Silvas

Hello !

I had this idea where somehow  i can connect the AC from the wall to an AD for signal analysis, visualizing harmonic contents, THD and so as a way to characterize AC power coming out from the wall as well as inverters, online UPS systems and so. Has anyone here done something similar ? I guess it would be some sort of a pad followed by a stepdown transformer for isolation and safety...Anyone ? And yes i know i could simply scope it  ;D ;D ;D Best regards.

Camilo Silva F.
Camilo Silva F. Mastering
Chia, Colombia


JohnRoberts

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #1 on: January 28, 2018, 10:18:59 PM »
You can crudely just look at the output of simple ac to ac  wall wart that will drop the 120V to maybe 15VAC

The bandwidth of the wall wart is not great but lightly loaded you can see what is going on.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...

Silvas

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #2 on: January 29, 2018, 07:52:50 AM »
You can crudely just look at the output of simple ac to ac  wall wart that will drop the 120V to maybe 15VAC

The bandwidth of the wall wart is not great but lightly loaded you can see what is going on.

JR

It totally makes sense !   :D Thanks !
Camilo Silva F.
Camilo Silva F. Mastering
Chia, Colombia

Speedskater

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #3 on: January 30, 2018, 09:21:07 AM »
An audio output transformer from an old vacuum tube power amplifier will work great.
Kevin

Silvas

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #4 on: January 30, 2018, 09:26:33 AM »
An audio output transformer from an old vacuum tube power amplifier will work great.

Sounds like a good idea ! I guess it will need some loading tho. Thanks !
Camilo Silva F.
Camilo Silva F. Mastering
Chia, Colombia

trobbins

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #5 on: January 31, 2018, 03:26:49 AM »
I guess it will need some loading tho.
Care is needed switching a highish voltage on to, or off, any transformer, not just an output transformer.    The worst outcome is that an over-voltage stress/arc can occur in the transformer primary winding.

It's not clear how accurately you want to view the harmonic levels, eg. the % HD level, or the span of the frequency spectrum, or ...?

You could also just extend the input of the ADC close to an insulated wire carrying mains voltage.  Capacitance coupling will give you quite a good view, and out to the frequency limit of your ADC.

ruairioflaherty

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #6 on: January 31, 2018, 11:34:30 PM »

Silvas

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #7 on: February 01, 2018, 07:01:15 AM »
I use one of these for looking at the mains with a scope

http://www.gryphon-inc.com/PDF%20Literature/Power%20Probe%20-%20AC%20Line%20Viewer.pdf

I wasn't aware that such gadget existed, thanks so much for pointing me out to it !
Camilo Silva F.
Camilo Silva F. Mastering
Chia, Colombia

ruairioflaherty

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #8 on: February 01, 2018, 09:53:46 AM »
It's a really useful unit. I've seen them sell used as low as $60, I think I paid $140 for mine.

Brian Roth

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #9 on: February 01, 2018, 01:52:21 PM »
I've had the VERY similar OneAC unit for years.  Here's one currently listed:

https://www.ebay.com/itm/Oneac-Line-Viewer-103-LV103-with-hard-case-manual-and-cables-ESTATE-FIND/292388882808

Bri
Brian Roth Technical Services
Salina Kansas, home of the best vinyl on the planet!

http://www.BrianRoth.com
recordingservicesandsupply.com/
www.qualityrecordpressings.com/
store.acousticsounds.com


abbey road d enfer

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #10 on: February 01, 2018, 02:43:22 PM »
Beware that, being transformer-based, they won't indicate when tehre's DC on the line. Not that it's so frequent. I have experienced that just once in my entire professional life.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Silvas

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #11 on: February 01, 2018, 08:12:03 PM »
I've had the VERY similar OneAC unit for years.  Here's one currently listed:

https://www.ebay.com/itm/Oneac-Line-Viewer-103-LV103-with-hard-case-manual-and-cables-ESTATE-FIND/292388882808

Bri

I just made an offer for it and the guy accepted USD40  ;D ;D ;D ;D Thanks Brian for pointing me out to it.  I guess i'll have some fun with it.
Camilo Silva F.
Camilo Silva F. Mastering
Chia, Colombia

Brian Roth

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #12 on: February 01, 2018, 08:24:37 PM »
My OneAC box has come in handy a few times when tracking down funny noises in recording studios.

