47 preamp related link

Found this looking for something else. Starts at about the middle of the page.

https://www.tubecad.com/2020/06/blog0506.htm

Think harmonic restoration

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I like this description.  Thanks for posting. 

fazer said:

I like this description.  Thanks for posting.

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Yeah me too.  "Harmonic Restoration" should be a feature button on all tube pres. 

It is unfortunate that as well as never having heard of the 47 he did not appreciate the subtleties of its design. For instance the gain of the anode follower is very deliberately chosen so as to largely cancel the second harmonic distortion produced by the EF86. There is a description somewhere of the design - I will see if I can find it.

Cheers

ian

ruffrecords said:

the gain of the anode follower is very deliberately chosen so as to largely cancel the second harmonic distortion produced by the EF86. There is a description somewhere of the design - I will see if I can find it.

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Yep, indeed.  I don't have it at hand but it's in the original manual for the REDD.47

Winston O'Boogie said:

Yep, indeed.  I don't have it at hand but it's in the original manual for the REDD.47

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https://www.dropbox.com/s/xk4d7dw91uq9pyf/EMI_REDD.47_docs.pdf?dl=0

Cheers

Ian

Thanks Ian. 
Sure, the amp is of its time and there are things we have access to now that could improve on it. 
But in talking with Ken Townsend (engineer at AR in the '60's, later managing director of A.R. Studios) about the only things that had been overlooked  and were considered negatives back then in regard to that amp were the heat dissipation of 30+ amps in a desk, and the fact that the desk had to be powered down to remove a module due to sharing of power supplies.