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guileman
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#1
9th February 2010
Old 9th February 2010
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Art Pro channel - Mod suggestion

Hi guys, im buying the Art Pro channel for vocal recording.
I have a CAD Trion 8000 tube mic that i will plug it in the Pro channel and then into my Digi 003 rack.

i have heard that the tubes in there are not the best possible for this.
So what do you guys suggest?
Is it a good idea to change the tube? Wich one should i get?

Is it easy to do it?
I have never changed tubes before on any gear.

Would there be any other mod, not too expensive and not too complicated that would worth doing to get the best sound possible?

thanks
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9th February 2010
Old 9th February 2010
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No one has ever answerd my questions about modding the Art Pro Channel aftr asking a a few years - however for tubes, IM a guy called BOWIE on here - he's the tube guru. i haev a balckplate RCA in the preamp, a Phillips JAN in the compressor and a Mullard in the gain tube (it's not really a tube eq - the tube comes after.)

Spend the money for NOS tubes - the difference is considerable.
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9th February 2010
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Sell the sucker
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9th February 2010
Old 9th February 2010
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+1 Bowie
#5
12th February 2010
Old 12th February 2010
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I put a NOS Mullard in the preamp and after several vocal tests, couldn't tell any difference. I put the chinese tube back in it. I imagined it was because the design was starved plate on the tubes. However, I took off the tube shields and powered it up to find that the tubes glow and get very hot. Not a starved plate design at all. I may try a few other tubes to see what result I get. Changing the tubes is very easy. Pop off the top, push down and gently twist the tube shields to expose the tube and simply replace with another tube in the socket.
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12th February 2010
Old 12th February 2010
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Go for it!

I highly recommend swapping the tubes. It's quick and very easy (no knowledge of electronics and no soldering necessary). I put NOS Telefunken smooth plates in mine and the change was positive and you don't need golden ears to hear the difference. I found that they made the sounds I was getting noticeably more clear and 3D. Other tubes will have different characteristics. BOWIE would do a better job of explaining the various nuances than me. But, all in all, I have found the ART Pro Channel to be a cool, useful box.
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#7
13th February 2010
Old 13th February 2010
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I changed the tubes for some Mullard (thanks Bowie)
And also the TL072 for OPA2134
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13th February 2010
Old 13th February 2010
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guze, can you just replace the TL072 with an OPA2134 without any modifications?

I am using a NOS tung sol in the preamp, NOS sylvania in the output but the compressor tube is still the stock chinese because it seems to work best. tried it with several tubes but the compression action gets very weird

it's a pity the preamp crapped out on me some time ago. I don't have a clue what's going on...
#9
13th February 2010
Old 13th February 2010
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Quote:
Originally Posted by Rob Coates View Post
Not a starved plate design at all.
take a look at the schematics, the prochannel does in fact use starved plate circuits.

see attachment.
Attached Files
File Type: zip reartprochannelschematicrequest.zip (150.0 KB, 677 views)
#10
14th February 2010
Old 14th February 2010
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I've put sockets and the OPA in, no problems at all. Also removed the tubes metal protection
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15th February 2010
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guze - what changes did you notice by replacing the op amp?

elektrovolt - you should run signal through a NOS tube in the compressor module for 24 hours to break in the tube enough for major squashing. I ran Kinks non-stop on an mp3 player over two days to break in my JAN Phillips for it and now it squashes swell.
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15th February 2010
Old 15th February 2010
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Quote:
Originally Posted by elektrovolt View Post
take a look at the schematics, the prochannel does in fact use starved plate circuits.

see attachment.
Thanks elektrovolt

This is a tad confusing as others on here have often said that the Pro Channel, the MPAs (old revision) and newer Pro MPA IIs were variable and not starved plate.

I wish someone would clarify which type these actually units are.
#13
15th February 2010
Old 15th February 2010
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I +1 to any telefunken tube statement..
#14
16th February 2010
Old 16th February 2010
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Quote:
Originally Posted by zippsinc View Post
Thanks elektrovolt

This is a tad confusing as others on here have often said that the Pro Channel, the MPAs (old revision) and newer Pro MPA IIs were variable and not starved plate.

I wish someone would clarify which type these actually units are.
the mpa gold has a switch for low and high plate voltage.
the high voltage should be around 150 voltsaccording to the schematics.
you can hear the difference when switching very clearly. after a few seconds the level rises, opens up and reveals more high end that was muffled before.

the pro mpa - I don't know, I think it is a low voltage design, like the pro VLA.
#15
16th February 2010
Old 16th February 2010
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The Pro Channel preamp gets about 60v.
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16th February 2010
Old 16th February 2010
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Hi
The schematic linked above suggests that the plate voltage is 45 Volts, as is the phantom power since they share the same supply.
It is a shame that they chose to make phantom 45 whereas the usual standard is 48 +-2 Volts.
There are a few mics that are fussy over this.
Matt S
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#17
16th February 2010
Old 16th February 2010
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Hey guys, this site is amazing. My searches always seem to end up here when it comes to anything about my gear. So thanks for all the help so far!

