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Posted By: Will_3 Best way to connect PC to PA ? - 07/05/09 09:08 PM
Best way to connect PC to PA ?

I'm wondering how you guys connect your PC to your PA system?

I've made up a rig of adaptors and cables to go from the small connector on the sound card to a "pair" of standard quarter inch jacks... and plugging those into my Amp... but I'm getting a lot of noise along with the sound.

And... is the Sound Out connector on a typical PC sound card a 1/8 or 3/32 stereo female jack?

And the ultimate question... What is the best way to get professional quality sound out of your PC for a live rehearsal or performance?

Thanks for any help.
Posted By: Mac Re: Best way to connect PC to PA ? - 07/05/09 09:21 PM
Quote:

Best way to connect PC to PA ?

I'm wondering how you guys connect your PC to your PA system?

I've made up a rig of adaptors and cables to go from the small connector on the sound card to a "pair" of standard quarter inch jacks... and plugging those into my Amp... but I'm getting a lot of noise along with the sound.





The earphone jack on the standard laptop is electrically equivalent to an unbalanced stereo line output. Use of adaptors to break the signal out to L and R channels and then into any set of Line Level inputs on your PA will yield a very good result. (TIP: When doing this, make sure that the software mixer of your laptop has the Master and Wav, Software MIDI synth, outputs turned all the way up! This will drive the line the hardest, which is what we need here, for lowest signal to noise ratio and fullest sound. Get your volume level at the PA with the hardware fader.)

Quote:

And... is the Sound Out connector on a typical PC sound card a 1/8 or 3/32 stereo female jack?




Actually, most of them today are likely to be metric, but the 1/8" size will usually work.

Quote:

And the ultimate question... What is the best way to get professional quality sound out of your PC for a live rehearsal or performance?

Thanks for any help.




If your laptop is fairly new, there really is not a good enough advantage to buying an aftermarket soundcard for playback of programs like BIAB. This is because today's laptops are shipping with very good D-A output converters in them due to the customer demands to watch (and hear) multimedia.

*ANy noise you experience is likely due to an AC GROUND LOOP. Use of a Radio Shack Ground Loop Isolator between laptop output and PA will safely eliminate that noise. Less than $20US


--Mac
Posted By: Ryszard Re: Best way to connect PC to PA ? - 07/06/09 12:22 AM
If you're using a laptop the ground loop is pretty much a given. But you are talking about a PC sound card.

Another potential source of hum twixt PC and PA is cheap audio cables. I had a nasty buzz coming from my DAW into my studio system until I trashed several 22-gauge Y-cords and multiple adapters for heavily-shielded brand-name home-theater grade AV cables. No more electrical noise. (And they look really cool!)

A surge protector with EMI/RFI filtering is a good idea, too, to keep hum from coming in on the AC line.

R.
Posted By: Jazzman Re: Best way to connect PC to PA ? - 07/06/09 10:14 AM
Hi Will,

Lots of great advice above which you need to use

When all this is done make sure that before each time you connect up you clean all jacks as they get smeared up with general handling (Perspiration/grime) and can bridge the seperators and also cause hum

A clean cloth and occaisionally an electrical contact cleaner fluid followed by a dry cloth wipe over works best
jazzman
Posted By: David Walker Re: Best way to connect PC to PA ? - 07/06/09 06:04 PM
Try buying a two prong power cable converter that eliminates the ground wire. I have a older laptop which I have connected to a Peavy KB300 watt Amp, equivillant to a PA System. When I first started using it as a stand-alone system, I got line noise. I went to this forum a got a suggestion for a fix from a user and it works great. The fix cost about $2.00.
Posted By: Notes Norton Re: Best way to connect PC to PA ? - 07/07/09 01:42 PM
I use a USB to Audio interface. They are reasonably priced, the bandwidth is better than the audio jack on the sound card (higher fidelity), there is none of that loose connection static you get if you accidentally touch the audio jack, and I've never had a hum or ground loop issue with it.

I have a couple of different Edirol models. The low-end UA-1A works fine. I think that one has been discontinued, but there is probably another low priced alternative.

