Sugden A21a-how does it really fare with hard to drive speakers?

Interesting thread!
Glad to know you have found hifi joy Saab

I've always dismissed the sugden because of its low power rating.

Would it work with a pair of dynaudio contour 1.3mk2s??? Notorious for being difficult to drive
sensitivity, 86db (2.83 V/1 m). Though a 4ohm impedence, but it's supposed be designed to be failry linear across the freq spectrum.

I don't play music really loud. I know, 'loud' is subjective. But say, the loudest is when it becomes difficult to have a conversation. And my room is around 13ftx14ft.

any thoughts?

 

I am not experienced enough to offer any opinion other than what i can hear at the moment,but.........to dismiss the A21 because of lack of power would be like dismissing Precious McKenzie because he was a short arse.

My longs is 21ft and the speakers are 4ohm 86db,and some recordings are not going past 8 oclock,and like you,on my own,the max i go to is "coversation" level,i regularly have the music on so at least my wife can say "make me a cuppa" and i can still hear it

anyone dismissing this amp because they want pub talk watts is missing a treat

because a class A watt is a cultured beast,educated at Eton and in fine physical shape,a class A/B watt is a Blackburn fan

now,i can enjoy my music without worrying about the kids asleep or the neighbours,which was one of my main aims when dumpoing the B&Ws and Puccini

 

Hi Dave (cross forum discussion)

Ther-in lies the problem with my comments re 21 running out of steam, I would only be able to hear my missus if I had married "Shouty McLoudvoice's" little sister "Bawletta", during the day and early evening I like it room shakingly loud! (live in detached house so no worries with neighbours)

Yeah but which one would be the better darts player?

 

Hi Kid

yep,you must like it really loud with the Sparks,I don't really get any additional volume after 10 oclock,i use it within 7 and 9,so anyone wanting thumping volume on occasion should test this amp first,like you did.I took a punt,because I listen at low volumes

ps answer B) for the darts question

 

A21a watts

In a Ken Kessler review of the A21a in Hi-fi News (available on the Sugden web page), he talks of the A21a's Class a watts being comparable to a 75 watt class A/B amp. I would reiterate that driving my Totems in a largish room I now never go past 12 o'clock. (With DNM cable it was sometimes 10 past 12)

 

My (1971 model) A21's driving a pair of ProAc Super Tablettes (approx 86db/w) and has more than enough welly to make conversation very difficult. This old amp is 12w/ch - I've not driven the amp to clip, the volume getting way too loud for comfort before it loses musical grip of the bass etc.

According to Sugden the latest A21a has a virtually identical design to its older brother - only the addition of beefier power supply, output stage etc (and removal of the tone control circuits of course).

 

Re: A21a watts

now that is what i call paying attention to detail


I suppose Analogue kid is the exception rather than the rule,in terms of listening levels,i tink you must really want it loud to run an A21 out of puff

 

Wrong time

Sorry, I should have said 2 o'clock

 

Where is zero on the A21a?
its at 6 o'clock on the Sugden Headmaster.

 

zero is at 6

I have had a very nice reply from Sugden,from the main man himself!!

I haven't asked for permission to publish,so will just give the gist.Basically,he has run the A21 will speakers as low as 85db and 4ohms with no problems,providing the room is about 4m square.If you want really loud in a bigger room then as,as Analogue kid says,you will want more senstive speakers.But that is for seriously loud music,way beyond neighbour bashing and conversation levels

But,he reckons the best speakers for the A21 are infact speakers like the Audio Physics,because the A21 likes to be worked hard! he believes i have a perfect combo

he also said the bass is improved whent he amp is driven hard,I must admit the biggest improvement over the Puccini i had is the bass depth and tightness,if thats the right word

 

The 21a don't drive the 989s properly - one or both channels kept crapping out and shutting down when Henryt and I tested some a few months back - this was with Red Hot Chili Peppers et all at medium volume.

That said, the amp managed to do a good job with Jah Wobble, which surprised me, and within its volume envelope with aforementioned Quads, it sounded very good.

 

TWENTY YEARS late to the party, but I was thrilled to stumble on this thread. I recently (finally!) acquired as set of Audio Physic Sparks 3 - a bucket list speaker for so many years but I could never afford....or they were never on the market! Anyway, talk about worth the wait....they are just perfection to my ears. So happy with them! Even on my cheapo yet very faithful Onkyo A9050 mega budget amp they sound really great.

I live in the Netherlands now, but I am from Leeds originally, so I've always been familiar with Sugden (lusted after!) but again, could never afford one of their amps, but told myself one day I would. I always sensed that Sugden and Audio Physic speakers would be very good bed mates, and you just confirmed it for me so I am very chuffed!

I wondered if you still have the amp and speakers after all this time? Still happy?

 

A Watt is a Watt no matter the Class of the amplifier at the end of the day.

