Furthering what Evenharmonics mentioned above, if you are married to the 2A3, the 2A3 will also pop right into the TubelabSE but you will end up with something less than 8W (around 3-4W). You need different B+ voltage, Filament voltage, and maybe a different output transformer primary impedance.
Tubes and Transformers
Tubes and Transformers
I was thinkig about parallel SE , which gives something about 8W ,but it's quite expensive (four matched2A3 woul cost a fortune) , so 3000B SE it is .Which design would be the best and what suitable speakers to match it?Curently I'm using ProAc Tablette 2000 (87-88dB) wit El34 PP , listening to all kind of music from jazz to The Cure , Depeche Mode ,Prince ,classical etc
With this kind of speaker sensitivity (which also implies a complex crossover) , the best design would be a El34 PP
Only for speakers that are happy with 15W or less and a still fairly high source impedance.
Possibly you might also want to consider PP 300B amps, they bring most of the virtue of SE 300B to the table with 30W being quite easily obtained on a B+ of 400V with fixed bias.
Tube wise the JJ300B has proven to be a good choice in both SE and PP designs I've done.
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If you are getting new speakers you may not need to limit yourself to 8W and can still consider a SE amp based on the 2A3. By all accounts the 2A3 looks like a very nice tube. I have a box of 10 of the Russian 6V heater equivalent (6C4C) and plan to build a nice SET with these some day.
Have a look at:
http://www.diyaudio.com/forums/tubes-valves/13813-finally-built-my-6sl7-2a3-6a3-amp.html
New 2A3
Have a look at:
http://www.diyaudio.com/forums/tubes-valves/13813-finally-built-my-6sl7-2a3-6a3-amp.html
New 2A3
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Hi
14-15W would give me more options while choosing speakers, I belive I could play it with 90-92dB as well as with high effieciency speakers .On the top of it I could still run amp. on my Proacs(hardly but still) and patiently look for new set.
I ask differently what brands(models) are worth considering if I built :
1. SE 2A3 (3-4W)
2. SE 300B (7-8W)
3. PSE 300B (14-15W)
PP is out of equation , I want to try pure SE.
14-15W would give me more options while choosing speakers, I belive I could play it with 90-92dB as well as with high effieciency speakers .On the top of it I could still run amp. on my Proacs(hardly but still) and patiently look for new set.
I ask differently what brands(models) are worth considering if I built :
1. SE 2A3 (3-4W)
2. SE 300B (7-8W)
3. PSE 300B (14-15W)
PP is out of equation , I want to try pure SE.
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I know all the conventional wisdom suggests you need ultra-sensitive speakers if you only have a flea powered tube amp but I haven't found that to be the case when I'm using my single full range driver based speakers. Heck, my current listening set up is a pair of my DIY Martello speakers which are around 85dB sensitivity and my tube amp puts out 1W. OK, I'm not using it for rock music and I do plan to upgrade the speakers to something over 90dB but my point is that it's easy to overestimate how much power you need. Your pro-acs may sound quite fine with 2-3W so long as you don't want to use it for parties.
I measured the voltage swing going into my speakers with an oscilloscope once and was quite shocked how little power normal listening levels require. I read somewhere that to get 'twice as loud' you need a huge increase in power, meaning the difference between 4W and 8W is probably insignificant.
Anyhow, there are people here with far more experience than me, I'm just trying to say that it was my thought that if you have a strong interest in the 2A3 I wouldn't give up that dream for a few watts of power that may just end up heating your room. You'll enjoy the project more if you build what you really want to build not what looks right on paper.
p.s. if cost of tubes is a concern, the Russian 6B4G is an equivalent to the 2A3 except that it's an Octal base and runs off 6V heater (which you'd want to run with dc not ac).
I would google for some further opinions too. e.g.
http://forums.klipsch.com/forums/p/62564/611244.aspx
http://www.6moons.com/audioreviews/fi/mono_2.html
I measured the voltage swing going into my speakers with an oscilloscope once and was quite shocked how little power normal listening levels require. I read somewhere that to get 'twice as loud' you need a huge increase in power, meaning the difference between 4W and 8W is probably insignificant.
Anyhow, there are people here with far more experience than me, I'm just trying to say that it was my thought that if you have a strong interest in the 2A3 I wouldn't give up that dream for a few watts of power that may just end up heating your room. You'll enjoy the project more if you build what you really want to build not what looks right on paper.
p.s. if cost of tubes is a concern, the Russian 6B4G is an equivalent to the 2A3 except that it's an Octal base and runs off 6V heater (which you'd want to run with dc not ac).
I would google for some further opinions too. e.g.
http://forums.klipsch.com/forums/p/62564/611244.aspx
http://www.6moons.com/audioreviews/fi/mono_2.html
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You are not equating SET sound with P-P sound, are you?
No, but 0fdbk class A 300B PP operation is surprisingly close in some key areas that attract people to SE in the first place. (Mids and highs) The additional power is always welcome and in general the performance is better below 100Hz than is usually the case with bogey 300B SE designs. No question that even loop the linearity is substantially better. My last designs achieved 1% thd @ 25W with no global feedback over a fairly wide (and now forgotten) range of frequencies.
Note that my personal preference is definitely towards fixed bias SE, however I designed a number of PP amps to cater to people who wanted to use speakers of normal efficiency with 300B amplifiers... It's a viable choice in many instances. I'm much less sure about PSE as IMLE they seem not to perform sonically as well in some ways as a single tube SE. (Entirely subjective on my part, nothing I could easily measure, and in the particular case other features of this design might have been responsible. It just seemed not to resolve the way I expected, and at the time I had no bias one way or the other.)
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From what I have read of the opinions and experiences of others I think both tubes can be used to listen to all types of music. From my own experience I suspect that your speaker choice will probably be more important than the choice between these two tubes.
In fact, I would go another step and say that I believe the circuit topology and choice of components around the tube will also be more important that your choice of which output tube.
I've only ever used RC coupling, not interstage. For reasons of cost. I believe interstage has some advantages over RC coupling providing you use a good quality transformer.
In fact, I would go another step and say that I believe the circuit topology and choice of components around the tube will also be more important that your choice of which output tube.
I've only ever used RC coupling, not interstage. For reasons of cost. I believe interstage has some advantages over RC coupling providing you use a good quality transformer.
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