Bri

Brian Roth Technical Services
Salina Kansas, home of the best vinyl on the planet!

http://www.BrianRoth.com
recordingservicesandsupply.com/
www.qualityrecordpressings.com/
store.acousticsounds.com

Silvas

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #13 on: February 01, 2018, 08:59:51 PM »
My OneAC box has come in handy a few times when tracking down funny noises in recording studios.

Bri

Guess what ? I landed here : https://www.gearslutz.com/board/geekslutz-forum/502071-ac-power-noise-sniffer-60-hz-hum.html
Camilo Silva F.
Camilo Silva F. Mastering
Chia, Colombia

Brian Roth

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #14 on: February 01, 2018, 09:19:08 PM »
LOL!  That now reminds me how long I've had the unit.

Bri

Brian Roth Technical Services
Salina Kansas, home of the best vinyl on the planet!

http://www.BrianRoth.com
recordingservicesandsupply.com/
www.qualityrecordpressings.com/
store.acousticsounds.com

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #15 on: February 10, 2018, 06:25:37 AM »
I read an article on someone servicing tube amps and he had a standard light bulb in some weird configuration..

abbey road d enfer

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #16 on: February 10, 2018, 07:26:36 AM »
I read an article on someone servicing tube amps and he had a standard light bulb in some weird configuration..
It's a very common trick-of-the-trade. Wire the light bulb in series with the gear you want to soft-start. If the device is shorted, the bulb lights fully and limits the current to the value  determined by the bulb's power. If the gear is behaving correctly, the bulb will briefly light at start-up and then dim.
I have such a contraption at the ready, and not only for tube amps; last time I used it was on my portable PA on which I had replaced a shorted output device.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

JohnRoberts

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #17 on: February 10, 2018, 09:37:07 AM »
It's a very common trick-of-the-trade. Wire the light bulb in series with the gear you want to soft-start. If the device is shorted, the bulb lights fully and limits the current to the value  determined by the bulb's power. If the gear is behaving correctly, the bulb will briefly light at start-up and then dim.
I have such a contraption at the ready, and not only for tube amps; last time I used it was on my portable PA on which I had replaced a shorted output device.
Yup, often the light bulb was wired in series with a variac to help with amp repairs. Slowly bring the rails up until lamp does not light, then you can short across the bulb for full power testing.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...

Silvas

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #18 on: February 10, 2018, 10:52:50 AM »
The OneAC live viewer is here ! Seems like a fun gadget and quite useful for a tech-savvy obsessed with perfection mastering engineer like me. Coupled with some analysis software you can get an FFT of your AC line common and normal mode noise (depending on your software and sample rate) and you can also take a look at the quality of your AC including a THD readout (maybe useful for characterising AC inverters from UPS units and so ?)

I guess i can record the outputs at 192K on a three-track session on protools for long-term analysis too.  This was exactly what i envisioned on my original post.



I've had the VERY similar OneAC unit for years.  Here's one currently listed:

https://www.ebay.com/itm/Oneac-Line-Viewer-103-LV103-with-hard-case-manual-and-cables-ESTATE-FIND/292388882808

Bri


Again, thanks Brian for pointing me out to it.   :D:D:D:D:D:D
Camilo Silva F.
Camilo Silva F. Mastering
Chia, Colombia

trobbins

Re: 120VAC line to line-level for AC line analysis. Has anyone done it ?
« Reply #19 on: February 14, 2018, 06:35:20 AM »
Is this to be a tool to meet a purpose (ie. with specs or requirements of some kind related to steady signal magnitude or frequency or transient characteristics - and related to a detrimental performance of some equipment that might be affected by anything other than single frequency with constant amplitude mains) or to equipment that may generate detrimental signals?