Which Tube for an ART Tube MP upgrade?

[XLR2XLR]

I have the original chinese Tube, what would you suggest I put in for a smoother
more mellow sound?

Many Thanks

[XLR2XLR]

It houses a 12AX7 currently I believe.

[woomanmoomin]

I guess a Sylvania or Philips USA 12AX7 type would be a reasonable choice if you want mellow. Or you could try a 5751 (slightly lower gain). I don't know whether this design incorporates a voltage-starved valve, though. If it does, there's not going to be much improvement.

[scrubs]

I don't really see the point of dropping an expensive tube into a cheap starved-plate preamp. A good tube will cost more than the pre, and probably won't change the sound much. I'd opt for a better preamp. YMMV.

[XLR2XLR]

The pre is ok, very good for the money I am wondering if
it can be improved, lots of gain, well built, better than many desk preamps
what more for $50.00, valves start from $14.00.

You think it makes no difference?

I don't have more money for better pre I can't buy a better pre
for $14.00 - $36.00 your solution is no solution.

[DeeDrive]

I don't really think of these cheap tube pres as REAL tube pres, just pres that happen to have a tube in them, for marketing reasons. Look at the LEDs behind the tube lighting it up! You could always try a new tube, but why not try some new IC's or capacitors too? There's probably an opamp in there adding more gain than that starved tube is. I do think the ART pres sound decent enough for the money, but I don't think the tube has a lot to do with their sound.

[dkelley]

the art tube mp sounds pretty good, but can be rather noisy if you need high gain (it's good for condensor mics and quite useful as a bass di though). It does the job, you can make great recordings with it, but if you use it for a lot of tracks you'll start to notice the background noise increasing (it prob won't bother you on only 1 or two tracks though, if audible at all). So you've got a useful inexpensive preamp there, yes, warmer than many mixer pres, go ahead and use it my friend.

But there is little to no point in changing the tube - the stock tube is (A) pretty good for a chinese tube, and (B) the tube isn't used in the basic circuit (it's op-amp based as someone else noted) so you aren't hearing the tube at all unless you crank that tube warmth thing or whatever it's called. The mp sounds pretty good though, so don't mess with it. I've never heard of it improving much, so spend that $15 or $30 on something else, new strings, rental of a great mic for the weekend, something like that. Enjoy it, don't try to improve something like the MP. Art made it as well as they could, it isn't a common DIY modification project.

Some mics are though, like the apex 460 which has actual circuit design that requires a specific type of tube and the idiots put in a different tube with higher output that wasn't designed for the tube, making the mic distort using the stock tube. replacing that tube makes it a whole new (very good) mic. The ART Tube mp doesn't have that sort of problem.

IF you owned something like an ART MPA GOLD mic pre, which has a true high voltage (if switched that way on front panel) tube gain section, then yes swapping the tube(s) makes some difference, but again, ART chose what they thought were good tubes at the time, and it's a subtle thing at best even with gear like that.

Hope you like the MP, I had a friend record a lead vocal for a radio released single indie track on one.

Don

[woomanmoomin]

Originally Posted by scrubs

I don't really see the point of dropping an expensive tube into a cheap starved-plate preamp. A good tube will cost more than the pre, and probably won't change the sound much. I'd opt for a better preamp. YMMV.

You're kind of right, but it's not hard to get decent NOS tubes that don't cost the earth. Fun to play with, I guess, even if this particular pre is never going to sound exactly phenomenal.

[beachhunt]

Originally Posted by dkelley

IF you owned something like an ART MPA GOLD mic pre, which has a true high voltage (if switched that way on front panel) tube gain section, then yes swapping the tube(s) makes some difference, but again, ART chose what they thought were good tubes at the time, and it's a subtle thing at best even with gear like that.

I've always wondered if that was really true. All the marketing material for the ART MPA Gold is very careful to say that it "provides the equivalent of a 300V power supply on the high voltage setting". "The equivalent"? That makes it sound like a "high voltage emulator", so to speak. I've heard almost entirely good reviews on the MPA Gold, but that line always makes me a bit wary.

Anyone know the actual details on the circuit?

[woomanmoomin]

Well, I'm no electronics expert but I'm pretty sure the actual mains power supplied to this unit must be less than 300V wherever you are. Aren't they just using a transformer or something inside the unit to convert the voltage at the plate to 300V? Ah, probably not. That would be too good.

