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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 44

post #646 of 8460

More EF91 goodness

 

Thorn/AEI CV138 KB/EN, made in 1951 in Sunderland, grey glass, tubes were a few months apart, one had dark grey military markings, the other one off-white, but markings were the same; same construction. These have a fairly wide soundstage, with some audible reverb that makes everything sound like 80s music (like a large room DSP effect). They have a very unusual sound signature, like a laid-back EF91 with unobtrusive bass and mids. The treble lacks the shimmering quality of the best EF91 tubes, and they aren't quite as resolving. Again, like the Brimar, the bass has a rather specific and unusual signature, that -might- work well with jazz. Overall, they should be very forgiving of poor recordings with their weird effects and loose bass.

 

CV138 KB/FB, made in STC, Footscray in 1951 (?), by Brimar (?), at least that's what google points to. These tubes have silver on the side of the glass (like the Brimar) in different surface coverage. Both tubes have an O-getter, one is medium sized, the other one oversized. These have a pleasant bass, yet another flavor (kind of like the Brimar -again- CV4014, but not as strong) that oscillates between being loose and boomy. Mids are -again, must be a EF91 specificity- unobtrusive. Soundstage is average for an EF91, and highs are tame and rolled-off with just enough detail to feel natural. The frequency response sounds fairly flat for this family of tubes, no U-shaped curve here (no elevated treble, even the bass while fat-sounding isn't even that loose).

 

MWT CV138 Z77, from letters one the tubes, these could be from late 1958 or 1959 (?). Not perfectly identical in markings but I suspect markings have been erased on one tube since they look and sound the same. One tube has the MWT logo (circle/spiral thingy with MWT) and aforementioned CV138 and Z77, while the other tube does not have the MWT logo. Both have grey glass and O-getters. The highs on these sounds fairly thin and a bit sibilant, mids are unobtrusive if useful at all. Bass is loose-ish with no particular special flavor. Soundstage is average for an EF91 tubes, instrument separation is good and resolution is OK but nothing exceptional. Treble quickly gets annoying on these tubes, hardly a very pleasant listen (which is what I'd read about MWT tubes).

 

Z77 mystery tubes, one might have been made in 1950 (not really sure for this one?) has a sticky paper "OSRAM" tag on it, other tube might be from 1952 (?) and has no tag, they were probably made later though. Both have silver glass in slightly different amounts and Z77 written in a square, and a two letter code that I assume is a datecode. They look identical but one flashes when switched on (like the late Mullard CV4014 whereas the other one doesn't, so... let's say these are similar. They sound identical though. These have a fairly wide soundstage and a fairly neutral sound. Bass is actually quite realistic for an EF91 tube and not too loose. Mids are OK, treble dominates the presentation just a little bit without being spiky. Just airy enough to feel detailed; but other EF91 tubes do this even better. Still, I could live with these if I had to. Pretty good tube for jazz recordings with having that ultra shimmering over-detailed treble. Pleasant overall.

 

So, my conclusion is -how surprising- that the EF91 with the most potential are the CV4014, especially the Mullards, but the Brimars call for more investigating; The old CV138 (the ones with 6AM6 also written) are pretty decent too.

post #647 of 8460
Quote:
Originally Posted by django1 View Post

Hi all.  I am in need of help.  I just purchased and received a Little Dot Mkii amp.  Delivery was blisteringly fast (2.5 days to Montreal).  However to of the two tubes were broken, one of each.  LD will send replacement tubes, shipping is  "15 to 45 days"blink.gif.

 

I don't have a lot of time for reading threads right now so I was hoping someone could point me to a a fairly cheap set of tubes so that I can try out the amp and see if it works and get a feel for it.  Phones are Grado SR80 and this is my first foray into headphones and amps so I would sure like to hear this thing.  Later when I have more time I will read up on tube rolling .

 

 

Thanks!

 

Go to www.tubebazar.com check out is site this guy lives in the east end of Montreal you probably could go and pick them up did bussiness with this guy once if you go and get them he usually checks the tubes while your there.

post #648 of 8460

django1,

 

Which headphones are you using?

 

Audiofanboy, great! , even more EF91 tubes. Wow, looks like a lot of time and listening.

As I am going through the text..., one naughty question: do you plan to look at a EF92 tubes as well? ;) Just because of the CV4015 being a really good tube... ;)


Edited by Acapella11 - 1/20/13 at 2:48pm
post #649 of 8460
Quote:
Originally Posted by django1 View Post

Hi all.  I am in need of help.  I just purchased and received a Little Dot Mkii amp.  Delivery was blisteringly fast (2.5 days to Montreal).  However to of the two tubes were broken, one of each.  LD will send replacement tubes, shipping is  "15 to 45 days"blink.gif.

 

I don't have a lot of time for reading threads right now so I was hoping someone could point me to a a fairly cheap set of tubes so that I can try out the amp and see if it works and get a feel for it.  Phones are Grado SR80 and this is my first foray into headphones and amps so I would sure like to hear this thing.  Later when I have more time I will read up on tube rolling .

 

 

Thanks!

it seems those are good upgrades for power tubes 6H30Pi and 6n1p and for drivers russian 6Zh1p, tung-sol 403b sylvania 6ak5w ,mullard 8100 . but stock tubes would be ok check in the book that came with your MK2 the make and number of the tubes are written in there somewhere..

post #650 of 8460
Quote:
Originally Posted by Acapella11 View Post

django1,

 

1.) Which tubes are broken? Power or driver tubes?

