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Post by ChrisB on Aug 19, 2014 23:36:03 GMT
There has been a lot of gear that's rarely seen in the UK & you have to wonder how good it is. So for starters does anyone know anything about the big Stax power amp from 1974- the DA-300?  Lots more juicy pictures here: www.hifido.co.jp/KW/G0104/E/0-50/C08-39816-31982-00/ |
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Post by John on Aug 20, 2014 4:21:14 GMT
Not even heard of it Chris Looks well made
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Post by ChrisB on Aug 20, 2014 5:47:15 GMT
It is supposed to be 150 wpc in class A, which would have been quite a rare feat in 1974! That, though, is the only fact I know about it!
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Post by danielquinn on Aug 20, 2014 7:31:43 GMT
I think my second hand technical knowledge suggests that 150w class a ain't possible. Now if only we had an expert member.
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Post by dvh on Aug 20, 2014 7:59:58 GMT
I think my second hand technical knowledge suggests that 150w class a ain't possible. Now if only we had an expert member. DaveC's an expert, surely? |
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Post by DaveC on Aug 20, 2014 8:01:55 GMT
Stax list it as "A Class" not "Class A" However 150W Class A is perfectly possible in both solid state and valves. So the jury is out !
Daniel, there is a good reason why I employ solicitors...........
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Post by dvh on Aug 20, 2014 8:03:08 GMT
Stax list it as "A Class" not "Calls A" However 150W Class A is perfectly possible in both solid state and valves. Daniel, there is a good reason why I employ solicitors........... If only we had a solicitor on here ….. |
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Post by ChrisB on Aug 20, 2014 8:16:18 GMT
I thought the classification might be a bit questionable, hence my choice of words - there's has been plenty of skipping around definitions from manufacturers in the past.
So, do you know anything about the amp then Dave? Have you ever seen or heard one?
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Post by danielquinn on Aug 20, 2014 8:17:19 GMT
I seem to recall reading that the first 12 or so watts were class A and thereafter class A/B ?
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Post by DaveC on Aug 20, 2014 8:18:49 GMT
I thought the classification might be a bit questionable, hence my choice of words - there's has been plenty of skipping around definitions from manufacturers in the past. So, do you know anything about the amp then Dave? Have you ever seen or heard one? No, but I would love to ! |
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Post by DaveC on Aug 20, 2014 8:19:20 GMT
I seem to recall reading that the first 12 or so watts were class A and thereafter class A/B ? Stick to being a lawyer ! |
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Post by Paul Barker on Aug 20, 2014 8:28:07 GMT
I think my second hand technical knowledge suggests that 150w class a ain't possible. Now if only we had an expert member. I don't know about solid state but oh yes it is possible with valves. you just need a output device of sufficient power. they may well be available as transistors, they most certainly are available as valves. you could parallel you transistors up of course to achieve it with those lesser animals. |
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Post by Paul Barker on Aug 20, 2014 8:29:24 GMT
I seem to recall reading that the first 12 or so watts were class A and thereafter class A/B ? Most likely. |
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Post by pre65 on Aug 20, 2014 8:36:37 GMT
I'm not totally sure, but I think you could get 150W from an 833a transmitter valve with the right HT and forced cooling.
With lower HT (around 1000v) you could get a sublime sounding 20W in class A2.
PS have smileys been disabled ?
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Deleted
Deleted Member
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Post by Deleted on Aug 20, 2014 8:59:01 GMT
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Post by Paul Barker on Aug 20, 2014 9:10:09 GMT
I'm not totally sure, but I think you could get 150W from an 833a transmitter valve with the right HT and forced cooling.
With lower HT (around 1000v) you could get a sublime sounding 20W in class A2.
PS have smileys been disabled ? Don't forget push pull Phill. |
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Post by Paul Barker on Aug 20, 2014 9:16:07 GMT
What I mean is. You can in Class A push pull get 150 watts from a pair of 833's. It is a great stretch of the imagination to achieve it in Single Ended, but one OEM makes such a claim (which I don't believe).
Also when you get up to those power levels you can't really use SE transformers you have pushed passed the diminishing returns level.
The driver would have to be some beast for the 150 watt push pull output stage.
There is also parallel push pull 212's to consider.
Before we start to consider the GM100, which again I would be looking at push pull output stage.
Once you aim for 150 watts in class A you may aswell design it so that past 150 watts it carries on (which means you can't CCS the pair of push pull valves).
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Post by Dave on Aug 20, 2014 9:52:22 GMT
IIRC the XTZ AP-100 power amp is switchable to run at 50wpc in pure Class A or 150wpc in AB
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Post by Eduardo Wobblechops on Aug 20, 2014 12:56:48 GMT
I seem to recall reading that the first 12 or so watts were class A and thereafter class A/B ? Depends on the design. To do SS Class A in high powers requires massive heatsinking though, the amp will produce huge amounts of heat. Think massive Krell monblocks and the like. |
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Post by Eduardo Wobblechops on Aug 20, 2014 12:58:31 GMT
For instance, the Jungsson JA-D 88 (I think it is) is touted as a Class A amp, and it is, but only for about 6W, not the quoted 30 or 40w or whatever they claim.
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