2A3 Set power amp


Kind of a newbie with tube power amps so humor me. How will a Single Ended Triode amp with tubes being 2A3,6F5 and GZ34 sound with speakers that are rated 88-89dB? The Amp is rated at 10 Watts. Thanks for your help.
fromunda
Your information is probably not correct. A 2A3 used as a single-ended output tube will put out within 3db of 2.5 watts per channel. That is not even close to pushing your speakers, it will run out of steam and fall apart, sonically.

Even ten watts would not be enough, unless your room is stunningly small and you have a love of solo folk music. For decent sound levels, your speakers would have to be 10db more efficient to work with a 10 watt amp. And even greater efficiency would be advisable.
2a3 SET amplifiers will usally give you 4 to 5 watts/channel. A 45 SET is in the2 watt range. Still you`re asking too much of your amp to drive this speaker. You should consider speakers with at least 97db minimum and thats assuming the amp has quaility transfomers and a stout power supply. How large is the room, music type and listenig volume?
The amp you are considering is almost certainly a push-pull design using the 2A3 DHT.

The answer you should get is that the sensitivity of the speaker is nowhere near enough information to determine how well it would work with such an amp. If it is a benign load, it could indeed work quite well to moderate volumes.
I agree that you're not giving us enough information to make a complete determination. I don't agree that you need 97-100db efficient speakers.

A friend of mine is currently using my 8 WPC 300B amps on 90 db efficient 6 Ohm Green Mountain Audio speakers. He thinks it is excellent so there is hope. Obviously that experiment is based on a different amp and tube. I use them on 92 db efficient speakers that are 14 ohms.

However 88 db for a 10 wpc push pull 2A3 seems like a gamble.
I am with Paul!

Mmike84, have you tried your 300B amp on a 100 dBor greater sensitivity speakers? If so, which one?

IMO, there's a big difference in the ease of presentation and dynamics between a 96 dB speakers and below to that of 97dB or greater sensitivity that does not have a benign impedance load using the same 8W 300B amp. Again, IMO, as you go higher (over 97dB) speakers, then noise and hum becomes a factor and you have to address it wether it is coming from the amp, preamp, cabling, crossover,etc. And once you solved this problem, you will hear what many people love in terms of transparency and dynamics that a low power amp/high sensitivity speakers can provide which are truly breathtaking!

To me, there is no way a 92dB speakers can reach that sound! Why bother, do the right thing first and think a little bit here rather than having "upgrades" as the solution later on. It is not a myth, its been proven time and time again by many, if you want to explore low power amps(less distortion) like SET using DHT's, you will have the highest probability of success to enjoy the experience when you have efficient loads(drivers) for the amp to drive. That's it! Forget about post like "my 89db speakers works well with my 2W SET...etc.", most likely, it is not the truth.

me,
04-22-10: Amandarae
I am with Paul!

Mmike84, have you tried your 300B amp on a 100 dBor greater sensitivity speakers? If so, which one?

Amandarae-

No I have not. Not yet anyway. The 300b Amp and the speakers were made by the same company though so you'd think they would pair well and they seem to. I'm still scouting for a 96-100db speaker currently.
Anyway I have purchased this amp made by Chris Barnett, with 2- 2a3 Sovtek, 2- 6F5GT National electronics and 1-jj rectifier tube. With my 88db B&W speakers I am astonished! This F-in thing sounds like a locomotive on the right track. Holy cow, so much for all the theories in this thread, most were dead wrong!
It will probably drive your speakers fairly well at low SPL.

However, once you push the speakers with challenging source material and/or raise the SPL, the amp will unravel like a cheap suit.

That's fact, not theory.
Audiofeil is correct, of course. You have undoubtedly been listening to recordings that have very limited dynamic range (meaning a very small difference in volume between the softest notes and the loudest notes). Try some well recorded wide dynamic range classical symphonic music to see what he means.

That kind of recording may have brief dynamic peaks that are 30db or more louder than the average volume level. You will set your volume control based primarily on the average level. 30db above that level corresponds to 1000 times as much power!

Regards,
-- Al
Anyway I have purchased this amp made by Chris Barnett, with 2- 2a3 Sovtek, 2- 6F5GT National electronics and 1-jj rectifier tube. With my 88db B&W speakers I am astonished! This F-in thing sounds like a locomotive on the right track. Holy cow, so much for all the theories in this thread, most were dead wrong!

I do not believe it. There is no way! You are just saying that because you are going to sell the amp in the future. Chris Barnett is not an amp designer, he's a technician as far as I know. Are you in the Bay Area?
Not the first time that I have been dead wrong. My wife is keeping track and I'm into the thousands. Enjoy your amp and honor the music.
Sell the unit? Amandarine you are being plain idiotic. Yes the Bay Area
A single-ended 2a3 amp rated at 10-watts is REALLY pushing the tube hard. A friend who makes amps actually likes to push 2a3s and 45 pretty hard, but, then again, he has hundreds of tubes of those types and doesn't care if the tube does not live for a long time.

From my experience with 2a3 and 45 amps, the music that would most show off the power limitations of the amp would be large scale choral music, particularly if their is an emphasis on bass voices. For some reason (unknown to me) the amp will show obvious headroom limitation at surprisingly low subjective volume levels. But, for most popular music, which have limited dynamic range, low-powereed SETs can sound very good at reasonable sound levels. B&W speakers are not known to be an easy load, and 88 db/w is supposedly outside of the recommended efficiency, but if it works for you, GREAT.

One of the other things about good amplifiers, and SET amps in particular, is that one tends to be fully satisfied with the sound when playing at lower volume levels; if you have to crank it up for the music to come to life, the amp sucks.
The reason SETs have that amazing 'dynamic' character is all about how they make distortion. At very low levels, the distortion is unmeasureable. But at full power, the distortion is 10% and includes odd ordered harmonics, which are loudness cues to the human ear.

Music has lots of transients. So the distortion that has the odd orders only exists on the transients, not in between. This makes the transients seem louder to the human ear with respect to the rest of the music, hence that 'dynamic' quality; distortion physiologically interacting with our ears as 'dynamic'.

I prefer a system without loudness cues- that is to say it remains relaxed at *any* volume level, even where I have to shout to be heard by someone sitting right beside me. To describe dynamic range in a system like that I use the word 'impact'.

There are Class A2 techniques that will allow a pair of 2A3s to make 10 watts. The driver circuit really has to be designed right to make it happen without a lot of distortion. OTOH a pair of 2A3s in push pull will do about 15-16 watts easily.
Fromunda,

Okay, okay, big mistake, I am just kidding(I thought you were my friend and just giving you are hard time! Wrong username!! Apologies).