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Old 2nd February 2003, 12:24 AM   #61
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Default PUB TALK.

Hi,

Thought you was...

Quote:
I meant to try reducing the value of the grid stoppers,
Doesn't really matter though...you catch my drift.

If you allow a litle tip:
Never make gridstoppers any larger than strictly necessary.


Ciao,
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Old 2nd February 2003, 12:40 AM   #62
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Since it is direct coupled you should be able
to take away the grid stoppers too, or....

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Old 2nd February 2003, 12:42 AM   #63
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Default NO.

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Old 2nd February 2003, 12:56 AM   #64
7N7 is offline 7N7  United Kingdom
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Default Re: PUB TALK.

Quote:
Originally posted by fdegrove
Hi,

Thought you was...



Doesn't really matter though...you catch my drift.

If you allow a litle tip:
Never make gridstoppers any larger than strictly necessary.


Ciao,
Of course and this is particularly apposite in this case, where I am anxious to have as low a source resistance as possible. However, I once built a 6SN7 line stage with cathode followers. The 6SN7s had 470 ohm grid stoppers - a typical choice - but the stage was oscillating at about 2.5MHz!

On the 6528A I have used the minimum recommended by the makers (1k) which is pretty low for an output stage - even EL84 uses 4.7k as a rule.

However, I am going to try 470 ohms and watch the 'scope!

Incidentally, I am considering using a similar arrangement of driver stage in the 13E1 amplifier. Here though bias is about
-51V, so I shall have to wring some more swing out of it

7N7
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Old 2nd February 2003, 01:03 AM   #65
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Default THE SHORT ANSWER.

Hi,

Although this was voiced by me before...

Don't design oscillators, gridstoppers as any other series R will eat microdetail and as such will reduce dynamic resolution.

I think this should make sense?

Cheers,

\Frank,the unipivot.
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Old 2nd February 2003, 01:12 AM   #66
dhaen is offline dhaen  Europe
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Hi,

I'm not clear on these gridstoppers.
What kind of oscillation are we talking about? Barkhausen (or however it's spelled)? If it is, there are other ways....

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Old 2nd February 2003, 01:15 AM   #67
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Default CRITTERS.

Hi,

Quote:
I'm not clear on these gridstoppers.
Mainly RFI osc.

The 6C45C is another matter,it tends to go into self osc.

Chin kampai,
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Old 2nd February 2003, 01:26 AM   #68
7N7 is offline 7N7  United Kingdom
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Default Re: THE SHORT ANSWER.

Quote:
Originally posted by fdegrove
Hi,

Although this was voiced by me before...

Don't design oscillators, gridstoppers as any other series R will eat microdetail and as such will reduce dynamic resolution.

I think this should make sense?

Cheers,

\Frank,the unipivot.
Design oscillators?

Perish the thort in the words of N. Molesworth.

I shall try to reduce the value of them for the reasons I gave above - and I shall be keeping a close eye on the 'scope.

When I've fixed the 13E1 amp I'll have a go and also try removing the grid leaks. I'll report my findings, gentlemen, for your perusal

7N7
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Old 2nd February 2003, 01:37 AM   #69
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Default WRONG POST WRONG PLACE...

Hi,

Quote:
The 6C45C is another matter,it tends to go into self osc.
This should have gone into the 6C45 thread...blimey...reducing Rg won't hurt though.

Sorry,wrong channel...

Back to the bunker...
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