Tested a Few New Preamp Tubes

[Ted B]

While going through a newly purchased '73 Hiwatt DR103, I found the amp contained a hodgepodge of preamp tubes. Wanting to start with a clean slate in the tube department, this gave me a good excuse to buy several different sets of ECC83/12AX7, and put them through audible testing while I was inside the amp. This test included:

Original Mullard
New (Russian) 'Mullard'
New (Russian) Tung Sol
JJ ECC803 (long plates)

The PI tube (V4) in this amp is a ECC81/12AT7, which remained a GE JAN 12AT7 throughout the testing. The remaining three tubes (V1, V2, and V3) were swapped.

V1 - First gain stage
V2 - Plate driven tone stack
V3 - Second gain stage


Observations:

To be honest, I found the new 'Mullards' to be surprisingly pleasant sounding, with good gain, and quite close to the originals. They give a firm bottom, cushy mids, and a gentle rolloff on the top. If I wanted to be nit picky, I could say they may not have quite the '3D imaging' of the originals, but the similarities were enough to keep me going back and forth several times. I bought a set to use in a new Marshall 100w plexi (12000 series) clone I just finished, and they're a very nice match for that amp. Like original Mullards, they soften some of the edginess that can prove to be raggedy and ear fatiguing with some other brands.

The new Tung Sols also sound nice, also with good gain, and give a bit of a different texture. They deliver strong lows, crystalline highs, and aren't quite as midrangy. Comparing the new Tung Sols to an original Mullard for reference is akin to comparing a G12-65 to a vintage G12M. They each have their own, different strengths. I find these to be a good match with my Marshall 18w clone when used with a closed back extension cab. They add some punch and clarity to the highs and lows that allow the small amp to sound a bit 'bigger'. I'm curious to try them in an AC30 as well, simply because they may be a worthy replacement for the wonderful, but discontinued Ei Gold ECC83.

The ones I eventually chose to leave in are the JJ long plate ECC803s. They have a big, tight bottom, smooth highs, and warm, fat midrange - not far off the real (and reissue) Mullards. The fits very well for this particular amp/speaker combo, that benefits from a broad midrange to balance the strong highs and lows inherent to this setup.

The good news is there are at least several current production preamp tubes that are pleasing to the ear. I should note that certain positions in some amps create a large voltage potential between cathode and heater (e.g. V2 in a Marshall 45-50-100w plexi), and only old production or newer short plate versions (e.g. Shuguang, JJ ECC83) should be used there.

[Tone Slinger]

Thanks for posting that Ted, very informative. I have some reissue Mullard pre's, a late '80's to early '90's Chinese made ' National' short plate, a JJ ecc88 short plate and an old Sovtek 7025. Good to know about the v2 spot.

That Chinese pre is what I have used in the v1 spot in my last few JCM 800's (alway's just one at a time, sold/traded for another) up to my last one a few yrs back. I've got a Metro 12xxx kit that I just completed ( took me nearly a year and a half ). I just havent got enough time, combined with 'option anxiety'. I simply kept changing my mind about what spec I wanted in it. I still havent tested the voltages in it yet, after having completed it it about 2 weeks ago.

I have heard good things about the 'regular' Electro Harmonix 12ax7, have you heard anything about this one. I've been told that they have a good upper mid type quality.

[Ted B]

The newer EH gets good reviews, but I haven't used one. In general, I prefer long plate tubes. I use the short plate type for cathode follower positions (tone stack), because they tend to hold up better. Long plate tubes tend to be somewhat more prone to microphonics, so it's best to use the quietest one in V1.

[BAinFL]

I have a hard time coughing up $10-15 for new 12AX7s when there are still so many options out there for NOS tubes in the under $20 range...some closer to $15. I got a mess of baldwin/sylvanias for cheap and love them.

[Ted B]

... there are still so many options out there for NOS tubes in the under $20 range...some closer to $15.

That's true, but those old production tubes almost always found in that price range aren't among my favorites.

... but then again, my favorite for one type of amp isn't necessarily my favorite for a different amp.

A few of the current production tubes (such as those mentioned above) I prefer to most of the cheaper old production tubes. It's a matter of taste.

[SteadyEddie]

I might have to get one of those new mullards.
I've been fighting this brittle bite in my amp, and I finally took out the newish Tung Sol in v1 and stuck in a JAN Philips 12ax7 in there. Smoother, but it's microphonic as hell.
The Tung Sol sounds good on some things, but I think it's a little too harsh for my Strat. Sounds great with my buddy's Les Paul though!

[Ted B]

If the amp is sounding gainy and brittle (as many Marshalls do), the Tung Sol is probably not your best bet. It's a nice sounding tube, but this probably isn't the best fit. The JAN Philips, GE, etc., are also good tubes, but again, not my favorite here.

Mullards, old or new, are a better fit here IMO. They roll off the highs a bit, which works well in an amp that is a bit too far on the bright side. I suggest you leave that JAN Philips in V2. It'll hold up well there, it won't really impact the sound, and the microphonics shouldn't matter.

[SteadyEddie]

Good deal. I just ordered a Mullard. Should smooth things out a bit.

[BAinFL]

i have a telefunken in V1 currently and its a very warm sounding tube. I'd recommend it for anyone trying to tame some brittleness.

[SteadyEddie]

Got the Mullard in, tested it, it's definitely warmer and smoother. Fatter, I'd say. Sounds very nice, but it's pretty microphonic. Is this normal for this tube? I can notice it while playing, and when I put the shield on, it didn't like that at all.