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ART PROCHANNEL II - Nightmare Buzzing Problem
Old 3rd May 2015
  #1
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ART PROCHANNEL II - Nightmare Buzzing Problem

Art Prochannel II Buzz Problem

I’ve been fighting with getting this preamp to work properly for months and months now, after sending the first one back and having a replacement sent out it was still malfunctioning and I was convinced the problem was at my end.

I thought i’d figured it out last night, when it was in mood 2(see below). I was doing some tests when somebody turned on the kettle and it started buzzing. Then it stopped when the kettle stopped and began again second after when my electric radiator kicked back into action.

When I sent the first one back it was a colder time of year, and in one of the rooms in my house there is an electrical heater that is always on in the cool months - this could explain the constant buzzing if the preamp was in mood 2, but that buzzing stops when not in a rack case with the MOTU, and I remember sitting with it, out of the case thinking “what the f**K”

I’ve got mood 1 and mood 2 because that’s literally what it’s like, one minute it’s fairly usable, then suddenly there’s a constant buzz that renders it completely unusable.

Default Signal Chain: MIC > ART PROCHANNEL II (Balanced +4dBu)> MOTU 8PRE > LOGIC PRO X

Mood 1 - unusable - Constant Buzz (Sample 1)


- In mood 1 the preamp is always buzzing when using dynamic and ribbon microphones unless I bypass the compressor.(Sample 2)

If I bypass the compressor but switch the unit into high voltage mode the buzzing returns.

If I unplug the input to the pre, the buzzing is still present, so it’s not coming from the input.

If I swap the output cable to my MOTU for a pair of headphones the buzz is still there so it’s not the MOTU.

If I connect a condenser microphone and turn on phantom power the buzz gets slightly louder with the poof of turning on phantom power then returns to the level it was at before I switched on phantom

In mood 1, the high tube voltage setting seems to have no effect other than returning the buzz when the compressor is bypassed.

With a mic connected if I turn the master output of the ART all the way down the buzz is still present

- The addition of household appliance interference (see mood 2) can be made on top of the existing constant buzz (sample 3, starts without the heater on, then switches on for a moment and off again)

Mood 2 - Slightly Usable - Buzz caused by electrical appliances

With the ART and MOTU both mounted in the same rack I’m able to start and stop the mood 2 buzz by switching on either a kettle, electric heater or a similar household device.

This buzz however, cannot be irradiated by bypassing the compressor.

If I remove the ART from the rack mount and place it on top of the rack on a thick piece of foam then reconnect the inputs and output and power cables, the household appliances don’t affect it and it becomes quite useable.

- However, if I turn on high tube voltage the buzzing returns? (90% sure it does this but i'll update when it starts being mood 2 again)

Any help on figuring out and suggestions would be really helpful, i'm not going to send it back and i'm confident with opening it up and replacing tubes, caps ect.

EDIT (further observations to mood 1):

**Bypassing the compressor gets rid of the noise, I thought this meant that the compressor circuit was causing the noise. However, with the compressor bypassed I engaged a switch on the EQ (Highs 6k or 18k) and the buzzing returned - I thought that in theory if I then bypassed the EQ the buzzing should stop, because the EQ circuit “caused” it - it didn’t stop. This made me think that if it’s not the circuits it could be something to do with the lights in the back of the switches.**
Attached Files

Sample 1 (BUZZ).mp3 (200.9 KB, 4306 views)

Sample 2 (BUZZ then COMP BYPASS).mp3 (200.9 KB, 4178 views)

Sample 3 (HEATER OFF:ON:OFF).mp3 (200.9 KB, 4192 views)


Last edited by tomwardplz; 3rd May 2015 at 08:42 PM..
Old 3rd May 2015
  #2
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DougS's Avatar
 

Over the years I've had two situations where a buzz like that was present and took some investigation to isolate and remove the problem.

1) One was Compact Florescent Light Bulbs. I had a mic that interacted with them. Lights ON - buzz. Lights OFF - no buzz. Replaced with LEDs.

