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class A/B power amp suggestions

B

bottleneck

pfm Member
Hi,
I'd like a little help putting a shortlist together. I dont want this in the classifieds, as at the moment I'm shortlist forming rather than anything else.


Looking for a used / ex-dem class A/B power amp.
Here's the criteria
150w+ into 8 ohm.
Class A/B , or Class A for first few watts, then class A/B.
No valves.
Absolutely no Class D under any circumstances no no no no no. no.
Also, no Switch mode power supplies. I like a capacitor bank for whopping trouser flapping transients.
Sound: Big Fat and Juicy please. Not too harsh sounding for horns if I ever go that way.
Age: Ideally less than 10 years. I don't want to buy a problem/antique


Budget - £2k, maybe £2.5k.
What would you get ?
Any ideas?
I'm a bit out of touch, so looking for some suggestions.

I've seen an audionet Amp1 v2 in budget, but don't know how well it fits the ''big fat and juicy'' part, having never heard one.

Open to you gents?
Thx!
 
Fat and juicy being relative terms when discussing solid state, Nelson Pass always does a great job getting that elusive tube like fullness out of his solid state designs.If they are available where you live, that’s where I would start. Pass Labs are superb sounding bullet-proof amplifiers. The company is also great to deal with.

A used X150.8, X250.8, Int 250, Int 150, or earlier .5 versions would all sound great.
 
Another VERY odd post/question.
Personally I'd want what I thought sounded best at my budget and sod how it achieved that. But hey...………………...
 
As they say "a little learning is a dangerous thing".

A class AB amp operates in class A and then switches to class B when you need more welly. Now amps are designed differently believe it or not so you might have an amp rated at 150W that operates in class A for say up to 1W or another similar one (but more expensive) but it operates up to 10W in class A. Guess which one probably gives the better performance?

Horns are a different kettle of fish as they are very sensitive and a 150W amp may be too noisy with such speakers. Here a quality 5 or 10W class A amp would be more than enough and a lot quieter.

Age is not so important than build quality. Amps built down to a price will need servicing often and the electrolytics may fail sooner as they are operated at too high a temperature and too close to their limits. My amps (they weigh in at 42Kg each) are 18 years old and there is no sign of hiss nor hum and run cool due to large heat sinks and enclosure. And against the rather vocal advice of a certain pfm member these amps are left switched on 24*7 as they were designed. They do however have a standby function that removes the drive to the output devices - all 20 per channel........

One last thing an amp should be selected to suit the speakers and not the other way around. Amps and speakers are horses for courses.

Cheers,

DV
 
Darth Vader said:
As they say "a little learning is a dangerous thing".

A class AB amp operates in class A and then switches to class B when you need more welly. Now amps are designed differently believe it or not so you might have an amp rated at 150W that operates in class A for say up to 1W or another similar one (but more expensive) but it operates up to 10W in class A. Guess which one probably gives the better performance?

Horns are a different kettle of fish as they are very sensitive and a 150W amp may be too noisy with such speakers. Here a quality 5 or 10W class A amp would be more than enough and a lot quieter.

Age is not so important than build quality. Amps built down to a price will need servicing often and the electrolytics may fail sooner as they are operated at too high a temperature and too close to their limits. My amps (they weigh in at 42Kg each) are 18 years old and there is no sign of hiss nor hum and run cool due to large heat sinks and enclosure. And against the rather vocal advice of a certain pfm member these amps are left switched on 24*7 as they were designed. They do however have a standby function that removes the drive to the output devices - all 20 per channel........

One last thing an amp should be selected to suit the speakers and not the other way around. Amps and speakers are horses for courses.

Cheers,

DV
Click to expand...

And your 42 kg amps are........(drum roll)............
 
I would add Coda power amps to the Pass suggestion above.
I believe that the two companies, along with Threshold, share some influential people in their origins.
My Coda amp certainly hits all of your criteria above in my system.
 
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It's odd that the criteria you have set are totally unrelated to the qualities you are looking for. If you'd said 'must be painted red as I love trouser flapping bass' it would make just as much sense.

But if you want a big old school AB amp, then i've no problem with that! There are so many options it's really very hard to know where to start. If you want reliability and somewhat 'boring but does what it says on the tin' i'd look at Bryston and Meridian as very good starting points, and sensibly priced second hand.
 
