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Class A amps question

H

hertz

Member
I have been eyeing the Sugden A21SE for some time now. I know many of you may have spent time with this amplifier and may have also considered and auditioned more expensive class A amps from the likes of Luxman or Accuphase. From a first hand experience, is there so much difference between these amplifiers ? Price wise, they are so different. In this scenario, I would like to assume the loudspeaker in question will be sensitive enough to be driven very well by the Sugden. I know higher powered Class A will drive difficult speakers better so I want to take that variable out of the equation.
 
Had the a21se here for a good while , fabulous amp that drove my tannoys so amazingly well with such dynamism and verve . 10/10 . the only reason i dont have one is like many amps the remote is just not enough fine control for me

Now the luxman and accuphase are just superb and have so many more adjustments on them like tone control etc. i have never compared the 2

I will say that some of the most cost effective class A amps are built by joe henry in coventry , been using his 25 watt first watt clones monoblocks [ F5 ] with an exceptionally good pre for some while . every bit if not better than the a21se and a fraction of the price . just worth a look if you want quality at an affordable price

https://www.ebay.co.uk/itm/13478680...pid=5338728743&customid=&toolid=10001&mkevt=1
 
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I have no direct experience of any of the amps in question, but I'll just add a comment:

Be wary of manufacturers claims about just how much their amps are Class A. The vast majority of said Class A amps are actually only such for a handful of watts, after that they revert to Class A/B. Unless the amp has large heatsinks and weighs over 30kg because of it (think 80's Krells etc), then it's not going to be anything more than 10W or so of Class A operation, no matter what the manufacturer states.
 
I’ve had an a21a, A21se, lavardin, and my favourite, mfa1000, all sounded completely different. More so than any class b variants, (around similar power outputs) I much prefer them to class b.
 
gez said:
I have no direct experience of any of the amps in question, but I'll just add a comment:

Be wary of manufacturers claims about just how much their amps are Class A. The vast majority of said Class A amps are actually only such for a handful of watts, after that they revert to Class A/B. Unless the amp has large heatsinks and weighs over 30kg because of it (think 80's Krells etc), then it's not going to be anything more than 10W or so of Class A operation, no matter what the manufacturer states.
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Yes indeed, back when I was interested in building such things for myself I did the sums for a Class A power amp design thinking this would be a fun project. It was at this point that I realized that this was a daft idea and that very few 'Class A' amps were actually true Class A amps.
 
I have a 21se but only compared it to class a/b amps (rega/naim).

The guy who owns pearl acoustics has a youtube channel and he compares his sugden with a pass labs (which costs more) and he preferred the sugden.
 
I built a Pass F5 clone kit from DIYAudio and it was a great project. Probably a great amp, but I didn’t keep it because I lived in Spain and having a heater on (the amp) only made sense for a small part of the year. For me a class A isn’t practical, and I probably wouldn’t get one again unless I end up living in a cool climate and would have the heat on anyway.
 
Gza said:
I have a 21se but only compared it to class a/b amps (rega/naim).

The guy who owns pearl acoustics has a youtube channel and he compares his sugden with a pass labs (which costs more) and he preferred the sugden.
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He preferred the Sugden mainly on the basis that the Pass costs four or five times as much though.
 
I have always lived with slightly smooth sounding amps. In past it was an LFD and then recently the Lyric audio ti100 SET. I loved the lyric but my fyne audio 501sp needs a bit more power when I play music with low recording levels. Stimela ( Hugh Masekela) or Tin Pan Alley and many classical pieces are examples. Hence I am exploring options. Another amp that I have shortlisted is the Rega Aethos.

With the Sugden A21SE, I have heard about the sensitivity issue. About the amp hitting max volume at about 9 to10 am position. About the lack of granular increments in volume because of the way the volume control and sensitivity is handled.
 
I’ve had quite a few Class A amps, integrated and power.

- Sugden A21 (original)
- Sugden Masterclass pre/power
- Sugden A21a
- Sugden A21p
- Sugden A21SE
- Musical Fidelity AMS35P
- Musical Fidelity AMS35i
- Krell KSA50 Mk2
- Krell KSA80B
- Krell KSA100 Mk2

I’ve heard plenty more, including Accuphase.

I really like Class A amps. All of the above made music highly enjoyable. But they do sound different to one another.

For instance, the Musical Fidelity AMS35i is only a few watts more powerful than the Sugden A21a/SE amps (33 vs 25), but the difference in percieved power is enormous. In fact, the Musical Fidelity comes across a high power amplifier with prodigious bass power, whilst also being ultra pure, transparent and intimate. I much preferred the AMS35 to the 500WPC M6500i, and it didn’t ‘seem’ underpowered at all by comparison.

