MIMF

I'm looking to grab a spare/replacement tube for my Marshall ValveState 8040 amp, and am wondering which manufacturer would be my best bet for overall consistency? I know in theory, the maker should be secondary to the application, but it's been since tubes were still fairly common in other gadgets that I've even fooled with them. I haven't opened the chassis up to see which brand is in there, but will be doing that soon to clean the pots and visually inspect everything anyway. Recommendations, anyone?

Hi Johnathan,
JJ (Slovakia) are what I stock for my business, they are reasonably priced, have been the most consistent in my experience, and my customers have always been happy with them. There've been numerous reports of bad batches (mostly microphonics, some people complaining of "low gain"?) but I haven't had any myself.
Marshall usually uses Shuguang (Chinese) in that series of amps, but sometimes they use "Reflector" Russia (anything by New Sensor) which includes Sovtek, Electro Harmonics, "Reissue" Mullard, "Reissue" Tungsol, "Svetlana", and probably some other brands in forgetting.

Other brands are Ruby, Tube Amp Doctor, Groove Tubes and Golden Dragon, most of their probucts are rebranded Shuguang. Groove tubes also rebrand Reflector and JJ tubes.

Historically Chinese tubes have been very inconsistent and low quality, suffering from high rates of premature failure and infant mortality, as well as the usual microphonics problems (but they've always been very cheap). In recent years though, quality has improved drastically, and they are often producing some of the most rugged current production tubes available, but consistency is still not high enough for my requirements yet (and I don't usually like the characteristic tone they produce).

I generally won't use Russian tubes, as most of the available options are not actually what they are marketed as (12ax7, GZ34, 6V6, etc), but often some Soviet tube that has no western designation, but is a close-ish (or sometimes not so close-ish) match to the characteristics of the originals. The biggest problem is that their "12ax7's" do not have maximum ratings as high as they should, specifically the Vh/k, and this leads to problems or outright failures in cathode follower positions (you shouldn't need to worry about this in your Marshall, from memory). There are enough amps out there that already exceed the proper Vh/k, I don't need tubes that don't even meet the specified standard.

Anyway, all current production tubes have problems, so I like to not spend a lot. Hope some of this info helps!

Oh, also, the pots are probably sealed type in that amp, so you probably won't be able to clean and lubricate them!

How handy are you?

http://www.youtube.com/watch?v=gl-QMuUQhVM
&
http://www.youtube.com/watch?v=9S5OwqOXen8

I've worked on a few ValveStates and I think they are pretty forgiving about which tube you throw in them.

Thanks everyone. JJ sounds like the way to go here. My pots have a tiny opening in the top, so I cleaned/lubed all of them. Nice difference!

If money is no object, the NOS JAN 12ax7 are the best available if you can find them. That's New-OldStock from the last Joint Army-Navy contract, I believe they were made in the US prior to 1990. I got a couple of them 2 or 3 years ago, they were $50 each for 12ax7. The JJ were about $12 at the time...

Jeez, after reading this I think I must be so old that should check for hair on my head. The last time I bought a 12AX7(a) they cost about $4. Maybe you could check in with a ham radio club in your locality to see if they have an old-school tube-tester for quality control purposes.

I should have found a place for the deluxe tester that I had 20 years ago for testing hospital physiological/cath lab instruments from the '60/ '70s -- for use when I shut down the Honeywell Electronics for Medicine DR-8/12 physiological recorders for only one day each year in January to test the amplifier tubes. They other days of the year, the recorder was on continuously, and it was a very rugged instrument.

Eeek, I remember my uncle's radio station from the 1930s, and my mother told me that she helped him to make inductor coils, capacitors, and ---tubes. That was back when you 'rolled your own'.

I have a Carvin B1000 bass head with a tube pre section and I changed out the 12AX7 with a TAD (Tube Amp Doctor) and it is a nice tube. I was trying to make the gain know push the amp, so I could get some distortion and this helped. I do not think it is posible with this amp to get the true tube grit I am looking for but it did help. I was looking for a higher gain on mine and it did help. These are priced ok from what I can remeber. Just look up an amp shop on line and some of them will break the tubes down for the tone you are looking for. And you can buy them in a set for the tone you want. They can mix and match them putting one rated tube in a different position on the amp changes things as well. I have no idea about this other than what I have read. So I hope this helps some.

JJ, TAD, or Tung Sol reissue are my favorite flavors... and affordable... that's for my Silverface Deluxe Reverb

Real NOS SIemens, Mullard, Philips. Minwatt, - 12AX7, - AT7, ECC etc sometimes fetch hilarious prices, as the HiEnd crowd lends their
Golden Ear evaluations... 100$ each or more is not uncommon.... Octal power tubes are even worse......

I have gotten rid of ALL of my tube type amplifiers long ago when ran out of my horde of new old stock GE tubes. I'm not at all sorry. I was paid really stupid money for the old, noisy, cranky, heavy, junk. I wouldn't trade my Fishman Loudbox Mini for anything other than another Fishman.

FWIW, the 12AX7 in my one homebuilt is a "very used old stock" Sears Silvertone, '60s vintage, and it does fine. It came out of the '30s floorstanding radio my grandparents used until they finally bought a portable transistor circa 1970.