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Author Topic: Laptop Playback cable  (Read 1113 times)

Tony Mamoh

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Laptop Playback cable
« on: July 28, 2017, 04:32:38 pm »

For those situations where one wants to use a laptop (with recorded music tracks)  as an input to a mixer; what is the preferred input type? Assuming a mic (XLR) input is the preferred input type; then I realize that one will need the appropriate cable/adaptor (mini TRS to XLR). However; if the gain optimization is such that a line level is more appropriate to use an the mixer input; then I would need a mini TRS to 1/4" TS cable.

So I will like to know which mixer input gives a better signal quality with playback from a laptop. I have deliberately excluded using a mixer USB input because that is not always available in some of the (older) mixers at my disposal.

Thanks!
« Last Edit: July 28, 2017, 05:16:45 pm by Tony Mamoh »
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Joel Mevis

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Re: Laptop Playback cable
« Reply #1 on: July 28, 2017, 04:41:11 pm »

Radial USB Pro DI. This is the best cleanest sound I have ever gotten.

Radial also makes a "stage bug" but the USB DI bypasses the laptop sound card. Its excellent I use it to run backing tracks every week.

I have always found 1/8 inch jacks to be troublesome after a while of using them the way you are describing. Or maybe its just the cables all went bad.

But the USB DI can get LOUD with out distortion.
« Last Edit: July 28, 2017, 04:48:53 pm by Joel Mevis »
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Mac Kerr

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Re: Laptop Playback cable
« Reply #2 on: July 28, 2017, 05:43:09 pm »

Most cost effective, Peavey USB-P. Balanced line level out on XLR, better audio than headphone jack, no drivers needed.

Mac
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Sammy Barr

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Re: Laptop Playback cable
« Reply #3 on: July 28, 2017, 06:02:55 pm »

Most cost effective, Peavey USB-P. Balanced line level out on XLR, better audio than headphone jack, no drivers needed.

THIS! Cheap and works great.
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Erik Jerde

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Re: Laptop Playback cable
« Reply #4 on: July 28, 2017, 06:07:51 pm »

Im not sure about current models, but older macs had a crosstalk problem between left and right in the built in headphone jack.  Not noticeable with a stereo track but very noticeable in a mono track + click situation.

I've used the radial usbpre and it's great, no drivers needed.  Output level knob and headphone jack for monitoring.

With Mac vouching for the peavy unit that ones gotta be solid too.
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Mac Kerr

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Re: Laptop Playback cable
« Reply #5 on: July 28, 2017, 08:31:15 pm »

Im not sure about current models, but older macs had a crosstalk problem between left and right in the built in headphone jack.  Not noticeable with a stereo track but very noticeable in a mono track + click situation.

Curiously I have tested this with my MacBook Pro and there is no crosstalk, however there is crosstalk with every Windows laptop I tried. This was an issue on the 4th of July fireworks in Boston this year. Fireworks vendor had all HP and Panasonic laptops that mixed L&R when playing back out of Audacity, my MBP did not. Headphone jack or USB interface same issue.

I own 3 of the Peaveys myself.

Mac
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Erik Jerde

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Re: Laptop Playback cable
« Reply #6 on: July 28, 2017, 08:42:09 pm »

Curiously I have tested this with my MacBook Pro and there is no crosstalk, however there is crosstalk with every Windows laptop I tried. This was an issue on the 4th of July fireworks in Boston this year. Fireworks vendor had all HP and Panasonic laptops that mixed L&R when playing back out of Audacity, my MBP did not. Headphone jack or USB interface same issue.

I own 3 of the Peaveys myself.

Mac

That's really interesting that it was regardless of the interface.  Which model MBP do you have?  A keys player I've worked with who does lots of tracks work has observed the crosstalk on multiple models but it goes away when using an external interface.
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Mac Kerr

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Re: Laptop Playback cable
« Reply #7 on: July 28, 2017, 10:22:20 pm »

That's really interesting that it was regardless of the interface.  Which model MBP do you have?  A keys player I've worked with who does lots of tracks work has observed the crosstalk on multiple models but it goes away when using an external interface.

I have a mid 2015 MBP, but I did not have crosstalk on my 2011 MBP either. It had been used for split track TC plus PGM, and I would have noticed. I was surprised that there was no setting on the HPs that would make the tracks isolated.

Mac
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Bill Koonce

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Re: Laptop Playback cable
« Reply #8 on: July 29, 2017, 08:16:58 pm »

Tony, if you're using older mixers, does that mean analog mixers too? I'd have two strategies: one for an analog signal path, another for a digital signal path. IJS

I do a regular gig where we must provide a 3.5mm TRS cable for whatever laptop the speaker might bring. The house supplies the gear, and I usually get a DI box like a Whirlwind IMP 2. What's important here is to have galvanic isolation, meaning a transformer between the unbalanced and balanced parts, and a ground lift to keep chassis grounds out of the equation. If the laptop is ever an unknown factor, this is the safest way I know for all-analog applications. If you need stereo, use 2 DI boxes. The same 3.5mm TRS to 2x1/4" TS cable that sums L + R channels w/ one DI will give you stereo w/ 2 DI boxes & 2 balanced lines.

