Wednesday, July 06, 2005

Electro Harmonix 12AY7 Preamp Review


The Electro Harmonix 12AY7 is a high voltage class 'A' tube path microphone preamp. It's also one of the most anticipated pieces of home recording gear to be released in a long time. Numerous folks who had used prototypes of the unit wrote glowing reviews of it on various message boards. Some people hailed it as a new dawn in affordable but professional-sounding home recording gear, while others dismissed it as marketing fodder and message board hype at its worst. I, being a sucker for hype, decided to take the plunge and plunk down $189.95 to purchase one for myself. Is it a project studio panacea, or is it a glorified paperweight? That's for me to know and for you to discover as you read on.

Boxes, Manuals, and Knobs - Oh My

The 12AY7 is built into a large stompbox case. It looks like it's a distortion box made for people with hyperactive pituitary glands. I'm sure that they did this to keep costs down, which turns out to be a recurring theme on this unit. It has an XLR input jack, a 1/4" TRS output jack, and an XLR output jack. There are two pots: one for input gain, and one for output gain. The output gain knob only works when you are using the 1/4" output jack. It has no effect on the signal when using XLR output. I would have loved a 1/4" HiZ input and an insert jack, but those were likely omitted to save space and money. There are switches for phantom power, a low cut filter, and phase reversal. Lastly, there are three LEDs: a blue one to signify that the unit is powered on, an orange one to indicate clipping, and a green one to indicate that phantom power is on.

My preamp came in a nice little wooden box. The box contained the preamp, power cord, an EHX catalog, sticker, and flimsy piece of paper with the "manual" printed on it. I would have gotten a warmer and fuzzier feeling if the instructions were printed on the same stock on which the catalog was printed. Again, it appears to be a cost-cutting measure. You can download the manual off of their website here, so it's not a big deal if your original copy disintegrates.


When I first powered on the preamp, I connected it to a Digi001 with an XLR to TS cable. This immediately led to an annoying electrical hum, even before connecting a microphone to the input. So, I tried using an unbalanced 1/4" to 1/4" cable. This made the hum even worse. Fortunately, using either a balanced 1/4" to 1/4" or an XLR to 1/4" cable eliminated the hum. The manual states that you can use unbalanced cabling, but I personally did not find that to be the case. There are other users who have had hum problems with this preamp, so I do not believe that this was an isolated issue on mine.

The phantom power circuit has a slow-ramp time, eliminating the transient "pop" sound that you get when engaging most budget phantom power circuits. This is about as close to a frill as you'll get with this preamp, but it's certainly a worthwhile one.

For my first test, I tried recording an acoustic guitar using a Studio Projects B1: an inexpensive, but fairly neutral microphone. I played the same guitar part through the 12AY7, and Art Pro Channel, an M-Audio Tampa, and a Symetrix SX302. The 12AY7 was clearly the "warmest" sounding of the bunch and revealed a level of detail that I had never heard out of the B1. While the sound from the Symetrix preamp was clean but lifeless, the sound from the 12AY7 almost felt like it was in stereo; it sounded very "alive." It would easily be one of my first choices for an acoustic guitar track, along with the Tampa. The noise floor is a little more than I would prefer for quieter work, but it's palatable and not overly distracting.

Next, I tried the 12AY7 on electric guitar using a Beyer Soundstar MKII microphone on a Fender DeVille 4x10 amp. I positioned the mic on the edge of the top right speaker, about an inch from the grille. It sounded, for lack of a better word, *big* on clean and lightly overdriven sounds. It sounded so large that I didn't want to stop playing! However, once I cranked up the distortion, things started to get a little muddy and less usable through the 12AY7. I later tried the B1 on some heavily distorted sounds, but the results were similarly muddy. In both cases, the sound was much less muddy (and actually quite nice) when going through the Pro Channel.

This leads me to one minor complaint about the unit. The input gain pot exhibits odd behavior around 8:00 on the dial. At 7:59:59, it's not quite enough gain for recording a loud source. At 8:00:01, it's too much gain for a loud source. If you breathe on the pot the wrong way, it will veer over the line one way or the other. In addition, the pot is very noisy and scratchy in this gain range. It's fine once the knob is set, but getting it set is a hassle. Again, this gives me the feel that this unit is, well, cheap.

