Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 60

Quote:

Originally Posted by mordy 

Can anybody tell me if there would be a difference in the sound between 6CB6 and 6CB6A tubes? Are 3CB6 and 4CB6 tubes good alternatives for LD MKIII. Any impressions about sound quality?
 

I'd expect more of a difference between the 6CB6A and the special quality 6676 than between the 6CB6 and 6CB6A, but there's probably some difference. And the different example I have of the GE 6676 I have both have 6CB6A etched in the glass and never 6CB6, so if anything the controlled heater type can't be worse than its predecessor.

3CB6 and 4CB6, having respectively 3 & 4V filament voltages, would not work in the 6.3V wired LD amps, nor would any other non-6.3V filament tube for that matter; not without a major change on the circuit board at least.

Alright, after 15-16 of burn-in, here are a few more impressions on the GE 8425A/6AU6A.

They are definitely extremely musical and detailed, the best example I've seen so far of "tube realism" (see earlier first impressions for what I mean by that with the "singer in the studio" and all). Paired with the 6N30P-DR, these make my amp into a truly excellent unit, surprisingly so. They are just liquid enough  to always be pleasant and toe-tapping while remaining perfectly neutral and controlled at all times over the whole frequency range. Best imaging and natural 3D feeling I've heard (3D as in how/where the song was recorded and no more no less, not fake head-in-a-cave kind of 3D or even head-in-a-bubble -pleasant in its own right- kind of 3D that I was often getting with last week's tubes).

Gain is on par with 6CB6 tubes or most non-EF91 300mA heater current tubes, with less gain than a CV4014. The tubes improved a fair amount with burn-in, everything just kind of fell into place, the chewy textured not-too-tubey-and-just-liquid-enough mids, the mellow detailed non-annoying very natural highs and the bass also improved noticeably (both in amount -slightly- and in quality and control), it is now nice and tight and precise, and reminds me a bit of the CV4015 bass with a bit more power and the same kind of articulation. These tubes have very good transient response and great decay, not ultra-fast like some good SS but natural and realistic and just normal fast. Near perfect separation and staging too (you wouldn't believe how real the singer's voice sounds with these on good records).

Overall, these might be the best driver tubes I've tried on my amp, A+ grade without a doubt and bordering on A++ (which would make every other tube go down one grade), actually I'm giving these a tentative A+(+) until I finish testing the other tubes I'm expecting. These are my new "best tubes" and favorites I guess, they do everything I loved about the CV4015 -that weren't powerful enough anymore for me- the naturalness mainly, and take it a whole other level and add extra power in the mix.

So, to update my "top tier" tube list or my three favorites I warmly recommend, I would suggest the above as N°1, the GEC CV4014 as N°2 (still a solid A+ tube as well with more gain, more liquidity, more impact and punch, but less neutral and natural and differently detailed and staged and maybe ever so slightly below the 8425A in those areas) and the Mullard CV4015 as N°3 (though not for orthos as they have much less gain, but their soundstage is on par with other two, and they are as realistic, natural and neutral as the 8425A, but less punchy than the CV4014 and have less authority than the two other tubes).

The list and "grading system" might evolve again very quickly as when I tested the other matched pair of GE JAN 6AU6WC before leaving it to burn-in for the work day, they sounded as good if not perhaps better than the 8425A unburnt-in... Then again, the 6AU6WC have the special quality 6136 etched in the glass, whereas the 8425A "only" had 6AU6A etched. Expect the answer this weekend!

Thanks for your reply - looking forward to hear more about the great tubes for the LD that you are discovering!
 

Quote:

Originally Posted by mojorisin35 


Mike i am very curious as to your take on the tesla's. the ones I have have stab written on the side and also have a white paint on The top of the tube making it look like it is wearing a elf hat. There are other tesla 6f32 tubes with yellow writing and no paint that I understand sound quite different which ones did you order? So far my tesla's are kicking everything else out of the sockets. I just received a pair of tung sol 6ak5 that are pretty awesome we will see after burn in.

heres the picture and data from store i got them from but havent got them yet .

About changing tubes from different families: There are available vacuum tube socket adapters that allow tubes with different amount of pins or pin patterns to be plugged directly into the tube socket.Below is an EBay link. Is there anything there that is suitable for use with LD amps?

http://www.ebay.com/sch/i.html?_odkw=6676+vacuum+tube&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313&_nkw=vacuum+tube+socket+adapter&_sacat=0
 

Quote:

Originally Posted by Audiofanboy 

So, to update my "top tier" tube list or my three favorites I warmly recommend, I would suggest the above as N°1, the GEC CV4014 as N°2 (still a solid A+ tube as well with more gain, more liquidity, more impact and punch, but less neutral and natural and differently detailed and staged and maybe ever so slightly below the 8425A in those areas) and the Mullard CV4015 as N°3 

How about the 6EW6?

