advertisement


Arcam SA20 Class A operation

RoA

pfm Member
According to Arcam this little amplifier has pure class A operation for its first 12/20 Watts 8/4ohm then rising to 80/150 Watts in Class G at 8/4 ohm.

Looking at it, do you think that is likely?

A Sugden A21 Signature has far more passive cooling surfaces although it is rated at at least twice the power (in Class A).
 
its a good question

hi fi plus says .

the SA20 has a Class G hybrid power amp section, which operates in Class A up to 12 Watts then switches in an additional power supply that produces Class B for situations that require greater power. The difference between this and a classic Class A/B design is that there is a transition area where both power supplies are operating which is claimed to eliminate the crossover distortion that typifies the latter. It’s worth noting that both power supplies are linear and that Class G is not a new thing; the theory dates back nearly fifty years, but it is complicated to implement successfully.

http://www.hifiplus.com/articles/arcam-sa20-integrated-amplifier/
 
Last edited:
Shame Arcam invested all their budget in their marketing fog-of-bollocks-machine and not in making their kit reliable - they might not have become just another Chinese dump-bin brand.

I quite fancied trying some used Arcam kit, but at times half of all the Arcam on Thiefbay is "spares-or-repairs" - usually from some clown bang in the middle of London with "Free collection in person" - like their laziness is doing you some kind of favour!

****s!
 
Shame Arcam invested all their budget in their marketing fog-of-bollocks-machine and not in making their kit reliable - they might not have become just another Chinese dump-bin brand.

I quite fancied trying some used Arcam kit, but at times half of all the Arcam on Thiefbay is "spares-or-repairs" - usually from some clown bang in the middle of London with "Free collection in person" - like their laziness is doing you some kind of favour!

****s!
Are you on those happy pills again?
 
its a good question

hi fi plus says .

the SA20 has a Class G hybrid power amp section, which operates in Class A up to 12 Watts then switches in an additional power supply that produces Class B for situations that require greater power. The difference between this and a classic Class A/B design is that there is a transition area where both power supplies are operating which is claimed to eliminate the crossover distortion that typifies the latter. It’s worth noting that both power supplies are linear and that Class G is not a new thing; the theory dates back nearly fifty years, but it is complicated to implement successfully.

http://www.hifiplus.com/articles/arcam-sa20-integrated-amplifier/

It’s sounds like clickbait. Class A still gets a Pavlov response from me just because I had Sugden amp once. Pathetic, but I’ve learned to live with it.
 
Nope, the marketing on my Arcam says it's class a up to 50w. But the designer said the following:

"The A49 thus behaves exactly like a classical class A amplifier up to this power level in terms of performance but without the heat penalty."

I suspect the sa20 is a cutdown version of the a49.
 
I must be lucky as had an arcam a85 working well for some while , I must confess plenty on eBay for spares or repair but I guess there are thousands of them. The arcam suits my horns quite well as a power amp .

The sa20 gets some good praise and several owners mentioned how they enjoy sa30
 
There is only one way to tell if this is codswallop or fair-dinkum - feel the heatsinks.

Given their modest size, they should be pretty much unbearable to touch if there is even 10W of class A going on. 50W? I don't think so.

I'm reminded of the Musical Fidelity A-100, which has its entire finned top-plate as a heat sink, plus a pair of small fans inside pulling in air. It ran hot, and it was class-A for maybe its first 10-12W despite marketed as a 50W class A amp.
 
I must be lucky as had an arcam a85 working well for some while , I must confess plenty on eBay for spares or repair but I guess there are thousands of them. The arcam suits my horns quite well as a power amp .

The sa20 gets some good praise and several owners mentioned how they enjoy sa30

They went to a lot of trouble to make the A85 reliable after the first couple of batches.
 
You can't even touch the heatsinks in my Luxman - they're covered over by a protective grille - but even the grille itself gets pretty toasty after even 30 minutes. Mind you, it IS a class A amp, and a good one at that. Like I said before on this very thread, it's likely marketing bollocks...
 
They went to a lot of trouble to make the A85 reliable after the first couple of batches.

thats good , i actually have a spare a85 in case mine packs up. !! its been fine so far , had quite a few amps on the horns i have , some are too much of a good thing [ sugden] some are too soft [ lavardin ] some are too expensive !! [ silbatone] and some are cheap compromises that sound remarkably good for the money [ arcam] actually if i covered it up and played you a track i suspect you would be surprised how good it is . helped of course by a heavily modded valve dac !
 
I had an arcam A85 when it first came out.
I found it very underwhelming, quite thick sounding through the midrange and monotone bass. Treble also seemed detached and overly sparkly.
Best part is that it kept shutting down when asked for a workout.
Dealer replaced it for an A22 and that was very dull and also shut down when asked to play at moderate levels for reasonable durations.
My Alpha 5 is infinitely better and very reliable.
 
glad the alpha is good ! I added a isotek syncro to the a85 as a poweramp and that tightened things up a bit. i guess it depends on the system its used in . These RFC taus are 93db sensitivity and need careful matching especially as its a fairly bright room
 
glad the alpha is good ! I added a isotek syncro to the a85 as a poweramp and that tightened things up a bit. i guess it depends on the system its used in . These RFC taus are 93db sensitivity and need careful matching especially as its a fairly bright room
Yeah like I say I had the early A85 model which was well known for having issues.
 
If it is delivering something like the claims, then the clue is the 'Class G' bit - this is where higher voltage rails are switched-in to cope with larger signal excursions. The lowest supply tier of rails can actually be quite low voltage.

To get 10-12w class A into 8 ohms you might get that with about 0.6A of bias running on just +/-15v rails, and that would incur about 18w/ch dissipation - so yes, might well be the heatsinks do look a bit small.
 
If it is delivering something like the claims, then the clue is the 'Class G' bit - this is where higher voltage rails are switched-in to cope with larger signal excursions. The lowest supply tier of rails can actually be quite low voltage.

To get 10-12w class A into 8 ohms you might get that with about 0.6A of bias running on just +/-15v rails, and that would incur about 18w/ch dissipation - so yes, might well be the heatsinks do look a bit small.

Agreed.
With alu heatsinks and a steel case, fairly high heatsink temps could be used without causing a burn hazard.
So it could probably do 10W into 8R with good airflow. It is very unlikely that it could do 10W into 4R though.
 


advertisement


Back
Top