Values for grid stoppers for 6922... - Page 2 - diyAudio
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Old 28th March 2003, 12:58 AM   #11
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Default SHORTSIGHTED VIEWS.

Hi,

Quote:
The volume pot in a typical valve amp is 100K so the maximal resistence ( pot is at the midle position) driving the grid of the first valve is +- 25K..in the others positions less ..so 25K more 2.2K(of the grid stopeer) doesn't make much diference!!
Only when the pot is physcally remote from the next tube would you need a gridstopper.

Stubborn idiots like myself use extension shafts and couplers to bring the pot or attenuator as close as possible to the next stage.

Ciao,
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Old 28th March 2003, 01:02 AM   #12
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Quote:
I agree with Joel about gridstoppers for the 6DJ8/6922 family . I have often seen little puffs of oscillation picked up on the scope with some 6DJ8 types , almost intermittantly
Yes...we can not forget that the 6DJ8 is designed as a video tube...,so the wide bandwith and less miller capacitance make it more prone to parasitics oscilations!

The price of speed!!
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Old 28th March 2003, 01:04 AM   #13
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Default 6922

Hi,

Quote:
From experience I find it best to use a 1k grid stopper , but this may depend on whatever operating point is used . Fit them : better to be safe than sorry , expecially if different 6DJ8 are to be used .
Yes, the 6922 are sensitive tubes with high tranconductance so a gridstopper may tame them to some extend.

A value as low as 33R may do the trick already.

And indeed it will probly take out some of the harshness ( which is quite likely RFI).

I did say, if not needed...than don't put them in, right?

Measuring tools and an understanding of layout will get you a long way in this department.

Cheers,
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Old 28th March 2003, 02:25 AM   #14
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Well, the volume pot isn't in the same chasis, it's quite a while away, so maybe that'll add to the problem. I slapped in 2.2k in series with the grid and I'll probe it with my scope when everything is good and done. Putting these back together was hell, have the psu on the bottom the the chasis, the MOSFET circuits on the heasinks on the sides and the tube circuits on the underside of the top, makes it real hard to work with, don't ask me why I did that.
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Old 28th March 2003, 02:33 AM   #15
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Default SPITTING DISTANCE.

Hi,

Quote:
Well, the volume pot isn't in the same chasis, it's quite a while away, so maybe that'll add to the problem.
Not such a good idea IMO for various reasons, one of them being that in this configuation ( as I undrstand it) frequency response is likely to change according to volume settings.

Quote:
don't ask me why I did that.
We won't...
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Old 28th March 2003, 02:55 AM   #16
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...Makes me wonder what you'd say about my preamp then... and yet...it sounds fantastic! Humm...

Tim
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Old 28th March 2003, 03:03 AM   #17
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Default GOOD FOR YOU...

Hi,

No idea what your preamp sounds like...

I only got this nagging feeling that I am a few steps ahead of the mere mortals...you can join us later on, it did not come overnight.

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Old 28th March 2003, 04:54 AM   #18
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Sorry to say it Frank, but I knew that the first couple of your posts I read.

Tim
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