Notes
Posted By: Lawrie Re: Best way to connect PC to PA ? - 07/08/09 01:26 AM
G'day Notes,
Quote:

I use a USB to Audio interface. <snip> ...and I've never had a hum or ground loop issue with it.




Thant's a very good and interesting point. I thought about it for a moment then I remembered: the USB interface is a current loop - NO ground reference, therefore (probably) no ground connection thus no ground (or earth) loop therefore no interference from it.

A little more expensive than a ground lift/disconnection but potentially safer...
Posted By: Ryszard Re: Best way to connect PC to PA ? - 07/08/09 02:22 AM
Quote:

I use a USB to Audio interface . . . and I've never had a hum or ground loop issue with it.

Notes




I had a bad hum in my portable system, which was comprised of a Compaq laptop and a TASCAM US-224 Audio/MIDI USB interface, which wouldn't go away until I used the two-prong adapter hack, so USB can't be the entire answer (unless I completely misunderstand the issue, which seems to be happening a lot lately . . . ) Never had it in a desktop except for the cheap cords I mentioned in my original post.

R.
Posted By: Lawrie Re: Best way to connect PC to PA ? - 07/08/09 03:19 AM
G'day Rich,
I went and did a little more reading... I was mistaken, USB isn't actually a true current loop signal, it is an Asynchronous an/or Isochronous differential NRZI (Non Return To Zero Interface) encoding system using voltage reference between the D+ and D- wires. Now, while there is no actual ground reference in the data signal, the Data lines are tied to voltage sources that are referenced to "ground". If this "ground" is tied to the external ground somehow, then a ground loop is still possible, in a round bout fashion.

In addition, there is a 5V and ground extended up the USB cable for powering downstream devices.

So much for gettin' all excited there...
Posted By: DrDUBose Re: Best way to connect PC to PA ? - 07/10/09 12:28 PM
Another way around AC noise is to run a laptop from batteries only. You need backups that are charged and ready to rock. That got old, and I got a Radial I/O box that accepts multiple L/R lead lines and outputs L/R balanced signals with pad boost options and ground lift button. It's the PRO AV2 box, but it sounds like there are cheaper options. This costs around a $100 as I recall, and has the options of flexible source input connectors inluding 1/8th" 1/4" mono and stereo. It's simple and is very quiet.
Posted By: Notes Norton Re: Best way to connect PC to PA ? - 07/10/09 07:12 PM
I also hook everything on stage to one outlet and I put a TrippLite power conditioner between the wall outlet and all my gear.

The power conditioner keeps the spikes and the voltage sags out of my equipment, and makes them all last longer.

Also, I play one-nighters, sometimes in places with less than ideal AC voltage supply and I've never had a ground loop problem. The only hum I've ever gotten is the mild hum from stage lighting from time to time. And it's so low that it is easy to ignore.

Notes
Posted By: Mac Re: Best way to connect PC to PA ? - 07/10/09 07:35 PM
That Tripplite can suppress transient surges and the like, provided the internal MOVs aren't worn out, but it won't do a thing to help with brownouts. Likely doesn't have to, either.


--Mac
Posted By: Ryszard Re: Best way to connect PC to PA ? - 07/10/09 09:33 PM
Yeh - a good isolating transformer with a brick-wall surge suppressor and an uninterruptible power supply, that's the ticket. Belt, suspenders, staples, superglue, mebbe some rivets . . . da whole wazoo. Shouldn't run ya more than a couple grand. Oh, wait, and a generator, just in case. Yeh.
Posted By: Mac Re: Best way to connect PC to PA ? - 07/11/09 01:16 AM
16 bux for the Radio Shack Audio Isolation Transformer will do the trick nicely enough for any laptop and PA out there.


--Mac
Posted By: Notes Norton Re: Best way to connect PC to PA ? - 07/11/09 12:03 PM
If I remember my AC theory (it's been years since I went to college), a transformer resists changes in voltage, both dips and surges will be held steady, as long as they are of short duration.

