I agree that in general, the answer to this question is going to be tube specific. Take for instance the famed 12AT7. It is the general wisdom that the Telefunken NOS ECC801s is the best of the best. At $350+ per pair, they better be! But I have been blown away by the sound of a humble pair of Chinese (Penta Labs made by Shuguang) 12AT7s ($30/pr) and by Mullard 6201 gold pins ($150/pr). I am not crazy about the JJ Teslas (a bit bright and grainy). Of equal importance to the tube itself, is the selection stringency of the tubes. The 12AT7 is used as the first gain stage of my VTL Siegfrieds and triode matching, low noise and low microphonics are critical. I highly recommend Doug's tubes (http://www.dougstubes.com) for his superb personalized service in this regard.
As far as ouptut tubes, I have been around the block on this every way from Sunday. First, let me state unequivocally that I am not a fan of 6550s as I believe the KT88 is simply a far more musical tube. 6550s have an inherent grain structure in the upper midrange that is rather characteristic of the tube style regardless of manufacturer. Having long ago substituted KT88s in my ARC Ref 300 MkII amp for the stock 6550s, I strongly believe that an ARC owner who has not tried KT88s in his amp doesn't know the true potential of their amplifiers. Unfortunately, ARC does not support KT88s (unlike VTL) so you have to do it at your own risk. Fear not, the bias is identical and the switch should be seamless. Regarding KT88s I definitely not a fan of the famed SEDs from Russia. Once again, IMHO the Shuguang factory is making the best tube of this type on the planet. These are available in several iterations and bottle shapes. However my search has ended with the beautiful Shuguang 88-98 which is available from several sources. This is also identical to the Valve Art KT100 and the PentaLabs KT88-98, both of which are OEM'd by Shuguang for these labels. The Shuggies are spectacular tubes and puts the Russians KT88s to shame. The Valve Art KT100s have been running in my VTL Siegfrieds for some time now and are simply fabulous. |
Hi Mr. Tennis, The 12AU7 does not have a lot of gain. If you are making a low output MC phono preamp, its not the best choice. I find the sound of 12AT7s to be better than that of the 12AX7 because you can get bandwidth, but we don't use negative feedback (phono EQ is passive) and that gets you a more relaxed presentation. With 12AX7s it is a lot more common to EQ the phono by using negative feedback. If running feedback on the 12AT7s I might be inclined to agree with you.
The bottom line is that while the tubes do have an influence, circuit design has an influence too and can often get around tube issues, although in the case of excess microphonics, there is not a lot you can do. |
I just stuck a '50's Chelmer (mullard) CV491 (12AU7 equiv.) in my AirTight amp, which tends towards neutral without being cool, and the expansiveness is luxurious, silences energized with presense...you know, Ralph, kinda like I recall your pre's sounding...(the rest in amp are: WE300Bs, RCA red letter 12BH7s, Natl Union 5u4)
My pre, a Joule LA200, comes stock with NOS tubes (a single Sylv green letter 5751 with a Sylv 6350 follower, GE 6EA7s and Russian OA2s in P/S), but I'm not sure that's unethical. Maybe sticking a CV491 in a stock unit would be that, but not a Sylv green letter - I think it depends on the circuit tube complement and the context, i.e putting the Sylv's in a circuit that needed five of em' might be disregarding the customer, but, on the other hand, paying for Kondo sure better get me primo NOS tubes with readily manuf-obtained back-ups! If not too many LA200/150s are manufactured, it outta work out over twenty years, a reasonable life for a tube unit, I would think.
Atmasphere is certainly right about the regulation, and others are right about the balance of tube characteristics when designing a unit. I just replaced the NOS GE 6EA7s in my P/S with some sweet-looking equiv's, Sylv 50s brown bases. Should be killer, right? Nope - collapsed into indistinct euphonics. Will a Sylv D-getter 6350 sound better than the the Sylv yellow letter I have now as stock? A green letter sq-getter Sylv 6350 that I plopped in yesterday had better dynamics but zero involvement, and the deepest field clapping went from flesh to distant crackles...I sub'd a world-beater Mullard U52 rectifier in for the 5U4 in my amp and everything went to compressed mush...