2) The 2nd was much more difficult. I originally thought the noise was coming from a Keyboard (elec piano). Whenever I plugged the keyboard into my interface the buzz would be there. I ended up systematically disconnected every wire from my rig and found that when I disconnected the USB cable to my interface the buzz would stop. So I thought I had a bad interface. Then I realized even when the computer was off (but the USB was still connected) the buzz would be there in the analog circuit.

With the computer off and USB cable connected I got a buzz. Computer off and USB disconnected no buzz.

Then I started pulling wires out of my computer: mouse, keyboard other peripherals. Finally the last wire a pulled was an HDMI cable connecting the computer to a flat panel TV. When I pulled that wire the buzz stopped. Something in the TV (whether the TV was on or off) was creating a ground loop or electro-static something - this was traveling across the computer (whether the computer was on or off) form the HDMI input to the USB cable - up the USB cable to the interface and interacting with only the elec piano. I pulled the HDMI cable and no longer use that TV as a large computer monitor. And the buzz has been gone ever since.

I suggest a systematic approach of pulling wires one at a time until you isolate it.

Hope this helps.
Old 3rd May 2015
  #3
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Did you try dropping the shield on the cable of the subsequent piece of gear inline..?
Old 3rd May 2015
  #4
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Hi Doug, Thanks for your response.

Was the buzz you speak off similar to the buzz in the audio files I posted?

The bizarre thing is that the buzz sometimes comes from the unit when it is completely standalone, connected to nothing apart from the IEC power cable and the output to headphones - maybe it could be from something in my house that is on/plugged in, something that only kicks in at a certain time. It's interesting what you say about the fluorescent compact bulb, i'm going to run round switching all my lights off one by one now haha.
Old 3rd May 2015
  #5
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Quote:
Originally Posted by Snatchman View Post
Did you try dropping the shield on the cable of the subsequent piece of gear inline..?
Disconnecting pin 1 of one end of the cable between the pre and interface? I haven't tried that. I do have a reamp box with a ground lift that I could try quickly.

Tom
Old 18th March 2016
  #6
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I'm experiencing the same problems with an ART pro channel I,
It is the same type of noise, it gets worse when I plug a mic in and sweep it over the transformer -
When I listen closely, I can hear the transformer emit the same kind of buzz as in your audio files.

actually I have no clue what could be causing this, I spent lots of time looking into the unit, but
as I am not an electrician by any means I couldn't fix it.

What's strange on my unit is that the main pcb has no screws, so maybe someone tampered with it before (got it from ebay years ago)

But I'm keen on repairing the unit, even if it takes me another century. The battle is on.
Also Art customer service won't reply to me at all. Thx Art!
Old 1st June 2016
  #7
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Hi all.
I have exactly the same issue. I live in Australia and bough two pro channels from an authorised dealer in the states, unique squared, stupid name. Anyway both were supposedly new but both had the buzzing sound you guys are describing. I thought maybe the tubes were bad so I took a look and low and behold I found a fender tube in one of them. I guess they are not new after all. So I contacted Unique Squared and asked for a refund. They refused saying they would only honour. 30 days refund period. They told me to talk to ART. So I contacted ART, after weeks go by Thom Davis finally gets back to me and says that ART won't honour the warrantee because I live in Aust and bought from the US. Thom even said that the buzzing was from incorrect use of gain staging. So I contact the Aust Distributer. They say that ART are good guys and they will get back to me. Despite numerous follow ups neither Jamie's or bill get back to me.

All I all I bought three ART products and two of them were defective. Neither unique Squared, the ART Distributer in Australia or ART globally would help me with there defective products so I'm down 1500 Aussie dollars.

Thom Davis I'm calling you and your ****ty company out. For anybody that reads this just remember ARTs quality control is equal to 2 out of 3 units being defective and their manufacturers warrantee is not worth a damn.

F_ck Unique Squared, ART Australia, ART global and Thom Davis.

