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##Manual/How to [Pictures]## Changing Tubes in Pro MPA 2
Old 5th December 2009
  #1
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Thumbs up ##Manual/How to [Pictures]## Changing Tubes in Pro MPA 2

Quote:
Originally Posted by lpkyer View Post
i.e: Unplug the unit and let it rest for a couple minutes, Dont wear any jewelry, Always put one hand in the unit and the other in your pocket when manipulating a circuit, use a glove to remove the tube etc.

This is for anyone who wants to change tubes in Art Pro MPA 2 or any other pre-amp for that matter.

I have tried to take as many pictures as I could, so here we go:

Part 1: Remove the screws (10 total) to remove the cover

2 on the top


3 on each side of the unit



2 on the back



Part 2: Remove the screws on the tube/tubes you are trying to remove (2 screws for each tube shield)




Part 3: Remove the tube shield, it will easily come off as it has a spring inside





Part 4: Remove the tube by holding down the white base at the stem of the tube, and hold the tube itself along the side of it. Grabbing as much of the surface area with your fingers as possible. (Wash your hands with soap as you need a good grip).

Rock the tube in circular motion. Don't be afraid, sometimes the tube is sitting there well, and you really need to rock it before it comes out. This things are actually more sturdy than they look, but still be careful not to break or bend the pins on the tube.

If the pins get bend a little bit, you can bend them back with your finger or a flat screwdriver, just be careful.




Part 5: Changing the tube, get the old one out of the way and stick the new one back into the holes, by aligning the pins.



Part 6: Gently rock the new tube back into the old position



Part 7: Re-attach the tube shield back on the tube.



Part 8: Screw the shield back in place.




Part 9: The tube is changed! (Repeat the process for the second one if needed)




Part 10: Tube/Tubes are in place


Part 11: Screw the cover back on the unit (10 screws total)




Part 12: Turn the unit on and let the tubes warm up for an a hour or two. There could be crackling noise when the tube is used at first, which is fine as it's going to go away very soon.

A little piece of advice: Tube Shields are used to protect the tube from Radio Frequency Interference. If you are going to remove Tube Shields then the High Frequency response will increase, which may be a good or a bad thing.

If you have a very brittle microphone it could be best to leave them on (Ex: BlueBird), but if it's actually a microphone that you want to sound bright and shiny, then removing the tube shield is an option.

In my case it wasn't needed. It sounds better without it on BlueBird.

Quote:
Originally posted by Bowie

Maintenance: Tubes do not require much in the way of maintenance. The glass does not need to be cleaned and fingerprints are ok. The lettering on the glass is usually fragile and may rub off when touched. I do recommend that the pins be cleaned annually to remove oxidation. Spray a solution like "Deoxit" or "Pro-Gold" onto a pipe cleaner and scrub between the pins. This is also good for any contacts on your equipment such as XLR pins, 1/4" jacks, etc. The pins on your tubes were polished and treated before shipping to you. The treatment may crackle for a few seconds when first powering up the tube.
A lot of thanks to Bowie for most of this information. So now you can be more confident about replacing the tubes and upgrading your gear.

Good luck

:)
Old 7th December 2009
  #2
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BUMP!!!!!!
Old 7th December 2009
  #3
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Another piece of Advice I have received from Bowie:

If you encounter cross talk, than it's most likely the metal shielding on the tube that is picking it up. The tube shield can be removed temporarily/permanently if you like. This will also increase the High Frequency response.


To check for the cross talk: Plug the mic into channel 1, turn up the gain and output to decent levels (half way), turn the phantom power IF NEEDED, now plug in your headphones straight into the output of the channel 2, turn the levels on channel 2 to the same level as channel 1 (channel 2 doesn't have a mic plugged in, just your headphones).

Talk/speak/sing into the microphone on Channel 1. You shouldn't hear ANYTHING coming out of the output of the Channel 2. If you hear static buzz everytime you sing/speak into the mic, you are getting a cross talk.

Cross talk is basically when you have one of the tubes on the opposite channel receiving interference from the first channel.

Some tubes are more prone to having this issue, some not at all. You can remove the tube shield which can help the situation on the tube receiving the crosstalk. (In our scenario Channel 2, since the mic signal is on Channel 1)

Old 18th January 2010
  #4
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Pictures

I just bought an Art Pro MPA 2 about an hour ago. I was just looking around and found this very helpful article on changing tubes. One question: Why are the pictures backward. Were they taken in a mirror?

Just curious...