It all depends. NOS tube rolling IS a mine-field of gas leaks, unmatched sections, bad sellers, etc. but you do get better at it over time.
And, manufacturers are pretty good at finding a balance, if they have good ears to match their technical abilities, in current production tubes.
With that said, however, it has been my experience, that regardless of the pitfalls, an expeirenced hand can balance a sound further towards meaning/truth/beauty, and its perception, using NOS tubes. Which is the foundational reason that people go to them, I assume. |
hi ralph:
of the following 12 volt tubes--12ax7,12au7,12at7 and 12ay7,
my experience points to the 12at7 as having the least pleasant treble response. i have used 12at7 in a cd player, amp and preamp.
why not use a 12au7 or 12ay7 ? |
Mrtennis, correct. I personally don't use the 12AX7 because you can't get much bandwidth (the 12AX7 trades off bandwidth for gain), which is essential to getting phase relationships right. So if I need high gain, I use the 12AT7; you can easily get bandwidth out to 200KHz with that tube.
To get day to day consistency, the key is regulation, not the tubes. Tubes generally degrade slowly- over months, not days (unless there is a gross manufacturing defect), but day-to-day issues are usually something else- often the AC power. Good regulation will take care of that. |
hi ralph
designing a preamp using a nos 12 ax7, e.g. is ethically neutral. obviously, the preamp would "work" with any 12ax7, but, would presumably sound different.
it is possible that using tubes currently in production, could still create performance differences as a result of variation in manufacture. there is no guarantee that the performance of a preamp is a "constant", from day to day.
so long as the buyer is aware of all of the facts about tube sonics and tube availability, the buyer can make an intelligent purchasing decision. |
Thanks a lot for your valuable opinions, I could filter three tubes from your inputs so far,
EAT ECC803S
EAT ECC88
JJ 6922 |
As a manufacturer, you have to consider the lifespan of the product itself. Any decently built amp or preamp is going to last at least 20 years. At the end of that time, where are you going to find the tubes? One thing is certain- if you built the initial design to only work with a certain NOS tube from the get go, you have saddled the customer with a curse. At the end of 20 years, how common is an NOS type going to be if it was only available NOS 20 years earlier??
Of course you cannot predict what conditions are going to exist in the tube market 20 years in advance! But its a good bet that a tube that is not in production now is going to be a lot harder to find in 20 years.
IMO it is unethical to design a tube product that only works with NOS tubes. |
you can design tube circuits so that they are relatively insensitive to changes in tube manufacturers.
i would prefer to allow for variation in sound from changes in tubes. i would not use any current tube in my circuit. sorry, i would insist on using a nos tube. i would use a 6cg7 or two in the line section and a 5ar4 as the rectifier. |
I have experimented with Mullards, Bugle Boys, and have found that a lot of hype is involved with these tubes. They can sound really spectacular in some situations, but not many. I have gotten the best sound with 12AX7, 12AU7 from Ei, and Chinese tubes. Unfortunately, the Chinese tubes do not last very long, 300 hrs or so. The old tubes NOS do last longer, but I find some a bit colored. The Chinese tubes are clean, dynamic, (You have to get the very low noise versions) and very big sounding, but a lot of them are noisy and the short life....no perfect tube. The new Mullard and Tung Sol, and the Sovtek, Winged C are very good. NOS does not mean all the rest are junk. They have their place, just like vinyl....all records don't sound great, but some are great. |
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Mr S- Actually, the cost of their ECC88 exceeds that of the pre-68, NOS Siemens CCa by 25 to 50 dollars(right now, for a very close triode balance, high transconductance reading CCa). I still prefer the CCa, as I feel it has a more accurate rendering of the original soundstage. Their team has been largely successful though, in their goal to reproduce(as authentically as possible) the sounds of live music(ala Siemens/Telefunken), rather than the classic "warmer" tube sound(say- Mullard/Brimar/Ediswan). If one prefers euphonics, the EAT tubes will not sate their aural palate. I've not heard the EAT ECC803S(compared say to the Telefunken of the same designation), but given the Euro Audio Team's goals- I'd have to assume it would possess the same flavorings(or lack thereof). |
Hi Ben,
For our Isabella tube preamp, which uses two 6922 tubes (one dual-triode per channel), I decided on the JJ E88CC (6922). http://www.jj-electronic.sk/
Why? I compared it to the equivalent tubes from Sovtek, Electro Harmonix, and some Chinese equivalents. The JJ E88CC had a less aggressive top-end (it was detailed, but sweeter) and more fullness in the mids (and I liked the vocals better) compared to the other new production tubes that I mentioned.
