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300B, 2A3 experiances wanted

I took the plunge and bought an Elekit 8900 which I plan to assemble later this year when the weather here in the Northeast starts to get too nasty to be outdoors. I have not bought the tubes yet and would greatly appreciate hearing from any of you who have direct experiance with this amp and the tubes it takes. It will be played into, at different times, Klipsch Heresy 1's, homemade open baffles featuring Lii Audio F15 full range speakers with no crossovers and maybe even my KEF LS50s on occasion.

I like detail, texture and tone as well as a sense of space and air. Generally listen to acoustic instruments in the jazz and classical traditions, 80-85 db being plenty loud for me. I'm interested in what you think are the best bang for the buck tubes as well as some that might be on the aspirational side.

My prior tube experiance included a Dynakit ST-35 amp i build last winter and a Decware Zkit SE84 I put together the year before that. I find the Deware strangely enchanting but a bit noisy, and the ST-35 is clean and clear but, perhaps because it is a push-pull design and and not a SET, sometimes not as magical as the SE84. Kind of hoping that the third tube amp, Elekit TU8900,  with the right tubes might be the charm. I might mention that I plan to build it stock initally but might consider investing in alternate caps and output transformers if the vaunted 300B/2a3 lives up to it's legend.

Thanks for sharing your knowledge.

bruce19

Showing 6 responses by alexberger

alexberger
938 posts
 

I have had a 300B amplifier with a 6f6 driver for many years.

I upgraded and rebuilt it many times.

What was an essential upgrade is adding an interstage transformer between driver 300B instead of RC coupling.

My experience shows that monoblocks are not essential for good soundstage and imaging. It is enough to isolate right and left channel power supplies by LC or even by RC filter. It gives enough channel separation except sub bass that is not important for imaging. But sub bass isolation is super important for the driver to output power supply. Otherwise we get PS feedback between output and driver and as result motorboating that leads to loose bass. As a result, it is better to separate driver and output power supplies.

Another important subject is power supply capacitors quantity and quality. The same thing is important for cathode bypass capacitors.

alexberger
938 posts
 

Hi @bruce19

My amp is DIY. The set of tubes was always the same 6sn7, 6f6 in triode and 300B.

But for 15 years I did different upgrades of this amplifier. A year ago I added IT between driver and output. Then I made a separate PS for the driver. After that I added IT between input and driver. And In the end I disassembled the amplifier and assembled it in the new chassis.

https://photos.app.goo.gl/isJsvYM3x7hDaput9

Here is the old version of my DIY amplifier

https://goo.gl/photos/S25aReL5jyTuAF1G9

alexberger
938 posts
 

I think I'll try another driver for 300B - 6v6 instead of 6f6. I already bought new cathode resistors to adjust the circuit for 6v6.

The question is what 6v6 can you recommend? Which NOS and modern 6v6 do sound best?

alexberger
938 posts
 

Hi @kmtang 

The link you gave doesn't point to any 6v6 tubes.

Which 6v6 did you mean?

alexberger
938 posts
 

There are a lot of vintage 6v6 tubes. Which of them sound good?

The new 6v6 I see Psvane. I have Pasvane 5u4g and 12ax7 and they do sound good. On the level of good (but not the best) vintage tubes.

There is a new JJ 6v6. But I have a JJ ECC803S and I hate the sound of this tube. They have such a bad midrange. They sound like a bad SS amplifier. So JJ tubes are not my cup of tea.

alexberger
938 posts
 

I upgraded my 300b SET amplifier. I replaced 6f6g Torvac driver tube to 6v6 Psvane. 6f6 worked with idle current 26ma. 6v6 withe the same cathode resistors gave 24ma. I changed cathode resistor to get 29ma. In result much better bass control and dynamics, better instruments separation. 

Conclusion, the more powerful driver is better for 300b. I know some folks (including Sacuma) end by 300b driver for 300b.

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