• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

What is the primary impedance?

Here is my Circlotron published more than 20 yrs ago.
Based on 6550s, KT88s or 6L6GCs. 50+ watts using KT88s or 6550s.
All the iron by Hammond. No special or boutique parts at all.
And a full page of test data, THD & IMD under various conditions.:D
(y)
 

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  • A Practical Circlotron You Can Build Short Vers.pdf
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Here is my Circlotron published more than 20 yrs ago.
Based on 6550s, KT88s or 6L6GCs. 50+ watts using KT88s or 6550s.
All the iron by Hammond. No special or boutique parts at all.
And a full page of test data, THD & IMD under various conditions.:D
(y)
I guess the Experience Electronic EL156 design has Chinese made EL156 I. Would it be any difference between the original from Telefunken and the sino version in terms of data of the tube?
 
The label on the PDF on Page One is deceiving. The circuit is not a Circlotron. (n)
It is a 'Plain Jane' PP amp. If it were the two B+ supplies would be identical, they are not.

Referring to the schematic, the plates will be at ~400V while the screens are at ~350V.
Without spending a lot of time trying to adjust the plate curves for G2 at 350V,
I'm going to go with a P-P load of 3K:)
 
Hello,

I bought old output transformers, initially given for ppEL84, in fact it is ecl86. The required primary impedance is not the same for these tubes. But after reading the article with 16 ohm speakers I found 8K4 in primary. And there, thank you for confirming, I think it's good?!

how I did it: 14v on the secondary of the ot
we measure the voltage which comes out at the secondary Vs : 320
we calculate Vprim / Vs which is the transformation ratio N : 23
we multiply by N² the impedance of the HP that we connect to the secondary and the result is the impedance that the primary presents to the BF output tube

ts ecl86 millerioux
320/14 = 23
23²x8 = 4K2
529x16 = 8K4

Regards, R