Ohh by the way in the intervening weeks/months I had a professional check the unit out. He said he's seem the same issue with ART units before. The power transformer is screwed causing the buzzing. He recommended throwing the unit away.
Old 3rd June 2016
  #8
My monitors speakers used to buzz like that and I was convinced it was some kind of firewire issue. After changing to a usb converter the issue went away. Dunno if that helps in any way at all.
Old 4th June 2016
  #9
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I'm having the exact same issue with my MPA II, even just plugging headphones into the output I can hear it. The unit is super noisey in general, if I push the button for +20db I can hear the tube inside rattle a bit.
Old 10th October 2016
  #10
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I've had a ART Pro Channel II since May and it has this same buzz issue I'm reading about. I brought it back to the shop where I bought it and I was brow-beaten into thinking it was something on my end but I tried many scenarios and the buzz is in the unit. I'm going to try and return this lemon. I was so looking forward to tracking with this piece of gear and have been foiled from day 1.
Old 18th October 2016
  #11
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Quote:
Originally Posted by isolotus View Post
I've had a ART Pro Channel II since May and it has this same buzz issue I'm reading about. I brought it back to the shop where I bought it and I was brow-beaten into thinking it was something on my end but I tried many scenarios and the buzz is in the unit. I'm going to try and return this lemon. I was so looking forward to tracking with this piece of gear and have been foiled from day 1.
Thanks all for helping me decide whether to return the Pro Channel II I just bought, which is doing exactly what the OP described in 2012. So not only does this problem appear to be baked in, it also appears that Art has no intention of fixing it. It's really too bad because, aside from the hums and buzzes that come and go, it's a lovely unit for a crazy good price. Built like a tank, full-featured, sweet sounding -- and all but useless to me.

I spent some hours troubleshooting, tried it in three different buildings, finally ran it powered by a sine wave inverter with no other power on in the building. Each configuration yielded a different combination of hums and buzzes, depending on which buttons were pressed, ground lifts, and the position of the output volume knob. Oddly, the unbalanced output was generally quieter than the balanced.

When the hum was absent, the tube saturation was luscious. But it's going back to the store.

Last edited by tuner; 20th October 2016 at 08:19 PM..
Old 16th November 2016
  #12
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Hello! Try using a different power cable. I was getting a bad hum from mine when I disengaged the high voltage button. Turns out I grabbed the wrong cable.

Make sure the output cable is balanced xlr/trs or xlr/xlr.

Are you going into a Furman or power conditioner of some sort? That will help with interference.

Sorry if you've already tried all of this. Good luck
Old 20th November 2016
  #13
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This is common to all Pro Channel II's I've used (including my own... which I sent back to ART a couple of years ago to get fixed... but it came back with the same hum at high volumes). I also believe the Pro MPA II has the same hum problem in one channel at high gain. The Pro VLA II probably has the same "flaw" but it isn't as obvious because the gain levels aren't as high. As "tuner" said, it is baked in.

I got fed up with it and asked ART for the Pro Channel II schematics, which they courteously provided. The problem is caused by a couple of 47 ohm resistors which were added across the +15V and -15V regulators in the Pro II series power supplies. Those resistors allow 120 Hz ripple from the rectifier to get onto the filaments/heaters of the tubes, resulting in the hum you hear in the units at high gain. (The original versions - Pro Channel, Pro MPA, etc - didn't have those resistors.)

It's a simple fix. Just snip the two 47ohm/5W power resistors on the pcb (R245 and R41 on the PCII) and the hum is gone. You can also de-solder them from the top with a pointy tip soldering iron... no need to take the board out. A few minutes and you're done and the unit is silent, other than some tube hiss you'd expect with the gain cranked.

Other than that, they really are excellent designs with a lot of features designed in to make the units clean and quiet... just a couple of badly placed resistors and you get hum in an otherwise excellent design.
Old 22nd January 2017
  #14
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Quote:
This is common to all pro Channel II's I've used ...
Mine too. Thanks for tracking this down and writing it up.

I think the problem is more a case of ripple on the 15v rail(s) getting directly into the audio path than coupling in through the tube filaments. Removing R245 was sufficient to eliminate the buzz. There is enough current drawn from the -15v rail for that regulator to work properly with R41 in place. Removing the resistors does make the regulators run hot (80C and 95C at 25C ambient), although no hotter than those in the original Pro Channel. I'm going to double up on the heatsinks to bring the temperature down "just because".

