More than 30W per chanel Class A transistor amps

The electrocompaniet was a disaster -- distortion, overheating, keeps cutting out. So back it goes!

I'm now interested in buying an Accuphase amp, and I've found one which looks as though it could be just the job, an Accuphase P-266. But it could need serious restoration.

I want to ask a favour. I have some images of the insides of the amp here. Could someone look at them and see if there's anything obviously wrong, any obvious red flags?

https://imgur.com/a/FyV3UcK


There's a description of the P-266 here

https://audio-database.com/Accuphase...p/P-266-e.html

On 17/02/2019 11:42 pm, Howard Stone wrote:
> I'm now interested in buying an Accuphase amp, and I've found one which looks as though it could be just the job, an Accuphase P-266. But it could need serious restoration.
>
> I want to ask a favour. I have some images of the insides of the amp here. Could someone look at them and see if there's anything obviously wrong, any obvious red flags?
>
> https://imgur.com/a/FyV3UcK
>
>
> There's a description of the P-266 here
>
> https://audio-database.com/Accuphase...p/P-266-e.html
>

**Two problems that I can see:

1) It is not Class A (though it is claimed to be). In fact, it is not
even remotely close to Class A. Personally, I would avoid any product
where the manufacturer has deliberately lied in the description of the
product. Look at the claimed power output and relate it to the power
consumption. The THEORETICAL efficiency of a push pull Class A amp is
50%. In the real world, the figure will be somewhere between 30% ~ 40%.
Accuphase lied. Liars should cannot be trusted.
2) It uses MOSFETs in a standard Class A/B configuration.

OTOH, Accuphase products are generally quite well built, using quality
parts. Obtaining service data is often challenging (impossible), as can
obtaining some spare parts.

Find an old Krell and rebuild it. MUCH better choice and offers real
Class A muscle. Even better, old Krells don't use MOSFETs and the really
old ones are fan cooled.


--
Trevor Wilson
www.rageaudio.com.au

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You are great help, much appreciated.

On 18/02/2019 11:09 pm, Howard Stone wrote:
> You are great help, much appreciated.
>

**No worries. And do seek out an old Krell (KSA100 would be my choice).
Parts and schematics are readily available for the old fan cooled
models. You'll find lots of people who have rebuilt them describe their
experiences on the net. Properly rebuilt, they are bullet-proof.
Personally, I would avoid the later, convection cooled models. Fan
cooled models are much better and the topology is less complicated.



--
Trevor Wilson
www.rageaudio.com.au

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I've just bought a KSA 50, it was practically given away. It blew its owner's speakers and he just lost confidence with it -- I've shipped it directly to a good engineer in the UK to do a full restoration.

Anyway assuming everything works out, my plan is to feed the source directly into the power amp, with no pre. I only have one source -- a DAC (DPA Bigger Bit) which has an output of 1.96V.

If not I have two spare preamps, a Quad 34 the pre section from my Electrocompaniet ECI-2

Everyone says that I should try it with am Audio Research valve pre -- but how can this possibly be an improvement over no pre at all???

On 4/03/2019 11:21 am, Howard Stone wrote:
> I've just bought a KSA 50, it was practically given away. It blew its owner's speakers and he just lost confidence with it -- I've shipped it directly to a good engineer in the UK to do a full restoration.
>
> Anyway assuming everything works out, my plan is to feed the source directly into the power amp, with no pre. I only have one source -- a DAC (DPA Bigger Bit) which has an output of 1.96V.
>
> If not I have two spare preamps, a Quad 34 the pre section from my Electrocompaniet ECI-2
>
> Everyone says that I should try it with am Audio Research valve pre -- but how can this possibly be an improvement over no pre at all???
>

**"Everyone says"? Not me. ARC preamps are HIGHLY variable in quality.
Some models are excellent (IOW: They introduce almost no colouration
into the sound) and some are highly coloured (distorted). Many listeners
like that kind of distortion. I am not one of those listeners. The
REALLY expensive ARC preamps (REF10, et al) are very good indeed. They
are also cripplingly expensive (for me). Models like the SP7 and SP9 are
(IMO) junk.

I don't know the Electrocompaniet, so I can't comment.
I am not a fan of the Quad 34. It was a pretty uninspiring preamp.

You could use no preamp at all, providing input/output impedances are
suitable and that should provide an excellent result.

Congrats on your purchase. Be prepared to pay reasonable Bucks (or Quid)
to have it serviced. Those old guys are worth the effort.

--
Trevor Wilson
www.rageaudio.com.au

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On Sunday, March 3, 2019 at 7:21:11 PM UTC-5, Howard Stone wrote:

> Everyone says that I should try it with am Audio Research valve pre -- but how can this possibly be an improvement over no pre at all???

It is called "Gain" and "Transient". For the sake of simplicity and discussion, let us agree on three things:

1. Whatever amplifier is in use, it is rated at its full RMS output against a 2V input at 1,000 hz.

2. It is a well-designed device using quality parts and assembled with great care.

3. The speakers in use are also good, well-made and rated at 90 dB @ 1 meter @ 1 watt. And rated at an 'average' of 50 watts.

Some basics: The transient associated with a snare-drum rimshot is approximately 120 dB. The transient associated with the onset of the organ Bombard pipes in the Saint-Saens organ symphony on a well-made recording very nearly, or actually peaks at 30 dB over average.

Most amplifiers are capable of momentary peaks and transients far above their rated RMS. Most speakers can handle transients and peaks far above their 'average' rating.

If a pre-amp has no gain over the original signal source, which is a nominal 2V, the peaks and transients will not be expressed - unless the actual listening level is a minimum of 30 dB below the average.

Pre-amps are awful things, just like democracy. Except for the alternatives..

Peter Wieck
Melrose Part, PA

On Monday, 4 March 2019 12:45:29 UTC, Peter Wieck wrote:
> On Sunday, March 3, 2019 at 7:21:11 PM UTC-5, Howard Stone wrote:
>
> > Everyone says that I should try it with am Audio Research valve pre -- but how can this possibly be an improvement over no pre at all???
>
> It is called "Gain" and "Transient". For the sake of simplicity and discussion, let us agree on three things:
>
> 1. Whatever amplifier is in use, it is rated at its full RMS output against a 2V input at 1,000 hz.
>
> 2. It is a well-designed device using quality parts and assembled with great care.
>
> 3. The speakers in use are also good, well-made and rated at 90 dB @ 1 meter @ 1 watt. And rated at an 'average' of 50 watts.
>
> Some basics: The transient associated with a snare-drum rimshot is approximately 120 dB. The transient associated with the onset of the organ Bombard pipes in the Saint-Saens organ symphony on a well-made recording very nearly, or actually peaks at 30 dB over average.
>
> Most amplifiers are capable of momentary peaks and transients far above their rated RMS. Most speakers can handle transients and peaks far above their 'average' rating.
>
> If a pre-amp has no gain over the original signal source, which is a nominal 2V, the peaks and transients will not be expressed - unless the actual listening level is a minimum of 30 dB below the average.
>
> Pre-amps are awful things, just like democracy. Except for the alternatives.
>
> Peter Wieck
> Melrose Part, PA

Aha, this is an argument for active pre-amps. Passive pre-amps presumably all have no gain.

On Monday, March 4, 2019 at 9:59:57 AM UTC-5, Howard Stone wrote:

> Aha, this is an argument for active pre-amps. Passive pre-amps presumably all have no gain.

Correct. Passive pre-amps are no more than switches.

Peter Wieck
Melrose Park.