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 Post subject: Output impedance
PostPosted: April 10th, 2017, 10:56 pm 
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Joined: October 10th, 2016, 10:23 pm
Posts: 41
Hi,
What can I expect by putting 5.6K output trannys in a push-pull ultralinear system designed for 4.3K trannys?
I presume coupling cap sizes may need to be reevaluated.
Long story: I was going to build a new "Dynaco ST-70" based on a new driver and the Dynaco iron I had. After moving back to DC, I can no longer locate my project parts, so on an impulse, I bought a pair of Sophia Electric 5.6K p-p output trannys (who knows, probably from someone in this group). So now I may be potentially building a Dynaco amp with no Dynaco parts or topology.
Anyhow, I am hitting the books again, but am curious as to what issues I may encounter if I tried a direct drop-in of the Sophia parts to a design for a different hunk of iron.


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 Post subject: Re: Output impedance
PostPosted: April 11th, 2017, 11:28 am 
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Joined: February 28th, 2013, 10:38 am
Posts: 1161
It shouldn't be a problem. You may get slightly less power output than you were expecting. If you're really worried about it, get some 6ohm speakers and run them on the 8ohm tap ;)

Roscoe


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 Post subject: Re: Output impedance
PostPosted: April 11th, 2017, 12:50 pm 
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Joined: July 24th, 2015, 4:17 pm
Posts: 949
Location: Parkville, Maryland
Looking at the EL-34 datasheet -- the EL-34s just may like the replacement transformers. Or -- you can try KT-88s and get more dynamic bang for your buck.

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Walt


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 Post subject: Re: Output impedance
PostPosted: April 12th, 2017, 7:41 pm 
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Joined: April 22nd, 2013, 12:58 pm
Posts: 179
Just like in triode mode, distortion tends to go down as primary impedance goes up. IIIRC, you don't lose as much power output as you do in pentode mode as you move away from the optimum power transfer point.


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