One other problem with having the resistors in place is that (I think) the 15V rails become uncontrolled if either of the tube filaments goes open circuit, or if the unit is powered up with a tube removed. Not sure if the voltage increase would be enough to damage anything ...

While I had the unit open I added a 470pF capacitor in parallel with C62. This makes the treble control center frequencies switchable between 6kHz and ~3kHz instead of 18kHz and 6kHz. Is the 18kHz setting intended for use by bats? I never found it useful.
Old 23rd January 2017
  #15
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ART ProChannel II buzzes

Quote:
Originally Posted by Brynner737 View Post
This is common to all Pro Channel II's I've used
I registered on this site to thank this person. I am the owner of an ART ProChannel II s/n S120843xxx. It has buzzed since the first day I tried to use it. Very strong buzz on balanced xlr output centered at 120hz. By using unbalanced trs output connection and turning master output knob fully clockwise it would kinda, sorta work.

I removed r245 and r41. Snip,snip. They are gone. At last, this unit functions like I had hoped it would when I bought it in 2015.

Thank you.
Old 23rd January 2017
  #16
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You're very welcome to both of you.

I think most PCII users have gone through the same frustration (unless they never use enough gain to notice it). I know I did. It's a shame too... such a nice unit other than that hum. Luckily the "problem" turned out to be a very easy fix.
Old 23rd January 2017
  #17
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Just out of curiosity:

Does this have anything to do with the flickering of the light on the channel one VU meter on MPA IIs? I have seen this on every MPA II I've encountered. None of them have been unacceptably noisy though, at least not more than expected from a low cost tube pre.

Still, I have to say that I don't understand all the praise the MPA and VLA have received around here. Both units been huge disappointments to me.
Old 7th February 2017
  #18
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Quote:
Originally Posted by Brynner737 View Post
It's a simple fix. Just snip the two 47ohm/5W power resistors on the pcb (R245 and R41 on the PCII) and the hum is gone. You can also de-solder them from the top with a pointy tip soldering iron... no need to take the board out. A few minutes and you're done and the unit is silent, other than some tube hiss you'd expect with the gain cranked.
Sure enough, this did the trick for me!! Just picked up this unit today and problem now solved thanks to you. I just cut one side of each resistor and the buzzing stopped. I already have the VLA-II and MPA-II (both of which I replaced the stock tubes), and both work and sound great, so I knew there had to be a way to fix the buzzing of the Pro Channel II. If I didn't already own those two, I probably would have assumed that's just the way the Pro Channel sounded and given up on it. All is now well in Tube-Land.
Old 14th February 2018
  #19
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Quote:
Originally Posted by jscheffman View Post
Quote:
Originally Posted by Brynner737 View Post
It's a simple fix. Just snip the two 47ohm/5W power resistors on the pcb (R245 and R41 on the PCII) and the hum is gone. You can also de-solder them from the top with a pointy tip soldering iron... no need to take the board out. A few minutes and you're done and the unit is silent, other than some tube hiss you'd expect with the gain cranked.
Sure enough, this did the trick for me!! Just picked up this unit today and problem now solved thanks to you. I just cut one side of each resistor and the buzzing stopped. I already have the VLA-II and MPA-II (both of which I replaced the stock tubes), and both work and sound great, so I knew there had to be a way to fix the buzzing of the Pro Channel II. If I didn't already own those two, I probably would have assumed that's just the way the Pro Channel sounded and given up on it. All is now well in Tube-Land.
Is there any solution like this for the ART TPS II? I see the ProChannel II is solved with this issue but I am also having an issue with the TPS II. I have taken a look at the PCB but there obviously is a different schematic for this unit. Any feedback would be appreciated!
Old 20th March 2018
  #20
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gsilbers's Avatar
 

so do all these art still have the buzzing problem or does it dependo on the unit?
Old 22nd March 2018
  #21
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gsilbers's Avatar
 

Quote:
Originally Posted by Brynner737 View Post
This is common to all Pro Channel II's I've used (including my own... which I sent back to ART a couple of years ago to get fixed... but it came back with the same hum at high volumes). I also believe the Pro MPA II has the same hum problem in one channel at high gain. The Pro VLA II probably has the same "flaw" but it isn't as obvious because the gain levels aren't as high. As "tuner" said, it is baked in.

