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Leave tubes in phono section if not using it?

Hi,

I just bought a mid 1980's Moscode Minuet preamp (not Minuet in A) on AudioGon. I haven't received it yet, but I think it uses 4 12AX7's (2 in phono section, 2 in line stage).

I don't plan on using the phono stage. I was thinking of just pulling the tubes in the phono section with the hopes of reducing noise/hum and saving myself two tubes. But, I know I could use shorting plugs on the phono imput jacks to possibly eliminate some noise that way.

My question: Is it possible that pulling the tubes can upset some critical design parameter and create a detrimental situation, or even do some damage?

I will not have a manual or schematic for this unit.

Any thoughts would be much appreciated.

Thanks,

Rich
richgib
richgib OP
16 posts
 
Thanks, Newbie. I'll just put cheap ones in the phono section. I was wondering if it could affect the line stage, maybe even send the unit into oscillation. I had an early Audible Illusions preamp that oscillated when I unknowingly put in some Hungarian tubes. They even warned about this in their manual. I was just curious if the circuit could be affected in some way, as Hifigeek1 suggested.
robetozian's avatar
robetozian
8 posts
 
Leave the tubes in. If you operate this preamp without tubes in place, it will "un-load" the regulators. Voltages in some places will rise, and may rise above the rating of some components. The repair bill will most likely be higher than the cost of a couple of cheap tubes.
boby
1 posts
 
Gentlemen I need your knowledge
hello possesses a minuet moscode (not in A) and I read that it had four 12AX7 but I have two 12AX7 and two 12AU7
precisions would you please?
so what tubes is dedicated for phono and which are dedicated to the preamp section?
do you know a way to know and tell me how I could understand?
it is a very very good preamp and I love it like working with my MOSCODE 300!
I search the shema of minuet and 300
thank you for your help because I never found anything on this subject and I despair
(anyone know what it is dedicated tube in the minuet in A? this is the same?)
thank you very much
Bob (France)
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mr_moscode
2 posts
 
The Minuet will be fine if you pull the 2 phono pre tubes out. They are the ones on the left looking at it from the front.
knghifi
1,668 posts
 
My VAC Sig MKIIa has a pair of 12au7 for tape and a pair 6922 for linestage. I don't use tape but found the 12au7 position very sensitive to tube rolling. All VAC owners that roll 12au7 had similar results.

Listen before removing or replacing with inexpensive tubes.
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