Quote:

Originally Posted by gibosi 

How about the 6EW6?

I think I gave my GE 6EW6 a solid A grade, which would place them at N°6 or 7 or something on my list (the 6GM6 would be N°4 or 5 but microphonic as they are they won't be used), the 8136, 6CB6A and 6GY6 would be at N°7 or 8 I guess, and a bunch of the best 6AK5 tubes and some other brand CV4014 would be somewhere before or at N°10. So something like:

1 - GE 8425A/6AU6A

2 - GEC CV4014

3 - Mullard CV4015

4 - GE 6GM6, 6EW6, 6GX6/6GY6

5 - GE 8136, 6CB6A, Mullard CV4014/M8083 (Mitcham), Tung Sol 6AJ5, Mullard CV4010/M8100, Voskhod 6J1P-EV (Gold grids), Mullard CV5377 (Mitcham), Mullard CV4014 (Whyteleafe)

6 - Brimar CV4014, Mullard CV138/6AM6, Voskhod 6J1P-EV (Non-gold grids), Brimar CV138, Mullard CV850 (Whyteleafe), Tung Sol 6AK5 (side getter, early shape, 1943), GE JAN 5654W

A pair of GE 8425A/6AU6As recently arrived and are now burning in. Interestingly, they appear to be identical to my standard GEs (8425A on the left and standard on the right). I wonder what the difference is? Perhaps the 8425As are simply standard tubes that have been tested and graded to be among the best? Anyway, after burn in, I wonder if I will be able to discern any difference.

I should note that my standard GEs are very quiet with no microphonics. They are currently my NO.1.

(Oh, these tubes are laying on their sides on a glass table top so the coin to the right is there to keep them from rolling. I wanted to photograph both of them together from the same angle.)

Quote:

Originally Posted by mordy 

About changing tubes from different families: There are available vacuum tube socket adapters that allow tubes with different amount of pins or pin patterns to be plugged directly into the tube socket.Below is an EBay link. Is there anything there that is suitable for use with LD amps?

 

 

 

http://www.ebay.com/sch/i.html?_odkw=6676+vacuum+tube&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313&_nkw=vacuum+tube+socket+adapter&_sacat=0
 

Interestingly, there aren't that many 7 pin (7BK generic base) adapters than can be used in LD amps. They exist and are quite expensive for what they do but considering the amount of 7BK base tubes that exist, and that few people have even tested the "modded" 6AU6 types yet, I'd say were still a long way from testing 8 and 9 pin tube for compatibility; and 7 pin to 7 pin adapters just to link two socket holes seems like kind of a waste. This being said, I know some octal base tubes could work in the amp as they have very similar characteristics but I haven't seen any logically compatible 9 pin tubes (often double triodes or triode-pentodes but not so much single pentode or beam tetrodes like we've been using). I've a number of 7 pin triodes, with more or less close pin layout; for these an adapter could be useful I guess, if there's more than two socket hole to bridge or cut. Then again, one could imagine a even larger adapter that would cover both tube sockets to use a double triode, like the 6922, instead of two triode-strapped pentodes. There's still a bit left to investigate I guess...

Quote:

Originally Posted by gibosi 

How about the 6EW6?

Brief update after more listening and comparing 6EW6  to CV4015:

Accuracy, transparency and neutrality: CV4015 > 6EW6.

Treble: CV4015 > 6EW6

Mids: CV4015 = 6EW6 just different with 6EW6 more seducing and CV4015 more clean

Bass: 6EW6 = CV4015, the bass is different though, CV4015 is better articulated, defined but  the 6EW6 goes deeper, there is more a deep bass vibe to them. In summary, I would say they come out similar.

Noise background: CV4015 better than 6EW6. CV is military grade after all. 6EW6 background improves over the burn in process to a decent level.

Overall, the CV4015 are more audiophile, I would say, also more treble oriented and clean. The 6EW6, more on the warm, seducing side and with more bass extension. CV4015 comes out better after all but they do not compete within the same signature. 6EW6 is like a higher gain "honey coated" CV4015, if that makes sense ;). Although the CV4015 in summary wins the competition, you would want Norah Jones rather whisper through the 6EW6 into your ears...

Quote:

Originally Posted by Audiofanboy 

 

I can only speak for the -DRs but they definitely have much better upper end extension, and a much more linear and extended lower end - they are in essence very linear imo, it's the driver tubes that end up "biasing" them to a more or less U or V shaped signature. Basically, I'd say the R -low-noise- trait does exactly what it's supposed to, the lower noise level allows for much more clarity and transparency, and for micro-details (airiness and instrument separation in the highs), texture of sounds and realism of transients (mids and bass) to be that much better than their non-R counterparts. Of course, that low noise effect is more apparent the more transparent you gear is up to the power tubes, including driver tubes, but not only (software, transport, DAC).