However, in different circuit designs, perhaps one of the other tubes would have been as good or even preferred. You should listen to as many brands as you can and then decide which gets you closest to the sound that you are after, and then voice the circuit (brand of caps, resistors, wiring, etc.) around that tube to optimize it.
Of course I still have plenty of customers who much prefer some of the finest NOS tubes in this tube family (e.g. Amperex 7308s, Siemens CCa's, etc.), as mentioned in our forum on audiocircle. The tube rolling is a big part of the fun for many of our customers, and I have to agree that it allows you to really fine-tune the sound. And there are some that end up in love with the resulting sound with the stock JJ tubes and don't want to change a thing! :-)
Cheers!
Vinnie Rossi
Red Wine Audio |
Western electric 417A simply the best |
Redman- have you actually used the EAT tubes yourself? Lots of folks are interested in hearing about their performance, esp considering that I'm told that their cost is up there with the good NOS tubes. |
I would have to choose one of these, as they are the only current production, small signal tubes that come close to the performance of the cream of the NOS crop: (http://www.euroaudioteam.com/ecc803s.php) (http://www.euroaudioteam.com/ecc88.php) |
Thanks for your inputs,Thorman, EI is also added to the NOS category since it has no production currently,yes Cruz as I have indicated there are a number of
very good current production power tubes but still I wait for any specific recommendation for preamplifier tube worth to produce a preamplifier around it, ie EH 6922 or JJ 12AU7,etc.. |
Although they are not NOS tubes, I know ARC and Conrad Johnson keep supplies of tubes in stock that have to meet their stringent tests. The drawback is that they are least double the price that you would pay if you purchase from an independent tube seller. Of course, they are not going to be offering a line of tubes, but only the ones they use in their components. I think that most of the great tubemakers of the past are dead and with them part of the art of tubemaking died. |
As indicated, there are a number of very good current production power tubes. Hopefully, this quality will ultimately trickle down to pre tubes. I will say that the VAC labeled 12AU7's (not sure who makes them) that came with my VAC Musicbloc's are quite good. I'm using NOS Mullards, but could easily live with the stock tubes. |
Most new preamps seem to use tubes made by Chinese (McIntosh) or Russian manufacturers. Seems a shame really as the quality of sound obviously isn't up there with older vintage tubes.....which is why their prices are high and these vintage tube places exist to begin with.
Regardless of who makes them, it doesn't make sense to me why a preamp manufacturer can't spec out a 'good' tube to the manufacturer that is as good as the vintage tubes....other than cost reasons but given the type of preamp above $4000-$15000, you'd think there would be more control of the quality of tube being made for an OEM's preamp.
Sounds like a business opportunity. |
For me it seems that each different tube Manufacturer has certain tubes that is very good and some not so good..That is why you will see many people saying Such and such 12ax7 is great and some el34 is great..I found the SED EL 34 is a great tube..But for some reason they no longer make the 12ax7..I also love the EI Cryo'd 12ax7 but can't say I like any of there other tubes..I think it really is a crap shoot..The NOS tubes are much more consistant but still need System Synergy....... |