The one major review of the unit that I do remember reading was very positive and sounded promising to me BUT included the proviso that at such a price you were really never going to get top-quality performance. Well, I guess that makes sense, but I wonder what it is that's missing. The idea that something probably was missing was enough to put me off the unit.

As for ART's having chosen the most suitable valves or whatever, I think a lot of times the manufacturers just go with whatever half-decent valves they can get cheaply and in bulk. There are a lot of valve audio devices out there with certain Soviet and second-rate US valves (let alone the Chinese ones) as standard, valves that I pretty much know I could improve on in most decent circuits because they're fuzzy valves or have high microphonics or don't have good frequency balance, blah blah. Anyway, if you know what type of valve you're dealing with, there will often be room for manoeuvre, and different valves in the same family can have surprisingly different properties.

[ulysses]

Originally Posted by beachhunt

I've always wondered if that was really true. All the marketing material for the ART MPA Gold is very careful to say that it "provides the equivalent of a 300V power supply on the high voltage setting". "The equivalent"? That makes it sound like a "high voltage emulator", so to speak.

That's interesting. I have no experience with or opinion of the MPA Gold, and haven't seen this marketing material. But that phrasing would make me wonder, and I can imagine a couple of different "equivalents" to a 300V power supply of varying effectiveness.
I can imagine a bipolar 150V supply being used in a tube circuit to achieve 300V across the tube without violating some jurisdiction's arbitrary standards or requirements.
I can imagine using a solid state current source as a plate load to achieve with a lower voltage the same dynamic range that you would get with a simple resistor and a 300V plate supply.
I can imagine other, less scrupulous interpretations of "equivalent" as well, but this last one seems likely and relatively legitimate (debatably).

[woomanmoomin]

Originally Posted by ulysses

I can imagine a bipolar 150V supply being used in a tube circuit to achieve 300V across the tube without violating some jurisdiction's arbitrary standards or requirements.

I need to study some electronics. Does this mean 150V across each of the two triodes of the 12AX7 or whatever it is?

It's a different thing, but I've noticed a lot of manufacturers boast about all the many valve stages in their rack gear, e.g. two input valve stages, one valve stage in a compressor and one more in the output... where each of these stages is actually one measly triode, i.e. half a dual triode like a 12AX7. Stuff like that. They even draw up bullsh*t circuit diagrams that make it look as if you're dealing with four valves or whatever.

[ulysses]

Originally Posted by woomanmoomin

I need to study some electronics. Does this mean 150V across each of the two triodes of the 12AX7 or whatever it is?

No, it would mean 150V on the plate and -150V on the cathode of each triode.

... where each of these stages is actually one measly triode

You can do a lot with one measly triode. I agree it's a bit misleading if all the work is done by a bunch of op amps and they stick one tube in there that's not really doing anything so they can call it a toob circuit. But there are plenty of circuits that only need a triode or two to get the job done. A Vari-mu compressor really only needs one dual triode. And a single 12AX7 (dual triode) is capable of being a completely useful mike preamp. And the U47 only has one tube device in it, but people seem to like it anyway.
I don't think it's a good idea to insist on a lot of parts in the box to justify its price tag. Good design is worth more than good parts, and good sound should be worth the most.

[woomanmoomin]

Oh yeah, definitely. It just annoys me that some companies manipulate the 'multiple valve stage' stuff to sell their products to people who think more valves mean better audio. Too cynical.

[dkelley]

wow, kewl, I really sparked a conversation about the mpa gold etc, I'll throw in my two cents worth.

I own the mpa gold, have opened it up, and it does have a decent sized power transformer inside, and the high plate voltage switch is interconnected with it somehow. That's all I can tell from looking at the circuit board and not screwing the unit up.

As an end user, the mpa gold sounds amazing, as good as any really high end pre I've used, with it's own flavour of course but certainly not lacking in any way. Exceptionally low noise with insanely high gain. I only run it in high plate voltage mode, which does sound significantly more transparent at high gains and doesn't distort at all with crazy amounts of gain, but with a quick test at low plate voltage, when the digital meter goes into the red it distorts terribly. when in high plate voltage there is no distortion with the digital (tube gain) meter peaked constantly, with maybe a slight bit of nice tube warmth but really virtually clean still. So it definitely works, whatever they're doing.