Power tube R suffix

This makes sense and I have observed the same with the two points you mentioned.

- Bass and treble are more extended with the 6N6P-IR compared to 6N6P-I.

- The IR's background is pitch black, so yes, micro details are better.

- However, the first thing you notice when listening to the 6N6P-IR is the larger stage, the overall greater spatial arrangement. This is - the - first big difference and immediate impression I had.

Guys, enjoy to see how deep the LD tube rabbit hole is...

Edit: Just on a side note: I am not sure how much of deal a gold grid really is. For example, I have two Voskhods, with and without gold grid - they almost sound identical. However, a third pair from 1975 is a bit better. It has more bass impact compared to either of the other two, but sounds otherwise very similar. I also heard that the 6N6P rather scale with the year of production. So, a 1970 should be way better than a 1990. Maybe gold adds some shine on it but I think year of production seems to have more impact.

Quote:

Originally Posted by Acapella11 

 

Brief update after more listening and comparing 6EW6  to CV4015:

 

Accuracy, transparency and neutrality: CV4015 > 6EW6.

Treble: CV4015 > 6EW6

Mids: CV4015 = 6EW6 just different with 6EW6 more seducing and CV4015 more clean

Bass: 6EW6 = CV4015, the bass is different though, CV4015 is better articulated, defined but  the 6EW6 goes deeper, there is more a deep bass vibe to them. In summary, I would say they come out similar.

Noise background: CV4015 better than 6EW6. CV is military grade after all. 6EW6 background improves over the burn in process to a decent level.

 

Overall, the CV4015 are more audiophile, I would say, also more treble oriented and clean. The 6EW6, more on the warm, seducing side and with more bass extension. CV4015 comes out better after all but they do not compete within the same signature. 6EW6 is a like a higher gain "honey coated" CV4015, if that makes sense ;). Although the CV4015 in summary wins the competition, you would want Norah Jones rather whisper through the 6EW6 into your ears...

 

 

 

Power tube R suffix

 

This makes sense and I have observed the same with the two points you mentioned.

 

- Bass and treble are more extended with the 6N6P-IR compared to 6N6P-I.

- The IR's background is pitch black, so yes, micro details are better.

- However, the first thing you notice when listening to the 6N6P-IR is the larger stage, the overall greater spatial arrangement. This is - the - first big difference and immediate impression I had.

 

 

Guys, enjoy to see how deep the LD tube rabbit hole is...

 

 

Edit: Just on a side note: I am not sure how much of deal a gold grid really is. For example, I have two Voskhods, with and without gold grid - they almost sound identical. However, a third pair from 1975 is a bit better. It has more bass impact compared to either of the other two, but sounds otherwise very similar. I also heard that the 6N6P rather scale with the year of production. So, a 1970 should be way better than a 1990. Maybe gold adds some shine on it but I think year of production seems to have more impact.

I pretty much agree with what you say about the 6EW6 and the comparison with the similar sounding CV4015. A higher gain, nearly as good but with a more in your head soundstage, more punchy bass-ed CV4015. The higher gain and stronger -trade-off for articulation- bass compensate for most faults this tube has compared to the CV4015 and make it an excellent versatile tube imo. It works very well with electronic music btw. While not as black background-ed as my absolutely quiet CV4015, my military non-mil spec 6EW6 are quiet after 10h+ of burn-in, enough not to have to worry about it.

About the -R suffix-ed Russians tubes, where you notice a larger stage (I assume "wider") with the 6N6P-IR, I noticed a "deeper" and "higher" soundstage (I had the "wide" trait covered), so basically a true 3D stage compared to an excellent 2D or pseudo-3D stage I had before. Again, I assume the low noise -R suffix to play a big part in that better and more precise soundstage pattern, both in 6N6P and 6N30P types. I think "gold grids" or gold and platinum grids just kind of come with the best mil spec Russian tubes made in the best times with the best quality control, and are not, in and of themselves, a guarantee of sound quality. I keep reading about how good some 6N6P made in the 60s are supposed to sound and these never have the gold grids trait mentioned; it's the tubes from the 80s and maybe late 70s that have it. The -R suffix-ed tubes seem to naturally have those too. I know my Voskhods 6J1P-EV made 15 years apart and with and without gold grids sound quite different, especially after the loooong burn-in -one improved and the other plunged.

