Bottlehead Forum
Bottlehead Kits => Mainline => Topic started by: dcham on December 05, 2013, 04:19:52 PM
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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.
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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
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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.
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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
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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 ;)
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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...
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It will work, but you'll put hours on the E80CC without really "hearing" it.
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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
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That's probably because Sovteks are rebranded Reflectors.
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That's probably because Sovteks are rebranded Reflectors.
Ah ha, that makes sense. Thank you good sir!
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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 ?
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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.
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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. :P 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? ;-)
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Well, if the 12AU7s have influence, its pretty subtle.
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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.
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Getting this thread up!
Anyone tried other regulator tubes in the Mainline?
Did it make a difference?
Anyone tried E80CC / 12BH7's?
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I would like to purchase a second pair of 6C45P-E tubes which have limited availability.
Sovtek tubes are the most widely available for as little as $28ea.
OTK tubes in kit sound great. Similar looking tubes on ebay from Russia or Ukraine available for a little as $10.90.
Any advise?
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Get the ones on eBay from the general area in the world where they were originally made.
-PB
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Can i safely ask the Mainline heater supply to provide 0.3A extra current for E80CC?
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Yes, but no more!
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I own B&K 707 and Jackson 648 tube testers.
The 6C45P-E is not on any chart for testing on these units.
Does anyone know how I can test these tubes?
Thanks.....Ross
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Plug them into the amp and if they bias up and sound good, they are good.
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Ha! OMG....now we have discovered besides using the Mainline as a great headhone amp it can also be used as a 6C45 tube tester!!!
:)
Alex
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I've always wanted to try a Western tube equivalent of the 6S45P in my Mainline. There was this one time PB said that the pentode E55L (triode connected) might just sound good in Mainline, someone just needed to try. It would involve some serious surgery though. In the collection there's both US Amperex New York and Mullard Mitcham factory made E55L. But the major work needed for the magnoval socket held me back all this time. It's the most left one on the line-up picture below. On the right you see the dwarfed 6S45P from the Mainline.
Recently another closely related valve, this time from Telefunken, found it's way into my collection (in the middle in picture). This is a triode from the 60's that equals or even surpasses the 6S45P performance named EC 8020. Fortunately the surgery needed for this tube only involves changing the tube pinout at the socket. It's close to plug and play! Be sure to add grid stoppers ( appropriate value) to each connecting pin as high transconductance tubes like this tend to oscillate.
How does it sound? Well, it's the known Mainline sound to me. No angels singing in my ears or anything. And Mainline sounds great! It's the best sounding amp I own from the technical point of view and now comes with "the queen of triodes".
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Pretty little tube too. I tried to track down a pair of these to try and found they really are made of unobtainium.
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PB converted a 6C45pi amp I built many years ago to run WE437As for a very good friend and customer. He was happy with the result and considered it an improvement. I thought the 437A sounded very nice but found that I very slightly preferred the 6C45pi. To me the difference was more of a flavoring thing than a measurable improvement in performance.
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How on earth did you recently find EC8020's, emphasis on recently?
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@DocB: That's exactly my experience with these. It's still just the Mainline, only with a different flavor. They have inspired me to experiment with a E55L as a spud speaker option. I'm now even considering rewiring the S3X "a bit" to get there.
@ Grufti: With some patience, persistence and luck. Like all tubes. For these's i've been searching four years now, ever since i figured i wanted to buy a Mainline at some point in the future.
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Tom-s did you try the e80cc? Any difference in sound?
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I can't say it does much. It might, but then again I tried it years ago. Can't honestly recall any of the influence it had. I would recommend tube rolling ECC82's from your Crack and see for yourself. The PT and/or LT regulator are pushed harder with E80CC.
In the end, went back to my trusted Philips Heerlen ECC82 (selected a very strong testing one for the job). Had this in for the past few years and am always happy to see it flash (even with the tube shield on) and confirm power is on. Now with the tube shields from the 6C45P gone, this flash is no longer "needed" but it's still in the same place.