Tube rolling in the Mainline

[dcham]

Wondered if it is worth it to replace any of the tubes or caps with higher grade ones. Unlike the Crack amp, I don't see many post on tube or cap rolling for the Mainline.

Any comments would be appreciated.

[Paul Birkeland]

There isn't really a whole lot to tweak with the Mainline.  Though there are a lot of 12AU7 variants, it's in the power supply, and not as influential as the 12AU7 is in the Crack.

The 6C45PI has very few variants.

There are 10uF parallel feed caps in the amp, and we intentionally left a fair amount of space for builders to swap them out as they like.

-PB

[Doc B.]

I have had a few instances where I could hear a small difference by changing the shunt regulator tube in a circuit, but more where I couldn't. I wish I could say which circuits, but the memory is foggy. It's possible that it was circuits with cathode followers, which would be a different situation than in a Mainline. But hey, if you've got a few extra 12AU7s lying around try them and report your findings.

[Grainger49]

Here is a list of 12AU7 tube equivalents from the Legacy Products folder.

http://www.bottlehead.com/smf/index.php/topic,1027.msg7554.html#msg7554

[dubiousmike]

Until around the end of last year, electro harmonix was manufacturing new gold pin 6c45pi's.  Then, right as the mainline, wa7 and ecp l-2 all came out (all of which are based on this tube), they pulled the plug on it. 

I had intended to order a pair to try, but almost all the etailers who previously carried them ran out of stock before I completed my build.  Last I checked, you could still order a pair off the wa7 page through Woo Audio, but at a hefty premium.  Cryoset used to sell cryo'd pairs at half of what Woo is charging. 

People in the wa7 thread on head-fi claim the EH's sound better, but you rarely see someone drop $100 on an "upgrade" in the audio world without reporting that conclusion     

[Loquah]

Would there be any issues (or benefits) in using an E80CC in the 12AU7 socket?

I happen to have a spare and thought I might try it, but don't want to break anything...

[Paul Birkeland]

It will work, but you'll put hours on the E80CC without really "hearing" it.

[swich401]

What are the stock tubes that came with the Mainline? Reflector? Sovtek? Mine have no Sovtek label on them, only 6C45Pi-E and code 0883

Comparison of the stock tubes with a set of Sovtek tubes - Can't find much of a physical difference
Comparison of the stock and sovtek tubes with Electro Harmonix gold - The EH seems to have a smaller halo getter and no wire leading from the central element to the post holding up the halo getter

[Doc B.]

That's probably because Sovteks are rebranded Reflectors.

[swich401]

That's probably because Sovteks are rebranded Reflectors.

Ah ha, that makes sense. Thank you good sir!

[swich401]

If I choose to use a Sylvania 12BH7A tube instead of a 12AU7, are there any changes to the amp that should be made? I have a bunch of 12BH7's that I have lying around and I thought I could scavenge the 12AU7 for another project.

Anything to be worried about using a 12BH7 instead of the 12AU7 ?

[rburrows]

Just wanted to chime in here with a 12au7 rolling experience in the Mainline.

I swapped the stock NOS tube provided with the kit for a JJ ECC802S I had lying around. The difference was pretty noticeable to me, on par with rolling the 12AU7 in the Crack despite the tube's different function in the amp design. The NOS was more balanced and tonally correct, whereas the JJ was more lit up, but a bit grainy and thin.

[NightFlight]

Cool. I have a few 12AU7's to try out. I received a relabelled GE with my kit, which is not a terrible tube to begin with. A tung-sol might be cool to try. *shrug* I also have a terrible sounding "Dumont".  Perhaps if I can make it sound worse it would be an indicator the shut regulator has a bit of play in this area.   Testing a 12BH7 would be interesting as well as its currently my favourite in the Crack.

Is this where PB is supposed to jump in about operating points? ;-)

[NightFlight]

Well, if the 12AU7s have influence, its pretty subtle.

[Paul Birkeland]

Well, if the 12AU7s have influence, its pretty subtle.

Yeah, I certainly agree.  In that block of the circuit, the TL431 does most of the work.