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August 21, 2019, 04:44:18 AM

Author Topic: Help with voltage checks, also noise and plug habits?  (Read 239 times)

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Offline SmashBruh

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Help with voltage checks, also noise and plug habits?
« on: May 13, 2019, 06:49:33 AM »
Hello! I recently purchased a pre-built Mainline! It sounds awesome, and I don't think I need to be concerned, but I wanted to run a quick voltage check to make sure everything was working as it was supposed to. Unfortunately the instructions it came with only cover where to place my leads when biasing my tubes. I was able to figure out how to read the voltages from the PSU board which came back as 275 and 6.31 (not sure whether to be concerned or not with the extra .01V) respectively. However I can't figure out how to read the IAs, the Bregs, -reg and Kreg boards. If anyone could give me any tips they would be greatly appreciated!

I also noticed that when paired with a 300ohm 99db/a headphone (ZMF auteurs) the amp outputs some electrical noise when the left attenuator is set to 0db and the impedence is set to high (The noise completely disappears when the attenuators are set to -9db.) Just wanted to ask if this too was normal!

Oh! And I was also wondering if it was safe to leave my headphones plugged into the amp when turning it on and off? I've been unplugging them so far everytime however I would much rather just leave them plugged into the balanced output if possible.

Online Paul Birkeland

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Re: Help with voltage checks, also noise and plug habits?
« Reply #1 on: May 13, 2019, 01:04:32 PM »
The extra 0.01V is not concerning.  The seller should have provided you with a copy of the manual, right?

If you have noise from the amp with the attenuators all the way turned up, but not with the attenuators turned all the way down, then you are simply amplifying ambient noise.  A set of shorting plugs connected to the input you have selected when doing these tests would likely eliminate that noise all together. 

There is no need to unplug your headphones when you power the Mainline on and off. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline SmashBruh

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Re: Help with voltage checks, also noise and plug habits?
« Reply #2 on: May 13, 2019, 09:31:58 PM »
Thank you so much for your help!
Unfortunately no, the seller did not provide me with a copy of the manual. However I just bought a copy from bottlehead so I should be getting that soon!

I discovered what triggers the noise (it's like an electrical static with a mid-toned beeping that happens at constant intervals.) The noise is only present when the amp is connected to my Modi 3 through the rca ins and when the modi is connected to a device (I've tried it across a few devices.) It was completely silent with my Cavalli Tube Hybrid, so I'm not sure why I can hear this now? I'm not sure how to fix the issue to be honest. I'm not sure if the unit is defective or if the mainline is just so sensitive that it can pick up a noise floor in the Modi 3 that the CTH could not or what. I have a Gumby on the way and I'm hoping maybe that'll fix this? (I bought the Gumby prior to this issue.)
« Last Edit: May 13, 2019, 10:17:50 PM by SmashBruh »

Online Paul Birkeland

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Re: Help with voltage checks, also noise and plug habits?
« Reply #3 on: May 14, 2019, 04:36:01 AM »
What is the Modi connected to?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline SmashBruh

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Re: Help with voltage checks, also noise and plug habits?
« Reply #4 on: May 14, 2019, 05:03:27 AM »
What is the Modi connected to?

It was connected to my PC via USB, however I've now also tried connecting it to both my monitors through USB as well as connecting it to my PC via SPDIF while having it powered through a wallwart. I unfortunately seem to get this issue regardless of the source the Modi is connected to...

I've also tried turning off my cellphone, PC, wireless router/modem and monitors to try and reduce electrical interference in the room but as of yet it's had no effect on the noise. You don't think my cables could be at fault do you?

EDIT:I tested connecting my phone to the amp via an RCA->3.5mm cable and can confirm that is completely silent at max power. So this narrows down the issue to either the Modi, my cables or my PC...
« Last Edit: May 14, 2019, 05:43:47 AM by SmashBruh »

Online Deke609

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Re: Help with voltage checks, also noise and plug habits?
« Reply #5 on: May 14, 2019, 05:57:18 AM »
I'd wait for the Gumby. It has Schiit's USB 5.0 "decrapifier" tech built in. 
Derek
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Online Paul Birkeland

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Re: Help with voltage checks, also noise and plug habits?
« Reply #6 on: May 14, 2019, 05:54:34 PM »
An optical connection will eliminate that noise.  Someone has also suggested using a USB hub with wall wart power as a way to accomplish the same thing, and that also certainly seems worth trying. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man