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Old 22nd July 2007, 06:53 PM   #31
Salas is offline Salas  Greece
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Default And with GTs

Sylvania thingies from the Ed Wood era.
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Old 26th July 2007, 06:50 AM   #32
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Arrow how about this?

hello everyone!

I am sorry for my badly english (japanese is OK ), but here is a special preamp circuit for 6V6 ,maybe interesting.
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Old 26th July 2007, 03:36 PM   #33
kmtang is offline kmtang  Canada
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Default EL84 Balance output

Hi Jane,

I don't think you can get the balance output from this output transformer. It can be only used for Single Ended output.

You need an OPT with CT.

Please correct me if I am wrong.


Johnny
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Old 26th July 2007, 04:21 PM   #34
rdf is offline rdf  Canada
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Hi foboleyns. Are you sure the part in red is correct? The output is shunted to ground by the cathode bypass.
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Old 26th July 2007, 04:50 PM   #35
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rdf,

It looks like the output is being taken off the screen. If you look closely, the screen does not appear to be connected to the bypassed cathode; the suppressor is however.
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Old 26th July 2007, 05:03 PM   #36
rdf is offline rdf  Canada
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Thanks Brian. Right you appear to be, though I'm not any less confused about this connection.
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Old 26th July 2007, 05:28 PM   #37
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The screen is being used as the anode. The plate is run at a very low voltage, almost turning it off. The screen's transconductance (dIc2/dEc1) will increase above its usual value when it conducts more current than the plate. The screen's dissipation is about 250mW, well below its 2 watt rating. Is all this advisable? I don't know.

I think that Steve Bench's site describes using the screen as the output anode.
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Old 26th July 2007, 06:42 PM   #38
Salas is offline Salas  Greece
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They use the screen as an anode. Somebody probably wanted to make a small tube out of a bigger one that was available. Maybe ill advised soundwise since the big current is a plus if used as a triode with output normally taken off the plate.
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Old 26th July 2007, 06:46 PM   #39
kevinkr is offline kevinkr  United States
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Default Re: EL84 Balance output

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Originally posted by kmtang
Hi Jane,

I don't think you can get the balance output from this output transformer. It can be only used for Single Ended output.

You need an OPT with CT.

Please correct me if I am wrong.


Johnny

Actually you don't need a center tap for balanced operation at all, particularly simple if the device on the other end is another transformer. Not a bad idea though to connect the chassis together through the xlr ground connection. Most transformer coupled pro gear does not use a center tap.
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Old 27th July 2007, 05:04 AM   #40
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yes,The plate is run at a very low voltage, almost turning it off in this case,it make the 6V6 look like be close to a triode with low internal resistance.

A=5.5V is necessary,we can use a regulate circuit to make it adjustable for the output gain.
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