I have a question about these pro channels. I actually have 2 of them in my rack (i bought one a year ago as my first preamp, and recently found a second one on ebay cheap). My plan was to not only have a backup, but start messing with some outboard processing instead of relying on plugins solely and I wanted to have the ability to use the two units for a stereo signal if needed. Plus, I want to mod one of the preamps (only the preamp, not the other modules, but if changing tubes in the other sections would make a huge difference, I would do that and just make mirror changes in each) so I can have two distinct preamp flavors to choose from when recording. I use this preamp for pretty much every signal that goes into my DAW (except of course when I have to record more than 2 channels at a time, ie drums), and even plan on starting to route some of my VI's out to them to fatten up the sound, including but not limited to vocals, guitars (both direct and mic'ed amps and acoustic), bass, hardware synths etc. So versatility is a plus.

I figure tubes is the easiest way to do this, and while I can solder and all, I am not sure I want to start messing with anything involving the actual circuit designs yet (my experiments with circuit design and modification is very limited, mostly to guitar pickups and one guitar amp, so I don't really understand opamps and all that other stuff yet, but I'm always learning).

Everyone mentions the different brands of tubes, but not the type. I see in the schematics that elektrovolt posted that the preamp uses a 12ax7 tube while the compressor and eq use 12at7s (please correct me if I am wrong). When you switch out the tubes, are you using the same types and just replacing with different brands, or has anyone experimented with different types as well? Can 12ax7s, 12at7s, 12ay7s, 12au7s, etc be swapped one for one without further modification?

Also, according to the manual, the 1/4" insert send/recieve jacks on the back are unbalanced. I am setting these up with a balanced patchbay and going into my 003+ rack that has both balanced ins and outs, so that way I can have the most flexibility with using the compressor and eq either during recording before the 003 or as an insert during mixing. Has anyone changed these jacks to balanced? Is it possible/not prohibitively difficult to do? If so, could someone point me in the right direction on to do so? Like I said, all my electronics modding up to this point has been on guitars and amps, which don't come anywhere near to the complexity of this recording gear.

Sorry for the long post and my relative lack of knowledge on these subjects, but thanks for any help someone can give!

-Jonathan
#18
16th February 2010
Old 16th February 2010
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Hi
You can swap 12ax7s, 12at7s, 12ay7s, 12au7 and their equivalents without damage to your gear. They use the same heater voltage and pinout. What different types and makes will do is only predictable to a point but as long as you don't physically break something while plugging you are free to 'play'.
Most valve manufacturers would not have tested their valves at such a low anode voltage, certainly not on an individual basis so you are largely 'on your own' to come up with your own conclusions as to whether any given valve has merit.
Regarding balancing the inserts, there are a few bits'left over' in there which could be harnessed but probably not worth the upheaval especially if you don't really know what you are doing or have the necessary gear to check it out.
Matt S
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16th February 2010
Old 16th February 2010
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Quote:
Originally Posted by guileman View Post
Hi guys, im buying the Art Pro channel for vocal recording.
I have a CAD Trion 8000 tube mic that i will plug it in the Pro channel and then into my Digi 003 rack.

i have heard that the tubes in there are not the best possible for this.
So what do you guys suggest?
Is it a good idea to change the tube? Wich one should i get?

Is it easy to do it?
I have never changed tubes before on any gear.

Would there be any other mod, not too expensive and not too complicated that would worth doing to get the best sound possible?

thanks
I know most of the posters fail to come back and respond to the answers, but for the sake of future readers I will give my HO.

I used a Cad 8000 with an Art Voice Valve and have to say it sounded better through my soundcraft board pre's and even the ONYX 1620 pre's than it did through the ART, it also sounded better through a RNP.

I do not know why this is, but I suppose it is because BOTH the mic and the pre have tubes which was overkill, at least on my vocals.
Again this is just my personal experience with mic and Art pre, it may not apply to all tube pre's when used with tube mics.

