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Phono preamp

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Burnedfingers

Member
Joined 2002
Thought I might dig out the turn table and so I will need a tube phono preamp stage.

I have some 6SL7's and 6SN7's tubes. Can anyone think of some good circuits to try. I have the normal shoe box full of 12AX7's but I would like to make something with an octal tube to stay with my linestage theme. Am I correct in assuming that I can take the output of the phono preamp and input it into my Aikido 6SN7 linestage?
 
kevinkr

kevinkr

Administrator
Joined 2004
kta-hifi.net
Paid Member
Yes you definitely can, and the 6SL7 is a pretty good choice for a phono pre-amplifier tube, my next one is planned to use these.

Keep an eye on the miller capacitance though, high output MC highly recommended or a MM type that likes input capacitance.

I'd go with passive EQ, and I'm also thinking about trying a cascode input stage, lots of gain and lowered miller capacitance due to the low effective gain of the tube in the lower section of the cascode, and not as noisy as a pentode. I'll probably use a CF to get low source Z to drive a low impedance passive network. We'll see. ;)

If you're interested pm me and I'll work out the details if you don't mind being a bit of a guinea pig.. :D
 
cerrem

cerrem

Member
Joined 2005
MerrenAudio.com
I would caution using a 6SL7 in place of a 12AX7, since you will fall short on the low frequency response due to reduction in mu....
The RCA phono stages are pretty high in distortion and were not intended for Hi-Fi...and also have major RIAA errors...
I design a few 6SL7 phono stages... the 6SL7 can be a great tube..
I posted the schematic on a Yahoo group for tubes... I will dig it up and send it to you...

Chris
 
Kofi Annan

Kofi Annan

Member
Joined 2004
homepage.mac.com/jasonandpatti/PhotoAlbum1.html
I built Thorsten's phono pre and I think it's great. Here's a looooooooong thread about the build (I came in half-way). I ask lots of dumb questions and people get p1ssed at me and stuff-- standard Kofi post.

Anyway, you might want to check that one out. It really sounds nice and was pretty cheapt to build. Also, Thorsten (Kuei Yeng Wang) gives me some pretty detailed advice on the grounding scheme that just killed the hum completely.

Good luck. Let us know what you decide to build and update us on your progess.

Kofi
 
EC8010

EC8010

Ex-Moderator
Joined 2003
burnedfingers said:
Gee, doesn't anyone else have an interest in a octal phono preamp that can be used in conjunction with their linestage? There are hundreds of 12AX7's and 6DJ8's and 6922's out there.
How about something different?
Click to expand...

Trouble is, octal valves were an earlier generation that was designed before low noise was invented. Now, if you don't mind Loctal, you could use 437A or 3A/167M as your low noise input valve and follow it up with 7N7 (Loctal 6SN7) or any octal you like.
 
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