2.) Which headphones are you using?

 

Audiofanboy, great! , even more EF91 tubes. Wow, looks like a lot of time and listening.

As I am going through the text..., one naughty question: do you plan to look at a EF92 tubes as well? ;) Just because of the CV4015 being a really good tube... ;)


Funny you mention EF92 tubes. Actually, now that I have found just how much variety there is in the EF91 (the quality EF91, basically the CV4014), I'm kind of wondering if there might not be some hidden gems in the -special quality- EF92 tubes.

 

At any rate, having listened to the Brimar CV4014 and old Mullard CV4014 (1958) for a day, I can say that just because they sound so different from the 6AK5/EF95, that makes them interesting to investigate.

 

So yeah, the hunt continues (not sure I'll find such a stash of cool EF92/CV4015 for that cheap though...).

post #651 of 8460

Looking forward to it!

 

Which ones are you going to burn in from those EF91 tubes?

post #652 of 8460

Django1, OK I was reading your post a bit too quickly. So, from the experience with LD MKIII, I would get pairs of 6N6P-IR and CV4015 ;) Now if they turn out to be too expensive for you, I would take just a pair of 6N6P from between 1970 to 1980 and still a CV4015. If the CV4015 are too pricey, I would get a pair of GE JAN 5654W or 6J1P-EV (Voskhods). At least from the Voskhods, you should get a really cheap pair.

Hope you get your amp quickly up and running.

post #653 of 8460

Listening (and burning in, even though  they sound mature and probably weren't new) to the '58 Mullard CV4014, which sound quite nice and relaxed on the HE-400 (I need to try those on the HD650 again), tame, detailed and balanced, which is a tall order for EF91s

 

Definitely gonna spend some more time with the Brimar (seriously otherworldly with the Senns) which I did some extended listening with yesterday already (again, I don't even know if they're new, they sound burnt in as it is, but these really picked my curiosity), and the later Mullard CV4014, the O-getter ones that flash (though I know what to expect from what I read but Istill feel like pushing them a little further).
 

Not all is perfect in the EF91 world, but I do love that soundstage and treble!

post #654 of 8460
Do any of the cool Coke-bottle/Shouldered tubes work on these amps? Seriously considering buying one, and that will be the turning point to get one if they fit!
post #655 of 8460

Normally no, at least not that I know of. But I read a thread somewhere around where people had made "bullplug" adpaters to change the compatible power tube types on these amps. And there might be some cool looking tubes in that family of tubes, whatever it is...
 

post #656 of 8460
I have these mullard cv4015 on the way
http://www.ebay.com/itm/150981791119?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

Are these large shield? Small shield? And what is the difference?

Want an amazing deal on hytron 6ak5... 0.99cents...yep and the seller has more.
http://www.ebay.com/itm/380554913502?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

I also have a pair of tung sol jan 6aj5 on the way
http://www.ebay.com/itm/400329930842?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

5 slyvania 5654 on the way

And finally
6n6p gold grids
http://www.ebay.com/itm/350688546177?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

I received my little do mkiii two days ago 3 days from china! Insanely fast shipping.

Love it and I cannot wait for the tubes to come.

Gary
post #657 of 8460
Great job. Some real nice tubes there. The CBS Hytron 6AK5 is my favorite Grados tube.

Cheers!


Sent from my iPad from Ultrasone Planet using Tapatalk HD
post #658 of 8460

A little input...

 

I just got the RCA 5654 Black Plate tubes for my Little Dot Mk II, and wow. Paired with AKG K702s they balance out their tenancy to be a little lighter on the bass, my god it's a perfect match. As well as that they're just a whole lot clearer than the stock tubes. Thanks for the incredibly helpful thread!


Edited by sassafras - 1/25/13 at 3:26am
post #659 of 8460
Quote:
Originally Posted by MIKELAP View Post

 

Go to www.tubebazar.com check out is site this guy lives in the east end of Montreal you probably could go and pick them up did bussiness with this guy once if you go and get them he usually checks the tubes while your there.

 

Quote:
Originally Posted by MIKELAP View Post

it seems those are good upgrades for power tubes 6H30Pi and 6n1p and for drivers russian 6Zh1p, tung-sol 403b sylvania 6ak5w ,mullard 8100 . but stock tubes would be ok check in the book that came with your MK2 the make and number of the tubes are written in there somewhere..

Thanks  a lot I will definitely look into this!

Quote:
Originally Posted by Acapella11 View Post

Django1, OK I was reading your post a bit too quickly. So, from the experience with LD MKIII, I would get pairs of 6N6P-IR and CV4015 ;) Now if they turn out to be too expensive for you, I would take just a pair of 6N6P from between 1970 to 1980 and still a CV4015. If the CV4015 are too pricey, I would get a pair of GE JAN 5654W or 6J1P-EV (Voskhods). At least from the Voskhods, you should get a really cheap pair.

Hope you get your amp quickly up and running.

Thanks for the recommendations.  Part of my wait being over it is making it harder to decide wether I should get some tubes before having heard anything.  I am down to only 7 to 38 day wait (if we are counting weekends...)

post #660 of 8460

To all,

     I'm new to this game, still waiting for my LD MK III to arrive so please excuse my ignorance.  Why is all the conversation is on rolling the driver tubes and not the power tubes?  or am I missing that in the long thread? 

Thanks, Jon

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