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K&K SST-70 PCB

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Posted on March 21, 2014 at 17:45:55
Brinkman
Audiophile

Posts: 52
Location: Pacific Northwest
Joined: December 4, 2007
 Kevin,

I am currently looking into parallel push-pull topologies using beam tetrodes (Triode configured, Class A1, 0NFB). Rather than bug you about issuing monoblock PCBs based off your ST-70 kit, I'm curious if you've experimented with reconfiguring the current PCB for 4xKT120 PPP monoblock duty. Further, is the LL1679 still the recommended OPT for this job?

Thanks in advance.

 

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RE: K&K SST-70 PCB, posted on March 21, 2014 at 19:00:23
KevinC
Manufacturer

Posts: 2984
Location: NC
Joined: April 19, 2001
 I have a well-tested circuit for PP parallel beam tetrodes triode-wired. It even exists as a pair of prototype monoblocks that have been to RMAF! However, I have not experimented with adapting the ST-70 board. It really wouldn't be worth the trouble. A PP parallel output stage really begs for a heftier driver stage than a pair of 6N23P triodes.

We used the LL1679AM/PP for the above referenced amp with great sonic success. Our speaker room share at the show, the U.S. ProAc distributor, said that the sound in that room was the best he had ever experienced in a audio show room share in his 20+ years.

Kevin Carter
K&K Audio
www.kandkaudio.com

 

RE: K&K SST-70 PCB, posted on March 23, 2014 at 08:14:19
Brinkman
Audiophile

Posts: 52
Location: Pacific Northwest
Joined: December 4, 2007
 Kevin,

What beam tetrodes were you using in the RMAF model?
If I were to get a pair of LL1679 OPTs, I'd like to restore my ST-70 to it's pre-SST-70 configuration; could the LL1544s from my SST-70 be reused in a PPP build?

Also, PM sent.

 

RE: K&K SST-70 PCB, posted on March 23, 2014 at 11:15:01
KevinC
Manufacturer

Posts: 2984
Location: NC
Joined: April 19, 2001
 We used the KT-120, but with a suitably large power supply transformer and cathode CCS heat sink, I would use the KT-150s to get more power. In a similar PP amp (one pair per channel) we compared the sound of the KT-120 near its max dissipation limit to that of the KT-150 at its higher limit (which meant the bias current per tube went from 100mA to 125mA), and the extra current resulted in more watts and better sound.

Yes, the LL1544As could readily be reused for input phase splitting.


Kevin Carter
K&K Audio
www.kandkaudio.com

 

RE: K&K SST-70 PCB, posted on March 24, 2014 at 11:13:51
Brinkman
Audiophile

Posts: 52
Location: Pacific Northwest
Joined: December 4, 2007
 Can you tell us anything about the speakers your prototypes were mated to at RMAF?

 

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