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Old 28th May 2012, 01:39 AM   #21
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Originally Posted by jmillerdoc View Post
Why do you need so much power?...
Yes, this salient question has yet to answered by OP...once it is, constructive and more refined suggestions can be made.
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Old 28th May 2012, 02:29 AM   #22
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Originally Posted by devilsindetails View Post
Yes, this salient question has yet to answered by OP...once it is, constructive and more refined suggestions can be made.
Thanks for all those who contributed their opinion.

I take the point about selecting efficent speakers. (I knew that already.)

I have a big listening room.

As I confessed up front, I don't have great knowledge of SE amps, so my question was part-practical, part-curiosity.

Anyway, your contributions have given me a number of leads to pursue, so thanks to all. The part count will be another factor. I admire simplicity.

cheers

Doug
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Old 28th May 2012, 03:30 AM   #23
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I would go with something like 10 of 4P1L in parallel. 500-600 Ohm primary OPT is easy for 25W of pristine clean SE power, and 250V B+ is easy to use.
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Old 28th May 2012, 02:32 PM   #24
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Originally Posted by Brisso57 View Post
I take the point about selecting efficent speakers. (I knew that already.)

I have a big listening room.
Solution = active bi-amp
SET amp for mid & high frequency drivers (high efficiency of course) and P-P amp for woofer.
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Old 28th May 2012, 09:51 PM   #25
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Originally Posted by Evenharmonics View Post
Solution = active bi-amp
SET amp for mid & high frequency drivers (high efficiency of course) and P-P amp for woofer.
That's almost the way I'm heading.
I have a pair of efficient vintage Peak 8CX50's (=Coral 8CX501's) and 2 pair of Eminence 15A's - in the spirit of MJK's dual 15A OB. I plan to bi-amp them using a miniDSP. The bass will be driven by a SS Yamaha M-70.

What is to be decided is the tube amp. I have most of the parts for a RH84, but was wondering what might be a little more powerful. (& yes, I know that I've got to more than double the power of the RH84 before there'll be any practical difference in SPL.)

The listening room is ~ 30' L x 20' W with a skillion ceiling sloping up from 9' to 17'.

cheers

Doug
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Old 28th May 2012, 10:12 PM   #26
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Quote:
Originally Posted by Brisso57 View Post
Thanks for all those who contributed their opinion.

I take the point about selecting efficent speakers. (I knew that already.)

I have a big listening room.

As I confessed up front, I don't have great knowledge of SE amps, so my question was part-practical, part-curiosity.

Anyway, your contributions have given me a number of leads to pursue, so thanks to all. The part count will be another factor. I admire simplicity.

cheers

Doug
You haven't explained why your proposed amplifier should be single-ended. As already suggested a push-pull design would be much more efficient and given the size of your listening-room I should say, essential - especially if very high voltages, and exotic valves or indeed complexity are to be avoided.

And yes, the old sound engineer's rule went "Ten times the power to double the [perceived] volume"

Paul
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Old 29th May 2012, 12:23 AM   #27
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Default same way with push pull amps

When you use higher impedance OT,you effectively lower the feedback and maintain the same lower distortion.Granted,you lose some power but you gain in sonics in a way thats incredible..A great example is the heath w5m..It uses a pair of kt66s and a typical kt66 PP application is 6k. The 16309 is around 11 or 12k which is almost double..The bandwidth is huge and the distortion is very low even on a stock unmodded unit.
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Old 29th May 2012, 12:30 AM   #28
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Originally Posted by 7N7 View Post
You haven't explained why your proposed amplifier should be single-ended.
Paul
Oh, OK.
Well I came across the RH84 design, and it seemed to me that it has a pleasingly small parts list.
My naive assumption was that more powerful SE amps would be similarly simple.

cheers

Doug
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Old 29th May 2012, 01:20 AM   #29
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Doug
Single ended amps are simple as they don't use a phase splitter and use very low if any feedback.The drawbacks to single ended designs are higher 2nd order distortion and output transformers containing lots more wire than a comparably powered PP design.
This can suppress the higher freq in some transformer designs because the signal travels thru much more wire. New SE trans designs have gotten much better but they are costly,
I have 360 tube amps and all but 6 are vintage..I have a single pair of Cary/AES SE811 amps that use sv572-3 tubes and I modded them with motor run caps..While they sound ok,I have literally sound the magnavox SE pentode 7189 amp to bury it in the dirt..I am not kidding.
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Old 29th May 2012, 02:24 PM   #30
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Originally Posted by michaelsamra View Post
The drawbacks to single ended designs are higher 2nd order distortion and
Higher 2nd (and following even orders) order harmonics is the main reason why people choose SET amp despite its low power. I wouldn't call that a drawback.
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