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Old 12th December 2011, 06:02 PM   #1
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Default Output Transformer question

So I have a class AB push-pull 6v6 amp and the load impedence is 6.6k at 8 ohms. I want to try 6K6GT's for output tubes so I used a 5U4GB to lower the voltage but I believe the 6K6GT's want to see something like 12000 load resistance. My question is can I us a 16 ohm speaker on the 8 ohm tap to raise my effective load resistance?
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Old 12th December 2011, 06:29 PM   #2
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Yes.
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Old 12th December 2011, 06:32 PM   #3
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Yes, in essences you can do that. Actually a 6V6, according to the tube manual and all amps I've seen or worked on, prefers 8 to 10K ohms plate to plate. So 6.6K is a bit on the low side. And, in my opinion, 6K6's are not as "good" a 6v6's. But give it a try.
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Old 12th December 2011, 06:33 PM   #4
cerrem is offline cerrem  United States
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The gm of the 6K6GT is much lower and requires a larger plate load for normal AB1 operation... If you go into AB2 operation, then you can probably use a much smaller plate load like 6.6K..... thats provided that the driver circuit is up to the task..

Chris
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Old 12th December 2011, 06:57 PM   #5
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I found some literature on the OPT and I think the turns ratio is 50:1, just got to remember how to put that info to use.

And say there were two cathode followers one for each of the grids of the output tubes would that drive the tubes into AB2?
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Old 12th December 2011, 08:31 PM   #6
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Quote:
Originally Posted by famousmockingbird View Post
I found some literature on the OPT and I think the turns ratio is 50:1, just got to remember how to put that info to use.
That does not seem to be correct: 50:1 is 20k to 8 ohms.
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Old 12th December 2011, 09:43 PM   #7
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Originally Posted by pieter t View Post
That does not seem to be correct: 50:1 is 20k to 8 ohms.

Yeah your right, 50x50=2500

2500x8=20,000
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Old 12th December 2011, 10:16 PM   #8
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To be sure it is rather simple to calculate the impedance ratios by measuring the voltage (winding) ratios.
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Old 12th December 2011, 11:05 PM   #9
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I think I figured it out the turns ratio, it is 29:1

I got it all hooked up and the 6k6gt's in and everything is fine. Thanks everyone for all your help.
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