per channel (transistor, vacuum tube) is simply a Class A amplifier.

[nonoise]

The old Audiolab 8000A had only one transistor per channel. When Tony Manasian demos his Tonian Lab speakers, the Audiolab is what he uses. And it sounds beautiful. He says the signal gets in and out so quickly and that is what makes it sound so good. I don't think that integrated was a Class A design but that is how it was built.  I asked if anything made after it would do as well and he told me no: they weren't made the same since so don't bother getting one unless it was the 'A' model.
It wasn't until I chanced upon the first version of the Burson intergrated that the sound bettered the Audiolab. It uses more than one transistor per channel so go figure. I guess its all in the implementation and the quality of the parts.
Good luck in your search.

[planet10]

An amplifier stage that uses just one device per channel (transistor, vacuum tube) is simply a Class A amplifier.

A single ended Class A amplifier. A Class A push-pull amplifier requires 2 devices.

dave

[Johnny2Bad]

A single ended Class A amplifier. A Class A push-pull amplifier requires 2 devices.


dave

Perhaps. There is some debate as to whether an amp that operates even partly in push-pull is Class A or AB. But, I will grant you that some manufacturers do describe some such amps as Class A.

You can also have a push-pull amp that is biased to Class A at all operating conditions; that would clearly be a Class A design.

But, regarding the OP's post, if there is one output device, there is no debate; it must be Class A.

[planet10]

if there is one output device, there is no debate; it must be Class A.

For an audio amplifier, but in the general case it is not true. For example a single device can run in Class C ... often used in radio transmission.

dave

[Johnny2Bad]

For an audio amplifier, but in the general case it is not true. For example a single device can run in Class C ... often used in radio transmission.


dave

Really? It's been my understanding that Class C is essentially similar to Class B but that the transistors don't conduct for the full half wave (or, put another way, neither transistor of the pair is conducting for a significant portion of the wave), creating significant harmonic distortion, which is not really a problem in RF since you have to filter to a limited frequency range anyway.


A lot of megaphones use Class C amps, by the way, so it's not true they never are used for audio. I have to admit, though ... I thought I'd never see anyone post suggesting the OP could be referring to a Class C amp here in AudioCircle. Perhaps I should be careful in the digital switching amp forums to make sure I don't inadvertently miss the possibility someone is talking Class E or F.


The idea of Class C as I understand it is to increase the efficiency beyond Class B, which would seem to make single ended Class C a very questionable design choice. Do you have an example I could look at? All the RF Class C amps I've ever seen use at least two devices, the idea is to get maximum power at maximum efficiency.

[Wind Chaser]

Richard,

Many years ago, Nelson Pass published some designs around one transistor per channel.  I think it was called a Zen amplifier, but you'd have to Google it.  IIRC the Aleph 3 had just one MOSFET per channel or was it one gain stage??  I should know this as I did own one but that was many years ago.

John