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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
 
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
11,784 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
2,983 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.  
oyie2000 OP
13 posts
 
@ kalali: Thank you for the correction. I'm the second owner of this Doge and the previous owner rolled the stock tubes. After checking the tube boxes, its the reissued Mullard 12AX7. With Mani running into one of the line levels - No issue with hiss I described compared to running straight to the phono section.

@ bsmg: I've tried different phono sensitivity setting and applying Doge's  (-8) gain reduction - still find the hiss an issue for me. I would definitely check out those tube recommendations (5751 & 7025). 

@ atmosphere: Being the second owner of the unit, I'm not sure if I'm able to avail any warranty on the unit. Without any other matching tubes around, I may have to pony up with replacement tubes to see if the phono section's hiss issue I'm having can be remediated.

@ chayro: Nice to learn more about different tubes. Glad to hear you had good experience with Black Sable and its characteristics. It appears everyone here are in consensus about the guys at Vintage Tube Services.

Thank you all for chiming in. Much appreciated!
oyie2000 OP
13 posts
 
Since I'm happy with the Doge 8's line level, it seems easier to just upgrade from Mani to a higher quality phono stage.... but I'm not quite ready to give up on the Doge's phono and where's the fun in that, right?

But hey, feel free to make recommendations for phono stage appropriate for my current system as described:

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

When i said "appropriate" to my setup, i meant each piece of my system cost me about +/- $1,000 (minus Mani), I guess I wouldn't want to spend 2 or 3 times the amount of my cart, etc. Not sure if that is a "sound" approach - no pun intended. 

Again, thank you in advance.
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