Melvoid
obSession Recording Studio - Spring Green, WI
Old 18th January 2010
  #5
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http://www.harmoniccycle.com/hc/imag...-schematic.pdf

As you can see, the tubes are the least of your sonic worries..
Old 21st January 2010
  #6
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Quote:
Originally Posted by melvoid View Post
I just bought an Art Pro MPA 2 about an hour ago. I was just looking around and found this very helpful article on changing tubes. One question: Why are the pictures backward. Were they taken in a mirror?

Just curious...

Melvoid
obSession Recording Studio - Spring Green, WI
No problem man

heh

It's not in a mirror, but taken with a MacBook built in camera, and it always takes the mirrored shot for some reason



Hope that didn't complicate things
Old 15th April 2010
  #7
Gear Maniac
this is excellent... anybody have any recommendations for tubes on this unit in particular?
Old 15th April 2010
  #8
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Quote:
Originally Posted by joshuarlyon View Post
this is excellent... anybody have any recommendations for tubes on this unit in particular?
There are probably several hundred posts on this very topic. Just search for "MPA GOLD" and "tubes"...or PM BOWIE.

Frank
Old 15th April 2010
  #9
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Thanks for the tutorial, and I didn't know about the tube shield - HF thing. I assume that would be the same for a Pro VLA?
Old 15th April 2010
  #10
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Excellent tutorial !
Perhaps you could put up some security advices before your tutorial though?
i.e: Unplug the unit and let it rest for a couple minutes, Dont wear any jewelry, Always put one hand in the unit and the other in your pocket when manipulating a circuit, use a glove to remove the tube etc.
Old 17th April 2010
  #11
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RDMS's Avatar
 

Quote:
Originally Posted by joshuarlyon View Post
this is excellent... anybody have any recommendations for tubes on this unit in particular?
Fitted a pair of Electro Harmonix 12ax7eh to mine.
Nice and smooooooth compared to stock valves.

Old 17th April 2010
  #12
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Quote:
Originally Posted by lpkyer View Post
Excellent tutorial !
Perhaps you could put up some security advices before your tutorial though?
i.e: Unplug the unit and let it rest for a couple minutes, Dont wear any jewelry, Always put one hand in the unit and the other in your pocket when manipulating a circuit, use a glove to remove the tube etc.

LMFAO!

Yeah I guess I should've done that...hopefully no one got electrocuted in the process heh

Thanks for dropping a comment. I'll add your post in my first post.
Old 17th April 2010
  #13
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Being that I just retubed my MPA II yesterday, I'd like to state that the step of unscrewing the tube shield is totally unnecessary.

The tube shield is actually a 2 piece design... if you look at it closely you'll see. All you have to do is push down slightly, rotate it a few degrees to disengage the locking lugs, and then it will lift right off.
Old 19th April 2010
  #14
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Quote:
Originally Posted by svart View Post
http://www.harmoniccycle.com/hc/imag...-schematic.pdf

As you can see, the tubes are the least of your sonic worries..
What do you mean? There ARE a bunch of Op Amps in there!
Old 19th April 2010
  #15
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Quote:
Originally Posted by djemberecords View Post
What do you mean? There ARE a bunch of Op Amps in there!

I wonder if he is referring to the fact it is NOT all tube and therefore less than desirable.
It is NOT starved plate design and it IS a low end theory
Old 19th April 2010
  #16
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Usually the people who hate on the MPA haven't actually tried it. Actually trying it usually shuts them up.

Frank
Old 21st April 2010
  #17
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Quote:
Originally Posted by Weasel9992 View Post
Usually the people who hate on the MPA haven't actually tried it. Actually trying it usually shuts them up.

Frank

It's definitely a character preamp, and doesn't always work on vocals...but not to many pres do work every time and for every song, I'm fine with it, I have SSL Alpha Channel which is an amazingly clean pre, that is extremely accurate and fast, but you don't need it always, and I have used PRO MPA II over it several times, that's just the way it goes.

People associate price tag with the quality, and quality with application, but it's not really the case.

I think it's more about the character of the unit, that either matches what you need, or you look for something else in your arsenal, I'm NOT selling PRO MPA II for sure, I like that flavor, and it's always a back up for many things, and not a bad one by any means
Old 22nd April 2010
  #18
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Quote:
Originally Posted by Lifted View Post
It's definitely a character preamp, and doesn't always work on vocals...but not to many pres do work every time and for every song, I'm fine with it, I have SSL Alpha Channel which is an amazingly clean pre, that is extremely accurate and fast, but you don't need it always, and I have used PRO MPA II over it several times, that's just the way it goes.
Exactly. I couldn't agree more. I don't like the MPA on everything either, but that's why I have other options.

