Art Pro Channel - modded into something really different!

[changeng]

I posted this at another forum, but some people on here were waiting to hear about this so...

I?ve had a Pro Channel for about 6 years now and dang ? it comes SO CLOSE to what I wish the thing could do. BUT it sounds flat ? 2D-ish. I?ve researched possible mods, but there really have been none. Changing the tubes gives you a different flavor of flat. It can act as a color box, BUT it?s preamp sounds flat.

Six years of use and mine was getting a little mangey ? poppy, crackly. I found a place online (in Boston) called AudioProz - Welcome to Audioproz.com where the owner, Vince Naeve, was doing odd things with the ART Pro MPA and the TPS. There was almost NOTHING online as far as reviews, except one detailed review of a TPS he modded on tapeop.com. And that one sounded ReeEeEly interesting.

So I called Vince and asked him if he works on Pro Channels. As it turns out, he has just started to. Kismet! Vince gave me a schooling on the phone (seriously ? Vince is an encyclopedia of audio knowledge and if you call him, make sure you have some time, because he?s IN IT to make sure you understand what he?s doing) Mine was getting grumpy ? there was a little hum and buzz and the VU light burned out, so I was either gonna throw mine out or give it to a mad scientist to diddle with.

I sent it to Vince two months ago and got it back last week. I?ve played with it for a few days and the change is substantial. First off, he repaired whatever was wrong with it, so now it?s KLEEN. Cleaner than it ever was. And then come the mods.

1) He modified the power supply ? I don?t know if he is pushing any extra voltage into the circuit (since the Pro Channel is a nicer starved plate) but the overall tone of the first preamp stage is cleaner, crisper and ?rounder.
2) He installed a Beyer microphone transformer into the vactrol compressor circuit ? so when you push the opto compressor and turn the transformer knob, it reduces gain by an extra 2dB while bringing up the lower end and making the higher end a little cleaner. Instead of that flat-sounding opto compression, it has more of a ?blend? sound, more natural, but still compressed, with a little transformer zing to the signal. It?s more obvious when you run a mix through it, but still there on a microphone or a clean guitar. The tube compressor is unaffected.
3) He re-jiggered the VU so it?s actually USEFUL now. If you have a Pro Channel, you know the VU meter is fairly useless, but now?it?s actually reacting faster, more like the led meters. This is cool.
4) A second new knob ? affecting the third-stage Master Gain knob, adds harmonics to the tube circuit - he calls it a ?variable cathode bias control?. At 12:00, there?s no real change. Turn it to the left and out-of-phase 2nd harmonics are added ?To the right, it adds in-phase 2nd harmonics. He says it?s only a 2% addition and it is very subtle ? but it?s definitely there on vocals and on a clean guitar, it?s very apparent (and seems to be what the Pro Channel has been missing all along).

There is much more ?tube? character in this starved plate design now. As many tones as the stock Pro Channel could originally generate, it has more now. Besides sounding even better on electric guitar now (one of the stock unit?s best uses), it?s now more useful on vocals. One fun discovery so far - if you think of the preamp and compressor as one unit, you can drive the new transformer built into the vactrol by pushing the preamp?s output and keeping the compressor at it?s lowest setting (2:1). Of course, if you push the compressor, the affect blossoms and gets downright plump the harder you hit the compressor. Also, it can now really crush a signal.

I won?t be able to use it in a proper recording for a week or two, but when I do I?ll post some clips.

The mods cost me $250, including the shipping from L.A. to Boston both ways. I don?t know if his prices will go up or not, since mine was one of the first units he modded. He?s doing a bunch now, so expect it to be gone for 1-2 months. Although it costs more to mod this unit than it does to buy a new stock one, this was very worthwhile to me. He sells the stock units and if I decide to get a second one to do stereo stuff with, I would just buy one directly from him, since he QCs each unit he sells. That would save some shipping and time. For a total of under $450, you?d get a helluva cool box.

[changeng]

as an extra thought - I've been rolling tubes into this thing since I got it - Vince says that the original tubes work very well, especially when the modded machine is calibrated for them. While this is true, I have found certain tubes definitely DO enhance the 2nd harmonic effect. AX7's work best (no surprise there) EH's specifically have been real neato in the cleaned-up machine. and last night I put an NOS Valvo in the output stage and it really sparkles there. Darker tubes, like old RCA blackplates or Mullards just kinda sit there. I'm gonna order some old GE or Raytheons next to see what happens.

[the brill bedroom]

That's great to hear. Vince is definitely in that special place where audio maniacs exist- you should talk to him about this stuff in person, he gets all worked up. it's great, though, he gets me excited about the possibilities of relatively cheap gear. I have a PRO VLA 2 that I've never had much luck with- although I've read all the raves about it online- i think I'll take that to him and see what he can do to it.

[changeng]

HA! He's quite the jolt on the phone. In person - THAT must be entertainment! If i wasn't on the other side of the country, I'd be there all the time. I'm thinking of picking up his TPS mod. I betcha he could do some wild stuff to your VLA.

[changeng]

just put a Raytheon 12AX7A into the preamp section and a Valvo ECC83 into the final gain stage. The "2-D" sound of the Pro Channel is now gone. And a Sylvania 12AU7 sounds real pretty in the preamp stage, just lower gain.

[changeng]

I uploaded some samples of the modded unit to a gearslutz page -
scroll down til you find them

http://www.gearslutz.com/board/low-end- ... -read.html

[Bill @ Irie Lab]

+ 1 to AudioPros. The shop is just loaded with cool stuff.

Vince really knows his stuff and although he is VERY opinionated about his likes and dislikes he will spend plenty of time with you and find out just what you're after. (he does not suffer wankers well, however!).

Does nice mods with Chinese condensers, as well.