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Showing 1 of 160 conversations about:
Jora
3
Jul 21, 2018
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Looking at the information on the amp they list OTK 2 as a tube type when it's actually an inspection stamp you see on lots of Russian tubes. So while it's great that the tubes have passed inspection, it doesn't really help me know what type of tubes are being used in the amp.
BrianCheng
7
Aug 14, 2018
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JoraI got mine from last drop, stock tubes are 6H5P and 6Ж8 ( not 6Ж4С ), the tubes work fine and no hum. I replace them with CSF 6080WA and RCA Jan 6SJ7, also work fine no hum.
aatjitra
4
Aug 14, 2018
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JoraNot really. A few types of sharp cut off pentode used for preamplifier stage like in this amplifier. The first stage is using 6SJ7 for higher gain to drive 6AS5/6080 at the power stage.
If they are Russian tube, most likely you will get 6J4 series. You can substitute to any 6SJ7 tube. They are many brands like RCA or GE wih reasonable price.
Red GE5673 tubes also can be considered for much better replacement.
Another option is to use adapter and use EF86 as replacement.
Both tubes are seldom used in hifi applications as pentode is high in odd harmonic. Normally we use triode in cascade configurations.
If they are Russian tube, most likely you will get 6J4 series. You can substitute to any 6SJ7 tube. They are many brands like RCA or GE wih reasonable price.
Red GE5673 tubes also can be considered for much better replacement.
Another option is to use adapter and use EF86 as replacement.
Both tubes are seldom used in hifi applications as pentode is high in odd harmonic. Normally we use triode in cascade configurations.
aatjitra
4
Aug 14, 2018
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BrianChengI like RCA 6SJ7 compare to Tungsol or Sovtek.
Red 5673 tube also can be considered for better replacement.
Red 5673 tube also can be considered for better replacement.
Jora
3
Aug 15, 2018
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aatjitraUsing a pentode as a driver for a triode output is pretty common, the high second order harmonic of the pentode driver inverts to the second stage and cancels the harmonics in the second. This goes back all the way to the Radiotron Designer's Handbook 2a3 design using a 6C6 to drive the 2a3 if not further than that. Your recommendation of the red RCA version of the 6SJ7 is a good one, however the red tube version of the 6SJ7 is the 5693 not 5673 (typo?). I'm not sure about the use of power supply regulator tubes as outputs as they're not very linear but they do have a low plate impedance which will make it easy to drive headphones, especially without any transformers.
Jora
3
Aug 15, 2018
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BrianChengI bet those were a good improvement over the stock tubes. Get your hands on the 5693, the red long life version of the 6SJ7 tube and it will sound even better than NOS 6SJ7 plus the red tube is a 10,000 hour tube so it's a good investment.
Davestef
239
Dec 2, 2018
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aatjitraDo you own a 339? Recommend it as an upgrade from the 336? I have the 6xx and 58x. There aren’t a whole lot or reviews or actual comments about the amp on massdrop. Mostly people asking for the 220V version
Horseknight
179
Dec 2, 2018
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aatjitraTotally agree. Once switch to the new pairing set of RCA 5693 (Red) and 6080(or 6AS7), more sound details jump out.
Both are not too costly to acquire. Good choice.
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