VMP-4000 Quad Valve Review
by Kurt Foster (Recording.org Emag Apr 10, 2003)
Often the hyperbole that precedes a piece of equipment leads one to think that it will be the answer to all their audio dreams. All too often, this anticipation is the best part of the audio purchase. I had been led to believe that the ~Sebatron~ vmp - 4000 was a high quality transparent mic pre of the uncolored purest approach. While I prefer mic pre’s that color the signal, because I work mainly in the pop genre’, I understand the need for uncolored mic pre amplification for acoustic instruments and classical recording techniques. I can’t tell you how pleasantly surprised I was when I discovered, that while these pre amps are neutral and natural sounding, there is much more to them. The minute I unpacked this unit, I was impressed. The review example exhibited a build quality one only finds with the finest hand built equipment and it is apparent that there is a lot of care put into the manufacturing of these beautifully crafted mic pre’s. I noticed there is a large “~ S ~ ” (the ~Sebatron~ logo) cut into the top of the case to facilitate cooling. A nice original touch! That can’t be cheap to do.
The vmp - 4000 is a two rack space box that is just a tad over 8” deep. The owners documents did not specify the weight of the vmp - 4000. I received a note along with the owners documents from ~Sebatron~ telling me that the unit I received for review was a precursor to the new vmp - 4000e and that it now had “a three position high frequency switch (bright/flat/air in) with the top position being a bright position, the middle being flat and the bottom position being air in.” It is explained that “this gives the user nine different recallable settings (with the deep switch). The EQ is designed to improve mic matching and to enhance the upper and lower registers that benefit from organic make up of the circuit. Rather than have a specific (or set) amount of cut and boost, the EQ varies according to the pad amount selected. It was suggested to “try feeding the unbalanced out of #1 into the DI input of #2” and to “try it for bass” and to “experiment with different deep/pad settings”. For reference, the unit I received is for all intent and practical purposes identical to a vmp - 4000 e. The only difference is that the front panel doesn't reflect the new setting positions for the “bright” and ‘air” circuit.
Everything about this piece says quality, from the clean finish to the large toggle power switch reminiscent of the switches on Fender amplifiers. The box is painted an Ivory color with large black legends. It is very easy to see all the settings even in low light even for an old blind bat such as myself. My only complaint in this department is the lack of a power on indicator lamp. A nice jeweled light like those found on old Fender amps would be a nice addition. I asked ~Sebatron~ about this and they replied that this was in fact a common request from customers and that future units would include a power indicator lamp. This gets a big thumbs up from me! A company that responds to customer input!
On the front panel for each of the four channels, the user will find a three way pad “to increase flexibility over valve coloration and to select an operating level relative to the sound source and valve gain. The pad is based around the amount of negative feedback the valve is seeing.” ~Sebatron~ says “This method has the advantage of affecting valve coloration and is also quieter than attenuating the signal at it’s weakest point in the pre valve grid.” The pad is also effective on the DI input. For each of the four preamps there is a three way deep switch to allow the user to either boost or subtract from the low frequencies at 120 Hz., a three way bright/air switch, to emphasize top register frequencies, “the most amount of boost being a smooth slope at about 2db per 2khz from 8khz, is in the -30dB pad position. The second setting seems to start around 8khz and extend right up over to at least 24kHz”! Also for each channel there is a phantom power switch, a +48v DC led light to indicate the activation of the phantom power a 1/4” phone direct input and output level control. On the rear panel there are 4 sets of balanced XLR ins and outs and an unbalanced 1/4” phone jack out for every channel. I must say was intrigued. Could this be an all in one solution to both the uncolored and aggressive requirements that most recordists place on mic pres?
I could hardly wait to give this box a spin. I immediately got on the phone to find a drummer to come over and record some rhythm tracks with me. My good friend Gary Morrello was available and we booked a date. For the purpose of this listening test, I recorded to Cubase 5.0 through Alesis AI3 converters at 24 bit/44.1. Monitoring was performed through Tannoy DMT 12’s and Yamaha NS10’s, pre amplified through a vintage Nakamichi 450 preamp and powered by Hafler P3000 power amps The first order of business was to lay down a click and basic kick drum, side stick and hi hat beat for the song I was going to work on. I had the drummer scheduled to come in a few days later and in anticipation of having to run the recording process while he played, I decided to lay down a few guide tracks for him to play along with. The four channels of the vmp - 4000 were just what were in order to accomplish this. I ran the 4 outs of an Alesis SR 16 drum machine to the direct inputs on the vmp - 4000 and from the pre amps to the line inputs of an Alesis AI 3 going into Cubase VST 5.0. As I brought up the input levels and trimmed everything out I was impressed at how robust the signal was. Very full, not colored but BIG … like that I had become accustomed to, when using a large format console. The range of how “fat” I could get the kick sample by varying, as was suggested, the pad and the deep / low cut switch was very gratifying. Just the right amount of tick could also be switched in with the bright /air switch. For the kick sample I chose the bright position. Very nice! I found the dual outs on each channel to be very handy, sending the XLR to the work station and using the 1/4” phone plugs to send to a Mackie SR 24 for no latency monitoring. Using both outs simultaneously had no effect on the sound of the signal.