Frank
Old 3rd March 2011
  #19
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Quote:
Originally Posted by Lifted View Post
LMFAO!

Yeah I guess I should've done that...hopefully no one got electrocuted in the process heh

Thanks for dropping a comment. I'll add your post in my first post.

I got shocked!

I'm still not sure how I got shocked when everything was unplugged. I guess some kind of static build up in the unit?

wasn't to strong a shock...I've had worse.
Old 3rd March 2011
  #20
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Quote:
Originally Posted by blackmajik2021 View Post
I got shocked!

I'm still not sure how I got shocked when everything was unplugged. I guess some kind of static build up in the unit?

wasn't to strong a shock...I've had worse.
capicitors hold charge for ages, did you short out one?
Old 25th June 2012
  #21
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Channel 2 not working

Channel 2 on my Pro MPA II is not working, I hear a noise sound as I turn the output level control and becomes louder when plate voltage is activated.

When I power-up the unit it does it's LED and Vu meter test on channel 1 only.

Could this be an issue with the tube ?
and does anyone know what the LED/VU meter test does at the beginning?
Old 25th June 2012
  #22
Quote:
Originally Posted by Gitzo73 View Post
Channel 2 on my Pro MPA II is not working, I hear a noise sound as I turn the output level control and becomes louder when plate voltage is activated.

When I power-up the unit it does it's LED and Vu meter test on channel 1 only.

Could this be an issue with the tube ?
and does anyone know what the LED/VU meter test does at the beginning?
To eliminate or confirm if the tube is the culprit, open your unit and swap the tubes between the two channels, put the cover back on and then power it up; test with mics in each channel. If Channel Two now works and Channel One does not, then you've located the source of the problem. If this doesn't work, then contact ART directly; they're very good at helping you with troubleshooting and offering a repair service.
Old 26th June 2012
  #23
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Well I am happy to report (after the swap) that only channel 2 is now working and that channel 1 is now exactly the same as channel 2 was before the swap.

I might buy some Tung-sols to replace
Old 26th June 2012
  #24
Quote:
Originally Posted by Gitzo73 View Post
Well I am happy to report (after the swap) that only channel 2 is now working and that channel 1 is now exactly the same as channel 2 was before the swap.

I might buy some Tung-sols to replace
The reissue Mullards aren't bad for new tubes (remember to burn-in your new tubes) however if you are looking for a great set of tubes, PM member BOWIE here at GS; he has a great selection of NOS tubes.
Old 26th June 2012
  #25
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I have three of the original MPA's, all with rolled NOS tubes. They get a lot of compliments from players I work with. FYI, you can remove the tube shields by pressing down and twisting them a quarter turn rather than unscrewing the bases from the boards, that's what the indentations on the side are all about.
Old 27th June 2012
  #26
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Quote:
Originally Posted by ivmike View Post
The reissue Mullards aren't bad for new tubes (remember to burn-in your new tubes) however if you are looking for a great set of tubes, PM member BOWIE here at GS; he has a great selection of NOS tubes.
To burn-in new tubes, I just leave it on for an hour or 2 ?
Old 27th June 2012
  #27
Quote:
Originally Posted by Gitzo73 View Post
To burn-in new tubes, I just leave it on for an hour or 2 ?
Run some music or white/pink noise through the unit for a few hours. When I first purchased the MPA II, I didn't burn the tubes in and got a nasty "pop" on a track that I was recording.
I'm not entirely sure how long is "long enough", however when I purchased my NOS tubes from BOWIE (for my MPA Gold, MPA II and VLA II) he had burned them in for me.
Old 27th June 2012
  #28
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I just retube mine today, tubes are now burning :D
Old 25th August 2012
  #29
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FYI, if the noise continued on the one channel, it could have been dirty or loose contacts, according to https://ssl.eurotubes.com/cart/index.php?page=faq#1. They have instructions how to handle both situations, on that page.
Old 28th October 2012
  #30
Hobbs_Won
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Question for anybody who may know....which is actually a 2 part question.

I was thinking about putting a 12BZ7 tube in the MPA II for more "in your face" type character.

Being that the the 12BZ7 is just 2 12ax7's run in parallel....it would draw double(??) the current as a 12ax7 tube...my question(s) are..

1 - being that the ART MPA II isn't a true valve amp and has some (or a good amount) of Solid State construction.....would it be unwise pulling that current through all the (most likely) cheaply made transistors and caps?

and 2 - The 12BZ7 is about 3/4" taller than the 12ax7... is there enough headroom in that thing to clear the lid when it is placed back on??
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