The info that came with the Power Conditioner says both transient dips and surges will be suppressed. According to Tripp Lite, "Extends the useful life of connected equipment by providing optimum voltage conditions for enhanced efficiency and cooler internal operating temperatures. Reliable transformer-based voltage correction circuits maintain 120V nominal output during voltage fluctuations between 89 and 147V."

I would love to bring a UPS, but the size (and weight) needed for the power amp and everything else is just too excessive.

But I do think the Power Conditioner is worth it's weight in gold.

My gear lasts a long time, when the AC or ice machine kicks in I don't get that short dimming of the lights, and unlike a UPS, I still get a sine wave AC - which I am sure the audio gear likes better.

Notes
Posted By: justthesaxman Re: Best way to connect PC to PA ? - 05/14/16 12:48 PM
I am running a Asus laptop x7515 to a Sanson expedition 150 PA. The lap top has Bluetooth and what I want to do is get some sort of monitor/mic. If I could use a Bluetooth headset like this-http://www.staples.ca/en/Blueparrott-B350-XT-Bluetooth-Headset/product_1678678_2-CA_1_20001 I could eliminate a microphone and stand I had planned to get for introducing my songs. The ear piece could be my monitor as well ?
Posted By: AudioTrack Re: Best way to connect PC to PA ? - 05/14/16 08:55 PM
justthesaxman

This is a good question, but probably best placed in a new thread, as it deals with something slightly more unique (bluetooth), and resurrecting a 6 or 7 year old thread mightn't be the best place to get all of the answers you could achieve.

If you wish, feel free to start a new thread on the bluetooth setup you're looking for.

Trev
Posted By: rich in ca Re: Best way to connect PC to PA ? - 05/15/16 03:06 PM
Hey Bob,

Good points that I also agree with...Power Conditioners solve many issues, and I always have them in my rack equipment. You never know what kind of power you are plugging into away from your studio or home.

Additionally, there is another product I have used for audio signals called the "Hum Eliminator" by EBTECH, made in the USA. These have worked well for me in many situations, especially when taking line outputs from various amplifiers or devices. The units use smart jacks that auto convert between balanced and unbalanced lines, have no power requirements and come in two channel (two-in, two-out)TRS, 2 channel TRS/XLR, and single space 8 channel rack mount TRS and XLR units. Most of the music stores carry these products.
Posted By: Matt Finley Re: Best way to connect PC to PA ? - 05/15/16 03:56 PM
I've used the Ebtech hum eliminator, the TripLite AC filter, and/or the Radio Shack isolation RCA cable as needed.

The one thing I WON'T do is connect a laptop to a PA using a 1/8" (or metric) headphone jack. Way too much potential for terrible, sudden noise.
Posted By: rich in ca Re: Best way to connect PC to PA ? - 05/16/16 01:34 AM
Good point Matt. I should have (clarified in my case) from my desk top or lap top systems, for that matter, I use Firewire to connect to either my Edirol or Presonus units. Plus, the units are in an environment (within a rack roll-around case), that don't expose any cables other than a power cable and heavy duty signal cables to the exterior of the case. In addition to the audio (TRS/XLR) distribution, they all go through a patch panel (studio or mobile).

If someone really does need to use the mini-jack audio out from a lap top, then I recommend they use a cable with a mini-jack on one end and TRS, XLR or ? at the other. And, tape/secure the mini-jack at the laptop to help prevent it coming loose. Mini-plug adapters (e.g, non-cable), in my opinion put too much strain on an already fragile laptop connector.

Richard
Posted By: westom Re: Best way to connect PC to PA ? - 05/25/16 06:53 PM
Originally Posted By: Will_3
Best way to connect PC to PA ?

Mechanical considerations are trivial (ie 1/8" or 3/32"). Critical is connecting to some other system without knowing its electrical nature.

Another noted unbalanced signals. Critical especially if a PA's safety ground is unknown - or worse missing.

Use galvanic isolation when connecting to an unknown system. This not only eliminates ground loops (ie hum). It also protects computer hardware.

No surge protector even claims to protect from noise or those potentially destructive anomalies. View its numbers. Near zero noise protection is virtually no noise protection.
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