OK, I just played my first record with this new phono preamp, but I didn't get it working the way I showed it below. The absolute voltage reference of the gas reg and the (slightly) mismatched sections of the 6N1P didn't allow enough leeway for the DC voltages to settle correctly. So I punted.

As you can see, I had to put cathode bypass electrolytics back for the 6SL7. I sure hope they break in :)

I'm not listening too closely, the air conditioner is making some noise (that's actually a GOOD thing, trust me) but so far I am not really impressed. I've got David & Igor Oistrakh on DG playing, a nifty record, and it sounds OK.

I'll keep it playing for a while and see what we get. Maybe I'll put in some film bypasses on those cathode caps, but that never seems to do much.

Any suggestions?



Blogger J Epstein said...

Well, the phono stage is only loaded by a few inches of twisted pair and a 100K volume pot so grunt doesn't seem necessary. The gain is OK, so that'd basically be adding a stage for little reason.


8:06 AM  
Blogger JLevro said...

How's about moving the battery from the grid to the cathode? Or, how about swapping the tubes, i.e. input = 'SL7, output = 6N1P? Probably need to rebias.

2:43 PM  
Blogger J Epstein said...

John: I built this after hearing glowing reports about the Artemis Labs PH-1 which John Atwood designed. So I thought I'd try his front-end, with 6N1P swries-grid-bias, just for fun. Wanted to try something new.

I've done a 6SL7-input phono (with battery cathode bias) and it was mushy and boring. Which does NOT describe this phono!


4:19 PM  
Blogger J Epstein said...

Christian, thanks, I had forgotten about that method. In the past - just using a bare LED, no additional current - I thought THAT method sounded greyish. I remember hearing about that method - one which Steve bench has discussed too, and thinking it sounded promising. Anytime Manfred and Steve agree on something, I expect it's worth a try.

BTW, the 6N1P is breaking in pretty nicely, I actually am in no hurry to revise it just yet.



5:59 PM  

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