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Old 12th November 2008, 05:05 AM   #11
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Default Why one channel use one more tube

Quote:
Originally posted by planet10
Here is a grundig EL95 SE schema (with a common PP woofer channel)
Hi,
I read the schematic, why the upper channel use one more tube than the lower, would this cause 180 degree out of phase between L /R channel, need to alter the red / black spk. wire in either one channel.
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Old 12th November 2008, 07:06 AM   #12
Yvesm is offline Yvesm  France
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Default Re: Why one channel use one more tube

Quote:
Originally posted by mitwrong


Hi,
I read the schematic, why the upper channel use one more tube than the lower, would this cause 180 degree out of phase between L /R channel, need to alter the red / black spk. wire in either one channel.
Very curious indeed !

There are 3 output transformers, one per channel for trebble and one common for basses.

The EL95 are used in SE mode for stereo/trebble channels and in PP for mono/basses amplification.
The additionnal unity gain stage is a paraphase/see-saw phase splitter needed for the PP mode to work while the correct phase for stereo/trebble is restored by swapping the connection at the secondary of the transformer (black/green wires) in the -so called- right channel.

Predicting the crossover behaviour looks like a nightmare involving transformers caracteristics, caps accross them and separates feed back loops

Not so stupid for a bean counting/industrial point of view

Yves.
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Old 12th November 2008, 11:15 AM   #13
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Default wiring colour system

Yves:
Thanks for Ur info.,another thing make me confuse, which is is there any standard or format that define the wire colour for what purpose, for instance green colour for right channel, yellow for left,----- etc.
is there any info. about this ? Thanks
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Old 12th November 2008, 06:28 PM   #14
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Here what I built some years ago:


A classical very simple circuit, sorry, just handdrawn.

Click the image to open in full size.

The result looked like this:

Click the image to open in full size.

As you can see, I replaced the ECC82 by an E80CC, this is a very very fine driver tube for this application!

Backside:

Click the image to open in full size.

Franz

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Old 12th November 2008, 06:37 PM   #15
Yvesm is offline Yvesm  France
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So cute !

The driver is larger than the output tubes ! !
What about a 6J6, just for the look ?

Yves.
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Old 12th November 2008, 06:47 PM   #16
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Cute? Thanks!

This how it looked inside:

Click the image to open in full size.

I used two torroid trannies: one to step down to 24VAC, the second one to step up.

The first one had some added windings (black wire) for the heaters of the tubes.

Most of the enclosure is filled with psu parts. Two output trannies from an old SABA radio.

The smallest part of the space is used for the amplifier circuit:

Click the image to open in full size.

Click the image to open in full size.

Franz

/Edit

I add a picture from the brainstorming phase from this project:

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Old 12th November 2008, 08:31 PM   #17
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1.55 ma is to low for good sound. Maybe it doesn't enought for
input capacitance of EL95 . Try to increase to 5 ma /put 50 kom aprox. in plate, and 600-1000 ohm in cathode of ECC82/. And put EL95 in triod mode!
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