AML Audio Maintenance LimitedThe 5003D Pre-AmpInterview /Review with ColinJan. 12, 2010Pan60: Hi, Colin :)~ ...Let's chat a bit!Tell us a bit about yourself. I always like to start here. Where are you from? Where do you live?Colin: The answer is one and the same; Manchester. I was born here and have lived here my whole life. That doesn’t mean I love it here. I just don’t think that I am he kind of person who likes change.I went to primary school very locally, and then secondary school in a town called Oldham (about 5 miles away). After that it was University in Manchester. This city just cannot seem to shake me off !!Pan60: What is your favorite food, ( I have to ask that based on our last chat ), as well as favorite drink?Colin: I wish that you had asked me what I don’t like to eat as that would be a significantly easier question to answer (Rhubarb and Celery. How can anybody think that these are OK to eat? They are just plant stalks. You wouldn’t eat the stalk of a tomato plant, would you? [Ooops! I slipped into a small rant, there... sorry]).My criteria for food is usually based around ease of consumption. I have always been a “big eater” (comes from the old fashioned “you won’t get desert if you don’t clear your plate”). I usually like to have Indian, Chinese, traditional British (stewed meat and overcooked vegetables) and, of course, a full English breakfast.To narrow it down to a “favorite”? Boy, that is tough. Too tough, in fact. I must abstain from your line of questioning and call upon my “right against self-incrimination” (5th amendment). My favorite drink? That’s easy. Tea. I drink enough tea, so that when I die, they will need to close a PG Tips factory. If you mean Alcoholic beverage, then that is Bacardi/Diet Coke/no ice/lime wedge. or red wine. I like Guiness, as well, but it goes down too easily. Pan60: Tell us something about your hobbies.Colin: I recall when filling out job applications and my CV, there would be a gaping great space for “hobbies and Interests.” I would sit there for hours trying to think of some interesting hobby to put down, such as “scuba diving” or “white water rafting” or “saving endangered species” or “climbing the 6 great peaks for charity.” I even considered putting “skiing down a pink run” at one point. Sadly, these would all have been an exaggeration of the truth. Maybe I am one of life’s “hobby-less” people. Of course, I “do stuff,” but I wouldn’t really describe them as hobbies.I guess that if you press me for an answer, I would probably say “DIY.” I do enjoy building, woodwork, plumbing... stuff like that. Although, currently, I don’t get the chance to do these things.I am a bit of a workaholic (I know you won’t allow me to say that the AML is my hobby), and when I am not working, I spend hours entertaining my 3-year-old boy. The only time left is spent asleep and eating.Pan60: What is you favorite car, motorcycle, boat, or even plane?Colin: I have no fascination for motorcycles (though I am sure you will try to convert me). I’ve never ridden one. Boats don’t float my boat either (I am sure there is some grammatical rule broken by that sentence). And planes? Well, as long as they land the correct way up, I’m easy. Cars. I would say that I like cars that are a bit like me, i.e. built for comfort rather than speed. If I were a lotto winner, I would probably go for a Bentley Continental.Pan60: You know I am going for the conversion as to the motorcycles: )~ I am more into the vintage stuff then anything. I get more out of working on them then riding, these days. I am also into old cool bicycles, as well.Are you a musician, mix engineer, producer? How did you get interested in electronics, and how did this lead you to the audio industry?Colin: I can play the guitar a little (used to play in a punk band). But, to describe myself as a musician would be an insult to anyone who ever picked up an instrument. I have never been at the sharp end of a mixing console either. I could use one easily, but the result would sound like **** (reader enter your own expletive here).Pan60: Give us some background in your experience in the audio electronics world?Colin: Let’s go in reverse chronological order (this way if the reader is bored they can skip to the next paragraph having missed nothing). Audio Maintenance Limited was initially set up to provide spare parts and support for all the AMEK products after we closed down the AMEK factory. When AMEK was still “alive” I was the Service Manager - responsible for the service and spares departments for the whole of AMEK worldwide. (I enjoyed that job... had some very good staff).Prior to being the Service Manager, I was a Project Manager for AMEK. I arrived at AMEK from AMS-Neve. where I was a service engineer for the Capricorn Digital mixing console. A thankless task which involved spending most of my time overseas making modifications to DSP cards, because it had been shipped out the factory before it was really finalized as a design. Although, I foolishly once suggested an improvement to the design of the touch sense circuitry for the control surface and ended up spending several weeks at Lucasfilm changing 6500 surface mount resistors (note to younger readers – don’t make suggestions which you haven’t thought through.).Most of the service work on Capricorn just involves fixing stuff that was designed wrong or built wrong. I can count on one hand the number of occasions when I actually went out to a genuine fault”.Before that I worked in high voltage engineering (and I don’t mean valves. I mean 400kV stuff, but not for very long, really. It just didn’t suit me. Before that, I was teaching electronics.Pan60: Tell me your thoughts on discreet verses IC. I am always hearing discreet is better, as well. But, some engineers feel that IC is better. What do you think? There is no right or wrong answer. I feel they both have their merits. I just like to pick the brains of you guys ( and gals ) that design great gear: )~Colin: It is really a question of “horses for courses.”As I see it, IC op-amps are an engineering compromise at the silicon level. For example, a circuit which has both PNP and NPN transistors is undesirable in terms of its efficient use of the silicon wafer and complexity of manufacture. If the circuit were all NPN (or PNP) it would be easier to manufacture, and hence cheaper. So, commercial (cheap) op-amps are usually all NPN (or PNP). Now, you should take that with a pinch of salt because I cannot remember where or when I came to that opinion, and it could be complete nonsense (I am not a silicon designer by any stretch of even the most vivid imagination). Certain parameters like slew rate and noise voltage may be simply unobtainable using discrete devices due to their physical limitations. Equally, there may be many commonly used circuit implementations which are simply impractical using discrete devices. Very high Q filters, for example. Of course, it could be done discretely, but you would end up with hundreds of transistors. Pan60: You pretty much run A.M.L. yourself, is that correct? Do you ever just close the doors and say, the heck with it, I'm a going fishin’?Colin: I essentially “run” AML but have a lot of help from a couple of other people. I have a person who does PCB assembly and some repair work and someone doing accounts. but they are not employees of AML they are sub-contract labour.. I do everything else. answer the phone . reply to emails. process the orders. PCB layout designs .. make the brews! It would be nice to just go “fishin”. unfortunately this is physically a lot easier than mentally. When you are so intimately involved with a business it is just not possible to switch off like that (maybe some lucky people can. but not me). So, in essence I don’t “run” AML. AML “runs” me. and it tries its hardest to “run” me 25 hours a day.Pan60: Often. when I speak with an engineer, or just gear freaks as a whole, I find, inevitably, it is the company the can run their lives. So, sometimes, we need to take a break and just go fishin’! : )~What made you want to get into the 500 format?Colin: It is purely a market driven decision. Ooh! Look at that big bandwagon! There’s space on it for AML!It also has much to do with the lack of safety certification (which is a CE requirement) as the safety aspects all fall in the lap of the lunchbox manufacturer. I’ll get to this later in the interview in more detail.Pan60: I see you have some nice discreet op-amps in your pre, as well as some nice transformers. Is the op-amp a specific design after a particular model or is this your own design?Colin: Generally “op-amp” refers to differential devices (with huge open loop gain, very high input impedance, zero output impedance, enormous bandwidth, etc.). The gain stages of the 5003d mic amp are single-ended Class A and are a modified version of a design that came from a well known text. Really nothing special about the electronics design at all. Obviously it has a few tricks up its sleeve to make it sound the way it does. But, these have to do with the implementation rather than topology. Pan60: Tell us about the transformers you chose and why. Get into as much detail as you like.Colin: Some time ago, Carnhill asked AML to become its exclusive “retail” outlet, as selling directly had no commercial benefit to them. It just gets in the way of manufacturing. Whereas, AML is set up specifically for direct retail sales. They generally accepted “best of the best” pro audio gear that has Carnhill inside. It is a brand that I strongly believe in, so it was perfect for the AML portfolio. Now, we stock a significant number of standard types. Obviously, when it came to the design of the 5003d mic amp, it seemed like a simple matter of using the transformers that we already stocked. That was fine for the input transformer (VTB9045, as used in Neve 1073’s, etc.), but the output transformer created a whole variety of issues. The result was a re-design of the electronics and a new design of transformer (which took several painful attempts to get just right). This output transformer required a new approach to some of the standard manufacturing techniques that Carnhill utilizes. The result is a transformer which exceeds all the design criteria, yet isn’t impossibly difficult to manufacture. Pan60: Were you going for a particular sound, a clone type, or just a great solid pre-amp?Colin: Your question