Monday, August 19, 2013

Greg Hanks BA-660 Tube Microphone Preamp aka "Monster"


Greg Hanks BA-660 Preamp/Limiter


OK, here's the deal. I've been communicating with Greg now for about a year and we have had many deep conversations, parts of which make my brain hurt. 

Yes, I do know a reasonable amount about audio engineering and manufacturing and I have good ears. Enough to hear some very subtle differences and ask questions that sometimes embarrass me and sometimes embarrass the person I'm asking. 

The only reason I ask questions is because of the reader; the person reading what I've decided to write. If I can't convey the information properly, I'm wasting my time and your time. I say this because I want you to know I'm thinking about YOU as I try to make sense of every piece of equipment.

When Greg first sent me the BA-660, there were some issues. There was something strange in the output section, the meter was a little wacky and there was fan noise from the cooling fan. He found solutions very quickly. The fan thing was a request from me. I told him that many recording environments today don't have separate control rooms and studios. Even if they do, I find  fans distracting in a control room. So, there’s a new multi-speed, temperature controlled fan that, at its lowest speed, I can't hear unless I put my ear within four inches of the BA-660. When planning where to put the BA-660, leave a little extra breathing room and the fan will run slower (and quieter).

The BA-660 is very different for a number of reasons. Yes, it's a tube preamp and limiter; nothing too different there except that it's very, very quiet and very, very clean. Greg chose tubes not for color but for capacity and how well he can get them to do what they do. For example, the preamp path has a frequency response of 7Hz to greater than 28kHz (+0/-3). 

The Line In path (so you can use the BA-660 just as a limiter) has a frequency response of 6 Hz to 36kHz. You may never need it because your mics and other sources may not have that kind of response, but it's there, waiting like a impeccably-dressed chauffeur in a yet to be imagined super car, ready to take you somewhere special.

Phantom Power (well, voltage really). While the BA-660 is designed to provide 48V DC, it can also crank out 300V DC @ 5mA for your Bruel and Kjaer mics. The BA-660 can handle balanced from minus 90 dB to +40 dB. This is possible due to a very complex input stage with relays, pads and transformer that are employed as needed to keep things under control.

BA-660 Rear Panel
The rear panel is simply laid out; IEC power connector, signal ground, chassis ground, balanced line level out via XLR, a -10 balanced Insert Send that can also be operated unbalanced, an Insert Return that runs at +4 and follows the preamp and line in circuitry, a Side-chain Input that runs at +4 balanced, the input to the dynamics control system linking multiple BA-660s, a balanced Class A floating solid state output capable of +34 dBv and will drive loads as low as 150 Ohms.

The front panel (see above) is populated by a wide-ranging input selector covering mic and line levels. The wide range is achieved by a combination of relays, resistive termination and a transformer. An input overload LED activates when the output of  either the first or second input stages exceeds +34 dBv internally. 

An Insert Bypass switch allows manual bypass of the Insert Points accessible on the back panel. These allow you to hard-wire bypass anything you may have plugged into the Inserts instead of making you crawl around behind the rack. When the jacks are unused the Insert circuitry is automatically bypassed. A continuously variable Input Trim pot allows +/- 10dB of range to establish proper gain staging. After that, the fun begins.


A Polarity Reverse switch is provided for the Mic and Line Inputs and is implemented between the Insert Return and Gain Cell. 


There are two (Three?) metering systems with the unit; LED Type Audio metering which measures the audio signal at either the input to the gain cell or at the output of the unit as selected by the input meter select described below. This meter combines VU type metering which shows up as a ‘dancing dot’ around the threshold control and Peak type metering which uses the same LED’s as the VU but shows up as a moving bar and measures in 10 db increments. 


There is also a mechanical (analog) Gain Reduction meter in the center of the front panel. A Meter Zero adjustment allows for calibration of the Gain Reduction meter. A Limiter Tip In adjustment is provided to accommodate different vacuum tubes properly. 


The Input Select switch toggles the audio meter between Gain Cell input and the final output. A Gain Reduction Bypass button provides a hard bypass of the Gain Cell responsible for the limiter.  


Not too well-versed with compressor/limiter settings? No Problem. The BA-660 has both fixed and variable presets, five of each. According to the simple but well-written manual, these presets emulate a Fairchild 660, LA-2, Neve Console Bus Limiter, SSL Quad Limiter and RCA BA-6. You can trim the attack, release and ratio of the variable presets or use the fixed values and make changes with the input level, threshold control and make-up gain control with 20 dB of gain.


The biggest dial on the front panel adjusts the threshold of the limiter from -40 to +20. There is a Gain Cell Clip LED to the right of the threshold knob. If you see it blinking and don't think the audio sounds bad, congratulations, you're a punk outlaw with no regard for fidelity. That's not a defamation, just an observation. 


Although you can adjust the attack time from 3ms to 35ms, it'll sound pretty gnarly at the fast settings. So for the second time in a few sentences, I'm saying it's not particularly difficult to make your audio sound really bad. It's a choice!


Release time varies from 45ms to 1.8 seconds. Faster is louder and pumps more. The Ratio control varies from 1:2.1 to a little over 9:1. A maximum of 18 dB of Gain Reduction is possible before the circuit behaves like a fixed attenuator. At that point many of your clients who don't care much about dynamics or fidelity will be thrilled...and probably flattened by the sheer density of the sound. This is where you, as the recording engineer, leave the room for a few minutes to protect your ears, turning up the monitors as you go, to let your clients bathe in their own reverie. Actually, it's healthier if you have a remote control for the monitors so you don't have to be in the room when you GO LARGE with the volume.


Is the BA-660 too much of a beast for you? Concerned that you're too much technology? Greg has written elegantly simple setup directions and posted them on his web site. Here they are. Not as simple as a dbx 160, but not so scary either.


Here are some links to audio clips recorded with various mics and the BA-660.


AT5040 > Greg Hanks BA-660 Kick Drum


Gibson Les Paul>FenderAmp>AT5040>Greg Hanks BA-660

D28S Martin>TLM103>GregHanks BA-660

You won't find the BA-660 at Guitar Center. As of this posting, there are BA-660s at DSP Doctor, Calistro Music and Vintage King Audio


For more details, reach out to Greg Hanks at Greg Hanks Design.

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