Slight Rant- No More NOS Tubes

I have to say with all this NOS, used, microphonic, shady practices, etc talk I am pretty pleased that it is pretty much just the direct heated pentodes (wired as triode) or DHTs that interest me these days Outside of EL34 for one specific amp.

 

I've had nothing but great experiences with Andy. I describe the sound I'm looking for and he delivers exceptional performing tubes for very reasonable prices.

 

Don't keep us in suspense! Which amp?

 

It's basically the Blue Hawaii electrostatic headphone amp I mentioned in post 36 (mine was built by Headamp), the new one I would like is by same designer Kevin Gilmore, just this amp has several improvements over the BH (more slew rate to drive the difficult capacitative electrostat load, more transparency in the treble, more robust power supply, etc). Here is an old photo of my setup: https://i.imgur.com/eeQzmsE.jpg

 

Nice rig. Justin at Headamp is a really great guy. I have a BH first generation and one of Gilmore's SRM-T2 clones. Both self built using boards from Kevin Gilmore. The T2 is totally insane - it pulls 200W out of the mains to drive Stax phones.

The Stax thread (New)

This was KG's first showing of the beast. The final casework was all black anodised.

 

New old stock (NOS) is a misnomer. If something is "old" it can't also be "new." It really should be called "unused old stock," assuming it truly is unused.

Even if an old item has never been used, it can be subject to decades of handling, dropping, poor storage conditions, etc. Unless a seller has a good return policy, then it's buyer beware for all vintage items.

 

I'm apparently far less cautious with vintage tubes lol. I just use eBay. I've had no issues personally.

 

After listening to a variety of music today I became less sold on the idea of life without NOS tubes (unfortunately).
So glad I ordered that batch of Tung-Sol 12AU7s for an "All Tung-Sol" cronus magnum.

 

I might be able to help you out if you're looking for some xF2 Mullards - shoot me a PM...

 

I have a quad of NOS RFT EL34's in an Audio Note Kit Amp and they sound wonderful. They are much less expensive than the NOS Mullard's.

 

I'd probably replace entire components before Id agree to replace my tele 12AX7's in my amp, if I were exploring to refine the sound in my 'setup' as a whole. They're just that pleasing.

 

Tektronix knew a thing or two about tube circuits - the 545A had 73 tubes, including 23 6DJ8's. All DC coupled and bandwidth of DC - 30MHz.

They adopted a method for ensuring that circuit performance remained constant as tubes aged. This involved taking the cathode to -150V via a reasonably high resistor (usually around 33k). The idea being that if the anode/plate current dropped as a result of aging, the voltage across the 33k resistor increased, and the grid cathode voltage decreased - hence causing the anode/plate current to increase again. It is essentially the same as using a constant current source taken from -150V

So the tube operation point is stable - the anode current stays constant as the tube ages. In fact I have pulled tubes out of one of my 500-series scopes that measured essentially dead on a tube tester, and still worked absolutely perfectly when in circuit.

All of this is described in detail in a 1962 Tektronix book called "Typical Oscilloscope Circuity", which was basically the entire design philosophy behind tubed oscilloscopes. Anyone remotely interested in this, the book seems to be available from Abebooks and Amazon for $15 to $20.

I have not seen this trick (ie taking the cathode to a high negative voltage via a high value resistor) used in audio amps, in which the tube bias point is very sensitive to tube aging.

 

The thing is, you will have to replace those tube some day. Like all tubes, they have a finite life, and even if the "work" for years and years, often the performance will slip. The degradation may be so slow and steady you don't even notice it -- a loss of transparency and detail, an increase in noise, softness at the frequency extremes, an overall darkening of tone. Then one day you pop some fresh tube in there, and it's like changing from a worn stylus to a new one. Tubes don't last forever, they're parts that will need replacing in normal operation.

 

I don't doubt it. Like I said the Winged Cs were good tubes, the '70s Teslas were good EL34s, too. But at least those two weren't like a Blackburn Mullard neither in terms of that tactile timbral character and sense of midrange presence; nor in terms of the tank-like over built quality that allow you to run 'em at the edge of viability (like a Dynaco ST70 did) according to spec for heat (or over that edge as some Eico amps did), and have them just shrug it off like it was nothing. I mean there are contemporary beam tetrodes that sound good too, but they don't sound anything like a pentode EL34, and they darn sure aren't buily like those Mullards.

 

This is the basis of my rational for buying new, I can just buy them for a decent price and go on about my business. I'm set up to replace my tubes on a yearly basis.

