laptop connection to mixer

[ange]

I need to connect my laptop to a mixer for the school show. I know you recommend an external sound card, but funds are not available to get one. What is the next best way?? I tried the other day using a 1/4" balanced cable into one of the channels. It was ok for the music play list, but extremely low for the sound effects. I constantly had to play with the control. And yes I did take all the sound effect files up in volume in the program. When I connected the laptop as a tape player to the sound board, of course every thing was fine, except I didnot want to play with the speaker controls all the time and the mics. Any info you can give me is appreciated. And donot get too techinical, I am a newbie with the program and only on my second show with the sound system.

[Mike Daniell]

The simplest solution is to plug a stereo lead into the headphone socket on the laptop, and feed the two outputs into two channels on your mixer. Your headphone socket on the laptop is probably a 1/8" (3.5mm) socket, so you will need a lead with a 1/8" (3.5mm) stereo plug at one end, and at the other end of the two leads either a 1/4" (6.3mm) plug mono or an RCA plug. I mention the RCA plug as it seems easier to find a 1/8" stereo to separate RCA's (eg see 6-Ft. Gold Series Phono-to-1/8" Y-Adapter). For 1/4" connections into your mixer you can then use RCA to 1/4" mono adaptors (eg see Gold-Plated Phono-to-Mono Adapter. I wouldn't worry too much using 'gold plated' components - the cheaper components without gold plating will usually be fine.

You mentioned using a 'balanced cable into one of the channels'. Your laptop output will not be balanced, so if you are sending the left and right channels from your laptop down the two signal lines of a balanced lead into one balanced input socket of your mixer (using a 'stereo' 1/4" TRS plug) then this would explain the very low levels. The 'tape player' inputs on your mixer will (I expect) be unbalanced, which is why you get good levels using the 'tape player' inputs. (I will explain more about the balanced/unbalanced connections if you wish, but you said you didn't want to get too technical.)

So make sure the stereo output from your laptop is fed to two channels on your mixer, with the left output going to the first of these channels and the right output to the second of these channels.

[ange]

Thank you. I will try it. But I do have another question. Does the external sound card help?? I was reading some of the other questions and they mention them. I know some are several hundred dollars, but I seen some- like a 24 bit from creative lab for $80. Will this help improve the sound effect files??

[Theatre III Sound]

The simplest solution is to plug a stereo lead into the headphone socket on the laptop, and feed the two outputs into two channels on your mixer. Your headphone socket on the laptop is probably a 1/8" (3.5mm) socket, so you will need a lead with a 1/8" (3.5mm) stereo plug at one end, and at the other end of the two leads either a 1/4" (6.3mm) plug mono or an RCA plug. I mention the RCA plug as it seems easier to find a 1/8" stereo to separate RCA's (eg see 6-Ft. Gold Series Phono-to-1/8" Y-Adapter). For 1/4" connections into your mixer you can then use RCA to 1/4" mono adaptors (eg see Gold-Plated Phono-to-Mono Adapter. I wouldn't worry too much using 'gold plated' components - the cheaper components without gold plating will usually be fine.

I have connected a laptop to a mixer in this manner and it seemed to work OK, but I'm curious about impedance/level matching of the headphone output of the laptop to the mixer's inputs. I've tried to research this but haven't found any info on what the typical sound card headphone circuit looks like. Would anyone in this forum know? Also, what about the physical volume control found on most laptops (at least older ones), i.e. how should that be set? I've always set it to max and adjusted the trim controls on the mixer channels.

Bruce

[Austin R]

I have used a couple of different notebooks feeding the headphone output into, either, two mono channels or one stereo channel on our mixer using the connectors Mike suggests. This worked fine. We have since upgraded to a Firewire external interface to take advantage of the added channel flexibility.

Given that your playlist cue(s) played at an acceptable level but your sound effects did not, is it possible that your source material for the effects is simply recorded at lower levels? See the following extract from the programme's help file under "Miscellaneous - Preparing Sound Files":


If your software provides the facility, you may find it beneficial to maximise the level (GoldWave provides this facility under Effects / Volume / Maximise). Maximising the level will not cause clipping, but if the sound file was recorded at a very low level you will not get a good quality sound, even with maximising. Generally speaking, maximising the level of the sound file provides you with the most flexibility as you do not have to pump up the level on the sound desk just to make a low-level sound file sufficiently loud.

