The Humble 12ax7: Or, how much am I overthinking things?

Boomhauer

Friend of Leo's
Joined
Aug 18, 2013
Posts
3,063
Location
Michigan
I have 2 amps: One's a Vox AD30Vt, and the other is an Ibanez TSA-5. I've convinced myself that both amps need new tubes. I bought the Vox as part of a super hot deal where it wasn't fully functional, but I've done a pretty good amount of work to it and gotten it 90% of the way there - there's still the issue where when you're playing and switch amp models mid chord, the volume drops out and it makes a sort of suboctave fuzz type distortion for 5-10 seconds. This is a characteristic of the amp, but something I read (maybe on TGP, maybe on Strat Talk, I don't remember anymore) mentioned that this can be lessened or reduced by replacing the tube.

The Ibanez has a constant white noise hiss, even while playing. The amp is over 10 years old, I've owned it for 8, and it came from the display rack at a guitar store, so who knows what kind of abuse it was put through there (not to mention I accidentally left it turned on for weeks one summer as I didn't visit the basement guitar room for a very long time). The hissing has gotten worse, which again, has me convinced that it needs new tubes.

But now I'm caught in the myriad of choices - NOS, used, or old-school tubes from Reverb? New tubes from EHX, JJ, or PSVane? 12ax7, 12at7, 12au7? Do I buy a matching pair (despite both amps only having 1 12ax7) to split between the two? Do tubes make that much of a difference in the grand scheme of things?
 

uriah1

Telefied
Silver Supporter
Joined
Feb 12, 2011
Posts
28,464
Location
Around
A 12AY or 5751 are the best sonically, but, they will reduce your immediate gain.
Which could be good or bad.
If you are just testing to see if you eliminate the white noise, that might not be it anyway.
Did you swap the tubes within both of your amps already.
(I love NOS tubes, but, only if you intend to keep amp forever)
or it is vintage.
If you go new, the Sovtek WA military are pretty stout and last. I have had
tungsols white out on me and EHX. JJ should have stuck with their good EL84s.
 

philosofriend

Tele-Afflicted
Joined
Oct 28, 2015
Posts
1,068
Location
Kalamazoo
Changing tubes is a fun and relatively cheap way to tinker with the sound of an amp, but don't expect it to fix problems that may well have a different cause.
12ay7 and 5751 in the first preamp tube will help keep a hot pickup from distorting that tube. This is useful for players who want no distortion as well as those who want to heap on lots of output tube distortion.
If you read the ads and reviews for 12ax7s you can get a vague idea of the character of the brand's tubes. There is still no substitute for swapping tubes in your amp, with your guitar, played at the volume you play at.
Changing speakers usually makes more noticeable differences than changing tubes. The first preamp tube makes more difference than the later ones. If the amp specifies a 12at7 for the phase inverter, it is there to reduce distortion from that source.
Sooner or later you will have to get new tubes anyway, so why not try some different (reasonably priced) ones? You could also try every 12ax7 you have in the first tube of one amp to see if any of them stand out. Taking a gamble on an expensive tube that I can't try before I buy it doesn't make that much sense to me.
 

archetype

Fiend of Leo's
Joined
Jun 4, 2005
Posts
8,663
Location
Western NY
I have 2 amps: One's a Vox AD30Vt, and the other is an Ibanez TSA-5. I've convinced myself that both amps need new tubes. I bought the Vox as part of a super hot deal where it wasn't fully functional, but I've done a pretty good amount of work to it and gotten it 90% of the way there - there's still the issue where when you're playing and switch amp models mid chord, the volume drops out and it makes a sort of suboctave fuzz type distortion for 5-10 seconds. This is a characteristic of the amp, but something I read (maybe on TGP, maybe on Strat Talk, I don't remember anymore) mentioned that this can be lessened or reduced by replacing the tube.

