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SSE sounds bad in UL

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w5jag

Member
Joined 2007
kevinkr said:
Are you sure your cathode feedback is correctly phased?
Click to expand...

That was the first thing I thought of.

I know when I had the Transcendars on my first SSE, and I was playing around with it in pentode, I could make it oscillate with the cathode feedback backwards. The oscillation was obvious, though - it squealed like a pig.

After awhile, I swapped out for 125 ESE's to take advantage of the different loads, and they hook up easy - just pick an unused secondary and connect it to the cathode feedback point on the board.

I have my low power SSE running 2E26's in UL and have not heard any unusual distortion in it with the small Edcors, but, I do not have the cathode feedback enabled. UL is enough feedback for me.

The cathode feedback seemed subtle to me - the 125 ESE's do benefit from it, but I would think with a better class of OPT's, it wouldn't add much.

Win W5JAG
 
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Tubelab_com

Tubelab_com

Member
Joined 2005
tubelab.com
I also suspect that you have the feedback phasing reversed. The amp should be louder without feedback, that with CFB, but this is not an easy test if you don't have a switch. If possible swap the secondary leads on one channel and see which channel is the loudest. The quieter channel will be the correct connection.

The feedback makes the most difference on an EL34 and the least on a KT88. I have seen EL34's oscillate on some OPT's when the feedback was backwards. Getting the feedback right will improve the sound in triode too.
 
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chilihed

Member
Joined 2014
Last night I tried swapping the feedback polarity and it still was breaking up at low volume levels. I am using KT88's and the big edcors you recommend csxe25-8. The amp simply sounds better in triode for some reason. My TSE 300b sounds fantastic with Electra print output transformers.
 
kevinkr

kevinkr

Administrator
Joined 2004
kta-hifi.net
Paid Member
I have found that not all transformers sound good with both UL and CFB applied, some work better with one or the other. Also sometimes taking the CFB from the 4 or 8 ohm tap rather than the 16 ohm tap helps. (If you have that choice otherwise a resistive divider between output tap and cathode might help.)
 
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