Monday, July 12, 2010

An Affordable Class-A Tube Mic Preamp?

If you're using any of this gear or have comparable alternatives, please chime in... 

While researching various affordable ($300-$500) high-voltage tube mic preamps (dual-channel preferred) in advance of a purchase for the Lantern Sound project studio in the not-too-distant future, I came across some other (i.e. not valve-state) VERY interesting pieces, the first and most notable being the single-channel Golden Age Project Pre 73, which is selling for only $299 US. If it lives up to the marketing-speak, it's probably quite a piece, or maybe this is just too good to be true:

"The PRE-73 is the first one-channel low-cost preamp on the market that is using a fully discrete signal path with three separate transformers for the balanced mic input, the line input and the output. The circuit is very similar to the classical preamp section of the Neve 1073 pre/eq module with a corresponding sound character that is warm, punchy, sweet and musical."

 Golden Age Project 73 Single Channel Preamp

Not to mention the fact that the input impedance of the microphone input can be switched between 300 and 1200 ohms. That's going to provide a lot of tonal variety.  Interesting and yes, tantalizing, especially when the name Neve gets tossed around.

People have apparently been talking highly of the Focusrite ISA One, which has a mic preamp based on the pre from their classic Forte console. Four switchable mic impedances, line input, headphone output for monitoring, a flexible independent DI input, insert point, and optional digital upgrade. This is something you'd probably use for a long time and you'd be guaranteed to get your money's worth... $599 US.

Focusrite ISA One

The Presonus Studio Channel is a 1U channel strip device that incorporates a VCA-based compressor and studio-grade three-band parametric EQ (mid-band has variable "Q", comp and EQ being position-swappable in the signal chain with the press of a button), with a class A tube preamp, with a VU meter and a hi-pass filter. Good reviews, but no variable mic impedance, and no digital interface, although there is an expansion slot for the future addition of digital output card (apparently currently in planning). Some OK reviews; one demanding writer said the unit was wanting for more headroom, and the compresser didn't pump and slam enough; but he also said he's looking for a "compressor that resells hard drugs and kicks up the tribute to the producer". About $250 US.

Presonus Studio Channel

The solid state "class-A mode" (huh?) Focusrite Trackmaster Pro ($300 US, and based on their Green range of pre's) improves upon the Presonus piece with the inclusion of a lo-impedance mic switch (hello, ribbon mic users), an opto-instead-of-VCA-based compressor, and the addition of a latency-free monitoring capability. It has mid-scoop EQ only, but has an A-D option that can be fitted later. Some strictlly OK reviews, and Focusrite says it's "ultra clean sounding but if you run it hot it will not sound quite as warm and forgiving as the original Track Master" (which, by the way, have been seen going for $150 on Craigslist). Hmmm...

Focusrite Track Master Pro

The Presonus Eureka ($500 US) is a step up from their Studio Channel; 1U, with a class-A discrete transformer-coupled mic preamp, variable mic input impedance, full featured compressor/limiter & 3-band true parametric EQ, promises ultra-low noise and high headroom, with an optional 24-bit / 192K I/O card.

Presonus Eureka

The ART Digital MPA-II IS a Class A tube device and has just about everything except EQ and compression sections: Variable microphone impedance, two channels of low OR high voltage preamplification (configurable for dual mono or stereo operation with a mid/side option), variable input impedance, full digital functionality. and big VU meters. Seems like a lot in one box, for a little over $300 US. Another case of "Too Good To Be True"?

 ART Digital MPA Pro II

Other Preamps

The Grace 101 ($550) reportedly offers transparent, uncolored sound, while the FMR Audio RNP ("Really Nice Preamp", $475; I already have their stereo RMC "Really Nice Compressor"), boasts plentiful headroom, compressor inserts, and takes up only 1/3 rack space, but it has stepped gain control, they admit that it is a bit noisy, and it's in an ugly box, if you care about that. The ART Voice Channel might be a nice choice if one channel in two rack spaces is an option (for me it's not); and the Groove Tubes Brick was an exercise in a no-nonsense stand-alone mic pre, but it doesn't have a 1/4" balanced output; only unbalanced instrument "throughs" to employ the piece as a DI. The utilitarian ElectroHarmonix 12AY7 (true Class A, XLR and balanced 1/4" outs) would perhaps prove to be a better choice in this type of box.

Conclusion: Leaning Towards Used.

I already have a Roland/Edirol FA-101 Digital interface (w/ two integrated mic preamps) to get things into the digital realm, the afore-mentioned RNC mono/stereo compressor is fine for tracking, and while EQ could be nice when re-amping, or with troublesome vocal sounds, I can do without it on the tracking side of things. In the end, what I really need is two balanced gozintas and gozouttas of real Class A tube pre-amplification, with variable impedance adjustment.

Drumroll, please...

Right now, the cost effective solution looks to be finding a used ART MPA Gold unit; these seem to have a good reputation, especially when upgraded with good tubes, i.e., not the Chinese ones they came with. One could even load the thing with two different tubes, for variety. Stay tuned: The search is on.



Some comments from over in Facebook Land:

"i have recently discovered the Golden Age Pre 73. also, a pal swears by the ART MPA II... oh - duh....wrote that before i read your blog. but great minds, etc. etc. etc." Chris B
"I've heard a lot of great things about the ART MPA II. I myself got a pair of old Ampex 601's from an old mono tape deck on eBay & use those" Buddy W
"I have a Eureka. It's pretty darn good. Not the greatest, but it's the ears, not the gears, right? I'll prlly get an MPA to match with my VLA and to do mid/side stuff... Also, can't remember if the 12AY7 is calss A, but it's really, really great for cheap. Especially for acgtr" Jason L

[ I'm due to pick up an MPA Gold for $100 on Saturday. In Williamsburg Brooklyn, of course. Yeah, that 12AY7 is sure getting some raves, especially with regards to recording the folk-box... and it IS indeed true Class A; at 200V, it is not power-starved. ] Mick H


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