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Bridge SE amplifier
Bridge SE amplifier
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Old 16th February 2006, 11:32 AM   #1
croccodillo is offline croccodillo  Italy
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Default Bridge SE amplifier

Hi all,

What about a SE amplifier connected as a bridge, like THIS ?

Of course it is necessary to create a driver circuit that drives the two KT88 in opposite phase, and another circuit that mantain the two tubes operating points exactly at the same voltage.
But it should be feasible, and should give a lot of power and a really fast amplifier...
maybe using Tubelab's PowerDrive modified to drive two tubes.

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Old 16th February 2006, 11:44 AM   #2
darkfenriz is offline darkfenriz  Poland
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What are advantages supposed to be compared to typical push-pull?
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Old 16th February 2006, 02:13 PM   #3
Tubelab_com is offline Tubelab_com  United States
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Hi Giovanni:

This circuit by definition IS a push pull amplifier since the two output stages are operating out of phase with each other. I tried something like this a few years ago when I was trying to use power (mains) toroids for output transformers. The idea was to eliminate any DC current from flowing in the OPT. After much experimentation I found no advantage over the conventional push - pull design, since DC flowing through the transformer is not an issue if the two currents are equal.

What I did find useful was to put the CCS's in the cathode circuit for an "auto bias" effect. This works great for class A circuits. If you leave class A and one tube cuts off the CCS may exhibit some recovery time effects that really sound bad.

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Old 17th February 2006, 02:58 AM   #4
Eli Duttman is offline Eli Duttman  United States
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Keep in mind that the object when strapping/bridging is to sum the voltage swings of the 2 sections in the load. If you take 2 sections with floating O/P trafo secondaries, connect the I/Ps in parallel and the O/Ps in series, you sum the voltage swings in the load without using out of phase drive signals. So, the composite is NOT PP.

I use the method described above with a pair of DECWARE SE84Bs and get good results.

The caveat about each amp section "seeing" only 1/2 the load applies to this method of strapping too.
Eli D.
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