Ingram Engineering: MPA685 mic preamp

I had seen the ads for a while in Tape Op. There were these preamps I had never heard of by a company I had never heard of — Ingram Engineering. They looked cool and somewhat retro. I had always thought that I’d like to try these out, so I jumped at the chance when offered the Ingram MPA685 for review.

The MPA685 is a 2-channel 19” rackmount mic preamp. It uses a discreet JFET front end, with a class-A solid-state output circuit. The inputs and outputs are transformer-isolated, using custom Sowters on the inputs and Jensens on the outputs. There are some nice circuit-design features such as providing constant impedance to the mic regardless of gain settings. It also has a balanced buffer to the output circuit that ensures the preamp won’t run out of horsepower when driving into a low-impedance device.

As for front-panel controls, it has a 24-step rotary switch for input gain and a continuously-variable attenuator for output. It has switchable phantom power; polarity reverse; a high-pass filter selectable between 70 or 140 Hz; and a 3-position input-impedance selector. The settings are marked Low, Medium, and High. The reason that the specific impedance values aren’t specified on the front panel is that the preamp can be ordered with two different ranges, depending upon your needs. The standard range is 600, 1.5k, and 2.5k ohms. The optional range is an ultra-low 60, 200, and 600 ohms. This is accomplished by use of a different Sowter input transformer. Lastly, there is a DI input on the front that uses a JFET front end. This also includes the nice feature of a 1/4’’ instrument loop-through, as you might find on a direct box. The preamp can also act as a “reamp” device if you need to send a previously-recorded signal back though a guitar amp at the correct impedance.

When listening to the MPA685, the first thing I noticed was the tremendous headroom this thing has. I love using well-designed high-voltage circuits. You just get the feeling that they’re never going to give up and slip into distortion, and that’s the feeling I get with the Ingram. It seems to have endless headroom and current capacity. I feel like I could drive a blender with the output. Although not a perfect comparison, I listened to the Ingram MPA685 alongside the UA 2108 (Tape Op #31), which uses FET-based class-A circuitry and transformer isolation on the inputs and outputs.

I first tried the Ingram on snare. There was plenty of body to the sound, without being at all muddy. It articulated well. The 2108 on the same snare didn’t quite have the depth of the Ingram; however, there seemed to be a little more harmonic content going on in regards to the upper midrange attack of the snare. The interesting thing is that I didn’t find this to be the case when comparing other instruments, as I will explain. It was an illustration that different pieces of gear can exhibit different apparent tonal characteristics depending upon the attack of the source. Perhaps a difference in slew rate? Although the Ingram doesn’t have a separate input pad switch, the stepped gain control and the variable attenuator allow you to optimize gain for lowest noise. I was able to dial the gain back perfectly on the hot signal from the snare without driving the input stage too hard.

Next, I tried out piano tracking, using small-diaphragm tube condenser mics as the source. I found these results interesting and slightly different than the results during the snare tracking. In this application, I found the Ingram to have more articulation than the 2108. The Ingram had a bit more clarity, although slightly less body to the sound. There seemed to be an additional level of harmonic content to the Ingram that the 2108 didn’t have. If you were intentionally going for a darker sound, this might not be the preamp you would choose for the specific application. But for most of the things I do, I did really like the presence the Ingram gave to the sound. Let me be clear — I don’t think the Ingram lacked body. I just think the tone leaned towards upper-end clarity, rather than adding much fatness.

I got very similar tonal results on electric guitar. The Ingram showed a nice balance and again seemed to favor clarity and harmonic content rather than girth. This did allow crunchy guitar tracks to stack very nicely in the mix. And as I found with other sources, the Ingram seemed to never even consider running out of headroom, no matter how much the amp was cranked.

I then did a session that was a little different. I had to record a classical piano and vocal in the studio. Instead of the normal close mic’ing, I needed to try and somewhat capture the sense of space of a live concert recording. I pulled the mics back from the piano and the vocalist. Now, classical vocalists can have big voices with a huge dynamic range. I needed a preamp that had no hint of clipping or overloading. The Ingram was perfect. I actually felt more at ease using it, because I knew that it wouldn’t ruin a great take. I know — some of you are thinking, “Well any properly gain-staged preamp can do that.” Mostly true. Even when carefully gain-staged, some preamps just have more headroom before clipping than others. It’s hell when an unexpected peak causes a preamp to break up.

So the Ingram MPA685 is a great preamp which seems to have a sonic signature that’s a little different than some. It seems to combine the neutrality of a JFET input with the headroom and gain of a class-A circuit. It isn’t totally in the “sqeaky clean” camp, but it isn’t a girthy preamp either. It’s fairly neutral, but certainly not boring.

One more bit of detail — when testing the Ingram, I did experiment with the different impedance settings. I tended to start with the “medium” setting of 1.5k ohms, and then switch to the “low” setting of 600 ohms. Transformer-based impedance switching can be a really useful tone-shaping tool, and it was here as well. If I have this option, I tend to run the impedance a little lower than some mic manufacturers recommend. It tends to thicken up the sound a little. Running at the lower impedance did add a little more body to the sound and didn’t really sacrifice the clarity. It would be interesting to see what the lower impedance range option might do.

The only issue I had with the preamp came before I ever plugged it in. One of the Sowter input transformers had dislodged in the long trek cross-country in the delivery truck. It took only a moment to reseat it back on the board. After speaking with Eric at Ingram, he assured me that this had never occurred before, but that for all units going forward, he would add an additional way to secure the transformers to the board, so that it wouldn’t happen again. As I’ve said before in other reviews, I love boutique manufacturers. They instantly respond to issues, implement real solutions, and continue improving their products.

Again, this is a preamp that can handle any source and sound great. If you’re looking for something a little different than the truly neutral preamps, but something with less of a sonic footprint than a preamp that is truly thick and gooey, the Ingram MPA685 is one you should check out. ($2425 street; www.ingramengineering.net)

–Kirt Shearer <kirt@kirtshearerproductions.com>