Duplicate Seduction, sort of...

vetmed · 1055

0 Members and 1 Guest are viewing this topic.

Offline vetmed

  • Full Member
  • ***
    • Posts: 245
on: March 25, 2014, 02:14:01 PM
I'd like to try my hand at building a phono stage and it seems to me that I could do a lot worse than starting with the Seduction circuit. Especially since I already use one :) Would give me something to compare to at the very least. I have a fairly large power transformer so current wasting stuff like shunt regulators or an extra gain stage should be do-able. This of course would be for personal use so I hope Doc has no objections, seeing as how it is now a "heritage" kit. Any and all ideas are welcome, currently thinking of using a 6N30P as an additional gain stage (seems to do very well with 20 ma and 50 volts on the plate). Then perhaps a single 0D3 per channel, or can you parallel them? Thanks for having read this far.

Robert Lees


Offline Paul Joppa

  • Global Moderator
  • Hero Member
  • *****
    • Posts: 5792
Reply #1 on: March 25, 2014, 02:43:39 PM
The gas shunt reg is a great approach. (Reduction has a Zener shunt reg upgrade kit.) The extra gain stage risks being overdriven unless you put a gain control between the last 6922 and the 6H30 grid. A gain trim would allow you to match gains, adn well as optimize them for the rest of the system (see my "signals and noise" paper on the Community page). Put a second output at the same point so you can compare, and decide whether the extra gain and drive makes up for the added stage - that's how the Tape Repro is set up. Different systems have different needs!

Paul Joppa


Offline vetmed

  • Full Member
  • ***
    • Posts: 245
Reply #2 on: March 25, 2014, 03:29:09 PM
What a great idea, never would have occurred to me that you could have 2 outputs :o As it so happens I have a pair of mono 250K stepped attenuators from another failed project that should work as the maximum grid resistance in the 6n30p is 300 kohms. The reasons for using the 6n30 are that the plate resistance is low (1300 ohms) and it seems it will be OK with the low B+, plus the mu is about 16 so that gain would be roughly comparable to the Eros (which I also use). OTOH grid voltage for the 6n30 would be 1.5 volts so I could see how the stage could end up being overdriven. Thanks Paul, looks promising :)

Robert Lees

Robert Lees