Is Your 'TUBE' Mic Preamp a FRAUD!?!

in this vid, we look at whether or not this ART Pro Audio "TUBE" mic preamp is really a "TUBE-driven" preamp. There are some reviews and circuit evidence that suggests maybe not. The unit was sent to me by a lawyer who wanted to find out whether this company was making fraudulent claims about its products. We'll run some tests on the circuit and see why these orange LEDs are necessary.

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#tubepreamp #electronics #micpre
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[TheGuitologist]

I think the takeaway from this should be know what you're buying and don't fall for the marketing hype on so-called "Tube Preamps" in the low budget range. This is what's called a "starved tube" design. The plates are running on low voltage, the filaments are also under-volted, so they barely glow at all, hence the need for LEDs to make the orange glow from the front panel. Is it a "fraud"? Technically, no. The tube is amplifying signal; however, there isn't enough of an amplification going on for the tube to reach saturation and compress the signal in the way one would expect from a true all-tube preamp for recording use. My advice is don't waste your money unless you just need something to amplify a signal for a basic project studio. If you want actual tube warmth, save your money and buy a high voltage all-tube preamp that is worthy of professional use.

[Adoratek]

There is no fraud to this. This unit was not designed to make amplification through the tube, but rather the tube only "colors" the signal with variable amounts of distortion and harmonics. The plaintiff in this matter is missing the point (and usefulness) of this design. This unit offers you both a clean sound, which in my opinion is pretty damn good. Add the fact that they actually have a variable impedance knob which can adjust the character of your mic, and this unit becomes a gem. I have 2 of these units and will buy another when the need arises for more inputs. These units are fantastic for giving various instruments a "place" in the mix, and with even the lowliest of microphones you can make them sound like much more expensive flavors with the impedance adjustments. Even for the full price, these units are a steal for what they accomplish.
To add a bit more insight on this, since the unit's output volume is not directly related to the tube itself, and since the tube on lower voltage is more prone to signal breakup (harmonic distortion) at lower gain... maybe the owner should consider trying other tubes besides the 12ax7... for example, the 12ay7 has a lower gain and quicker breakup than the 12ax7 and imparts even more warmth. This is evident in the fact that many tube mic designers have made use of the 12ay7 in their tube mics. Why not even try a 12at7? 12at7 will still give a little cleaner emphasis on the upper frequencies. In the 2 units I have one has a 12ay7 RCA and one has a 12at7 JAN and I use them for different purposes. Good Luck!

[Jester-Riddle]

I can see an irony here ... Maybe they felt that they had to artificially light up the tube to prevent lots of returns because customers couldn't see the tube glow and thought it was faulty ...

[moushunter]

I sometimes use the small ART microphone tube preamp with a loop switch circuit for a boost. It makes a fantastic clean boost into a guitar amp.

[vibrolax]

12AX7 has about a 2 watt filament (6.3V @ 300 mA / 12.6 V @ 150 mA), so most of them do not produce much of a light show.

[cigarettesmokingman]

This has been done for years. I had a berhinger mic pre with a tube that had LEDS behind it.

[DrSimonBignell]

But you tested this with the V3 dial at flat (6 o'clock) on both channels. The tube gets more voltage to saturate and becomes 'warm' when that's turned up. It was at minimum gain when you had a meter on it, so it barely kicked in. 😮

[robtitheridge]

I think all that happens with the 12ax7 in the signal path is that it adds second order harmoics.giveing a warmer sound.

[rsn]

I've got one of these. I've used it a lot. Which preamp circuit is in use depends on what you have selected in the front panel. It has a selector switch that lets you choose between different kinds of preamp circuits... I design my own preamps now. You can run some tubes on a lower voltage and some are okay but some distort too much and lowering the filament voltage can cure that but it's not going to be super clean. I'd rather just use an INA217 or INA849 based preamp for most instruments and a version of INA preamp with a soft limiter for drums...

[PooNinja]

At least it’s got wall power for the tube unlike a tube pedal running on a dollar general 9 volt.

In pre amps and restaurants it’s all about hot plates

[JClay-lfnx]

It's a recording preamp not a Fender Twin. Lower voltage results in lower noise...but still adds color.

[mikemikemike]

It would be cool to see a follow-up video modifying this preamp with a high voltage circuit.

[ibanezleftyclub]

It’s just legit enough not to get sued lol shady AF.

[kuzWich]

Wonder if anyone done similar tests with the Joyo bantamp "collection" growing popular lately.

[bernard]

Maybe the colder filament is providing already the litttle current needed with such a low plate voltage. So, maybe the low filament voltage is a just a deliberate choice? Possibly to reduce heating of the entire device.
Thanks for sharing Brad!

[johnabbottphotography]

I love any video where the person doing the video is willing to say that they were wrong about their original thoughts.

Thanks!

[skycarl]

Good conclusion Brad, , , Nice that you got to give him a professional unbiased evaluation of his circuit. Nice job bud.

[GearjunkieJasonBallou]

Thanks for that. Ive been using the lil ART tube pre single channel boxes for a condenser Mic..warms it up a little. Works really well in mixer XL loop to saturate the mic sound a hair before recording. Not crazy but enough to hear a pleasant difference. Dig the channel btw.

[glenwhatley]

Most of the modern pedals/effects have 'Backlight Leds' to make the tube stand out, but in the ones I've worked on, the tube is actually functioning.
Also, tubes can function in very low plate voltages, just in a different part of the load curve. If the signal gain is small enough, it doesn't matter that it it's running in a non linear portion of the curve.
Don't know about this item, tho.

[GuitarJawn]

06:24 I was playing my '73 Twin Reverb and listening to the video. Thought that sound was from my amp, I got so scared