Austin

[Mike Daniell]

Thank you. I will try it. But I do have another question. Does the external sound card help?? I was reading some of the other questions and they mention them. I know some are several hundred dollars, but I seen some- like a 24 bit from creative lab for $80. Will this help improve the sound effect files??

An external sound card is no guarantee of better quality as it depends on what sound card you get and what built-in card or chip it is replacing. Generally speaking, you get what you pay for. Although an $80 card from Creative Labs may work OK I do not recommend anything from Creative Labs. This is mainly because you have to set a particular audio driver option in SCS, and select your speakers in a particular way, and you may also need to change some default settings in the sound card's control panel. No other manufacturer's cards give as much trouble.

With more professional cards or modules you usually have the option to select an output level of +4dB, which is significantly higher than the -10dB output provided by domestic cards. This extra level can help reduce hum. Some external modules also provide balanced outputs.

My recommendation to you for your school show is to start with the cable connections I mentioned in my first reply, and maximise if necessary your files as suggested by Austin. If you're still not happy with what you hear, let us know what still needs attention.

(Corrected 5 April 2008: previously mentioned outputs levels of +10dB and -4dB instead of +4dB and -10dB.)

[Mike Daniell]

... I'm curious about impedance/level matching of the headphone output of the laptop to the mixer's inputs. I've tried to research this but haven't found any info on what the typical sound card headphone circuit looks like. Would anyone in this forum know? Also, what about the physical volume control found on most laptops (at least older ones), i.e. how should that be set? I've always set it to max and adjusted the trim controls on the mixer channels.

Bruce

Can't say for sure, Bruce, but I've always assumed the headphone output is a line-level output, but subject to attenuation from the PC's volume control. So connecting the headphone output to the line inputs on a sound board should be OK - but I'm not an electronics expert so I'm willing to be corrected!

Regarding the setting of the physical volume control on the laptop, that should be set to max. This gives the greatest signal-to-noise ratio.

[Theatre III Sound]

I finally found a reference that states the output level(s) for a PC sound card. It's a document titled "PC 2001 System Design Guide" produced jointly by Intel and Microsoft. There appear to be two standards depending on the codec chip's supply voltage: Full-scale line (headphone) output is 1.0Vrms unless the supply voltage is 3.3V or less, in which case it's 0.7Vrms. I'm guessing that laptop on-board sound chips fall in the latter category.

Assuming this spec is followed by the manufacturers, this makes me feel a little better about plugging a laptop's (stereo) headphone output into a couple of mixer channels. And as Mike said, you probably only get full-scale output with the volume control all the way up. Still, for this and other reasons (like more than 2 channels), I'd prefer an external interface, but in a pinch, the on-board audio via the headphone jack will do.

Bruce

[jkowtko]

I've done this many, many times. The line levels coming from the headphone jacks are fine (at least on my Dell laptops). I use Hosa CMP-153 or CMP-159 for the cable. Just be sure to turn up the volumes on the audio control panel .

-- John

[ange]

I am just making sure you are referencing the audio levels on the laptop and in the scs program need to be turned up.
Is this right?

[jkowtko]

yes. I once forgot to turn up the audio volume on the laptop and sat there for 10 minutes trying to figure out what was wrong with the input channel on the mixer, until I remember to check the PC volume control (both WAV volume as well as main Volume). I think the SCS master volume and the audio main volume are linked, but check them both in any case.

Also pre-test the volume with headphones if you want. Get them nice and loud in your ears, and that should give you a good mid-level volume going into the board. You can raise the volume on the PC more from there. I've run it at max and it works just fine with no apparent clipping. Obviously trim it out on the board input channel.

But remember -- use a Y cable that splits the stereo headphone output into two mono 1/4" jacks, and use the two jacks going into the board to get L and R separately ... I tried once using a stereo-to-mono converter and it didn't work so well (was either way too loud or way too quiet).

-- John

[ange]

Thank you to everyone. I got the right adapters for my cable, plugged it into at last slider that has a stereo hook and and great sound. Thanks to all.

[ange]

The show went off without a hitch. I love the program. THanks to everyone for the information and help. :