could imply that I had some idea of the actual end result at the start of the design. An “audio goal,” based on my listening experience, but, as a service company we spend all day listening to test tones and looking at meter readings. The monitoring system is laughably poor (a single JBL monitor that measures about 7 inches by 5 inches) and my hearing is pretty poor. I was going for a “particular sound”, even though I don’t actually know what that “particular sound” will be. Another way to describe it is that I was looking to achieve a particular “performance characteristic” based upon my experience and what users say they like. This “performance characteristic” was achieved by knowing which particular components/brands give certain desired effects and measurable artifacts. I was attempting to create a pre-amp which has a “sound,” but not too much of a “sound.” It is all too easy to go overboard with the “performance characteristic.”Pan60: Without having a front panel Hi-Z input, why did you add the Hi-Z / Lo-Z button? Or is it line level / Lo-Z?Colin: This is simply for use with 50 Ohm microphones. although since they are relatively rare I expect that most users will simply use it as an “effect” to change the sound. and of course it boosts the level because the input transformer turns ratio changes.Pan60: I think, when we last spoke, you mentioned yet another pre your were working on. Can we mention that or keep it quite for now?Colin: There is a “Langley” mic-pre under development. As promised earlier in the interview I will give an explanation of why we started with the 500 series format.. Many moons ago, shortly after we closed the doors of the Amek factory, Graham (Langley) decided that he would develop a new product . Basically, a full channel in a rackmount format (something similar to the AMEK Channel in a Box, but based on some of Graham’s old designs, but brought up to date). Graham had designed much of this unit, but had to put it on the back burner because of one particular design issue - the output driver circuit. Fortunately, THAT Corporation had just the solution up its sleeve. The problem was that it hadn’t been released, yet. Since AML already manufactured the “Langley” upgrades for the AMEK/TAC consoles, we had a standing commercial arrangement in place. It then occurred to me that we could put the mic-pre/DI part of his new product in a 500 series format. This was just about the time when THAT Corporation released the part that Graham had been waiting for. It then became an obvious step to do the same with the EQ and compressor. So, we began development on the mic-pre/DI in the 500 format. it is now at the stage of a second prototype and is (to quote Graham) the best specification mic-pre that he has ever designed (the noise and distortion figures for the prototype are disturbingly good). The reason that it has taken so long is that Graham has been trying to squeeze every last ounce of performance out of it that he can to make a mic-pre with absolute clarity (a good compliment to the transformer based designs). So, even though it was started first, the 5003d has reached the marketplace before it. Pan60: Of course, you know I will want to get my hands on one the “Langley” mic-pres when they become available. : )~you know I am going to change the conversion to include the motorcycles. : )~ I am more into the vintage stuff then anything. I get more out of working on them then riding these, days though.I am also into old, cool bicycles, as well.Colin: There’s nothing wrong with that! Most of us have a passion for what we do or we would not do it, but if you can do it and make some money, that’s very cool!I would love to see ( and feel we are seeing and will continue to see ), even more companies getting on board with the 500 format. I think this is great.I feel the more quality gear coming to the format, the more widely accepted they will become, leading to yet more gear for the format.Pan60: What made you choose '' 5003D '' for the name?Colin: This is pretty lame. The 500 is obvious. The 3d is because Carnhill transformers (when applied properly) give you a perceived depth to the audio (3rd dimension). All we are really talking about is expansion.Pan 60: I have to ask, what is your favorite color : )~ and what made you choose gold for the 5003D pre? It is cool and it does stand out. I find the knobs to be very cool and I love the feel.Colin: I don’t know. Aquamarine with magenta spots and cerise flecking, or perhaps blue or red or black. I’m sure some psychologist would have a field day with that. Why a gold faceplate? We actually started the 500 series with the Langley mic pre, and we decided upon the classic AMEK blue with yellow text. Since the Langley designs are a polar opposite to the AML designs (Langley is very low noise/distortion) it seemed a natural choice to make them the opposite color scheme. The first prototype was more of a bronze color (with blue text) but that was hopeless, as the text just didn’t have enough contrast. So, prototype 2 had a gold faceplate with blue text (and red “zero” markers). That was perfectly readable and was the intended look. When it came time to make some demo units, the gold