Lexicon mpx100 and S/PDIF

[keny]

I am trying to hook up a Lexicon MPX100 to my 001. I get occasional pops, and I'm wondering what's causing this? My session is 24 bit 48K and the MPX is 24 bit 44.1K. Should that be causing this?

Any Help is apreciutated,
Keny

[thepontif]

Yes. The session should match the sample rate of the MPX. You may also want to set the PTLE sync to S/PDIF (Setups>Hardware). Not sure though. Pops and clicks is your answer. If the S/PDIF in is clean with internal sync, leave it there.
-Mike Pope

[IOP Drummer]

When hooking two or more devices up digitally, you must have one clock master only. Usually in PT setups, PT is always the master. Almost all digital devices with digital Inputs give you the option to clock to them. You need to clock your Lexicon to it's digital input.

[keny]

I opened a session in 44.1 and it worked with no pops. Whoppee! Anyways I'm still going to spring for the mpx 500, Because It has a 48K setting.

The mpx100 was owned by a friend of mine

Thanks Mike

Keny

[merwin]

Keny:

Say, why do you want to record at 48K anyway? You'll just have to go through a nasty sample rate conversion stage if you want to go digitally to CD. Of course, if you're planning on mastering analog, then there's no problem recording at the higher rate, but I wonder if you're doing that or not.

Michael Erwin
Synthtank Studio
http://www.Synthtank.com

[keny]

merwin,

I'm just trying to get the highest resolution possible, to get more headroom.
I'll try to find some info on the different frequencies. I'm pretty sure that 48K Sampling allows 24Khz tones, which may be beneficial when working with effects that produce harmonics at the higher frequencies.

I've got this obnoxious book that I'm reading:
Curtis Roads, The computer Music Tutorial.
It may reveal the answers.

I also just purchased the mpx 500 so I should have no more worries.

Keny

[thepontif]

Not to be smart ass...but if your name isn't Rover, you can't hear above 20k. There is an issue with aliasing at half of the sample rate but even at a SR of 44.1k that's 22.05k which is above the range of humans. Some folks say it still makes a difference, but I believe going from 16 to 24 bit is a WAY more significant leap. 48k really probably isn't worth the hassles. My opinion...
-Mike Pope

[merwin]

Keny:

>> I'm just trying to get the highest
>> resolution possible, to get more headroom.

Okay, couple of problems here. First of all, headroom and sampling rate have nothing to do with each other. Headroom is the amount of gain you have left before clipping a signal. It is measured in dB. Sampling rate is the number of samples per second in a digital signal, measured in Hz or kHz.

If you record your session at 48K and then attempt to go direct to a CD, you'll have to sample rate convert your mixdown from 48 to 44.1 kHz. Not only will you lose all those high frequencies you think you're preserving at 48K, but you'll also introduce sonic artifacts caused by the sample rate conversion.

Secondly, in a demo/project room type situation, which is where 90% of Digi001 systems are found, I can assure you there ain't much of anything up there between 22.05 and 24 kHz. Certainly not enough to justify the sample rate conversion stage that will ultimately need to happen.

And don't kid yourself into thinking your effects processor is adding frequencies up that high. For most studio effects, the spectral makeup of the wet signal is closely correlated with the dry signal. If the original signal doesn't have spectral content up there, the MPX isn't going to add any. Besides, effects like reverb, chorus and delay often sound much better (warmer and more natural) when bandlimited from 8 to 12 kHz.

As I mentioned in an earlier post, if you're planning on mixing down to DAT at 48k and taking that to an analog mastering house for CD prep, then you've got no problems. Not many of us are lucky enough to afford that type of thing on all of our demo tracks, though. <g>

You're doing a good thing by reading the CMT by Roads. It's one of the bibles of the digital audio field and should explain in more rigorous terms the concepts I've talked about in this post. Good luck with it and keep reading the DUC.

Regards,


Michael Erwin
Synthtank Studio
http://www.Synthtank.com

[keny]

merwin,

Thanks for the insight,

I may consider that, But mainly, i am recording like that because I can.

Anyways, Here's my setup.

Digi 001 running the buggy LE5.1
Windows 98 1GHz P3 processor / Cusl2 M/b
3 7200 Rpm WD hard Drives
Alesis AI3, making the studio 16tracks
A new mpx 500
DBX 576
Yamaha NS10 Monitors
Vintage Dynaco A25 Monitors
Allen & Heath Mixer
a couple Mackie Mixers
2 Tascam DA38s
DA30 MkII

A Drum Isolation Booth, With a Big Ass 3X8 Glass window

Mics:
AKG 414 ULS
2 Sm 81's
AKG D112
A bunch of 57's

As you can see, This is not a demo studio but just a investment to develop an expertise in PRO Tools to justify buying a full blown TDM system

Regards,
Keny

[bstaley]

keny, I have to second what merwin is saying. If the ultimate destination of your songs is a 16 bit 44.1khz CD, then record at 24bit, 44.1khz. The difference between 24 and 16 bit is much more than 44.1-48k. You WILL lose quality converting from 48-44.1 unless you are going to a super high end mastering house.

I have the Lexicon mpx-1 and it only does 44.1k. It doesn't matter because that's all I would record at anyway.

Just my $.02