Which 12AX7 for Milkman "The Amp" 50 watt early version?

Steve Lipsey · From: Portland, Oregon, USA

What's the latest on what brand and where to get a good 12AX7....been a couple of years on this one, probably time to replace it. My awareness of tube brands/sources is quite out of date...

And would a lower gain tube be good? I only want clean tone, never overdrive (got pedals for that), and never can raise the gain very high without starting to fuzz up...or does that just change where you set the gain and not actually help the tone at all?

and there is a strange background noise I haven't been able to isolate in my signal chain, no matter how much I separate stuff...when it all is together I get it. So maybe a new tube will help...
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Stephen Cowell · From: Round Rock, Texas, USA

Not sure why you're wanting to replace a tube that's working... your signal chain stuff is probably ground loop-related.

You should own another 12AX7 anyway... have one around spare for backup/troubleshooting/etc. You can either pay more for pre-selected good ones or buy several and try them out. NOS tubes are very expensive, but for a good reason... they really don't make 'em like they used to.

Other tubes that will plug in that hole go by 7025, ECC83, 5751, and others I forget. Just get another one and swap it... if it's the same, now you have a spare.
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Steve Lipsey · From: Portland, Oregon, USA

I do have a spare...a random one I picked up just to have a spare...I've had tubes die at gigs...

For this one, since Tim runs his 12AX7s at high voltage, I suspect that their life isn't the typical "almost forever" 12AX7 life, and would rather grab a recommended one and swap now...I don't care enough to start a tube testing thing to find the "best", I figure enough people with good ears have done that already (my ears aren't really up to fine distinctions any more).

Re the mystery noise....All stuff in the chain is running off the same AC cord...direct to the Milkman and through a One Spot to the pedals...whole chain on the same pedalboard...so I'm not sure where to look for a ground loop, although I certainly believe that always is a possibility..I guess I could turn the One Spot around....
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Charlie Thompson · From: South Carolina, USA

Hi Steve those one spot plugs can be noisy

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

How many and what type of pedals are you running off that single One-Spot? Some pedals, especially some high-drain digital pedals, do not play well with other pedals on the same power circuit and really need isolated power. This is not about the One Spot - they're great supplies, but if a pedal needs an isolated supply, that's that. My One Spots can generally handle 5-8 simple analog pedals, but the minute I start adding sophisticated, high-draw digital pedals, that can go out the window.

As far as 12AX7 tubes go, I find recent production spotty. I'll find two of the same exact batch with very different characteristics, 'premium sorted' or not. I've been accumulating NOS when they're not ridiculous and good used old stock tubes when reasonable for a long time - guitar shows, electronics shops, music stores, old electronic gear at salvage, whatever. Good old-production preamp tubes like 12AX7 and others in a typical preamp circuit - i.e., around 250-300 VDC or less - last essentially forever for me. Is Tim really running his 12AX7s harder than that?

One exception to the offshore production were the Chinese Beijing-made 12AX7A tubes from the 1990s. Ruby Tubes marketed a lot of these, and I have found them to be excellent - in some amps I prefer them to old US-made production. But I have to try some different tubes to tell what sounds good. Nobody can measure that. They may tell you that they can, but that is emphatically not my experience.

Steve Lipsey · From: Portland, Oregon, USA

What is the One Spot driving? A bunch...but only the little Ana Echo delay, Xotic EP compressor, Aura, Boss tuner, and a Saturnworks stereo combiner under the board, are on all the time...I don't think those are high-draw?....and when any of the others are on, they would hide whatever noise they might create...

Although now that I think about it I seem to remember maybe reading that the Xotic likes its own supply, maybe...?? I'm not sure...turning on the compressor certainly brings up the noise, but you would expect that, it is what a compressor does....I tried various combinations of "on and off" for pedals, and cabling around them, and strangely, re-cabling and then going back to exactly the way it was actually killed the noise for a while, but now it is back...maybe it is a cable?

This is my stereo rig for the CooderNator reso with Fishman and string-through pickup...

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Steve Lipsey · From: Portland, Oregon, USA

TUBES
Here's what's commonly available...any messes or not for any of these? I know that some are just private labels of others....

Mullard, JJ, Electro-Harmonix, Tung Sol, and a bunch more from The tube Store
https://www.thetubestore.com/preamp-tubes/12ax7-ecc83-tube-types

Some say what country they are from, and some what years...and here is one that is "This 7025 is a high quality and very rugged custom 12AX7 tube produced for us in China by the Shuguang factory. The plates are manufactured out of a premium metal imported from Germany and supported with extra thick mica spacers to insure against microphonics."
https://www.thetubestore.com/preferred-series-7025-12ax7

Bewildering.....prices are all pretty much $15-30, not really different...
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Jon Light · From: Saugerties, NY

The best source for info on reliability of in-production tubes is going to be a builder of some reasonable output volume who is also a trusted individual. That would be Tim Marcus, for starters. He would have his finger on the pulse of the manufacturing market (I would think).

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

To track down hum, start out with guitar straight into amp. Ideally some type of humbucker to remove single-coil hum. If it hums, look for tubes.

Now add pedals back one at a time, individually. See if any hum. Yeah, heavy compressors can add significant hum - factor that in. So can high-gain preamps, distortion pedals, etc. If none of them have unreasonable hum, look for combinations of pedals.

