Pete's Place BAC 500 Series CompressorAn interview withdesigner Brad Avensonpan60 Brad, how long have you been into electronics in the audio industry?Brad After spending some time programming computers, I became frustrated with creating things that weren't physical or lasting. So, I started tinkering with electronics. About twelve years ago, I built a few guitar pedals for friends and started working as a repair tech at a radio station.pan60 What made you want to start designing your own products?Brad At first, it was really about making little tools to help me at the radio station. We recorded a weekly hour-long live music show. So I started with patch-bays and adapters. Really, anything to make the shows go smoother and quicker.pan60 Patch-bays are so underrated. So many people do not understand just how invaluable they can be when set up properly. What was the first piece of gear you designed?Brad I guess it was a really simple version of what later became the Avenson Audio STO-2s. It was the next tool I needed for recording. I naively thought, "how difficult could microphones be to create?"pan60 LOL! It's easy, all right! Too funny! So, Brad, do you run a studio these days or are you only designing gear, or are you involved with both?Brad All my studio gear is in road cases set up for live recording. I haven't done a real studio session in awhile, but I have done a few live recordings. Live recording really makes you think about reliability and backups in a new way. I've been working on a few custom bits to really make my rig rock solid.pan60 Do you collect vintage gear? Brad You mean old stuff? (chuckle). I have a Wurlitzer electric piano habit that I doubt I'll kick. You really cannot ever have too many microphones. But, in general, I don't feel like a vintage gear collector.pan60 My wife says I'm a junk collector. I prefer, simply, collector. I guess she cannot see the beauty that I do in old things : )~. For gear, I most often prefer to just get new or second-hand “almost new” gear : )~. Maybe modern would be a better term. When I want to use something I do not want to have to spend my time working on it. I prefer to work on things when I feel like it. Then it’s a pleasure, and not a job. Do you have any hobbies, other than making cool gear for all of us studio owners, engineers, and/or producers?Brad I enjoy home-brewing. Its another hobby that requires borderline obsession and cool gear.pan60 I have a couple of friends that are into the home-brewing. I would love to try some home-brewing, but I figure they would jail ME for MY brew :(~.Where did the idea for the BAC come from?Brad Pete and I had talked about working on a compressor, off and on, for a couple of years. Many ideas were bounced around and the basic topology kinda bubbled to the surface. It borrows inspiration from tools of the past, but we put a bit more modern spin on it for manufacturing, reliability and flexibility. We wanted something that would produce the colorful tones of vintage pieces, but also be a bit more clear and flexible.pan60 First, I see this as an IC base input.Brad We are using a nice input chip made by THAT Corp. It is super clean and does its job without RF, noise or other evils that creep into inputs.pan60 The BAC is a feedback-style FET, correct?Brad Yes, the BAC is a feedback compressor that uses a FET shunt element as the gain control. We used an IC-based side-chain to give us many tone shaping options like the side-chain filters and the DIST circuit. The DIST circuit allows you to drive the FET a bit harder and subtly turn up the 2nd harmonic distortion.pan60 From here, it really starts getting cool. Can we chat about the discrete op amps coupled to that monster CINEMAG transformer? Tell us, why did you choose this design method?Brad There are two discrete amps. One is the makeup gain for the FET and the other is the output driver. Being able to drive the output and the FET stage differently made for more color choices. The output transformer was chosen for its color and how it complimented the sound of the compressor.pan60 A CINEMAG fan here! So far, I seem to really like the color CINEMAG transformers impart to the overall gear sound.Brad, let us all know what BAC stands for.Brad Ask Pete. ;-) Apparently I'm inducted into acronym fame now for the “Brad Avenson Compressor”.pan60 LOL! Peter told me it stood for “BAD ASS COMPRESSOR”!Tell me why you chose not to have a stereo link on these. Was it just the space constraints with the other functions already on board?Brad A bit of a space issue, but really, the format doesn't have a clean, consistent stereo link method available.pan60 I hear the terms feedback and feed-forward from time to time, when engineers are talking about compressors. What is the difference between a feedback and a feed-forward design?Brad This really refers to where the input to the side-chain comes from. Feed forward takes the side-chain input from before the compression element. Feedback takes the side-chain input after the compression element. pan60 Are there any advantages to one over the other?Brad Feedback was used for most of the vintage units because the control law of the compression elements (tubes, jfets, optos) was not as predictable as you need for feed forward. By taking the signal from after the compression element, the compressor can "check" how much gain reduction it just applied and adjust. Feed forward really came into play with the VCA compressors, which had very nice control laws. So, you could tell the VCA how much gain reduction you wanted and trust that it did the job. pan60 Brad , do you care to chat a bit about the ratio control, and the threshold interaction? The hotter input and lower out, seems to let the BAC become a bit more aggressive, or am I just being fooled by the gain?Brad Since the threshold is fixed, the input does control how much compression you get, but it also is controlling the signal into the FET. The larger the signal on the FET and its amplifier stage, the more coloration. This makes the coloration and