The big Krells are equally brilliant but quite old now and at their best when serviced. And benefit from a top class preamp, preferably of a similar vintage.

The original Sugden A21 was possibly my favorite of the Sugden amps. It’s astonishing that it is 55 years old - it’s so clear and transparent. But at only 10WPC, it was very limiting on speaker choice and volume.

For me, vintage Krell if money and practicalities (size / space / power consumption) are not an issue. For an integrated, the MF AMS35i is very hard to beat IMO. It made a NAP250DR sound underpowered, small and muddied.
 
I have actively avoided A's because of the electricity use and heat created. However, my 20 year old S/S home amp runs at over 50 degrees on the surface anyway, and still uses a fair bit of power (about 200W on standby). I'm not too knowledgeable about it so will ask, would amps that run this hot be likely to be Class A at low volume before reverting to AB? .... or would all that wattage be lost in heat energy somewhere else?
 
I suppose the same could be asked about class A/B and class D amps.
As always, go and listen and decide if it is worth the extra outlay.
 
Furyous said:
The original Sugden A21 was possibly my favorite of the Sugden amps. It’s astonishing that it is 55 years old - it’s so clear and transparent. But at only 10WPC, it was very limiting on speaker choice and volume.
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Like you I have owned the A21SE, the A21a and two A21s. I agree about the original, for me it's the best amp they have made. In reference to the OPs question I loved the SE, it's such a crystal clear amp and wasn't bettered by the Luxman that replaced it. I would definitely be trying before buying as the amps in question are not cheap.
 
I understand the heat issue, especially if someone lives in a hot climate. But moving from a class a/b amp to a class a hasnt increased my energy bills, not that Ive noticed anyway.
 
artoly said:
I have actively avoided A's because of the electricity use and heat created. However, my 20 year old S/S home amp runs at over 50 degrees on the surface anyway, and still uses a fair bit of power (about 200W on standby). I'm not too knowledgeable about it so will ask, would amps that run this hot be likely to be Class A at low volume before reverting to AB? .... or would all that wattage be lost in heat energy somewhere else?
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My guess is that any amp that runs very hot is likely to be Class A for a good few watts as you say before going to AB for the rest. What on earth have you got that runs at 50 deg C and 200W *on standby*? That's nut for solid state, those are valve amp numbers.
 
stevec67 said:
My guess is that any amp that runs very hot is likely to be Class A for a good few watts as you say before going to AB for the rest. What on earth have you got that runs at 50 deg C and 200W *on standby*? That's nut for solid state, those are valve amp numbers.
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It's a Conrad Johnson Premier 350 (350W into 8 and over 600 into 4). I just found the email from C/J where they advised it is a little less wattage than my memory suggested, but still 180W at idle. I also have an ARC valve amp and a thermometer sitting on top shows almost exactly the same temperature. I don't leave either of them on when not in use.
The Naim 250 that I'm listening to right now at work is barely warm.
 
artoly said:
I have actively avoided A's because of the electricity use and heat created. However, my 20 year old S/S home amp runs at over 50 degrees on the surface anyway, and still uses a fair bit of power (about 200W on standby). I'm not too knowledgeable about it so will ask, would amps that run this hot be likely to be Class A at low volume before reverting to AB? .... or would all that wattage be lost in heat energy somewhere else?
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That's almost certainly running in Class A for at least the first few Watts. I'm judging mostly on the 200W power usage on stanby. A classic characteristic of Class A is that the amp is using full power even when it's just "idling". An A/B amp could get up to 50 degrees, but only when it's actually being used. A lot of the "big name" well known and respected traditional amplifier manufacturers in the high end of the markets amps are Class A to some degree then "switching" to Class A/B for higher power outputs.
 
artoly said:
It's a Conrad Johnson Premier 350 (350W into 8 and over 600 into 4). I just found the email from C/J where they advised it is a little less wattage than my memory suggested, but still 180W at idle. I also have an ARC valve amp and a thermometer sitting on top shows almost exactly the same temperature. I don't leave either of them on when not in use.
The Naim 250 that I'm listening to right now at work is barely warm.
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I'm going to go out on a limb and state that is almost certainly running in Class A for some part of it's output, especially given it's size/weight and the size of the heatsink it has:


According to the measurements that site made, it's drawing 1.65A at idle on a 120V supply. That's 198W.
 
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