When dealing with laptop stereo TRS outputs, look for a "line out" and use that instead of "headphone out" whenever possible. If it's your laptop, choose one with a line out, so you're better prepared. Also, if your mixer has a spare set of RCA inputs and the laptop is right there, you're not gaining anything by going to a balanced line for 3 feet. If a simple 3.5mm TRS to 2x unbalanced cable works, use it.

For all-digital, I like to use the Toslink optical interface, again for galvanic isolation at home. And that's the laptop that I'll bring, so if there's an AES3 input handy, I'll use a Hosa Toslink <--> AES3 box and keep it all in the digital domain whenever possible. This will vary with your gear; you may have better results using Dante if that's being used. Digital isn't going away, so thinking about how to make a digital link to digital gear makes sense to me.

I have a growing collection of devices that will function as USB DACs, and yes they'll work, and even if you're making some unnecessary D/A & A/D conversions, a good one will sound better than the headphone jack. But since this is a piece of powered gear, you might want to check to verify that the improvement in quality is worth the extra complexity.
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Niels Hempel

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Re: Laptop Playback cable
« Reply #9 on: July 30, 2017, 12:31:02 pm »

I am really happy using both the radial J+4 and the radial JDI Duplex for stereo sources.. Both have 3.5mm, rca, and 1/4".  The J+4 is active so you need a power source but it has a volume knob that is helpful. 

The passive JDI Duplex is a beast!  It is a bit more $$, but it isn't bad considering you can actually run two stereo sources through it (assuming you can balance the levels between the two),  it is linear from 10hz-40khz and has two Jensen trannies that seems to help with super hot/clipping signals (*chough* ...dj's). 



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Tim Weaver

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Re: Laptop Playback cable
« Reply #10 on: July 30, 2017, 01:37:18 pm »

The cheap route is a bsic cable.

http://www.zzounds.com/item--HOSHMXY?siid=177858&-cSx1QIVCA5pCh3RSAofEAQYBCABEgKs8PD_BwE=

If you use a mac or another apple device, this is likely all you'll need. Aplle has pretty decent audio outputs.

If you use something other than mac, I have noticed that the audio quality is sometimes questionable, but more often than not they have a ground buzz if the power supply is plugged in. On battery power they typically work fine, but plug it in and there's that old 60 cycle again.

If you work with a variety of devices, the USB DI is a wise investment.
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Jonathan Johnson

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Re: Laptop Playback cable
« Reply #11 on: August 01, 2017, 03:27:34 pm »

I like the Peavey USB-P that Mac mentioned. I have one myself. It uses a "class" driver that's built into every modern version of Windows and MacOS, so there's nothing to install. You just plug it in and it works (you might have to select it as the output device). Of course that might not work with mobile devices like tablets and phones -- in which case you're stuck with a 1/8" TRS output.

If 1/8" TRS is your output device, then the simplest way is to use a cable that splits it to 1/4" TS left and right channels and connect it to the line input of the mixer channel. It probably depends on the mixer (others will know more about this than I do and are welcome to correct me), but I think that the mic input goes through a preamp that the line input doesn't. So using the line input should give a "purer" signal. (Unless the mixer pads the line input and feeds it through the same preamp.) This is only recommended if the connecting cable is less than a couple meters long, as the unbalanced line may be subject to interference.

If you have to go a long distance, the better option is to use the 1/8" TRS to 1/4" TS cable into two DI channels (I recommend passive DI with transformer isolation/impedance matching and ground lift), and balanced XLR from the DI to the mic input of the mixer (with padding on the DI if necessary) or if your mixer has true balanced 1/4" line inputs, then balanced XLR from the DI to an XLR to 1/4" TRS adapter into the mixer's line input. Whatever you do, don't just plug both left and right outs into both input/thru jacks on a single-channel DI -- this can cause problems in some cases.
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Jean-Pierre Coetzee

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Re: Laptop Playback cable
« Reply #12 on: August 02, 2017, 10:58:36 am »

I like the Peavey USB-P that Mac mentioned. I have one myself. It uses a "class" driver that's built into every modern version of Windows and MacOS, so there's nothing to install. You just plug it in and it works (you might have to select it as the output device). Of course that might not work with mobile devices like tablets and phones -- in which case you're stuck with a 1/8" TRS output.

If 1/8" TRS is your output device, then the simplest way is to use a cable that splits it to 1/4" TS left and right channels and connect it to the line input of the mixer channel. It probably depends on the mixer (others will know more about this than I do and are welcome to correct me), but I think that the mic input goes through a preamp that the line input doesn't. So using the line input should give a "purer" signal. (Unless the mixer pads the line input and feeds it through the same preamp.) This is only recommended if the connecting cable is less than a couple meters long, as the unbalanced line may be subject to interference.