compression a bit interactive with all the control settings.pan60 One, do I like the company and is the service there? Well, Peter is involved, so I say yes! I know Peter believes in service and quality, so there’s not even a question in my mind, and I am sure I am not alone.Two, build quality. I love the BAC. It looks great, feels great and it has built great performance!!!The BAC is a feedback-style FET compressor utilizing two discrete op amps, and a beefy custom wound output transformer.Three, so how does it sound and perform? I would have had a much different opinion, or choice, last year, in regard to a compressor for MOJO, but, not this year. The BAC has clearly won me over! It does deliver a very nice color, or as I like to say, MOJO!I I was fortunate enough to be given the opportunity to help with beta testing, as well as spend the time I wanted with the new Pete's Place BAC compressor. The “pan60 mad lab” has had a Pete's Place BAC compressor for evaluation for a great deal of time, and I’ve got to say, this WILL, be the compressor I reach for, for my many sources. And, surprisingly, for a great deal of vocals, it will rank at the top of my list. The BAC is stunning on bass, kick, as well as, other percussion sources. I have used it on vocals. It can go from Mr. Cool, doing it's job and aside from its inherent color, it can do it without really being heard much at all. Or, you can push it and Mr. MOJO to rear it's stunning head. And, yes! It maintains the original clarity while imparting it's footprint. The frequency band stays nice and tight particularly in the high frequencies. This thing just drips, with a VOODOO MOJO vibe, that will be very difficult to match.The bar has been raised, and in what better than my favorite format, the 500 series, to boot. If you have never felt the need to look at a 500 format system, now is the time. Got my grubby little hands on the BAC, and it ain't goin’ nowhere. Sorry, guys, I am keeping this one.Starting at the top, the BAC begins with the Input, and from that point, down, you see the Attack. The Attack can run from being prompt (and to the point) to outright fast.Release. The release delivers a fairly wide range of control, enabling the compressor to go from “pumping fast” up to approximately a second and a half. There’s a very nice hang time when using this more as a leveler or limiter. Ratio. The ratio features, a rotary switch and brings six positions to the table. The range is from 2:1 to 20:1 with position six marked as 4!.. [infinity-exclamation point]What does Brad say about position six, 4!? The infinity control has a little exclamation point next to it because, not only is it really flat, but it also puts you in that spot where you can do some over-compression and other interesting things. It changes where the threshold starts to compress as well, so it gives you different varieties of tonal characteristics to play with. Just below the Ratio you see the side chain toggle, as discussed in our interview with Brad, the side-chain toggle switch is a three position switch: Flat, High-pass filter, and the third setting acts somewhat like a De-esser fed into the side-chain, just a bit wider. Avenson tells me, it is also "quite good for taming a variety of things that are ‘overly bright.’" I see the BAC has a nifty little side-chain function built in. There is a high-pass, a flat setting and what appears to be a nice notch on the top, as well as a cut on bottom. What is the high-pass frequency?Brad The high pass is a gentle roll of set for around 40hz. It seems like a bit of an odd frequency, but it was chosen to be a bit below the low E on bass guitars.pan60 Where is the notch on top and where does the low end cut out?Brad The low cut stays the same, but you add a high boost of about 5-6db that is very wide and centered around 7-8khz. This makes the compress cut a bit harder when the higher frequencies come into play, but also still ignores the deep bass.pan60 The Output. With all of the controls cranked from the input to output and all in the middle, the BAC can be capable of delivering close to 50 dB of gain. Awesome for making up gain after the big squeeze! Squeeeeeeeze!!!!!!!!!!!!At the bottom there is the Distortion feature, The distortion button, will overload the FET for color when engaged. The designer says, “This switch allows you to play with how much of the distortion characteristics of the FET you get. By engaging it, you’re getting a lot more second harmonic distortion. It’s basically a way to kick in a more aggressive sounding compressor without changing any of the other settings. You can dial in the amount of dirt you want.'' Sweet!And the bypass. The bypass is a true relay bypass. And, at last, to the far right, there is the eight LED lights making up the gain reduction meter.pan60 Brad , please tell us a bit about some of the other gear you create. I would like to squeeze that in here somewhere as well. We all want to support our small boutique manufacturers....Brad, are you lost in Europe?... Brad Sorry, the last email got sorta lost in the shuffle. I’m catching up here at the office.pan60 LOL! -- Sounds like me: )~ Here, lately, it seems I am running like a maniac!Brad Avenson Audio produces tools for engineers. The STO-2 is a matched pair of small omnidirectional condenser microphones. The SmallDI is a phantom powered transformer-less DI box. There is a new IsoDI coming out that adds two options for ground isolation to the Small DI circuits. I also designed a very clean, powerful reference headphone amplifier. pan60 I have heard about the headphone amp (the other gear as well). I keep telling Peter he needs to send me his: )~. I am sure I need it more than he does! He is not buying into that, though, I fear. I will have to give one a try sometime. Any other cool gear coming down the line, anything that you feel comfortable chatting about, or do we need to keep that top secret for now?Brad There is always cool gear coming down the line, but its all a bit “hush-hush,” right now.pan60 Thank you so very much!