I need a tube lesson

[jpatti75]

Hi gang,

I need a lesson on new vacuum tubes on the market. While there are many review of modern tubes on the net, many of the reviewers represent the guitar amp crowd, while limited reviews that I have found reference modern tubes for use in vintage HiFi stereo applications.

Quite a few guys here helped me through the restoration process on a 1961 Motorola HiFi console. As probably a budget model Motorola with no reverb, the preamp in my unit has one 12AX7, and the amp has two 12AX7s and four 6BQ5s/EL84s. I’ve read lots of talk of using different 12AX7 in preamp applications versus those for the actual amps, but I don’t understand why this would matter. In my ignorance on any real difference between tube brands, I purchased JJs to replace some bad (highly microphonic) original tubes in the unit. I find the JJs slightly noisy, but no real complaints on tonal quality. I have read positive reviews for brands like Mullard Reissues and Genalex Gold Lion for HiFi applications, for both the overall sound quality and low noise, but am not really sure what makes them better?

I appreciate everyone’s ears are different and this is highly subjective topic. While not looking necessarily for brand recommendations, I am more curious if there are new issue vacuum tube brands on the market that are designed more for stereo vice guitar amp applications to narrow down what to consider. And, in the case of 12AX7s, is there different considerations for use in pre-amp versus amp? Or, is a lot of that talk just a bunch of hubbub?? I just want quiet, nice sounding tubes for Classical and Jazz music, but I don’t know how to be a smart consumer.

Appreciate a “vacuum tubes for dummies” explanation to set me straight.

Thanks I’m advance for anyone’s thoughts.
JP

 

[zackthedog]

It's not hubbub. ;-) It's a matter of tighter tolerances and better quality control. Yes, there are some differences in opinions about which tube is best in a given application. But I have found that a tube that scores high with guitarists can serve very well in hi-fi applications. They're pretty picky. I very much like the Genalex 12AX7s in my DAC--and they'd better be quiet here! You can tap them--no ringing or boinging. They have a warm, focused midrange.

 

[robert_kc]

Here’s my thoughts on 12AX7 from 6 years ago: best new production 12ax7?

 

[oldtexasdog]

For a tube that was basically designed for stereo audio applications the KT120.

 

[trainbuftony]

Dont be a consumer.
You have tubes that work run those.
If you come across 12AX7s in the wild acquire them, but you dont need to buy them just because they're for sale.
I've got enough 12AX7S for a lifetime of amp building and not a one of them is younger than 40.
If you require brand new tubes.
Jim Mcshane is your guy.
He can tell you which brand will work best with your gear among the currently available stock.
Real good dude.

 

[kward]

If you are purchasing someone else's amp that they built or a commercial amplifier, then there's no discussion really since you use the tube types it was designed for. If you are designing and scratch building your own amplifier then you can design around whatever tubes suit you. In this latter category, many people prefer to walk the ground less trodden and use seldom seen tubes in their hifi designs. Excellent results can be obtained that way also. Not every tube is good for hifi of course. There are bazillions of tube types and it would take an entire book to list them all. Several people who are very passionate about these things keep an on line database of every tube data sheet they can get their hands on, and put it all into a searchable database. Frank of Frank's Electron Tube Data Sheets is a great example. He lives in the Netherlands somewhere I believe. I emailed him one time. Great guy!

Most data sheets will state somewhere in the opening paragraph whether or not the tube was designed for audio applications. But notably some tubes that were not originally designed for audio applications are excellent tubes to use in audio applications!

 

[maxhifi]

more curious if there are new issue vacuum tube brands on the market that are designed more for stereo vice guitar amp applications to narrow down what to consider.

A lot of this comes down to marketing. There are subtle differences between brands, but in general all tubes of the same type (e.g. 12AX7 or equivalent) will do basically the same thing unless one of them is defective. You are very unlikely to be able to hear the difference between brands of 12AX7 on a 1961 console stereo - the guys who obsess over tubes are often putting them into a system which costs as much as a decent car, with extremely high resolution speakers.

Think about how car guys who will spend hundreds or thousands of dollars to get a tiny bit of extra performance out of their sports car. That's what people are doing with fancy tube brands and high end amps. With Mom's van, the same kind of expenditure to get "extra performance' you get out of expensive shocks, plugs, tires, etc will never be noticed and it would just be a big waste of money.