Add combinations of two pedals. Same deal - see if combinations give trouble. If you find a pair hums unreasonable together, you probably need to isolate their supplies. Now try combinations of three, four, all the way up to all together. You may find some pedals that need to be isolated from each other.

Honestly, I think new tubes are a crap shoot. You're right, the choices are bewildering. There are only a handful of factories making these, yet there are dozens of different marketing choices. If I had to buy tubes like that, I'd insist on a seller with a reasonable return privilege, buy a bunch, and then send back the ones that weren't good.

Tubes are a PITA. What works great in one amp may suck in another, and vice-versa. That's why I have been culling these for decades.

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

BTW - I'm answering the 12AX7 question generically. Have you asked Tim what he suggests right now for his own amp? Seems like he might have an idea what current production would work best. He has to be on top of this. Of course, priorities for production might differ from what one might want to put in for a specific purpose in a service application.

Bill Sinclair · From: Waynesboro, PA, USA

Re: noise in signal

If it's a high pitched whine, I've found that pedals with octave capabilities (like your sub n up) quite often create an oscillation on the power supply so that even when the pedal has true bypass, it still adds the whine to the other pedals through the power supply connection. Next time you hear it, try unplugging the power from the octave pedal and see if it goes away.

Dave Meis · From: Olympic Peninsula, Washington, USA

New Sensor recently released a 7025 branded Electro Harmonix that I've used in my Fenders and a Peavey Delta Blues 1-15. I've had good results with them.

Steve Lipsey · From: Portland, Oregon, USA

Dave - can't tell if this is that or not
https://www.thetubestore.com/electro-harmonix-7025-eh
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Donny Hinson · From: Glen Burnie, Md. U.S.A.

It's not like they're super expensive, so buy a few different brands and do some A&B testing on your own. What YOU think sounds good may be completely different from what someone else thinks sounds good. Winking

Steve Lipsey · From: Portland, Oregon, USA

Well, as I said above, my ears are the last ones I'd use for an audio quality test...I'm 65db down in one ear, almost that in the other, and what the hearing aids hear isn't what most folks hear....so I use OPE (other people's ears) for tonal quality judgments....the hearing aids are fine for playing and making EQ decisions, but not for fine testing...
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Dave Meis · From: Olympic Peninsula, Washington, USA

@ Steve: Those are the ones I was referring to. Iâ€™m not a fan of strident highs, and these sound very musical to my ears.

Steve Lipsey · From: Portland, Oregon, USA

Dave-
maybe that 7025 is old news...and maybe I don't need to worry about it....just got this from Tim Marcus:

"I am using JJ ECC83S because thats what I can get these days. Avoid the new sensor stuff - Ruby factory closed in 2019 but if you can find one that is a decent option. Or splurge for NOS.

The 12AX7 in The Amp actually does not run on that high a voltage compared to my other amps. The B+ is 250v and then there are dropping resistors to the plates. That combined with a low heater voltage should make the tubes last very very long"
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Dave Meis · From: Olympic Peninsula, Washington, USA

He would know! ðŸ˜„

Steve Lipsey · From: Portland, Oregon, USA

actually, he DOES like the new one:
"yeah they have that new 7025 and they sent me some samples and they are fine but very expensive for a Russian tube"

I'm not sure which that is...the Thetubestore one isn't that expensive...$18....but maybe there is a new-new one that is different....

As I said, bewildering...
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Brad Sarno · From: St. Louis, MO USA

I'm with Tim on his choice of the new JJ ECC83s. It's a really good, sweet sounding 12AX7 and generally with VERY good control over microphonics and good reliability. It may be my favorite modern and available 12AX7 today.

But, it's hard to beat a vintage "used-tests-good" or "NOS" 12AX7 or 7025 by RCA, GE, Sylvania, Amperex, Tung-Sol, Telefunken, etc. Personally, I favor vintage RCA's for pedal steel, something especially smooth about the top end. And in that amp of Tim's, should last a lifetime.

B

Steve Lipsey · From: Portland, Oregon, USA

OK....so here's the outcome, for both the tube and the noise:

Tube:
Still not sure which 7025 is the "good one", the one at thetubestore may or may not be, depending on how you interpret the various comments. The JJ seems to be fine, as per people who make and sell stuff with tubes ....but it seems that The Amp isn't stressing the tube and there is no need to replace it (given that I figured out that it isn't the source of the high-pitched noise.

The Noise:
Well, I'd tried all the obvious things before posting...but Bill Sinclair gave me the clue that led to the solution. I run in stereo, with the Fishman Nashville/ Fishman PowerChip into an Aura, and the Lollar string-through into a bunch of pedals, then joining up for tuner, delay, overdrive, and The Amp. All running off a stereo cord from the guitar.
The noise started with the Aura, bled into the other pedals through some combination of power (all sharing a One Spot) and spreading through the stereo guitar cord plus guitar electronics. Unplugging the Aura power stopped it, as did using a mono cord for one channel at a time instead of stereo. Putting in a separate power supply for the Aura fixed it.
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Bill Sinclair · From: Waynesboro, PA, USA

Glad you figured it out and thanks for letting us know. So many of these threads are left open-ended. It's always nice to know when a solution is found and what it was.

Dave Grafe · From: Hudson River Valley NY

I have new JJ preamp tubes for days:

ECC81/12AT7, ECC82/12AU7, ECC83/12AX7

Not everyone's favorite but other folks swear by them. I owe you one Steve, email me your address and I'll send you a few.

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