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Doge 8 Clarity: 12AT7 replacement for phono stage

Hello fellow enthusiasts... My apologies in advance for the noob question.

I've put together my first all tube system, as far as preamp and amp combo is concerned. Looking to see IF replacing the phono section's 12AX7 (Mullard ECC81) tubes with lower gain 12AT7 in my Doge 8 Clarity 2017 ed. will help lower the "hiss"/ tube rush coming off with my current set up. Doge's phono setting is on MM (using Bob's Device Sky 20 SUT), Phono: 47k, tried both normal and low sensitivity, (- 8) gain reduction, but "hiss" is still audible from my seat 7' away from the speakers. 

I'm looking at replacement tubes from Upscale - Mullard 6201 which they claim to be the "quiet" ones. Not sure if it will help in lowering the hiss I've described.

Doge's line level still holds the stock 12AT7 tubes and to me - they sound nice as the reviews online says. I'm sure it can do better with tube rolling. No audible hiss from my seat. Switching between any line level onto phono input clearly augments the hiss.

To take advantage of Doge's much improved line level over the phono, I've utilized my only external phono stage - Schiit Mani. Not ideal but i can handle that better than deal with the hiss using the Doge's internal phono stage. I've contemplated on just upgrading to a nicer phono stage but that's another topic.

So, will it work to replace the 12AX7 with lower gain tubes 12AT7 to decrease hiss in my system? 

Thank you in advice for your time and responses.

Current system:
Rega P3 (2016), NEO ttpsu, DV 20X2L
Schiit Mani to line level vs Bob's Device Sky 20 to phono level
Doge 8 Clarity 2017 ed.
Mystere PA11 
KEF R3 on stands



oyie2000
kalali's avatar
kalali
1,977 posts
 
"...replacing the phono section's 12AX7 (Mullard ECC81) tubes with lower gain 12AT7..."

Just to be clear, ECC81 is the equivalent of 12AT7. 12AX7 tubes have the designation of ECC83. Double check your stock tubes.   
bsmg
296 posts
 
+1 for Vintage Tube Services and Andy. I would try the 5751 tube or a 7025 tube (the 7025 is one of the few tubes specifically designed for hi fi). And if your phono stage has switchable gain settings, just use a lower setting than you now use; that may fix your problem. 
kalali's avatar
kalali
1,977 posts
 
One other thing you may want to try is experiment with the different gain settings on the Mani to better match your cartridge and see if that helps reduce the noise. 
atmasphere's avatar
atmasphere
12,404 posts
 
Before you try any swapping, I would look into the fact that if you have a high performance tube phono section, that its a simple fact that no matter where you get the tubes for it, they have to be hand-picked. About the only way to do that properly, assuming that otherwise the tubes check good, is to listen to them.

The Chinese 12AX7 is not bad in the noise department, which is to say that out of 100 of them, you'll probably find about 85 that are acceptable. Tubes do have a way of going bad, even new ones, so I would contact Doge and see if they can provide you with a proper replacement. 
chayro
3,092 posts
 
I have had good results with Black Sable tubes from Tube Depot.  They are hand-selected for low noise and microphonics.  Andy at Vintage Tube Services is also great.  
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