If you have to go a long distance, the better option is to use the 1/8" TRS to 1/4" TS cable into two DI channels (I recommend passive DI with transformer isolation/impedance matching and ground lift), and balanced XLR from the DI to the mic input of the mixer (with padding on the DI if necessary) or if your mixer has true balanced 1/4" line inputs, then balanced XLR from the DI to an XLR to 1/4" TRS adapter into the mixer's line input. Whatever you do, don't just plug both left and right outs into both input/thru jacks on a single-channel DI -- this can cause problems in some cases.

This, also don't use XLRs.

Apart from the mic input being through a HA it also has phantom power which the 1/4" inputs do not and phantom power kills electronics, most OP amps aren't  so happy receiving a 48V DC signal.
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Rob Spence

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Re: Laptop Playback cable
« Reply #13 on: August 02, 2017, 12:46:55 pm »

When I need to take inputs from an 1/8" I use a Radial SB-5.
Easy and not too expensive.

Good note above to the dangers of inadvertently putting phantom into someone's phone or laptop.


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Jonathan Johnson

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Re: Laptop Playback cable
« Reply #14 on: August 02, 2017, 12:57:29 pm »

This, also don't use XLRs.

Apart from the mic input being through a HA it also has phantom power which the 1/4" inputs do not and phantom power kills electronics, most OP amps aren't  so happy receiving a 48V DC signal.

At this risk of putting words in Mr. Coetzee's mouth, you shouldn't connect a laptop or other non-XLR device directly to the XLRs because they could be damaged by the phantom power. In the case of a DI box, you *can* connect the XLR output of the DI box to the XLR input of the mixer, even with phantom power, because that is what DI boxes are designed to do.

Just wanted to (hopefully) clarify that, because I think I misunderstood Mr. Coetzee's statement the first time I read it.
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Bill Koonce

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Re: Laptop Playback cable
« Reply #15 on: August 02, 2017, 10:33:58 pm »

IME most mic preamps do have the option to turn off phantom power. For those that don't, using a transformer for impedance matching will ensure that no DC passes to the other transformer windings, or on to the laptop.

Since most unbalanced connections are high impedance, the reason to use some sort of "black box" between hi-Z and XLR is for impedance matching, as well as a balun. You wouldn't need a box to feed a pair of hi-Z 1/4" TS or RCA input jacks, and most mixers I use do have one or two of these. For headphone outputs, the impedance may an unknown.

The main reason to convert to a balanced line with STP cabling is for long cable runs. If the laptop is 100' away from the mixer, then you need the STP cable for common mode rejection. Whether the STP cable is terminated with XLR or (1/4") TRS is immaterial. If the distance is 3', then using STP is not strictly necessary.
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Mac Kerr

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Re: Laptop Playback cable
« Reply #16 on: August 02, 2017, 10:41:21 pm »

This, also don't use XLRs.

Apart from the mic input being through a HA it also has phantom power which the 1/4" inputs do not and phantom power kills electronics, most OP amps aren't  so happy receiving a 48V DC signal.

The Peavey USB-P is transformer isolated. It won't be damaged by phantom power.

Mac
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Jonathan Johnson

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Re: Laptop Playback cable
« Reply #17 on: August 03, 2017, 06:10:15 pm »

IME most mic preamps do have the option to turn off phantom power. For those that don't, using a transformer for impedance matching will ensure that no DC passes to the other transformer windings, or on to the laptop.

Many mixers have only one switch for the phantom power on all XLR inputs. So if you need to power one thing with phantom power, you're delivering phantom to every device that's connected to an XLR input. Transformer isolation to the rescue. Or you turn off phantom at the mixer and use an inline phantom power adapter.

Quote
Since most unbalanced connections are high impedance, the reason to use some sort of "black box" between hi-Z and XLR is for impedance matching, as well as a balun. You wouldn't need a box to feed a pair of hi-Z 1/4" TS or RCA input jacks, and most mixers I use do have one or two of these. For headphone outputs, the impedance may an unknown.

The main reason to convert to a balanced line with STP cabling is for long cable runs. If the laptop is 100' away from the mixer, then you need the STP cable for common mode rejection. Whether the STP cable is terminated with XLR or (1/4") TRS is immaterial. If the distance is 3', then using STP is not strictly necessary.

Good advice.

(STP=Shielded Twisted Pair)
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Bill Koonce

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Re: Laptop Playback cable
« Reply #18 on: August 03, 2017, 07:49:41 pm »

For anyone with an "all or nothing" phantom switch on their mixer:

http://repforums.prosoundweb.com/index.php?topic=20612.0
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Jean-Pierre Coetzee

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Re: Laptop Playback cable
« Reply #19 on: August 06, 2017, 12:02:05 am »

At this risk of putting words in Mr. Coetzee's mouth, you shouldn't connect a laptop or other non-XLR device directly to the XLRs because they could be damaged by the phantom power. In the case of a DI box, you *can* connect the XLR output of the DI box to the XLR input of the mixer, even with phantom power, because that is what DI boxes are designed to do.

Just wanted to (hopefully) clarify that, because I think I misunderstood Mr. Coetzee's statement the first time I read it.

This is what I meant... Sorry for the confusion.
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