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Super 6BG6 vs. 6550

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I've been doing a fair bit of messing about with amps incorporating a non-standard tube set, like the 6LR8 and screen-driven sweep tubes. I have a hankering to do a standard-issue triode-connected pentode amp, especially as I have a pair of 3k impedance Transcendar SE output transformers looking for gainful employment. These transformers have no screen taps, so UL is out of the question.

I have a bunch of the super 6BG6 tubes on hand as well as a quad of Reflector 6550WCs. Which is more likely to be the best sounding tube triode-connected?
 
Very interesting, SY - according to scuttlebutt, the Tung-Sol 6550s are supposed to sound preety nice, so bettering them for a fraction (and a small fraction, at that) of the price is a real coup. What sort of output iron were you using?
On another note, do you think that the screens on the 6BG6/7027 would be troubled excessively by 400V B+?
 
I'm using 6BG6GA's along with Hammond 1628SEA OPT's.

I compared them to SED EL84's, Shuguang 6L6GC's, and old Chinese KT88's. The 6BG6's won by sound and price. I had four, and then bought a bunch more.

On the same note I also tried some old Sylvania 8417's. Those were the best yet, but good luck on finding any.
 
Look for the Sylvania 6L6GC STR curves if you can find 'em. That's about the closest thing I know, to the plate structure in the "super 6BG6". Should work fine as a modeling tool...

BTW: I'd order a set of these... if I didn't already have a quad of Sylvania STRs... kinda obviates the need, I guess... :D

Regards,
Gordon.
 
SY and Burnedfingers. Can you guys please contact me via email?

I've got several questions to ask about using the 6BG6GA tubes in a couple amps. I'd like to try them in my Quicksilver 8417 amps as I just don't want to have to deal with the 8417 issues, and because the EL34 conversion just doesn't sound promising. I'd also like to try them in a Stereo 70.... well..... just because.

thanks.
 
Do you know the plate to plate impedance of the Quicksilver output transformer? Though the "6BG6" will work fine with 4500-5000 ohm, a bit higher is better. The best I've tried so far was a 500 volt rail and 6600 ohms.

The difficulty for a direct drop-in is that the "6BG6" has a higher drive voltage requirement. You'll have to modify the bias supply to get a higher voltage and ensure that the driver stage is capable of the extra swing. That said, it will end up being a much more rugged and reliable amp.
 
Thanks for the information. I don't readily have the answers to your questions.

The reason I also asked burnedfingers to respond is because he stated he already had a Quicksilver 8417 converted amp, and could possibly run through the exact changes he made. That would be a plus.

Also, not stated earlier, I have some of the SND 6BG6GA tubes just gathering dust . I was able to snag a box of 100 several years ago when he was willing to let them go for cheap, about $3.25 per tube at that quantity as I recall. So I've been looking for places to use these other than as just replacements for my standard 6L6 stuff.
 
I sent you an email Ohighway.

First try them in your Stereo 70 and you will be amazed at the difference. If your a convert then we will do the Quicksilver mod.

Convert your stereo 70 to individual tube bias first and then change the first 10K resistor in the bias circuit to 6.7Kor so and see if they will all bias up correctly. If they do then enjoy and if not go to a slightly smaller bias resistor and bias it again. I put a switch in so I could used the stock bias resistor for the EL34's.

You will need the conversion tube bases or you will have to rewire the output tube sockets for the 6BG6GA's. I purchased the bases and this way I can pop the EL34's back in if I desire.

I think the stereo 70 is 4200 or 4300 ohm output transformers and so is the Quicksilver.

My personal opinion of the EL34 Quicksilver mod is that it doesn't cut it. I assume part of the problem might be the modifications to the front end.
 
Thanks for the information. I have a scrappy looking stereo 70 that needs a rebuild anyway, so I'll likely use that as a testbed.

Though I haven't personally heard it, I recently talked with an original 8417 Quicksilver owner who had Quicksilver perform the EL34 conversion. His take on it...... "the magic was gone".

My audiophile type friends hold the EL34 in very high esteem, however I don't personally worship at that altar. I tend to prefer the sound of tubes like the 6L6, 7591, and even the 6V6. They have a cleaner more crisp sound than the EL34 ( or EL84 for that matter).
 
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