Next in the order was a rhythm guitar track. I chose to use my late 80’s Stratocaster. I have owned this guitar since it was brand new and the only modification I have made to it was the installation of a vintage 59’ pickup in the bridge position. I like this guitar for rhythm basics because it intonates very well and holds tune. Great for laying down a foundation to build upon. The vmp - 4000 being a tube pre amp still held a few surprises! I had already come to expect nothing but stellar sound and it delivered! The Strat sounded very natural and un-hyped at the flat settings. Full and fat sounding without any muddiness and bright but not harsh. Reminecent of a sweet old Fender tube amp like my ’55 Tweed Deluxe. Reading the note that ~Sebatron~ sent along with the review piece confirmed my impression. “~Sebatron~ uses RC networks to derive and regulate the voltage rails. Under certain, operational conditions the rails soak loud sources subtly (not too dissimilar to the classic Fender amp with a valve rectifier).” I’m sold ! Time for a quick bass guitar track. I was hoping that my wife would play bass on the song so I didn’t want to spend too much time on the scratch bass part. I plugged in a re issue Danelectro Longhorn bass into the vmp - 4000 and ran the output from it to a Manley EL OP.
The result was heart stopping. I brought the input pad down to the -30db setting and engaged the deep switch as was suggested in the literature and dialed in 3dB of gain reduction on the Manley. Big fat warm bass tone in abundance but not over the top. So often when you chain two pieces of tube gear together the effect is overwhelming but these two played together very well ! This thing keeps getting better! I’ll take two! Not being able to wait any longer I set up my Neumann U87i and prepared to cut a guide vocal track! With a popper stopper and the U87 in the cardioid position, once again I ran the vmp - 4000 into the Manley EL OP and then directly to the DAW. At first I tried the “bright” and “air” settings and although they were very nice and not over the top or too sibilant, for my voice I choose to not use them. I did however engage the “deep” setting with great satisfaction. This was the first time I ever heard my U87 sound the way it looks! I have always been dissatisfied with U87’s always wondering what it was that made them so popular but as Don McLean said, “Now I understand.” Very full and ballsey. Smooth in the midranges while having that Neumann sheen at the top. It would seem that the vmp - 4000 was designed with the U87 in mind. But to be honest I found myself thinking this with everything I plugged into it.
The resolution and accuracy of this preamp brought the U87 to a point where I can hear anomalies in my recording room that I have never heard before. I heard a “roominess” that simply wasn’t present in previous recordings done in the same space with the same mic. This is an obvious nod to the purest approach of the design. The closest thing I can come up with to describe the characteristics of these pres is they remind me very much of the sound the Beatles got on their records like “Rubber Soul”,” “Revolver”, “Sergeant Pepper” and “The White Album” when they were using Telefunkin V72 and V76 pres in the EMI designed desk at Abbey Road.
I asked the folks at ~Sebatron~ about this and I was informed, rather pointedly, that the vmp - 4000 has nothing similar in design to the Telefunkin V72 or V76’s. This was their response. ”We build valve gear for a valve/organic sound. Earlier circuits (pre 1965) do seem to have that. Then we build for flexibility so the user can twist and tweak that sound to taste and interface it with existing sounds. We have stuck to 12AT7 valves for availability and reliability and usually sift through ten or twenty valves to settle on a final matched four for each vmp - 4000e. Valves differ significantly between themselves and between manufacturers so we always have to be careful with what's acceptable and not. Amongst the listening tests that are conducted, we spend literally hours (sometimes days) in front of the oscilloscope looking at how waves (usually sine and square) change and what changes 'look' musical. We push a circuit as far as it goes, always looking for the weakest link.....and always design with minimal circuitry (less is more.....like music). So, we kind of prefer the vmp - 4000 to be viewed in its own context....encapsulating existing pres by its flexibility, yet having its own distinct character/sound. You see we spent at least ten years repairing pro audio. What stuck out were the weak links...components that were introduced later on like: Zener diodes, integrated circuits, and some transistor types. certain caps etc. We avoid them. Then there are other criteria like availability of components and budget constraints that a production design needs to adhere to. It’s quite a mix really. Each unit needs to be super because it has our name on it. Otherwise we would've called them “John” or something like that.