Cesare said:
It's odd that the criteria you have set are totally unrelated to the qualities you are looking for. If you'd said 'must be painted red as I love trouser flapping bass' it would make just as much sense.

But if you want a big old school AB amp, then i've no problem with that! There are so many options it's really very hard to know where to start. If you want reliability and somewhat 'boring but does what it says on the tin' i'd look at Bryston and Meridian as very good starting points, and sensibly priced second hand.
Click to expand...
If you want red, and bass, then, ahem, may I draw your attention to the Albarries in the classifieds... ;)
 
fegs said:
Just out of interest, why no Class D?
Click to expand...

No Class D - I have ''highly regarded'' Class D monoblocks now, and really don't like them.
No valve - mixture of little kids and replacement cost of tubes on high power valve amps. I also had one burst into flames infront of me (and som PFM members) about 10 years ago. Sideshowbob might remember that spectacle. At least we got to cook some marshmallows.

A few others I'm very tempted by, and general extra info@

Meridian 557 - so cheap, but it's over 25 years old now. I'm not looking for something that old. Some people say it's a bit 'dark sounding' , but it's more the age, and the fact I have more budget.
Electrocompaniet has made the short list. I have heard they (electrically) have problems with ... (impedence?) of either certain cabling or partnering equipment. Trying to dig into that, as I've enjoyed the sound of every amp I've heard by them. Right up my street.
Really, a 250w Electrocompaniet, and the Audionet are the best I can see in budget right now.
Pass? - I've had a really good search. Cheapest '150' I've seen is £3k. It's over my ideal budget. Love the sound of Pass (and Mcintosh, and Audio Research)
What's all this about horns? - the kind of horns I might eventually get like getting goosed with decent power - like big old JBLs. We're not talking flea-watt into a lowther (although that sounds great, not disparaging)
Other kit: Ayre K1 preamp, Revel Studio Mk1.
What about an Ayre power amp? - their smallest units are a bit low on power, and the big ones cost too much. Bought the K1 just because it sounds great.
 
NB I read this:

"If you think of your preamp as a source, and your power amp as a load, then you may consider that maximum power transfer can occur when the output impedance of the preamp matches the input impedance of the power amp. However, in high fidelity audio, it is typically considered optimum to have a source with low impedance connected to a load with high impedance. In that case, the power that can pass through the connection is limited by the higher impedance (so power transfer is not maximum), but the electrical voltage transfer is higher and less prone to corruption than if the impedances had been matched.

When matching preamps to power amps, a general rule of thumb is for the load (amp) input impedance to be at least 10 times higher than the source (preamp) output impedance to provide a suitably flat frequency response. Many prefer using a minimum ratio closer to 20 to 1, or having an amp with input impedance 20 times or more greater than the preamp output impedance."


K1 specifications are here: https://www.stereophile.com/content/ayre-acoustics-k-1-preamplifier-measurements

If anyone can help me understand power amp matching, that would help. Ive generally ignored this factor, but since some people reading this will know the answer I wanted to take advantage of their knowledge. So thanks in adcvance.

NB electrocompaniet:
Output Impedance (20 Hz - 20 kHz) < 0,008 ohm
XLR (balanced) input impedance 110 kohm
Input sensitivity for rated output 1 V
Max. peak current > 100 A
THD (measured at 1 kHz
half power, 8 W) < 0,001 %
THD (measured at 1 kHz
-1 dB, 8 W) < 0,001 %

Audionet:
Damping factor > 1000 @10 kHz > 4000 @ 500 Hz Intermodulation < -110 dB SMPTE 100 Hz : 20 kHz, 4:1, 50 W/4 Ohm THD+N < -102 dB @1 kHz (35 Watt / 2 Ohm) Harmonic distortion k2 typ. –120 dB @ 25 Watt into 4 Ohm k3 typ. –123 dB @ 25 Watt into 4 Ohm SNR > 106 dB @ 10 Veff Inputs 2 Furutech RCA line, gold-plated 1 Audionet Link, optical Input impedance 37 kOhm, 220 pF
 
ATC?
Krell? ( might be Class A and older but I think serviceable)
Jeff Rowland?
Maybe some of the solid state amps from Audio Research or CJ?

I don't know what country you live in but the last time I looked Electrocompaniet had no distribution or agents in the UK.
 
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