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Old 21st January 2008, 11:59 PM   #1
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Default Line-Stage w/ balanced output

I have a line-stage design that uses a 6SN7 in a cathode follower config. and I want to rig the output to drive balanced inputs on a SS power amp,and suggestions?
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Old 22nd January 2008, 02:00 AM   #2
billr is offline billr  New Zealand
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the simplest way would be to use an output transformer to create a balanced output.

the other, more complicated way, is to build a balanced preamp.

bill.
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Old 22nd January 2008, 02:36 AM   #3
SY is offline SY  United States
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If the load is balanced, you can convert the cathode follower to a split-load inverter.
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Old 22nd January 2008, 03:08 AM   #4
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Quote:
Originally posted by SY
If the load is balanced, you can convert the cathode follower to a split-load inverter.

SY,

Will the O/P impedance of a "concertina" phase splitter be low enough to drive a potentially very nasty load? Remember, the IHF "standard" is a wretched 10 KOhms.
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Old 22nd January 2008, 03:15 AM   #5
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Should be. It's the same as the output impedance of a cathode follower, as long as the load is balanced.

Let's see, with a plate current of 9-10mA, the transconductance of a 6SN7 is roughly 2.5 mA/V. So the source Z is about 400 ohms, not too bad for driving a 10k load. An ECC88 would be better, but a 6SN7 should be fine.
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Old 22nd January 2008, 03:16 AM   #6
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Could I add an additional Cathode follower stage, and "paraphrase",or use the two stages to form an "anode follower" phase splitter?
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Old 22nd January 2008, 03:19 AM   #7
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Quote:
Originally posted by denny9167
Could I add an additional Cathode follower stage, and "paraphrase",or use the two stages to form an "anode follower" phase splitter?
For an extra tube and higher parts count, an anode follower and cathode follower combo will offer performance somewhat worse than a split load.
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Old 22nd January 2008, 03:37 AM   #8
billr is offline billr  New Zealand
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you could try a LTP with a ccs in the tail, then have two cathode followers drive your amp.
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Old 22nd January 2008, 03:39 AM   #9
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wouldn't it just be simpler to use a small signal output transformer with a center tapped secondary winding?

small signal outputs with center tapped secondaries are pretty common in both new production as well as vintage examples being available.

MSL
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Old 22nd January 2008, 04:08 AM   #10
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Quote:
Originally posted by MQracing
wouldn't it just be simpler to use a small signal output transformer with a center tapped secondary winding?

small signal outputs with center tapped secondaries are pretty common in both new production as well as vintage examples being available.
I agree on the transformer, but what's the center tapped secondary have to do with it? The +/- signal should be taken from the transformer with the third connection coming from the chassis.

Click the image to open in full size.
http://www.rane.com/note110.html

Anyhow, here's some for cheapish.
http://cgi.ebay.com/Jensen-JT-123-S-...QQcmdZViewItem
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