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D3A-300B Amplifier
D3A-300B Amplifier
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Old 11th June 2018, 04:10 PM   #61
santitrucco is offline santitrucco  Argentina
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45 and you know how is his performance ?
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Old 11th June 2018, 06:31 PM   #62
Wavebourn is offline Wavebourn  United States
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6Ж52П
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Old 11th June 2018, 08:42 PM   #63
45 is offline 45  Italy
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Quote:
Originally Posted by santitrucco View Post
45 and you know how is his performance ?
Excellent.
The DR version has become quite expensive though but as a driver, run not too hot, the "e" version is just as good.
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Old 12th June 2018, 03:31 AM   #64
santitrucco is offline santitrucco  Argentina
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Ok , i will bought some tubes 6E6P E , maybe in the future could be some comparisons..
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Old 12th June 2018, 10:02 PM   #65
pl802 is offline pl802  United Kingdom
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Read here http://www.bartola.co.uk/valves/2012...thd-benchmark/
And here www.bartola.co.uk/valves/tag/6e5p/

Oh dear I see 45's done so already......my apologies

Last edited by pl802; 12th June 2018 at 10:06 PM. Reason: Didn't read thru whole thread
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Old 12th June 2018, 11:54 PM   #66
Wavebourn is offline Wavebourn  United States
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Different tubes require different conditions for best performances. I would never compare 6J5P and 4P1L on the same current, voltage, and signal levels.
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Old 13th June 2018, 03:28 PM   #67
santitrucco is offline santitrucco  Argentina
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Is true that 6e5p is 500 hs duration?
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Old 13th June 2018, 04:18 PM   #68
popilin is offline popilin  Argentina
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That is service life guarantee by the manufacturer.

The best linearity on benchmark for the driver does not guarantee the best linearity on the output, especially with the 300B, sometimes you must consider distortion cancellation, mostly for the third harmonic.

I am obtaining good results in simulations with more pedestrian valves like the ECC81/12AT7, belly curves seems to help more than exotic valves.
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Old 13th June 2018, 05:41 PM   #69
rongon is offline rongon  United States
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It would be nice to be able to use a plate (anode) choke on your driver triode, to make use of the choke's energy storage for brief bursts of voltage peaks. However that would mean the driver triode should have low rp (ra), so that the driver stage will have good low frequency response using a plate choke capable of >20mA standing current and with achievable inductance (50 to 60 H). That disqualifies ECC81/12AT7, even with two triodes paralleled (rp = >8k under real-world conditions).

That's where something like a triode-strapped small power pentode might be good. Perhaps a triode-wired 6P14P or 6P15P with a plate choke?

But will that yield enough input sensitivity for a 2-stage power amp? I don't think so.

That's when we get to Wavebourn's suggested 6J52P. Or 6S45P? (Both tend to be really microphonic, but maybe okay for a driver stage.)

If trying to fulfill popilin's suggestion, you'd need to find a triode with so-so linearity, high mu, and high gm. Hmmm... triode-wired 6JD6A? (Semi-remote-cutoff RF frame grid triode with 14mA/V gm -- https://frank.pocnet.net/sheets/127/6/6JD6.pdf)

Oh well. I guess that's why there are so many 3-stage SE 300B amps, and why WE designed the original 300B amps with a pentode driver.
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Old 13th June 2018, 07:18 PM   #70
Wavebourn is offline Wavebourn  United States
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Quote:
Originally Posted by santitrucco View Post
Is true that 6e5p is 500 hs duration?
It means, you can't sue the manufacturer if the tube failed after 500 hours.
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