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Old 8th February 2013, 09:49 AM   #1
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Default 6SL7 in parallel driving 6550

http://www.anc-tv.ne.jp/~suzuki3/amp...EL34%20AMP.pdf

Has anyone tryied this amp??
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Old 8th February 2013, 12:09 PM   #2
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Not tried exactly that schematic but almost similar.

Some comments:

- there is no reason to "waste" two triode sections for driving EL34, not even when triode connected
- grid resistor can be larger than 100 k when auto bias is used, this improves the linearity of 6SL7
- there are few odd component values; cathode bypass capacitor do not need 450 V voltage rating, 50 V is sufficient, and grid resistor do not need 3 W power rating
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Old 8th February 2013, 01:02 PM   #3
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I agree with all the points artosalo brought up.
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Old 8th February 2013, 01:19 PM   #4
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The two sections of 6SL7 could be implemented differently
Attached Images
File Type: gif EL34_SE.GIF (19.2 KB, 206 views)
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Old 8th February 2013, 03:21 PM   #5
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Strongly disagree with comments about not doubling 6SL7, which is a low transconductance tube. Search on experiences and designs of member yvesm
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Old 8th February 2013, 03:36 PM   #6
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Quote:
Strongly disagree with comments about not doubling 6SL7, which is a low transconductance tube. Search on experiences and designs of member yvesm
Which posts out of the 900 or so?

The thing is. For some applications doubling up might be beneficial. For a tube as easy to drive as the EL34. It really is not needed in my opinion.

I would suggest the OP finds out for himself. There really is no substitute for trying things out for yourself.
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Old 8th February 2013, 03:42 PM   #7
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Quote:
Originally Posted by Bas Horneman View Post
The thing is. For some applications doubling up might be beneficial. For a tube as easy to drive as the EL34. It really is not needed in my opinion.
A 6SL7 has a wimpy transconductance of 1600, and the EL34 is in triode mode in that design. Bad idea to not double it. Just calling it like I see it.
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Old 8th February 2013, 03:43 PM   #8
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Old 8th February 2013, 04:11 PM   #9
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Quote:
Originally Posted by leadbelly View Post
Strongly disagree with comments about not doubling 6SL7, which is a low transconductance tube. Search on experiences and designs of member yvesm
I in turn fully agree what Bas said. And I have my own experience about this too. Actually 6SL7 with CCS is a very good driver.

leadbelly; what do you think that would go wrong when one 6SL7 instead of two is used to drive triode connected EL34 ?
Distortion ? Frequency response ? or what ?
But please, do not just say that it does not sound good. Then we nothing to discuss about this.
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Old 8th February 2013, 04:29 PM   #10
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I also agree with all the points artosalo brought up.

I was just curious because i never tryied the 6sl7 in SE aplication as driver...

Yes! The grid resistor can be increased, and i am thinking of changing the EL34 with 6550.

And what do you think that would go wrong when two 6SL7 parallel triodes are used to drive a 6550???

Last edited by nomiconxp; 8th February 2013 at 04:33 PM.
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