No, SY did not mean the 1960 article which you posted. But the 1957 article (I think...), which can be found here. p.39-p.44.
Smileys was an answer to Smoking Amp . . .
But not private, you or Stuart may enjoy them as well 😀
Yves
But not private, you or Stuart may enjoy them as well 😀
Yves
No, I meant the November 1959 Audio article which specifically deals with the Mac implementation.
They meant "agreed 200%"
It's always a pleasure to do not have a subject of dispute 🙂
Yves.
Look, my UC amp output stage can be driven to clipping with an input signal of ~460Vpk-pk. The UC transformer presents a 6.4k plate-plate load to the tubes with an 8 Ohm load on the other side.
A cathode follower with the same plate-plate (cathode-cathode?) load would take roughly twice that input signal to drive to clipping.
To me, that makes it blindingly obvious that there is gain greater than 1 in the UC circuit. If not, magic is happening. After all, how else could you drive a unity-gain output stage to clipping with half the input voltage required to drive a cathode follower to clipping? If it is working into the same load impedance and same B+ and it takes half the voltage to drive to clipping, it has to have more gain.
Others have made the argument that the UC output transformer presents some much lower plate-plate load impedance to the tubes because of their parallel winding arrangement (am I representing that fairly?).
I do not buy this, and I think this is where the confusion lies. RDH4 says that two 1k coils in a UC transformer give a 4k plate-to-plate impedance. Is RDH4 in error?
A cathode follower with the same plate-plate (cathode-cathode?) load would take roughly twice that input signal to drive to clipping.
To me, that makes it blindingly obvious that there is gain greater than 1 in the UC circuit. If not, magic is happening. After all, how else could you drive a unity-gain output stage to clipping with half the input voltage required to drive a cathode follower to clipping? If it is working into the same load impedance and same B+ and it takes half the voltage to drive to clipping, it has to have more gain.
Others have made the argument that the UC output transformer presents some much lower plate-plate load impedance to the tubes because of their parallel winding arrangement (am I representing that fairly?).
I do not buy this, and I think this is where the confusion lies. RDH4 says that two 1k coils in a UC transformer give a 4k plate-to-plate impedance. Is RDH4 in error?
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So much for MY memory, it was October, not November. 😀
Note well on p56, the section marked "50 Per Cent Feedback."
Note well on p56, the section marked "50 Per Cent Feedback."
Sorry, I didn't see the other thread. In any case, Crowhurst was doing this work for Mac at the time, so I think we can consider it a horse's mouth statement.
It is a bit like ultralinear % definitions, they differ if referred to the turns or to the impedance.
In this case it's 50% (or near) feedback if referred to the gain while it's 100% if referred to the turns of the cathode feedback winding in comparison to those of the plate. But it should be clear from the definition "unity coupling" (not unity gain).
Yes, the analogy drawn earlier (I think it was you) to the cathodyne is an excellent one. Equal voltages when equal loads, but differential gain is ~2.
Another analogy used by Langford-Smith was "half-way towards a cathode follower", which again suggests that the output stage has greater-than-unity gain.
The guys that wind the transformer are saying unity gain. This is true in the case of Doc Hoyer and the other gentleman that posted that winds mac iron...My only question is,why do the people wind the mac opt transformers say the circuit is unity gain..There are very few people I know of that can wind these trafos. If there is someone other than Doc,I would love to know whom that does it currently because he's rather expensive. He gave us pretty logical reasons why you can't treat this as a cathodyne and the only reason I tend to trust these guys is because of their talent in winding these.
Now if he and Hoyer are full of baloney,I will be the first to speak up.
Now if he and Hoyer are full of baloney,I will be the first to speak up.
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