The one thing you definitely want to avoid is certain tubes which have a reputation for being unreliable. Spend some time around here and you will figure that stuff out.

 

[tonyg88]

I run 4 jjs 12ax7 short plates in my fisher 800c they are great because they are the cheapest and actually light up unlike the Russian preamp tubes.ohh and sound great I have 2 of them in the phono and 2 in the tone section... If they were noisey id definitely pick up on it. I also run the expensive new frame grid jj 12ax7 in the phase inverter section.

 

[jpatti75]

Thanks for all of the excellent input and perspectives on tubes. The knowledge on this forum is incredible. One follow-up — are there 12AX7s specifically designed for preamps, and those designed specifically for amps? Or, are any such discussions more of a matter of taste vice and actual technical reason?

 

[Lavane]

There are a few variations of 12AX7's. Heaver duty construction, made to be less microphonic, etc. Heck, I have a couple that were from a box used for testing those military sonar devices they drop from planes and choppers into the ocean.
So they had to be able to handle up to 6G shock, have very low michrophonics, be low noise and triode matched to within 1%. But there isn't really any made just for amps or preamps.

 

[jpatti75]

There are a few variations of 12AX7's. Heaver duty construction, made to be less microphonic, etc. Heck, I have a couple that were from a box used for testing those military sonar devices they drop from planes and choppers into the ocean.
So they had to be able to handle up to 6G shock, have very low michrophonics, be low noise and triode matched to within 1%. But there isn't really any made just for amps or preamps.

Thanks … appreciate the clarification!

 

[trainbuftony]

If your system uses multiple 12AX7s you would want the quietest ones, least microphonic in the first section that the signal goes through. Any error here will be multiplied (amplified) by subsequent stages.
You could even go as far as to ask your supplier about screening for noise and let them know what you're planning on putting them in.
People who handle and test thousands of tubes know which ones are good.
I highly recommend jim Mcshane for real quality old tyme service.

 

[grindfix]

I think short plate tube versions would be a better option for AF section because they are generally less microphonic and lower noise types.
From new production types - you have to experiment with different types and can ask Jim McShane for his opinion. He will not sell you the highest dollar tube if his lower price option will work better for your application. Great and helpful guy to deal with.

 

[jpatti75]

Thanks guys! Sounds like Jim McShane is the guy to talk to.

 

[crispycircuit]

McShane is the man. However you can test for noise just by installing in your amp and then listen with the volume up with no signal and tap the tube for microphonics . Electro Harmonix make 3 different 12 ax7s... The 12ax7-WA is normal gain. The 12ax7-WB has more gain and the WC has even more gain.... I would guess for guitar amps. Guitar amp tubes are made for a rugged environment. Such as being moved around by drunks and having the tubes sit 5" away from a speaker playing at 100db... The Tube Amp Doctor sells ruggizied tubes which could be of interest... For audio I just use old American pulls. One other thing is to replace the plate resistor on any noisy tube & scrape the tube pins with a razor blade...

 

[likebike23]

I'm in the process of restoring a Webcor tube consolette and have been investigating this very thing. My thoughts are that tubes that work well for combo guitar amps would work well in a console.

The speakers are in the same box as the amp, so microphonic tubes wouldn't be a great match in the preamp. Short plate ruggedized tubes like the Mullard CV4004/Sovtek 12ax7WA(B) might be best there. The phase inverter can be long plate, people seem to like the Sovtek 12ax7lps there.

Honestly, I am starting to believe that the tubes from the same manufacturer like the Mullard 12ax7 long plate and the Sovtek 12ax7lps are the same thing. Check out this link and notice the similarities between "different" brands of the same tube type. https://www.tubesandmore.com/tech-articles/12ax7-comparison-current-made-tubes

I found this article helpful also https://valvetubeguitaramps.com/sovtek-wa-wb-wc-12ax7-differences/

In the end I'm not sure how much difference there will be between "different brands" of new tubes that were made in the same factory. From another forum (first post is relevant, the rest ) https://www.thegearpage.net/board/index.php?threads/current-tube-manufacturers-list.1740893/

Basically there are going to be 3 flavors of new manufactured tubes. So my feeling is to get the cheapest JJ, New Sensor, or Shuguang tube in the type I need and not worry about it too much seeing as they are going into a console anyway.