Lastly, I tested the 12AY7 on my voice using a Studio Project C3 mic in its cardiod pattern. Wow! While the C3 is usually a little too brittle and shrill on my voice, it sounded downright lovely when going through the 12AY7. It worked well for voice-overs as well. The sound in both cases was big, detailed and alive. I performed the same tests using an Audix i5 mic (not necessarily a vocal mic, but I had it handy) and the Beyer mic, but the results were not as earth-shattering. They sounded a bit muffled and muddy in comparison. However, even if it doesn't work well with any other vocal mic in the world, it's worth the price of admission for how well it pairs with the C3.

The Verdict

So, is the 12AY7 worth the money? In my opinion, it is. It's not perfect and it has its quirks, but it sounds good if not great on multiple sources using budget microphones. I assume that this was the ultimate goal of the designer(s), and I do believe that they have succeeded. It brings a real tube preamp sound within the reach of folks who could only otherwise afford starved-plate preamps.



  • Inexpensive
  • Sounds good on most sources, sounds fantastic on some
  • Slow-ramp phantom power circuit


  • Electrical hum with unbalanced cabling
  • No 1/4" HiZ input or insert
  • Moderate noise floor
  • Scratchy input gain pot


Anonymous Anonymous said...

where is the .MP3/.WAV files of the Electro Harmonix 12AY7 vs. M-Audio Tampa ?

i do recomend MXL V67 mic or 2001

what sound card was used ?


10:09 PM  
Anonymous Anonymous said...

Enjoyed your review. Maybe you can give me some advice. I'm looking for a nice, warm, relatively inexpensive little tube preamp for micing my acoustic. I was hoping to find one with inserts so I could use my presonus parametric eq and maybe a reverb pedal. (I guess I could use a balenced to unbalenced converter but would rather not.) First of all, is there a small, relatively inexpensive preamp with inserts? (I'm only aware of a samson preamp that seems to get poor reviews)Secondly, is the Electro-Harmonix preamp the nicest sounding preamp you've tried (for the money) when used with an acoustic? Thanks!

11:07 AM  
Anonymous said...

I've just bought a 12AY7 and have tried recording vocals with an AT4050 running it into both mic and line inputs of my Digi02R. In both cases I need little gain on my digi and keep the 12AY7 below 9 o'clock (probably about 15% of it's travel) above which there is some distortion (pleasant if you like that sort of thing but I'm after warmth and depth rather that grunge). I like the sound at this level. Has this been your experience ?

3:49 PM  
Blogger mike kuehn said...

I'm selling a couple of these, but thinking about keeping one for acoustic guitar use. I feel that's their best application... that and toms (more on that later)

RE: INSERT JACKS... why would you want an insert jack on a preamp? it just makes no sense. on a console, the insert jack gives you options to insert external processors while using the board pres. if you're not using the board pres, just connect your other processors in between the preamp and the converter / recorder. simple!!!!

the hum issues are because the unit is not tranformer balanced, certainly a huge cost saving measure. however you can use it with unbalanced gear if you use an isolation transformer in between (like the ART cleanbox).

the volume pot issues are, i'm pretty sure, a cost-saving issue as well. linear pots are cheaper than logarithmic pots. its really annoying. i used to use these preamps on toms a lot and setting the gain was just the worst. i eventually stopped using them because half of the time the pot would move in the middle of doing takes and the rest of the tom tracks would be distorted. at the right setting, they can sound really great for warm, thick, downtuned toms however.

meh. not a quality piece overall but they do offer a good sound for the price... not the best sound... not the only sound i'd want to have available... but a good sound.

12:13 AM  
Blogger Caleb Brennan said...

Thanks for the review. I went and bought a few days ago and it sounds great but the hum is obnoxious.
I'm confused because in your review you said you got rid of the hum using balanced cords. Well I'm using two mic cables in and out of the 12AY7 into the xlr input on my M-audio Onmi i/o. These are store bought mic cables so they should be balanced?
I'm still getting hum. I went and re-read your review and you mentioned using a 1/4 in to xlr. That doesn't make sense, are you using the 1/4in monitor output to go into your board? Shouldn't I stick with xlr mic cables as they are balanced? Any advice would be welcome.

8:56 PM  
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Blogger Self said...

fine, neutral review. rare!

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