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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Re: 6550 Winged C posted by Mark D. on January 30, 2006 at 11:38:33:
The monoblock amplifiers that I built use the Dynaco MK-3 Board sold by Triode Electronics and are fully adjustable, they have individual bias controls on each power tube.From that PC board design the amplifier is a clone of a Dynaco MK-3 except that the Power Transformer is a Magnequest Dynaco substitute and the Choke in the Power Supply is a Hammond 193J 10H, 200ma, 82 ohms with a bit more DC resistance than the stock Dyna choke @ 55 Ohms yet lots more inductance!
The output transformer I used is a Bartolucci MK-V model that has 4300 Ohms Primary and is connected as the original Dynaco was in ultralinear mode. The Bartolucci OPT claims (individually serial numbered and tested spec. sheet included in each) a frequency response (+/-) 3 dB from 15 Hz to 52 KHz @ 60 Watts.
Title: Bartolucci Output Transformer for 6550/KT-88/KT-90/KT-100.I have adjusted and listened to the matched quad of Winged-C Svetlana tubes up from 55 ma Cathode Current up to 60 ma, never exceeding the maximum plate dissipation of 35 watts even at 70 ma/tube. But once I pass the 70ma point; the 6550's begin to exhibit an ever so slight red plate condition. They seem to prefer 60 ma at most and 500 Volts on the plates (about 30 watts). At 55 ma the plate voltage increases to 505 Volts. But the higher I push the tubes in curent, the plate voltage sags a bit to settle at about 490 Volts at 70 ma, slighly under the maximum plate dissipation of 35 watts. And I am measuring Cathode current, not Plate Current as my Shurite 0-100 ma meters are in series with the cathode curcuit and ground, thus having the Grid Currents along with the Plate Currents.
When I installed a matched quad of JJ KT-88's and set the cathode current to 60 ma the sonic difference was just startling.
It was as if someone had removed a hat covering the tweeters and changed my 8" woofers for 10" types. The musicality went through the roof. I have gone back and forth between quads and also have rolled Phase Splitter and Input tubes, yet the verdict is that the KT-88 is a better match for my monoblocks.
I had several of my audio enthusiast friends over and the general agreement was that the JJ KT-88 appeared to be a much better match for these amplifiers than the Winged-C 6550's.
Not having connected the amp to any sphisticated test equipment and actually checking it out on a scope, my references here are only limited to what we heard and continue to hear.
I have contacted the dealer for the Svetlana tubes and they agreed to exchange them for a quad of JJ KT-88's and I pay the difference plus a small restocking fee.
As I am new to the 6550/KT-88 world, I have heard over the last 10 years only amps unsing EL34/7591/7355/6F6/6V6 all in Push-Pull configurations.
The added presence and power that I hear from KT-88's over 6550's is quite impressive.
I just wanted to ask if anyone has had good experiences with Winged-C 6550's and if anyone has used them in a Dynaco MK-3 amplifier circuit?
And what amps then are specifically designed for 6550's where KT-88's would not work well? Non-adjustable Cathode biased designs maybe? Guitar amps?
Also I can add that a Quad of KT-90's briefly sounded great, but blew the HV fuse on the LCH amp, and that fuse was 1/2 amp! Somehow KT-90 tubes seem a bit risky.
Thanks for the replies.
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Follow Ups
- Re: 6550 Winged C - shermanr@prw.net 12:30:20 01/30/06 (2)
- Re: 6550 Winged C - sayntjack 22:31:39 01/30/06 (0)
- Re: 6550 Winged C - Mark D. 14:45:09 01/30/06 (0)
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