Small hum at higher volumes and tube covers [solved]

[ffivaz]

I just wanted to say thanks for the Reduction kit. I received it on friday, it took the better part of the weekend to build. Since sunday, I just can't stop playing through my LP collection (with an old Thorens TD 160 and even older Stanton 500). I like the small details you put in the manual, like the longer screws that tell there will be upgrades in the future. And I like the layout with the black and yellow capacitors.

Two questions :

1) My Reduction is quiet, but not dead quiet (if possible). At higher volumes, there is an audible hum, something like a white noise. Is that normal ?
2) I prefer the tubes without covers. Is there a definitive reason to use them ?

[Grainger49]

Congratulations!

Hum and hiss are two things.  Hum is a low frequency noise while hiss is something that sounds like SSSSSS or FFFFFF.  If you have hiss look at FAQ Thread

If you have hum, post back.

The tube covers are there to limit RFI interference.  If you need them you will hear background noise or a radio station with them off.  But looking at the tubes is part of the enjoyment.  So try it both ways and see if you have a noise problem (other than the one above).

Good luck!

[ffivaz]

Ok, looks like a hiss, a shhhh, only at high volume, inaudible at normal volume, especially with music playing. I'll wait for tubes to burn-in.

BTW, the sound is just beautiful. Thanks again.

[Mmaxed]

What phono stage were you using before?   

What differences in sound are you hearing?

I have one coming and am getting a little impatient.   But then I have to get it assembled.

[ffivaz]

I had a Lehmann Audio Black Cube, a SS preamp from Germany. The sound was good, but the highs were too harsh. There was a precision that was too cold. I don't want my LPs to sound like CDs. The Reduction has better mids, the sound is full. My LPs sound definitely like LPs. I like it, and I hope you will!

[Grainger49]

The Shhh noise will most likely quiet down by 50 hours of run in time.  Music doesn't have to play through the tubes for the cathode to form. 

Just let it run and report back.

[ffivaz]

I Wanted to keep you updated. Well, the hiss went away in one channel. I swapped the tubes, hiss changed to the other channel. It definitely comes from the tube. I'll let it settle down for another 20 hours

I just checked at really high volume, without being cabled to the TT, there is a small hum (not hiss) that isn't there  without the Reduction connected. Is it normal ?

[jimiclow]

What tubes are you using. Mine came with 6N23P and it's very quiet.

[ffivaz]

Same for me.

[Grainger49]

I'm surprised you are having trouble with this tube.  This is not to say that the tube isn't the problem.  Typically the 6N23P is new old stock, NOS.  I have some from the 60s and 70s that I sought out on purpose (year and month are on the side, I think the month is a letter, year an Arabic number).  I used them in my Seduction and now in my Eros. 

BTW, the -EV are tighter spec and a bit better sounding.  USSR military surplus tubes are unusually inexpensive for well made tubes.  THis makes them a great bang for the buck.  There are many more expensive tubes that are better but the sound for the cost of the surplus tubes is amazing. 

BTW, the Seduction was developed around one that turned out wouldn't work with the transformer supplied.

[ffivaz]

I changed the tubes to some NOS Philips JAN 6922 and the Reduction is now completely quiet. And it still sounds great.