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In the Forum: Analog Playback
In the Thread: About EAR 834P Modifications
Post Subject: Phonostage: EAR-843PT-VVPosted by Romy the Cat on: 2/13/2006

There are many ways to deal with EAR-843PT. To my ears it works wonderfully, this in my case it coupled with Expressive Technologies ET2 transformer that probably takes in totally new league. I kind of so addicted to this transformer that I even run even the high output 3mV cartridges into it, but it would be a totally different subject. The interesting fact is that as many phonostages I have tried no one sounded with ET2 as beautiful as with EAR-843PT. The key of feedback circuits is to set up a proper HF equalization of the open loop and in case of the EAR-843PT (that do not use fast tubes to begin with) the equalization it taking place naturally due to the nature of the 12AX7.


I perfectly in peace with the way how rebuilt EAR-843PT works with mica caps in feedback loop. Still, if you wish to take the EAR-843PT up to ridicules but beneficial extreme than you might try to work with feedback caps.

A cap sonic qualities are mostly derives from the mechanical and electrical characteristics of cap’s dialectic. The dialectic is basically an abrupt termination of a transaction line and the dialectic, being hit by current begin to micro-vibrate, defusing or coloring sound. If you even tried substituted in EAR-843PT with the capacitors that have no-mass dialectic then you instinctually here a HUGE benefits. Practically it is important in the  EAR-843PT case, as the feedback cap are constantly being re-charged. For instance "it" was done in 7788-7721 using air caps in feedback loop:

So, if the material of dialectic is the bitch then why to use any dialectic at all. Here is when the EAR-843PT-VV phonocorrector comes, where WW stated form 2 vacuum capacitors in feedback. The are wonderful and not very large caps make by Russians for their military needs:

They are smaller then Western caps and have more reasonable size of the contact surfaces, they also cost practically nothing. The values are 100pF and 300pF that is 10% then the EAR-843PT needs. Boosting the feedback resistor does not resolve the problem and the EAR-843PT equalization is quite complex and winded around the entire first stage. Anagnostopoulos Antonis from Greece simulated how the EAR-843PT-VV might look like with 100pF and 300pF:

Feel free to experiment with it.

I personally, due to multiple reasons, am in a process of redoing my analog setup and am trying to convert all my analog to ET2-EAR-843PT phonostages, considering it  as a reference.

Romy the caT

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