I got fed up with it and asked ART for the Pro Channel II schematics, which they courteously provided. The problem is caused by a couple of 47 ohm resistors which were added across the +15V and -15V regulators in the Pro II series power supplies. Those resistors allow 120 Hz ripple from the rectifier to get onto the filaments/heaters of the tubes, resulting in the hum you hear in the units at high gain. (The original versions - Pro Channel, Pro MPA, etc - didn't have those resistors.)

It's a simple fix. Just snip the two 47ohm/5W power resistors on the pcb (R245 and R41 on the PCII) and the hum is gone. You can also de-solder them from the top with a pointy tip soldering iron... no need to take the board out. A few minutes and you're done and the unit is silent, other than some tube hiss you'd expect with the gain cranked.

Other than that, they really are excellent designs with a lot of features designed in to make the units clean and quiet... just a couple of badly placed resistors and you get hum in an otherwise excellent design.
this might answer my previous comment. based on this post, im guessing its on all units. which makes me wonder why many reviews dont mention this.

i wonder if its still worth getting it and do the snip fix.
Old 8th March 2019
  #22
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Just bought a secondhand Pro Channel II. Saw decent enough reviews and acquired for a good secondhand price. Unit looks great and is functional... except for that hum, right out of the box, exactly as described above, without a doubt coming from the unit.

Had I seen these issues I may not have bought the thing! But since I had it, and there's no warranty to void anyway, I figured, why not try the snip fix on R245 and R41. Opening the unit was pretty straightforward, despite the screws being super tight and stripping quite easily.

Snipping the big resistors seems to have totally fixed the issue! Thanks to those who figured this out. After this fix, it's super quiet at neutral gain, as opposed to compressor being totally unusable. And there's plenty of headroom
Old 8th March 2019
  #23
I bought an Art MX822 line mixer for my synths a couple years ago, new. After a bit, its started developing a hum from the PSU as well, and it is noticeable in audio out if i turn up the volume. I have a lot of stuff in my studio, and this is the only noise maker. I contacted Art as well, twice, with no reply. I've completely written them off as company I'd ever buy anything from...
Old 8th March 2019
  #24
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Pro Channel II no problems here.

I have a Pro Channel II, bought new here in Brazil. I've never had problems, it works perfectly and its integrated peripherals, both the equalizer and the compressor, are very good. Sounds hot and works quietly.
Old 15th April 2019
  #25
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weave's Avatar
Thanks!

I also had the buzz on my Art Pro Channel II - And the snip on R41 and R245 helped me as well - I changed out the stock tubes (marked as China 12AT7 and 12AX7B) with some JJ’s and I am feeling really good about things!

Attached some pics for those wanting to do a closed hood reconnoiter... before and after. I just snipped one side and let it hang just in case.

Thank you for the fix!
Attached Thumbnails
ART PROCHANNEL II - Nightmare Buzzing Problem-4da3a07b-ab66-4a7d-9739-f980660a6a9b.jpg   ART PROCHANNEL II - Nightmare Buzzing Problem-6e872437-464f-4e15-8eae-f956ab0b708b.jpg  

Last edited by weave; 15th April 2019 at 02:52 PM.. Reason: Added clarification
Old 17th July 2019
  #26
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mattrico's Avatar
Just wondering if anyone has tried this on a Pro VLA II? I opened mine up and couldn't see anything similar to the above pictures so I'm a bit lost. I was gonna chat to one of the techs at work (I work in a radio station) who is far smarter with this sort of thing than I, but without it being similar I'm not sure if he'll have much of an idea either. Any help is appreciated, this buzz is driving me nuts!
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