Just put some Penta KT88SC's in my Herbert..oh my...

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kayman121

kayman121

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Absolutely fantastic. These tubes are amazing. I replaced the SED 6550s that were in there. I instantly noticed the amp took on a darker, even more "hi-fi" character. It smoothed off and rounded off the high end, so I guess some people would consider that a loss of aggression, but for my tastes it's perfect. The amp took on the deepest, most menacing lo-mid growl I have ever heard. It was an earth-shattering rumble. There is now a very deeply set in more low-mid to mid-mid oriented crunch thing going on. The 6550s are definitely more raunchy and raw, if that's your thing. Any else have any experiences with KT88 vs 6550 in their Herberts? Specifically even the Penta KT88SCs?

This amp sounds unreal, you did a great job Peter.
 
Smooth & round high end with more low-mids emphasis? with KT-88's??? Wow, I'd not have guessed that. I mean, I know those tubes typically provide a really pronounced low end, but rounded off highs? that's surprising
 
studiojig":7zoifzxn said:
Smooth & round high end with more low-mids emphasis? with KT-88's??? Wow, I'd not have guessed that. I mean, I know those tubes typically provide a really pronounced low end, but rounded off highs? that's surprising
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It's not really rounded off per se, it's all relative to the 6550s that came with it. Still plenty bitey, but less of that and some less sizzle than the 6550s.

Also, I biased each pair to ~101 ma. That might be of some relevance.
 
i also use KT88's in my herbert they sound awsome i did have a pair
of 6550's in with 4 KT88's at one time that sounded good but i still
prefer all KT88's
 
Interesting... guess I'll have to try those at some point. Just got a full set of new Ruby EL34BHT's installed and biased up though so I'm content. Good to know though for future reference.
 
Good information mate. I wondered how the 88's would compare to the 6550's. What did you bias the same as the SED's?

Steve
 
steve_k":2l9o7czr said:
Good information mate. I wondered how the 88's would compare to the 6550's. What did you bias the same as the SED's?

Steve
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I biased the KT88s about 2-3 ma higher per pair than the 6550s.
 
stephen sawall":1ntme7iv said:
How many ma was that ?
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We suggest 50mA per tube or 100mA per pair for our 6550

65 mA per pair for EL 34
 
stephen sawall":1crwpy12 said:
How many ma was that ?
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The 6550s were biased at ~99 ma per pair, and the KT88s I biased to 101ma per pair.
 
I think that 6550 are like a pumped 6L6 and KT88 a pumped EL34.
But how they sound at low volume?

My vh4 with sed "c" El34 is 130/131 watt..you really need more power?
 
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