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Stereo amp to monoblock

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The Cawleys

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Apr 10, 2001, 11:20:58 PM4/10/01
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I have seen a few tube amps that have a switch that enables
the amp to function as a monoblock. If you have 2 identical
amps is it possible to modifiy each to perform as a mono
amp? How would combine the outputs, etc?
Thanks
Mike C.


Auke Dost (Tubelar)

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Apr 11, 2001, 5:36:41 AM4/11/01
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It is easy
Use the 4 ohms windings from transformer. Disconnect the Ground connection
from one of the tranformers and connect that one to the" HOT" side of the
other trannie (basicly you put the secondairy windings of output transformer
in series).

Feed both amps with the same signal and you will have double the power at 8
ohms

Remarks are to be made that not every amp is capable of handeling this trick
al depending of quality of construction and builders used technics.

It is Known that KITTY HAWK amps build a serie 6550 amps specialy for Bass
Guitar in this way.
They were used (or still are in use ) By MANOWAR (Hardrock band)

Regards Auke http://www.auke.myweb.nl


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Corné Janssen

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Apr 11, 2001, 5:45:45 AM4/11/01
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"Auke Dost (Tubelar)" wrote:
>
> It is easy
> Use the 4 ohms windings from transformer. Disconnect the Ground connection
> from one of the tranformers and connect that one to the" HOT" side of the
> other trannie (basicly you put the secondairy windings of output transformer
> in series).

If the amplifiers use feedback you have to modify the feeback circuit of
the
amplifier that has the ground disconnected and tied to the "HOT" side of
the other amplifier.
Connecting both channels in parallel is safer and less complicated.

Corné

Buffstereo

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Apr 11, 2001, 11:43:36 AM4/11/01
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>Connecting both channels in parallel is safer and less complicated.

That's what I do, (connect the outputs in parallel). Keep in mind that to
parallel the output impedances, reduces that same overall impedance by half.
So, if I have 8 Ohm speakers, I would tie together the 16 Ohm transformer
outputs, and also the grounds. That would give me 8 Ohms out, and proper
matching with the 8 Ohm speaker.
Good luck with your gear!
Robert Thompson
Live and let live!

The Cawleys

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Apr 13, 2001, 2:02:34 AM4/13/01
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Thanks for your replies. I think this might be a little difficult since the
amps in question are a pair of VTL ST-80's which have no multiple taps.

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