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6V6 line preamp
6V6 line preamp
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Old 21st March 2013, 02:31 PM   #1481
vgeorge is online now vgeorge  Greece
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6V6 line preamp
And some with the pot half way.
Last is on the output of SSHV2 on the anode choke, full BW and gain with 10X probes on my 20 MHz scope.
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Old 21st March 2013, 02:39 PM   #1482
buzzforb is offline buzzforb  United States
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not bad for a tube
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Old 21st March 2013, 02:45 PM   #1483
Salas is offline Salas  Greece
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Grid stopper is good to be minimal as long as you don't see more wiggles than with a reasonably higher value. Bandwidth looks 0.25MHZ -3dB indeed when comparing 1st and last pic. Not bad for 20dB gain high capacitance power tube used for line duty. 20kHZ square looks OK too. 1kHZ square is a bit wavy, not edge ringing. Some termination thing maybe, or the signal picking something? Changing x1, x10 on probe, or changing the crock ground point, changes something there? Or when using the 1K original grid stopper?

P.S. You posted the second set meantime. Losing only 50kHz at half pot position is not bad at all. The SSHV2 on your choke load looks absolutely behaving and not noisy (10x probe at full scope BW and max vertical sens is challenging). Well done.
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Old 21st March 2013, 03:03 PM   #1484
vgeorge is online now vgeorge  Greece
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Quote:
Originally Posted by Salas View Post
Grid stopper is good to be minimal as long as you don't see more wiggles than with a reasonably higher value. Bandwidth looks 0.25MHZ -3dB indeed when comparing 1st and last pic. Not bad for 20dB gain high capacitance power tube used for line duty. 20kHZ square looks OK too. 1kHZ square is a bit wavy, not edge ringing. Some termination thing maybe, or the signal picking something? Changing x1, x10 on probe, or changing the crock ground point, changes something there? Or when using the 1K original grid stopper?

P.S. You posted the second set meantime. Losing only 50kHz at half pot position is not bad at all. The SSHV2 on your choke load looks absolutely behaving and not noisy (10x probe at full scope BW and max vertical sens is challenging). Well done.
I always had this wiggle on the 1kHz and puzzled me a bit. Should I increase the grid stopper or it's not important?
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Old 21st March 2013, 03:05 PM   #1485
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Suspect small oscilation?
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Old 21st March 2013, 03:12 PM   #1486
vgeorge is online now vgeorge  Greece
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Don' t know for sure. High up it clean as you see.
Maybe it' s not important.
Just seeking advise before starting to unsolder.
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Old 21st March 2013, 03:14 PM   #1487
Salas is offline Salas  Greece
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Difficult to tell before comparisons with another stopper or by setting the probe and its GND differently. Could be something riding, not typically a ringing profile, and vanishes in the 5kHz pic even, it should have been even more pronounced up to 20kHz sqr wave. DC couple to scope, probe ONLY after the output cap, go x1 100Hz, crock to closest ground point, or even better use the short to GND coil that comes with probes to output RCA from inside. Lets see if it is 50Hz or 100Hz riding.
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Old 21st March 2013, 03:15 PM   #1488
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What does your generator signal look like?
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Old 21st March 2013, 03:19 PM   #1489
vgeorge is online now vgeorge  Greece
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Generator signal is clean. I will check again though, you never know.
Understood Salas, will do some more checks later on and revert before changing values on the grid stopper.

PS. checked the generator, squares are perfect at 1kHz.
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Old 21st March 2013, 04:31 PM   #1490
vgeorge is online now vgeorge  Greece
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DC coupled 1X, at 100 and 500 Hz.
At 100 Hz there is a small wave not clearly seen on the picture.
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