While I'm at it, here's my review/feedback of my GE JAN 6AU6WC, etched 6136, made in 1978, which might have been a bit late. After 15 hours of burn-in, these sound very similar to my GE 8425A, with a bit more bass -not better- and maybe a tiny bit more micro-detail and a tad less gain. BUT, they make music sound like it comes from behind a thin veil, curtain or foam (like foam used to roll-off spiky treble). It reminds me of that muting pedal on pianos that make piano notes sound muffled -keeping their harmonics and detail but muted or sounded a bit "choked" but not muddy either. In this case, you can still hear all the details, but they just don't leap out at you like the 8425A -or CV4015 and GEC CV4014 for that matter- you have to focus to actually hear everything, but it's all there. Overall, a solid A grade tube, that would work well with "Norah Jones" singer/songwriter type music, where intimacy and smoky curtains are preferred to ultra-detailed and analytical tubes -which the 8425A is not as it is just natural. Again, the details are all there, but you have to relax to hear them which I don't always have time to do/feel like doing. Last thing, bass is more muddy than the 8425A, fuller too but not articulate, and that takes the "+" off that A in my book.

Listening to the 8425As again, these are definitely less muffled, more natural, musical and fun (not V-shaped sound fun, just... well, fun). Stuff just falls into place with these, and the bass goes looow -and is articulate- which hadn't struck me the first time around. Definitely my new A+(+) tube. Acapella, if your reference is the CV4015, you would love these!

I'm starting to wonder if GE still had their Schiit together making tubes starting in the mid-70s and worse in the 80s. I had bought some GE JAN 5654W half a year ago, made in 1985 by GE for the military and they really weren't that good; I mean you could tell the quality control had gone down the drain. The construction was nothing like what I read about, not clean or best in class but kind of lackluster (the innards weren't straight and the tube base was all weird looking, even the silk writing was a little off), the tubes crackled and popped when I first tested them, and it got better and quiet after a few minutes -a far cry from what I've been used to with mil-spec tubes, including GEs- and after 25h of burn-in they just didn't make the cut; they weren't unpleasant but just not as detailed or fun or well soundstaged like my other basic 6AK5 tubes in those days. I wonder if my -still excellent- GE JAN 6AU6WC from 1978 aren't a bit like that. They look great (although the getter flash made from their halo getter doesn't actually cover the top part of the tube, but made a donut shaped flash that makes my tubes look like bald monks, I can see the filament light from a small hole above the tube; looks amusing but first signs of QC issues?), sound nice but just aren't as good as the 8425A/6AU6A from the same brand -non JAN- made in 1964, like the QC process gradually went downhill as demand for tubes did -apart from the government that bought lifetime stocks of whichever tubes they still needed, tubes that are now massively on fleebay ;) .

Oh the rabbit hole is deeeeep, and getting deeper by the second! "Off with their tubes" said the Queen... Even though I'm not done testing the 6AU6 family, I'm already on an other tube type, and I have two or three more lined up for investigation. There is no end to this, and the 8425A/6AU6A are already forcing me to revise my grading scale... Who's next?

Quote:

Originally Posted by Audiofanboy 

About the -R suffix-ed Russians tubes, where you notice a larger stage (I assume "wider") with the 6N6P-IR, I noticed a "deeper" and "higher" soundstage (I had the "wide" trait covered), so basically a true 3D stage compared to an excellent 2D or pseudo-3D stage I had before. Again, I assume the low noise -R suffix to play a big part in that better and more precise soundstage pattern, both in 6N6P and 6N30P types. I think "gold grids" or gold and platinum grids just kind of come with the best mil spec Russian tubes made in the best times with the best quality control, and are not, in and of themselves, a guarantee of sound quality. I keep reading about how good some 6N6P made in the 60s are supposed to sound and these never have the gold grids trait mentioned; it's the tubes from the 80s and maybe late 70s that have it. The -R suffix-ed tubes seem to naturally have those too. I know my Voskhods 6J1P-EV made 15 years apart and with and without gold grids sound quite different, especially after the loooong burn-in -one improved and the other plunged.

Just for your information: wider and mainly deeper, actually. The overall representation reflects more a hall if that is what it was during the recording. So, more agreement here.

Yes, the years of production really seem to be a key point of tube sound quality (old wisdom here I guess, just putting it together with gold grids). Unfortunately, the labels on my gold-grid Voskhods are washed out in a way that I cannot read a year.

Have fun mate.

So turn out when my amp freaked due to a bad jumper it killed one of my GEC CV4014 tubes, now that i got the jumpers replaced one of them has no volume but if I tap the tube itself it generates this high pitched ring that grows louder and louder. Got worried that I broke the amp but once i popped in my M8161 tubes it was happy again.

Quote:

Originally Posted by mab1376 

So turn out when my amp freaked due to a bad jumper it killed one of my GEC CV4014 tubes, now that i got the jumpers replaced one of them has no volume but if I tap the tube itself it generates this high pitched ring that grows louder and louder. Got worried that I broke the amp but once i popped in my M8161 tubes it was happy again.

That's really crummy... But for sure, it's good that it was only a tube, and not your amp! And now you have an excellent excuse to try a nice GE 8425A/6AU6A! :)