Rackmount gear, proximity & interference

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earth tones
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Rackmount gear, proximity & interference

Post by earth tones » Sun Mar 21, 2021 10:24 am

Hi folks.

I have a rackmount with an Aurora Audio GTQ2 preamp racked on top of a Pultect EQP1A (DIY Drip build). I have been using this chain in this racked congifuration for months to record voice overs. Today I noticed that increased 60hz noise was present in the audio signal and was eventually able to isolate it to occurring only when the Pultec was poweredon ..the noise persists whether or not the Pultec was in the audio chain. Therefore, it seems as if something within the Pultec enclosure must be transmitting interference by proximity into the GTQ2 preamp.

Any thoughts on what would cause this and why it would start all of a sudden?

Later today I will unrack the Pultec to see if the interference decreases as distance from the GTQ2 increases.

Thanks for your feedback.

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Re: Rackmount gear, proximity & interference

Post by digitaldrummer » Sun Mar 21, 2021 12:03 pm

unless it occurs only with the EQ, then its likely been there all along and maybe you just didn't notice before? If you have the gain up, you are more likely to notice. But yeah, move them apart and hope that it's the easy fix. It's not uncommon for power transformers to affect another device close by. making sure the entire chassis is grounded well can help (if any lid/sides are separate, make sure paint is not impending the contact) but may not completely stop it from occurring.
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Re: Rackmount gear, proximity & interference

Post by Scodiddly » Sun Mar 21, 2021 12:08 pm

Probably magnetic coupling between transformers. The power transformer for the Pultec is probably in the same spot as a signal transformer in the Aurora.

Really hard to stop with just regular metal rack enclosures, but distance will take care of the problem.

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Re: Rackmount gear, proximity & interference

Post by Colorblind » Sun Mar 21, 2021 12:37 pm

I have the same issue with my GTQ-2. Channel 2 has a lot more of the hum than the other. Like 5-10db. Can’t remember to what extent I tried to troubleshoot this, but I seem to recall still having some hum (however less) with the unit completely out of the rack. I reached out to Geoff Tanner/Aurora about this a while back, and never received a reply.

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Re: Rackmount gear, proximity & interference

Post by earth tones » Sun Mar 21, 2021 4:24 pm

Colorblind wrote:
Sun Mar 21, 2021 12:37 pm
I have the same issue with my GTQ-2. Channel 2 has a lot more of the hum than the other. Like 5-10db. Can’t remember to what extent I tried to troubleshoot this, but I seem to recall still having some hum (however less) with the unit completely out of the rack. I reached out to Geoff Tanner/Aurora about this a while back, and never received a reply.
It is troubling to hear this. I have perceived the exact same issue with my GTQ2 but wasn't convinced that this current increase in noise was necessarily the same thing. Over a year ago, after much troubleshooting, I had determined that channel 2 of my GTQ2 had a markedly higher noise floor than channel 1. I spent quite some time trying to get ahold of Geoff but never received a response, either.

I recall at that time reading this thread, which made me wonder if my unit was experiencing a similar issue:
https://www.gearslutz.com/board/high-en ... users.html

I will try to reach out the Geoff & Aurora Audio once again to see if I can have this unit inspected and sorted out.

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Re: Rackmount gear, proximity & interference

Post by vvv » Sun Mar 21, 2021 6:05 pm

One of the great values of this (and other forums, I s'pose) in discussing gear is to point out problems with the product out there, as well as non-responsive companies.

I, personally, will now never buy anything Aurora Audio - there's enuff other stuff out there without such issues and lack of support.

I hereby grant explicit permission for anyone to quote me to "Geoff Tanner/Aurora".
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uite a character,.

Post by Nick Sevilla » Sun Mar 21, 2021 6:48 pm

vvv wrote:
Sun Mar 21, 2021 6:05 pm
One of the great values of this (and other forums, I s'pose) in discussing gear is to point out problems with the product out there, as well as non-responsive companies.

I, personally, will now never buy anything Aurora Audio - there's enuff other stuff out there without such issues and lack of support.

I hereby grant explicit permission for anyone to quote me to "Geoff Tanner/Aurora".
I met Geoff a few times. Quite the character. Never got him to produce replacement parts for my Neve console, no matter how many times he insisted he could. Instead I found BAE, who are OUTSTANDING people, even the new owner is a cool dude.
Howling at the neighbors. Hoping they have more mic cables.

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Re: Rackmount gear, proximity & interference

Post by earth tones » Sun Mar 21, 2021 7:32 pm

Yeah, I was quite disappointed by the lack of response from Aurora Audio, especially after having encountered a technical issue with a brand new unit. I was really excited to purchase this GTQ2 and had decided after much research to make it the sole preamp in my small studio. I would really have liked to have given the company a chance to make good on fixing the technical issue with my new unit. When companies that produce boutique, high-dollar items stand behind their products with expedient and thorough customer support it only confirms the notion that the customer invested in the "right" product. Now that so much time has passed, even if I did hear from Geoff, the repair service would be out of warranty and I would have to incur expensive packing and shipping charges to have it looked at. I know that a lot of these boutique shops operate with a skeleton staff but I would think that the last thing you'd want to skimp on would be customer support. You're kind of shooting yourself in the foot as a retail operation.

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Re: Rackmount gear, proximity & interference

Post by Nick Sevilla » Sun Mar 21, 2021 8:24 pm

I trust very few companies:

Focusrite.
B.A.E.
SSL
Waves
PSP
Apple (I have a business account, maybe they give me better repair treatment?)
Allen & Heath
UAD (they also repair older Teletronix hardware like the LA2A and 1176/1178 compressors)

Other than that... I have little in the way of having to deal with other companies.
Howling at the neighbors. Hoping they have more mic cables.

