Schiit Mjolnir 2 Listening Impressions
Sep 19, 2021 at 7:17 PM Post #6,136 of 6,220

G0rt

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Researching 5965's, WRT cathode poisoning specifically, I came across the '62 RCA book on electron tube design. Never copyrighted, and FULL of fascinating info.

I don't recall seeing it mentioned here, apologies if it's old news.

(Google 'electron tube design' for a multitude of links, some of just the TOC, if you don't want a blind download of a ~30 Mb pdf.)

BTW, those old Arcturus 5965's definitely DO NOT suck. At all. In Valhalla2.
 
Sep 25, 2021 at 11:18 PM Post #6,138 of 6,220

bcowen

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Sep 27, 2021 at 1:44 PM Post #6,140 of 6,220

Blacksun

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I am running a Mjolnir2 with a Matched Pair of Amperex JAN 7308/E188CC Gold Pin tubes. I have been reading a few posts recommending the 12AT7 CV455 KB/FB BRIMAR RARE TRIPLE MICA 1956 NOS VALVE/TUBE. Curious on thoughts if this is a worth while consideration?
 
Sep 27, 2021 at 2:53 PM Post #6,141 of 6,220

jonathan c

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I am running a Mjolnir2 with a Matched Pair of Amperex JAN 7308/E188CC Gold Pin tubes. I have been reading a few posts recommending the 12AT7 CV455 KB/FB BRIMAR RARE TRIPLE MICA 1956 NOS VALVE/TUBE. Curious on thoughts if this is a worth while consideration?
~ Those CV455s are a “holy grail” quality tube without the “holy grail” price. Being made in the Footscray plant and being triple mica with square getters make these tubes special. The Amperex tubes which you are using are very good tubes. The Footscrays are better in many ways. [I own Amperex PQ 7308s.]
~ If you decide to use the CV455s, a pair of 12A**—> E88CC adapters is needed. These are available from Pulse Tube Store, located in India. I have ordered tubes / adapters from PTS numerous times: no problems and longest delivery time to me has been ten days.
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Sep 30, 2021 at 6:17 PM Post #6,150 of 6,220

busseysound

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So I've had a few weeks with the new MJ2/Gumby and trying different tubes. Here's what I've discovered so far:

First, Zack at ZMF makes some insanely good headphones. My VC stabilized are breaking in nicely - which helps for tube rolling analysis of course. Classical and Rock are the main genres for testing. I also tried to give each set time to burn in a bit. On to the tubes (in order of preference - best last):

Amperex 7308 6DJ8 White Lettering: Overpriced in my opinion. They had decent dynamic range but had lots of artifacts and seemed to get congested quite easily. I just didn't like this one much at all.

Tungsram ECC88 Grey Plate Solid Disc Getter: I didn't have the black nickel plates in yet (thanks to Wes for the info on those) so I got some gray plates instead. Not bad. Pretty balanced but lacked clarity compared to some of the nicer tubes. If you can pick some up cheap these aren't bad. Before nicer tubes came in I found myself using these most actually.

Brimar KB/FB 12AT7 CV455: Now these were impressive. They slam REALLY hard in my opinion. A bit too much for my taste, and lacked just a bit of clarity from some of the others I liked better, but these are really great tubes. I got them from Langrex so not the greatest CV455's out there for sure - but they were pretty darn good for the money.

RFT ECC81 With Folded Plate Tabs: Thanks to Wes for the heads up again on which RFT tubes to roll. Very, very clear tubes - but a bit bright for my taste. I think that's true for maybe all RFTs? I also tried the ECC82 with the folded plate tabs and I liked them just a bit better. The clarity is pretty crazy in these. If you don't mind a brighter sound these are outstanding for the money.

Amperex ECC88 6DJ8 PQ Orange Lettering: These things are pretty sick. Great soundstage, clarity, balance. Only flaw I find is that in the 600 to 700 Hz range there's a bit of a bump. They can be a bit more difficult to find but I actually picked up 5 of them for $20 each!

Tungsram ECC82 Solid Disc Getter w/Nickel Black Plates (no holes): Yep the one that Wes likes so much. Took A LOT of searching, but I found some (at not too bad of a price). These have been the best overall. Great dynamics (outstanding actually), very balanced, great clarity, just about everything you could ask for.

In the next couple of weeks (as they come in) I'll be trying some Tungsram E88CC's and some Philips 6201 E81CC SQ (not pinched). I'd love to hear a pair of the 6201's pinched, but the pocketbook has been hit hard enough for now. Thanks again to Wes for all your help and others on here that share such valuable info!
 

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