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Current-drive by a valve amplifier
Current-drive by a valve amplifier
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View Poll Results: What do you think about the SEP current-drive idea?
Brilliant idea 2 16.67%
May be good but not exactly this way 2 16.67%
Bad idea 3 25.00%
I don't know / no opinion 5 41.67%
Voters: 12. You may not vote on this poll

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Old 3rd December 2020, 03:03 AM   #91
Wavebourn is offline Wavebourn  United States
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Quote:
Originally Posted by 6A3sUMMER View Post
“Those who do not know history, are not aware that we are 'in' Deja Vu.
It is even better to learn the theory in depth, and solve math problems for themselves, than pretending to be a guru while learning, opening topics inviting to discuss opinions about Ohm law implementations
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Old 3rd December 2020, 04:47 AM   #92
6A3sUMMER is offline 6A3sUMMER  United States
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"Poll: What do you think about the SEP current-drive idea?"
Before answering this poll, I want to be sure about what an SEP is.

I think that Three Letter Acronyms are confusing (TLA).
When is a TLA not a Three Letter Acronym?
When it is a Thirty Letter Acronym.

Now back to the SEP . . .
Is that a Single Ended Pentode?
Just wanted to be sure.
Thanks!

Still having doubts . . .
I always thought that AMA meant American Medical Association.
Then I learned about AMA, the American Management Association.
Now, I see Slang on the internet, it says:
AMA is "Ask Me Anything" or "Against Medical Advice"

I try to write out 'Output Transformer' instead of 'OPT'.
And many other similar things, to avoid Three Letter Acronyms.
Newbies are trying to learn.

Just my opinions.

"Vote Early, and Vote Often" Deja Vu for the youngsters who were not alive then.

Last edited by 6A3sUMMER; 3rd December 2020 at 04:50 AM.
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Old 3rd December 2020, 06:27 AM   #93
NickKUK is offline NickKUK
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As a very nieve beginner view - in my book the tube is a current device.. only resistance gives it a change in voltage.

Sure an OTL driving a low impedance is a current drive (tongue in cheek) - typically the intermediate steps use voltage amplification due to the grids.

If you used an inverted triode, then used that to drive the grids for the next stage? An inverted-triode OTL is a simply a current drive but todo it properly the B+ needs to run through the end load.

All the 'current drive' in the pictures is doing is causing a feedback loop with additional gain needed that then causes a higher current? No real difference when using feedback to lower output impedance for driving low impedance loads.

Just beginner thoughts..

Last edited by NickKUK; 3rd December 2020 at 06:29 AM.
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Old 3rd December 2020, 06:12 PM   #94
Nikolas Ojala is offline Nikolas Ojala  Finland
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Arrow Single-ended indeed

Quote:
Originally Posted by 6A3sUMMER View Post

Now back to the SEP . . .
Is that a Single Ended Pentode?
Yes.
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Old 3rd December 2020, 10:48 PM   #95
6A3sUMMER is offline 6A3sUMMER  United States
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Use the 2nd harmonic distortion of a single ended pentode amplifier to partially cancel the 2nd harmonic distortion of a loudspeaker driver.
One is long on the positive alternation, and short on the negative alternation.
The other is long on the negative alternation, and short on the positive alternation.

We tried that experiment with a DPDT phase reversal switch, a single ended 2A3 DHT amplifier, and a Spica tc 50 loudspeaker.

It might be time to try it with a single ended pentode amplifier that has little or no negative feedback, and a loudspeaker.
Phase is everything if you want to try this. The DPDT might allow you to fairly easily hear the difference in tonality/timbre of the two switch settings.
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Old 4th December 2020, 08:28 PM   #96
Nikolas Ojala is offline Nikolas Ojala  Finland
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Wink 2nd harmonic, vanish now

Quote:
Originally Posted by 6A3sUMMER View Post
Use the 2nd harmonic distortion of a single ended pentode amplifier to partially cancel the 2nd harmonic distortion of a loudspeaker driver.
One is long on the positive alternation, and short on the negative alternation.
The other is long on the negative alternation, and short on the positive alternation.
Yes. I had almost forgot but thanks for reminding. Eduardo de Lima wrote about that in his article "Why single-ended tube amplifiers?"

The essential part of his conclusion:
Quote:
The really good sonic performance of a well put together system using single ended amplifiers can be understood if we consider the whole system performance. A system made using single ended amplifiers is a perfectly valid way of achieving a very good sound also from the measurements point of view. We just have to measure the correct parameter. The output of the whole system.
One may use that wisdom with any amplifier and speaker combination. What you hear is what you get, and if you don't trust your ears, then use a microphone.
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