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Romy the Cat

Boston, MA
Posts 9,967
Joined on 05-27-2004

Post #: 1
Post ID: 19199
Reply to: 19199
EMIA Phonostage.

Here is some kind of MM phonostage with around 45dB gain.  Two stages direct coupled with input pentode and output capacitor.



It looks like output impedance is a bit too high – 2k. I like hat official blurb: … of course no feedback. They however forget to tell that pentode operation by default implies feedback but let do not think about it. 

Generally, of cause this phonostage need a step up transformer. I however was not so lucky to be able to use step up transformer with pentode input. I have no idea why but I feel that if you use high gain input stages than go for 3 fully active stages and get your 70dB of gain with no transformers. If you already get your 20-30dB input gain by magnetic then there is no need to go with input pentodes.

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
04-09-2013 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,408
Joined on 10-12-2006

Post #: 2
Post ID: 19200
Reply to: 19199
Not Much Info
Looks like another case where clean AC wall power is demanded and supposed.  Since they use triode output, I wonder if the "gain path" of the pentode is "wired triode", as well, or if they just want the extra gain to scrub in the upcoming RIAA; or maybe they are just "getting a jump" on the RIAA with the pentode feedback?  7788 is optional for the pentode.  I think they said RIAA is LCR shunt, off the output stage.  Seems like most current correctors use a "second stage" of 3 stages for this.  RIAA correction choice must factor in to the (high...) 2k Ohm output.  Nice, low values for the caps, although still not in air cap territory...

Paul S
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