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Re: Rackmount gear, proximity & interference

Post by earth tones » Sun Mar 21, 2021 8:34 pm

So I've rearranged my rack. I swapped the Pultec for an 1176 and there is definitely a reduction in 60Hz however it still increases when the 1176 is powered on. I suppose that this most likely is just a complicated ground loop and/or EMI due to proximity sort of thing. I'll probably just put the GTQ2 at the top of the rack and leave a 3U gap below it. Gremlins!!

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Re: Rackmount gear, proximity & interference

Post by Colorblind » Mon Mar 22, 2021 7:46 am

Cool, sounds like you've made a bit of progress with it. Also, I wasn't attempting to crap all over Aurora Audio, but thought I should share my experience in the interest of transparency. I do still use the unit regularly. Digging through my old notes, I found this recap of some basic troubleshooting I did. Not sure if it's helpful, but...

-ch 2 1/4" output is barely there. very quiet, distorted, and thin. oscillates/whines at highest gain settings.
-with lid off and no input connected, ch 2 xlr output is around -89db with the gain at -30. compared to roughly -94db on ch 1.
-with lid on, ch 1 stays the same, but ch 2 gets another 5db louder.
-overall, with lid on, ch 1 is approx 10db quieter than ch 2.
-with both outputs at minimum, ch 1 is still about 6db quieter than ch 2.
-going from 1200ohm to 300ohmon ch 2 makes hum slightly duller/quieter.
-both channels seem to have more hum once racked, but I didn't do any tests to prove it.

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Re: Rackmount gear, proximity & interference

Post by MoreSpaceEcho » Mon Mar 22, 2021 8:31 am

^^^^^^^^ that list is pretty :crazy:
earth tones wrote:
Sun Mar 21, 2021 7:32 pm
I know that a lot of these boutique shops operate with a skeleton staff but I would think that the last thing you'd want to skimp on would be customer support. You're kind of shooting yourself in the foot as a retail operation.
I don't understand how/why any company, especially a small one, would operate like that. If I blew off clients I wouldn't have any.

I'm sorry I don't have any helpful advice for you but this thread reminded me that years ago I had a similar issue with an EL FATSO, it developed a buzz in one channel. They said send it in, despite it being way out of warranty. When they couldn't duplicate my problem there, they just sent me a new one. And got a loyal customer for life.

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Re: Rackmount gear, proximity & interference

Post by digitaldrummer » Mon Mar 22, 2021 9:03 am

I had a pair of Vintech 573's and one was out of phase with the other (but got them both from Sweetwater). I called Vintech, they had me check to make sure something wasn't obviously mixed up (and that I couldn't easily just resolder) and then sent me a new one. Excellent.

I had an old Aphex 207D (that I got used) and one of the channels was out of phase again - got one of their engineers on the phone, he took the time to walk me through identifying where a couple wires were crossed (literally) and I was able to fix it myself. Yay!

I also had a buzz going on in my API 500 racks and was noticing it in my Avedis MA-5 and A-Designs pres (that I had in it at the time - and still have). I emailed both and I got calls from both - spoke to Avedis and then Peter Montessi and they both helped me track down the issues. I don't even remember now what it was - maybe ground loops or proximity - but they both took the time to help and I really appreciated that. Again, both are great companies, and if I needed more of their gear right now I would definitely buy more!
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Re: Rackmount gear, proximity & interference

Post by markjazzbassist » Mon Mar 22, 2021 10:10 am

digitaldrummer wrote:
Mon Mar 22, 2021 9:03 am
I had a pair of Vintech 573's and one was out of phase with the other (but got them both from Sweetwater). I called Vintech, they had me check to make sure something wasn't obviously mixed up (and that I couldn't easily just resolder) and then sent me a new one. Excellent.

I had an old Aphex 207D (that I got used) and one of the channels was out of phase again - got one of their engineers on the phone, he took the time to walk me through identifying where a couple wires were crossed (literally) and I was able to fix it myself. Yay!

I also had a buzz going on in my API 500 racks and was noticing it in my Avedis MA-5 and A-Designs pres (that I had in it at the time - and still have). I emailed both and I got calls from both - spoke to Avedis and then Peter Montessi and they both helped me track down the issues. I don't even remember now what it was - maybe ground loops or proximity - but they both took the time to help and I really appreciated that. Again, both are great companies, and if I needed more of their gear right now I would definitely buy more!
yeah A designs Peter is awesome. my REDDI got trashed on a european tour by baggage handlers (it was in a flight case of its own). i called and said hey man i'll pay for the repairs, i sent it out. it arrived back and he called me "merry christmas, don't worry about the cost". customer for life!

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Re: Rackmount gear, proximity & interference

Post by Recycled_Brains » Wed Mar 24, 2021 7:44 am

Similar issue with my MC77 and Daking pre/eq. If I use the 125hz band on the EQ, and the MC77 is turned on the Daking hums. Doesn't matter if the Purple is patched in or not. My tech suspects the power transformer in the Purple is causing some interference with the inductor in the EQ circuit. If I move the MC77 away, it definitely gets quieter. He said the rack rails can contribute to it too. It's not loud enough that it's problematic with most stuff I mix (signal is much louder than the noise), but on quieter stuff it can be annoying.

2020 and so far, 2021, has been the year when all my shit started being stupid. I've had stuff in / out of the shop more in the past 15 months than I have in the past 10 years.
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