THe CAD 8000 has a great sound on it's own, once it is modified even better, that is why I would suggest a pre with a bit less flavor than the ART, not necesarrily a pristine clean pre, something inbetween may work too, like I said it sounds great through a few board pre's (soundcraft) as well as the RNP.

keep shinin

jerm
#20
16th February 2010
Old 16th February 2010
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Hi
The 12XXX7 series of valves and their equivalents were designed to work properly at much higher voltages than even the 150 Volts reputedly on the later version Art Pro.
They are used to give a 'valvey flavour 'on the cheap' by using low supply voltages.
Proper valve gear would be using nearer 300 Volts at which point the different valves will work properly and is in the area intended during manufacture.
There are low voltage valves around intended for battery operated radio sets and the like where HT was around 90 Volts. These are far less plentiful and there are few intended for audio work.
To have a valve mic amp of useable subtlety while retaining quality is expensive, the rest are just 'toys' which can be useful in some applications but when pushed fail to make the grade. It is also niot simply the presence of a valve in an audio circuit, it is more a case of the surrounding circuitry which enables a valve to give it's best.
Matt S
#21
16th February 2010
Old 16th February 2010
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well, 150 volts is okay, they can take up to around 300 volts, give or take.
150 volts is not bad but the tube will have slightly different characteristics and so the circuit has to adjusted.
a proper high voltage power supply is expensive.

The compressor in the Prochannel is great, but if you want a 'mojo box' you'd better look for something that is not a hybrid.
#22
16th February 2010
Old 16th February 2010
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Quote:
Originally Posted by guze View Post
I've put sockets and the OPA in, no problems at all. Also removed the tubes metal protection
Did you notice any changes with the different op amp? What kind of changes?

Also, what do you mean by "metal protection"? What does removing that do?

-Jonathan
#23
16th February 2010
Old 16th February 2010
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Quote:
Originally Posted by elektrovolt View Post
the mpa gold has a switch for low and high plate voltage.
the high voltage should be around 150 voltsaccording to the schematics.
you can hear the difference when switching very clearly. after a few seconds the level rises, opens up and reveals more high end that was muffled before.

the pro mpa - I don't know, I think it is a low voltage design, like the pro VLA.
Thanks elektrovolt

Does this make the MPA, Pro VLA, Pro MPA II and Pro VLA II Starved Plate?
#24
16th February 2010
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I think all of them are starved plate designs, but the mpa gold and the newer pro mpa II have the low / high voltage switch that gives you starved plate (around 45 volts) or high voltage (around 150 volts)

I used the high voltage setting on my mpa gold most.
if you have one, try it. when switching from low to high it takes some time, around 15 seconds or so till you get audible result, but the difference is clear
#25
16th February 2010
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Quote:
Originally Posted by elektrovolt View Post
I think all of them are starved plate designs, but the mpa gold and the newer pro mpa II have the low / high voltage switch that gives you starved plate (around 45 volts) or high voltage (around 150 volts)

I used the high voltage setting on my mpa gold most.
if you have one, try it. when switching from low to high it takes some time, around 15 seconds or so till you get audible result, but the difference is clear
Thanks elektrovolt
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16th February 2010
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anyone know how to modify the Pro Channel to accept a higher voltage like in the MPA Gold? Sounds kinda dangerous.
#27
17th February 2010
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Hi
It is only analogue electronics so easy to mod. New transformer and power supply parts and 'upgrade' various bits to cope with the increased voltage.
The question is 'is it worth the time and expense' for this piece of kit (transistor and IC mic amp +comp with some valves thrown in for fun)?
Accept it as it is and move on.
Matt S
#28
17th February 2010
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true,
to me it is a bit like chavvy car pimping

they are okay, but get a real tube machine instead if you want real tube / tranny sound. GT brick, hamptone, DIY...
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#29
17th February 2010
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Quote:
Originally Posted by Matt Syson View Post
Hi
It is only analogue electronics so easy to mod. New transformer and power supply parts and 'upgrade' various bits to cope with the increased voltage.
The question is 'is it worth the time and expense' for this piece of kit (transistor and IC mic amp +comp with some valves thrown in for fun)?
Accept it as it is and move on.
Matt S
Quote:
Originally Posted by elektrovolt View Post
true,
to me it is a bit like chavvy car pimping

they are okay, but get a real tube machine instead if you want real tube / tranny sound. GT brick, hamptone, DIY...
+1 and +1

Put in some fun tubes. If it still doesn't do what you want it to,
move on. I spent an afternoon and some dollars fiddling with the guts and part swaps and all that.
It was a total waste in the "time vs. sonic improvement" coefficient.
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#30
25th February 2010
Old 25th February 2010
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YEp!

but you got to do something there buddy

cause as I said, you are not going to be happy with the combination of the stock tubes on the Art and the Cad8000.


keep shinin

jerm
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