The Ibanez has a constant white noise hiss, even while playing. The amp is over 10 years old, I've owned it for 8, and it came from the display rack at a guitar store, so who knows what kind of abuse it was put through there (not to mention I accidentally left it turned on for weeks one summer as I didn't visit the basement guitar room for a very long time). The hissing has gotten worse, which again, has me convinced that it needs new tubes.

But now I'm caught in the myriad of choices - NOS, used, or old-school tubes from Reverb? New tubes from EHX, JJ, or PSVane? 12ax7, 12at7, 12au7? Do I buy a matching pair (despite both amps only having 1 12ax7) to split between the two? Do tubes make that much of a difference in the grand scheme of things?

Seems to me the amps need troubleshooting and service without respect to what might be causing the issues. Swap tubes between the amps. Do the issues travel with the tubes or does each amp have it's same issue?

You need at least one spare 12AX7 just to have it on hand. Just get an NOS one. Any make US/EU/UK/Japan will sound fine. Use it for troubleshooting when you need to. If the tube doesn't solve the problem, then off to the tech with the amp.
 

VintageSG

Poster Extraordinaire
Joined
Mar 31, 2016
Posts
5,864
Location
Yorkshire
For the Vox, look for any relays and electrolytics associated with switching. It isn't just power filters that go iffy over time. Even some solid caps can get dementia. Tantalums don't last forever, and ceramic discs are a pain from day one. Dry joint hunting also awaits you. Get up close with a lupe. A single tin-whisker can create chaos. A good scrub down with a dry toothbrush will knock most, if not all whiskers free.

For the Ibanez, it may or may not be the valves. Valves don't get any hotter over time. They reach an equilibrium and stay there. Again, electrolytics may be involved. Normally more a hum than a hash though. Hash noise -may- be a carbon composite. Chopstick any large resistors.

Having spare valves is a good thing.
 

Boomhauer

Friend of Leo's
Joined
Aug 18, 2013
Posts
3,063
Location
Michigan
Did you swap the tubes within both of your amps already.

Seems to me the amps need troubleshooting and service without respect to what might be causing the issues. Swap tubes between the amps. Do the issues travel with the tubes or does each amp have it's same issue?
So, I'm starting from basically zero in my knowledge of tubes here - it didn't even dawn on me to swap the tubes between each amp!
 

archetype

Fiend of Leo's
Joined
Jun 4, 2005
Posts
8,663
Location
Western NY
So, I'm starting from basically zero in my knowledge of tubes here - it didn't even dawn on me to swap the tubes between each amp!

Yep. The painless, free Step 1. Does the problem travel with the tube to the other amp?

Buy a spare, too. I've bought from the following vendors multiple times. You don't need high-end tubes. They've got ones that will sound good at lower prices. Don't be afraid to buy tested, used tubes. They'll last a long time in the amps you've got.

Brent Jessee at Audio Tubes.
Matsushita, $39.00
GE, short gray plate, $50
Various US brands, $50

KCA NOS Tubes, the main guy is a member over at Strat-Talk
Various US brands that you can specify, used, starting at $40, don't buy Grade 2
 

Boomhauer

Friend of Leo's
Joined
Aug 18, 2013
Posts
3,063
Location
Michigan
Yep. The painless, free Step 1. Does the problem travel with the tube to the other amp?

Buy a spare, too. I've bought from the following vendors multiple times. You don't need high-end tubes. They've got ones that will sound good at lower prices. Don't be afraid to buy tested, used tubes. They'll last a long time in the amps you've got.

Brent Jessee at Audio Tubes.
Matsushita, $39.00
GE, short gray plate, $50
Various US brands, $50

KCA NOS Tubes, the main guy is a member over at Strat-Talk
Various US brands that you can specify, used, starting at $40, don't buy Grade 2
Ok, thanks!

What about the 6v6 in the Ibanez amp? Is there anything in particular to know about that?
 

archetype

Fiend of Leo's
Joined
Jun 4, 2005
Posts
8,663
Location
Western NY
Ok, thanks!

What about the 6v6 in the Ibanez amp? Is there anything in particular to know about that?

