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August 14, 2022, 11:14:43 PM

Author Topic: 6v6 tube rolling  (Read 2224 times)

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Offline oldtriode

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Re: 6v6 tube rolling
« Reply #15 on: September 30, 2021, 04:18:28 PM »
After many hours of use, with several pairs of 6K6-GT tubes in the Moreplay, here are my initial impressions of their performance.

First of all, I believe that the Moreplay circuit, and it's operating parameters, is well suited to this tube type.  Or maybe, it's the reverse...the tube is tolerant of the Moreplay design.  Whatever the case, all the ones I have tried work well.  These range from various manufacturers, RCA, GE, Tung-Sol, Sylvania...all original 1940s and later tubes.  Some are smoked glass, others clear, you name it. All have slightly different plate structures compared with each other.  So without naming favorites, I'd suggest users that want to experiment with this type will not be disappointed in the sound, and your Moreplay will treat you to slightly different presentations, with no duds.  All based on my subjective results, so expect a bit of variation.

I initially wanted to try some early G varieties, but could only find one pair, used, that tested fair on my tube tester.  They were branded Wards Super Airline, very dark smoked shield, with bottom getters, so I can't say who the maker was.  They were nice and smooth, a little rolled off in the highs, but good bass and great definition.  No real objection to them, and they look cool, with that ST-14 bulb.

Next up, a pair of RCA NOS clear glass 6K6-GT with black oval plates.  One had a date code of 1956, the other was probably a bit older.  These were superb, great air but not harsh, midrange just right for vocals, and plenty of clean bass.

Third, a pair of GE clear glass, gray plates, one dated 1964, the other undated, but similar vintage.  These were a bit smoother overall, and even more bottom end compared to the RCAs.  I almost stopped with these, being very happy with their presentation of a wide variety of recordings.

Fourth, a visually and gain matched pair of Sylvania NOS Clear glass, round black plates with stapled flanges, top getter, yellow print on the bases...production dates not present.  These were very close to the GEs for overall sound, a little more top end, and a little less bass. but nothing affecting the overall balance that would make them objectionable. Still very clear and quick.

At this point, any of these NOS tubes would good to go with, very minor differences between them.  Not hard to find, inexpensive, and real old-school quality.  Get some and try them out!  You'll be amazed...at least I was.  And the Moreplay is still a great bang-for-the-buck preamp that can hold it's own against anything costing 3 to 4 times the cost.  Great design, Bottlehead folks!

Keep up the good work!

--stereo71

Offline David Joiner

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Re: 6v6 tube rolling
« Reply #16 on: December 16, 2021, 04:11:41 PM »
Hey Oldtriode,

Quick question, did you need to modify your Moreplay to use the 6K6 tubes? In another post by Paul Joppa, he noted, for the 6K6 tubes:

"Different heater currents up to 0.75 amps should be OK with AC heating, but the dropping resistors must be changed, and when the DC heater upgrade is available, it will not tolerate more than 0.45 amps: 6K6 - 0.4A heater so may need slight change in dropping resistors"

Thanks for your post and I'm hoping I can tube roll 6K6's into my Moreplay without any mods.

David

Offline Paul Birkeland

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Re: 6v6 tube rolling
« Reply #17 on: December 17, 2021, 04:59:34 AM »
The heater voltage should still be well within tolerance with the 6K6 in the stock Moreplay circuit.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Cary

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Re: 6v6 tube rolling
« Reply #18 on: December 17, 2021, 05:45:30 AM »
I was looking up the price for 6K6 tubes, they are even cheaper than 7C7 tubes. Thanks for the review oldtriode!

Offline Tubegopher

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Re: 6v6 tube rolling
« Reply #19 on: December 19, 2021, 08:24:10 AM »
My son has a Moreplay and I gave him a couple of 6K6 tubes for him to audition. His response back was that he did not experience any discernible difference in sound. He does love his Moreplay!
300B amps with 6SJ7 in Triode mode, dc fil. volt. for 300Bs. BeePre with Bill Milosz built Eros Phono. Teres Turntable, Pete Riggle "12 inch Woody Tonearm" Grace F9  with Soundsmith ruby cantilever stylus.Cambridge Audio CD with MHDT Labs Orchid DAC Rega NAOS Spkrs, Atelier Rullit super tweeters

Offline oldtriode

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Re: 6v6 tube rolling
« Reply #20 on: January 03, 2022, 03:20:39 PM »
Yes, I think the 6K6 is a winner.  Very slight differences among the ones I tried, none had a problem with the Moreplay circuit as built.  And you can afford to sample a lot of them, for the price!  Keep the good sounds coming!