It's in my rack and I'm not really sure if I want to rip it out, open it up, and try to run it open to see if the tubes actually light up when in high plate voltage mode, but I suppose I could if it was indicative of anything. What do people think?

And by the way, I'm curious to try replacing the tubes with NOS or something modern but more exotic in my mpa gold. What I meant in my first post about art choosing the appropriate tube for the gear was actually meant to say the appropriate TYPE of tube for the gear, with appropriate output levels etc (even so far as being ax or at or ay or au). The famous example being the apex 460 tube mic who's circuit with the stock ax tube (and any ax tube for that matter) has too much output for the crappy transformer in the mic, overloading the tranny in loud transients, creating bad sound. That's one and possibly the only example where a company blatantly chose a tube that actually wasn't suited to the product, and a lower output tube like an AT will perform much better (all other things being equal).

I do feel that stock chinese tubes still perform well and do a good job on many things, and can be preferably to some other supposedly better tubes for certain situations (they last forever for one thing). However for high end tube preamps they use exotic tubes, and this pre really does perform like a high end unit, so might as well try a high end tube in it.

I don't recall if it uses one or two tubes, but doesn't matter. Like someone said, you can use one dual triode for a two channel device just fine, or for more complex circuits.

Don

[woomanmoomin]

Nice post. Everything I've read (good reviews, mainly) suggests the ART circuit here is indeed nicely optimised for the valve type used, at least until you go for the low-voltage option for distortion gross-out. I think the valve type is the 12AX7A. That's just a low-noise 12AX7. You can try any 12AX7 in there without any problems. These come in a few other guises, e.g. as ECC83s and 7025s. 12AX7s generally are at the top of their family for standard gain rating (100 mu), so you can have fun trying lower-gain alternatives like the 5751 (70 mu) I mentioned earlier and maybe 12AT7s (60 mu), but... yeah... the 100 mu valves are probably best in this case. If you replace a high-gain valve with a lower-gain alternative in a circuit that's optimised for the higher-gain version, you can actually end up with more distortion, not less.

I would recommend sticking to the 12AX7s/7025s/ECC83s etc. (all at 100 mu) but using valves from different companies etc. to see which give the nicest tone.

[ulysses]

Originally Posted by dkelley

It's in my rack and I'm not really sure if I want to rip it out, open it up, and try to run it open to see if the tubes actually light up when in high plate voltage mode, but I suppose I could if it was indicative of anything. What do people think?

No, preamp tubes don't really light up other than the dull glow from the heaters which would not be a variable. The only way we would quench our mild curiosity would be to look at a schematic. So unless you want to trace out the whole circuit, there's no need to remove it from the rack.

[ToneTaster]

Hi,
I have created a 5 part video review series of the original ART Tube MP and put it on YouTube. There are quite a few audio tests that you can listen to and in the third video I try different tubes inside the MP and compare the sound. You can clearly hear the differences. I thought some of you might find this very helpful or interesting. I also include some tips for how to get the best sound out of the Tube MP with the assumption that most people using it are not pros. Here is the link to my channel page in case you are interested.

YouTube - ToneTaster's Channel

[Old Goat]

Yeah, I just put a JJ in mine and it's a little smoother.

Anyone still interested in the schemo for the MPA Gold, it's here.

[Wavebourn]

Originally Posted by Old Goat

Anyone still interested in the schemo for the MPA Gold, it's here.

Try to stick a couple of 2SK170, or even pair of 2SC1815 in tube socket, you will be surprised!

[fruitsnake]

Originally Posted by ToneTaster

Hi,
I try different tubes inside the MP and compare the sound. You can clearly hear the differences. I thought some of you might find this very helpful or interesting.

YouTube - ToneTaster's Channel

I have two art tube mps, both of which I put "The Fisher" Telefunken smooth plate 12ax7s into. HUGE improvement in tone color, better dynamic range, and essentially no noise to speak of, even when using dynamic mics (57, senn e609, shure green bullet) at very high gain. Of course, the only reason I put such amazing tubes into the cheapo art pres is because I got a whole NOS stash of the tubes for free and was looking for things to put them in. It would be a little silly to spend $50 on an NOS Telefunken tube for your $30 art pre, although it does sound fantastic for guitar and bass di, better than almost any other di box I've ever used - the low end is thunderous.