I just looked at that schematic. I never dreamed that the Ibanez would have a tube output stage. Go to those two tube vendors and look for low cost NOS 6V6-GTs.
 

Boomhauer

Friend of Leo's
Joined
Aug 18, 2013
Posts
3,063
Location
Michigan
Yep. The painless, free Step 1. Does the problem travel with the tube to the other amp?

Buy a spare, too. I've bought from the following vendors multiple times. You don't need high-end tubes. They've got ones that will sound good at lower prices. Don't be afraid to buy tested, used tubes. They'll last a long time in the amps you've got.

Brent Jessee at Audio Tubes.
Matsushita, $39.00
GE, short gray plate, $50
Various US brands, $50

KCA NOS Tubes, the main guy is a member over at Strat-Talk
Various US brands that you can specify, used, starting at $40, don't buy Grade 2
Hey, good news I guess - I took the tube out of the Vox and placed it into the Ibanez, and...well, didn't get the exact same problem (that is, weird distortion when switching between amp models), but I got a weird ticking or popping when the Tube Screamer was activated and I adjusted the knobs.

Bad news is I fat-fingered installing the tube from the Ibanez into the Vox and bent the pins, so I gotta buy a new tube anyway.
 

archetype

Fiend of Leo's
Joined
Jun 4, 2005
Posts
8,663
Location
Western NY
Hey, good news I guess - I took the tube out of the Vox and placed it into the Ibanez, and...well, didn't get the exact same problem (that is, weird distortion when switching between amp models), but I got a weird ticking or popping when the Tube Screamer was activated and I adjusted the knobs.

Bad news is I fat-fingered installing the tube from the Ibanez into the Vox and bent the pins, so I gotta buy a new tube anyway.

You need a vacuum tube pin straightener.
 

hepular

Tele-Afflicted
Joined
Feb 17, 2019
Posts
1,406
Location
abilene, tx
@Boomhauer check those raytheons out carefully. good chance they're rebadged soviet era crud.

aside from that: nos. do a little digging, some messaging with sellers and engage your bs detector, then buy a few.
 

Boomhauer

Friend of Leo's
Joined
Aug 18, 2013
Posts
3,063
Location
Michigan
@Boomhauer check those raytheons out carefully. good chance they're rebadged soviet era crud.

aside from that: nos. do a little digging, some messaging with sellers and engage your bs detector, then buy a few.
Hey man, that's all I needed to hear. Sounds like eBay might not be the place for someone such as myself who doesn't know much about tubes...I'll start looking elsewhere; I mentioned the ElectroHarmonix tubes I have saved on Reverb, but I've also got a recommendation from tubedepot.com and from tubesandmore.com.
 

W.L.Weller

Tele-Afflicted
Silver Supporter
Joined
May 20, 2014
Posts
1,562
Location
Queens
Amplifiedparts.com also carries new production tubes.

I have purchased new and used old stock tubes from this seller, and did not have a bad experience:


Obviously caveat emptor, your mileage may vary, guarantee void in Tennessee, etc.

I have also purchased new and used old stock tubes from this eBay seller, and did not have a bad experience:
https://www.ebay.com/str/vintagevalvesanddrivers

Same statements regarding sample size, buyer beware, etc. and so on.
 
Last edited:

archetype

Fiend of Leo's
Joined
Jun 4, 2005
Posts
8,663
Location
Western NY
Hey man, that's all I needed to hear. Sounds like eBay might not be the place for someone such as myself who doesn't know much about tubes...I'll start looking elsewhere; I mentioned the ElectroHarmonix tubes I have saved on Reverb, but I've also got a recommendation from tubedepot.com and from tubesandmore.com.

Get NOS tubes from one of the vendors that I and others have recommended. This isn't a time to try to get off cheap and then wonder about the quality of what you bought.

BTW, Tube Depot charges premium prices. I've bought plenty of tubes from Tube Depot before, but only when they've had a sale that brought their pricing down to the level of everyone else.
 




Top