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Parallel SET with sufficient power

Hello all:  I'm looking to move back into SET land after 15 years. I have a pair of KEF Reference 3's at 88 dB sensitivity which I'd like to keep, so I'm considering a parallel Single Ended design with at least 30 WPC. I do like the '300B sound' so friends have recommended the 6C33c tube in parallel to deliver 30-40 WPC. I've read some very positive posts on Audio Mirror and Wall Audio of Germany was briefly mentioned. Smaller boutique like companies give me some concern as most of these fine designers or engineers build amplifiers in their spare time, and quality control may be compromised.  I'm not a huge fan of 211 or 845 sound but these amps are another option.  Thanks for allowing me to think out loud and I do appreciate all opinions!

normie57
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almarg
9,670 posts
 
I'd be cautious in extrapolating from experiences others may report with various SET or PSET amps, unless they were using the same or similar KEF speakers.  As shown in Graph 4 of  this review the impedance of your speakers varies from around 3 ohms in parts of the bass region to as much as 18 ohms in the upper mid-range/lower treble.  The interaction of that impedance variation with the relatively high output impedance of most SET and PSET designs will in many cases result in weak bass and an over-emphasized upper mid-range/lower treble.  To a degree that will vary considerably among different SET and PSET designs, due to their differing output impedances.

An audition with whatever amplifier you may end up considering, using your speakers, would therefore seem particularly in order. 

Good luck.  Regards,
-- Al
 
keithtexas
352 posts
 
I know Vlad Bazelkov with Audio Mirror personally, and can attest to his knowledge and helpfulness.  Great guy, and his gear both sounds great and is very well built. He does some unique things with his designs, and he can answer any questions and concerns you might have about speaker match-ups.  contact@audiomirror.com.  Tell him Keith sent you :). Good luck!
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atmasphere
11,844 posts
 
@ normie57,

You might want to read this; it will help you understand the issues of driving a speaker with various kinds of amps.

http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

If you are planning to use an SET, the speakers you have in mind do not seem appropriate. They are intended as Voltage Paradigm devices where the amps you are contemplating are Power Paradigm devices. The combination often results in a tonal coloration (which Al mentions above). If you are planning an SET, more efficiency is recommended to really hear what the SET can do. As a general rule of thumb the speaker in the room should be efficient enough that the amp never exceeds about 20% of full power.

Good Luck!
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