faceplates were sent to the printer and he said “I only stock black aluminium paint. The blue and red will be GBP 200 each.” So, the original demo units were done in black (with the intention of the production units being blue/red). When I took them to the studio for testing, the consensus was “black looks better.” Decision made. And the knobs, well, they were just the closest thing I could find to a classic “Bakelite” knob off the shelf. The overall result reminds me of Marshall Guitar amps, and that can’t be a bad thing. Pan 60: As you know, I love the 500 format. I see a future with a lot more 500 format products available for the producer, and engineers. (Size DOES matter)! : o~ The 500 format really allows a lot of awesome gear to be contained a small footprint. It’s perfect when real estate is limited, as is often the case with studios, these days.What would be, some of the difficulties encountered when designing for the 500 format in your view?Colin: Because you don’t have to deal with mains safety issues the format encourages you to do all sorts of experimental designs. There are huge numbers of designs which you could try. The problem is there just isn’t enough space to do what you want (easily). More power per slot would help. We are looking at something, at the moment, which is fused at 250mA per rail. The only way to get a lunchbox version is to limit its output level/spec.Pan 60: Possibly some things would probably just be better left to the 19'' rack?Of course, most know I like the VPR Alliance a lot because it allows the customer to know the product has been checked out and approved for the lunchbox rack or console. Do you have any thoughts on this?Conceptually an excellent idea. Although, I see that the rate at which lunchbox products are currently coming to market could exceed their ability to test them. The specs are a little “bare”. There is little, if no info on inrush currents, case dimensions etc.The VPR ALLIANCE has placed a work load on API. I do not think they expected the large number of units being produced that the are now seeing. I know they are working on getting some more informative specks together for the Alliance. Inrush current and case dimensions have been brought up, as well as a number of other items. Pan60: Aside from the “Langley” mic-pre, anything else in the works?Colin: There are a few items, but it is too early to discuss them. They are simply ideas at the moment.Pan60: You will have to keep me in the loop on anything new? : )~ Do you have a press release sheet?Colin: No. Currently, we loan units to clients and then take their order. I suppose that I should really do one.Pan60: Can you tell us a bit in the way of specks on the 5003D?Colin: That is a tough question. I don’t really believe in “specmanship” as it doesn’t really do any good. I can give you a list of its functionality, but it pretty much, “does what it says on the tin”.1.Gain +10dB to +65dB2.Gain trim -10dB to 0dB3.Max input +14 dBu4.Max output – a lot of beans5.Distortion – yes it does6.Frequency response – of course7. Pan60: I have to try and get as much info as I can. : )~ So, as always, there are three major points to cover: 1. Do I like the company, the man and/or the people behind the company?; 2. Is the quality there, and can we get service if ever it was to be needed?; 3. How does it sound? But, first, the negatives... : (~Well, I’ve got to say, although the color stands out, and it is very cool, Colin and I have different tastes in this department. 1. Do I like the company? Yes, yes, yes! Colin has made it clear throughout our chats and emails that he loves what he does. He is a pleasure to work with, and I look forward to many future chats. Also, he is a small boutique manufacture, so he falls right in the category of manufacturers that trip my trigger.2. Quality and Service?The 5003D is a quality pre, with a great feel. He has made great component choices and some very nice transistors. These units are very well built, the assembly is top shelf, and for all you Carnhill transformers lovers this will be a treatat! : )~As for service, I say, no fear! Colin is very easy to reach and responds promptly. AML does more then just make the 5003D, and Colin has a very well-respected reputation.3. How does this bad boy sound? Very, very sweet! The 5003D has some great lineage behind its design, so it comes with some heavy expectations, expectations that it really must live up to, and pony up it does!The 5003D delivers, a robust vibe, with a nicely detailed tight top, and bottom. It’s not too aggressive, or over-hyped mids. Everything from the top to the bottom filled more then my expectations.The 5003D works on whatever you want to throw at it, whether it’s vocal, a jingling jingle tambourine or anything in the middle. I tracked vocals, electric and bass guitar, acoustic guitar, kick drum, and snare, as well as a few more instruments, I like this pre.Do I like it enough to keep it here? Yep!This bad boy, the 5003D has been, and will be, in my rack and getting called to duty on a regular basis. A thumbs up here, if you are looking to add another 500 format pre to you system. I say add this one to the list of units to audition.