There are several ways of approaching the design of a Class A amplifier, some are inherently limited in current but the most common type is exactly the same as a Class A/B amp but with big enough heatsinks and PSU to allow the bias to be turned up much higher. It's quite literally that simple with this most common variety (the Sugden is not of this type BTW) and many Class A/B amps could be made Class A just by turning up the internal bias controls... BUT DO NOT DO THIS as the unit would of course overheat to the point of self destruction within a few minutes!

The quoted output of most Class A amps is in to an 8R load BTW as the lower the speaker impedance the higher the Class A bias (the standing current or quiescent current) must be to keep it in Class A. Hence with the most common type as above an amp specified as 30W into 8R and advertised as Class A can be expected to virtually double its power into 4R as you would expect with any Class A/B amplifier BUT only the first 15W would now be delivered in Class A. It's a pretty smooth transition from the Class A region to the A/B region so don't worry you won't hear it...hence the phrase "the first Watt" being bandied about!

Some other varieties of Class A amplifier use circuitry quite different from a Class A/B amp and can only work in class A. With these the standing bias current defines the maximum power output as they "current clip" at this point. This means that instead of the power doubling into half the load impedance as with most conventional amps, it halves. The Sugden (with a little jiggery pokery that gets too technical for this thread) is of this latter type and hence gives around 25W into 8R but only around 16W into 4R and even less into still lower impedance's. (These are not intended to be precise figures BTW so please no "but it says X watts in hifi monthly mag" etc. They will vary a bit according to how Sugden set up and built the myriad variations on the A21SE etc etc over the years and eg in the case of the original 1969 A21 they went for a compromise by making it give it's max into 6R, about 12W, but in combination with the way the PSU was designed it could give about 10W into 8R and 9W into 4R)

Bear in mind though that if listening at only "loud conversation" type volumes then you are probably averaging only half a Watt ish and peaking at maybe 1-3 W on loud drum hits etc if it's a very well recorded and dynamic source.

 

I think there is a system on youtube being the ATC SCM19 (or maybe SCM11) driven by a Sugden 21A. Even via laptop, dac and headphones the sound was so inviting, melodious, lovely textures... The ATC speakers are reknown to love current delivery and the Sugden 21A despite its power output seemed to be doing a good job, no straining..

 

It is important to have a good load characteristics (loudspeakers) as a poor match can cause excess heat to be dissipated in the amplifier (heatsinks). Under these circumstances, output power falls. So good impedance/phase matching across the the working range is important.

An A21 driving a pair of electrostatic headphones is sublime for this reason. If loudspeaker manufacturers achieved the same response, the original Quad ELS have, being full range panels similar to; for instance, Stax Electrostatic Headphones, there should be no problem at any point on the frequency response of the loudspeaker - assuming the amplifier is not overdriven at it's front end.

I have seen on other forums where individuals have promoted the idea of changing amplifiers to suit loudspeakers. This is akin to "Putting the Cart before the Horse".

One day maybe, I will get myself a Sugden P.A. to compliment my Bijou Pre - Amp.

 

Erm.... no..... It's class A and actually gets cooler when thrashed! This is because more power is being sent to the speakers relative to the amount the heatsinks are dissipating.

Electrostatics are not an easy load. At very low frequencies the load is basically the primary resistance of the driver transformer in the ESL's and as frequency increases the capacitive nature of ESL's becomes more and more apparent and is reflected back through the transformer to often result in a load of typically only say 2 Ohms at 20KHz.

 

1. Heat Dissipation and Efficiency:
   
   • The efficiency of a Class A amplifier is relatively low because it dissipates a significant amount of power as heat.
   • When you drive a Class A amplifier with an audio signal (i.e., play music), it does not necessarily run cooler. In fact, it may run even hotter during peak signal levels.
   • The reason is that the amplifier is now converting electrical energy into sound energy (through the connected speakers), but the majority of the energy is still lost as heat.
2. Peak-to-Mean Ratio and Average Power:
   
   
   • Music signals have a peak-to-mean amplitude ratio (the difference between the highest and average signal levels).
   • During normal music playback, the amplifier rarely operates at its full output power. Instead, it handles the average power required by the music.
   • As a result, the average power dissipation in a Class A amplifier is lower when playing music compared to a continuous full-power sine wave.

With regard to the Quad ELS, the power at 20khz in the audio envelope is relatively small. However, as the ELS's impedance will decrease as frequency increases. This is natural and in essence the "Panel" is acting as a low pass filter.

The impedance of the ELS is problematic at lower frequencies as you say, because of the Transformers. But it not a purely resistive problem. It is however also a question of how far the electrostatic diaphragm can move when handling low frequencies. The answer being - not very far! Quads original Electrostatics were always "Slated" for their apparent lack of Bass response.

But in essence, my point is, both Quad's original ELS and Stax Electrostatic headphones are single - full range devices, where no cross-over networks are employed, resulting in extremely good phase response across the whole audio spectrum. It is for this, and many other reasons, the Quads were used as both reference loudspeakers for designers and broadcasters alike, not to mention 1000 seater theatre performances where double stacked Quads were used for pre - recorded concerts.

 

Life's too short... can't be bothered.... but I am a professional electronic engineer and I design amplifiers for a living... amongst other things.