M~

 

It's one thing to replace your small signal tubes with NOS tubes, same thing with EL84's. Even then, you can still buy decent used tubes of these families for really cheap. They last so long, so, if they test good, it is a good chance that they will give you many years of excellent service. At the prices you can buy these tubes on the used market, when one fails, you just toss it away, throw another one in and go on about your business.

But when you get into the larger power tubes, like the KT88's, it's a totally different story, as they are very difficult to come by and also very expensive. Which makes NOS tubes like the RFT EL34's a relative bargain.

 

I gave up on most "desirable" NOS tubes over a decade ago; nearly all the stock left available for sale was microphonic junk that had been set aside when new. Signal tubes last almost forever, pulls can be a great source of great sounding tubes - they're likely to be good sounding and not microphonic, or they would have been replaced. My Scott 355 tuner/pre has Telefunken smooth plate 12AX7s s in the line section and long plate Mullards in the phono; all pulls, sound great.

 

I understand this. On the other hand, a well functioning set of vintage pre amp tubes, can serve well for 10-20 years. Power tubes for quite a few years as well. It depends on the tube really. I'm not going to spend crazy money on NOS 845 and 300B tubes, no thanks. However, with something like a 12AX7, how long they last and the heavy influence they have in the pre amp stage, it is worth it to spend $100 or so on a good old pair IMO

 

I agree with what you've said. In my case I've found New Production tubes are equal to what I've NOS tubes used for. NOS in my case are CV4004, 5965, and 5751 for my PV5. The difference that I hear in my system is not worth the monetary difference in price between NOS and New Production to me.

M~

 

They can last for years and years and thousand and thousands of hours of use, but they don't always still sound their best or perform with the lowest noise or best dynamics and amplification in circuit, or best noise, or with twin triodes, the triodes don't stay balanced, as they age, and sometimes it's not something you even notice (other than the noise), until you swap in some new tubes.

 

Sadly, I'll never go back to current production power tubes, specifically the 6L6 and variants, as the vintage 'old stock' (NOS) tubes sound much better. The same for nine pin signal tubes too. However, some of these lower priced 9pin tubes can get you very close to the most sought after tubes for a fraction of the cost. Trial and error is the name of the game, definitely not for everyone.

I've had the best experiences with eBay for value and quality. Matter of fact, the tubes which got noisy quickly all came from one reputable online dealer. It stinks too because he shares a huge amount of knowledge and customer service is top notch... just hadn't had much luck with the tubes.

 

The big exception to this are the all of the JAN tubes. Those were nicely kept on ice for us by the military for a couple of decades after first world tube production had ceased. These are not all microphonic Junk. And some can still be had for not outrageous prices (although this is changing quickly, now that the supplies of these are dwindling).

Also, while small signal tubes can indeed last for decades inside of some designs which are very easy on them. Other high-performance units may consume tubes much more frequently. And those old tubes, which still test strong after thousands of hours of use, do not sound the same as they did when they were virgin tubes. These old used (yet still strong testing) tubes gradually become mushy and dull sounding they longer that they are used in my experience.

 

I believe that @chervokas has already pointed this aspect of old tubes out, two posts prior to yours.

It's no different than anything else, shop thrift stores for old records, some will be good, others no so much. It comes with the territory that everything vintage, or should I say, mostly everything vintage may be shopworn to some degree (speaking of used vintage here).

Those who spend time combing through thrift store records will find hidden gems here and there, but there will still be a lot of trash records. Sometimes that is not bad. Sometimes I have a shot album, which physically shows no wear. I simply toss it, if it is unlistenable.

But, maybe the cover is in good shape. I still save the cover. Maybe I will find another one with a bad cover and with the record itself being in playable shape. It's a perfect match.

The key thing is not to overpay, reaping good NOS signal tubes is still more likely than getting inferior ones.

Many vintage tube receiver's, amplifier's, preeamps, and integrated amps found on eBay, are still equipped with many and sometimes all of their original tubes, and they usually sound better than fine.

It is important to keep in mind, that vintage tubes, NOS or not, are going to sound different than modern day production tubes, that may or may not work for someone. If you are not at least after a vintage sounding tube, just buy new ones and be done with it.

 

Back when I had an all tube system, NOS tubes were the only way to go.

The Russian EF86, for example, sounds so dry and "black and white" compared to the colorful NOS Mullard or GEC version.

Even the new Gold Lion 12AX7, at least in my system, didn't have the presence or soundstaging depth of a 1960s era Mullard or RCA.

Part of me, however, doesn't miss tubes much at all. Yes - superior sound compared to my current el-budget setup, but also less family friendly. My Adcom gear is usually left on most of the day and I don't have to worry about my wife dealing with an output tube going south!