Building a HD recording PC?
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Posted on Nov 28, 2006 03:43 am
jonno6766
Member Since: Nov 28, 2006
I have an interest in live multitrack recording. The limiting factor is enough dollars to make it happen. Over the past two years I've collected a few P4 computers and many sound cards. A few weeks ago I thought that maybe I could build a cheap HD recording PC using an array of sound cards with homemade balanced/unbalanced inputs that plug into an array of sound card's left/right: CD, AUX and TAD inputs. I'm not sure if there are GUI programmes that can be configured to record, route to effects, and sweep Eq. I suspect that some Linux platforms may be flexible enough but not sure of a programme that will do the rest. The balanced inputs are simple enough with TL082s (low power consumption), resisters, capacitors, RF chokes and include phantom power so I'll need to find 48volts from somewhere.
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Noize2uCzar of MidiAdministrator
Since: Apr 04, 2002
Nov 28, 2006 10:37 pm First off, are you running Windows or Linux? It sounds like your running Linux. If that is the case Zek will be the one to help you out there. Most run Windows and a few run Mac. zek is the only one running a succesfull Linux recording rig at the moment.
And I'll be kind of honest here. If you are assembling your own electronics to work into a sound card I will hope you have a good deal of experiance. And as well I hope you are starting with a fairly good quality card to begin with. As the cheap onboard sound cards will only result in poor audio quality no matter what you attach to them.
zekthedeadcowEat Spam before it eats YOU!!!Member
Since: May 11, 2002
Nov 29, 2006 03:11 pm sorry for taking so long... been taking possession of a house...
yes it's possible in linux (never did it myself) but requires a small and from the looks of it fairly simple hardware modification to the soundcards and creating an ALSA config file...and the soundcards have to be the same make and model...
It's known as the "El-Cheapo Howto"
www.geocities.com/dn_liit...El-cheapo-howto
The hardware mod should work in windows too... the trick with linux is that JACK will only load one driver per instance so all the cards should use the same drivers.
Nov 29, 2006 04:40 pm you are better off droppin' 100 bucks on a cheap soundcard with two preamps (usb)...you're wasting time and money, tryin' to go about it the hard way...MHO.
Nov 30, 2006 08:05 pm Thanks Noise and Zek,
I have access to XP or Linux although I'd like to use Linux FreeSpire due to it's simular appearance to XP. I may need to wait for the second version of FreeSpire when it's become stable enough. But it seems that Fedora is the way to go at this point.
The sound card mods are simple. The ALSA editing seems simple too. Making the balanced inputs is the worst of it but there are plenty of schmatics to work from. Not sure how the cards will cope if the phantom power is turned on if the system is live. I may need to tune the input resisters so it doesn't create any DC bias post op-amp or spikes.
What's the current pro thinking on Nyquest frequency theory with respect to 44.1 kHz. Are most sound cards digitally limited too 20 - 20,000 Hz so 22.05 kHz is not a problem?
Nov 30, 2006 11:11 pm you are correct, 'pros' often record at much higher samplerates for that reason (48khz for dvd, then there's 88.1, 96, 176.2, and 192khz) but you're perfectly ok to record at 44.1.
you're biggest problem is gonna be the soundcard's preamp, espically if you are using a condensor mic, phantom power and all.
Dec 01, 2006 09:16 am So if the crystal is suited to a higher frequency such as 48khz then will this overcome the cheap 44.1?
Are the preamps on the line and mic ins the same as the preamps on the CD, AUX and TAD inputs. If I'm using the CD, AUX and TAD with separate input amps then will the input preamp quality be resolved.
Dec 01, 2006 10:11 am don't get me wrong, 44.1k isn't necessarily the "cheap" part...that's the standard commercial audio cd sample rate....that's not the problem
there are no preamps on the line in, cd, aux, (and i'm gonna guess) not the TAD either...those are already at 'line level' a microphone puts out far less energy than a cd player's RCA line outputs, so it needa a preamp to get the weak 'mic level' up to 'line level'....
and all those line inputs you have would be fine (for all intense purposes) if you get a preamp in line before the input and after the microphone.
what exactly do you plan on recording? vocals? electronic music? guitars or drums even?
Noize2uCzar of MidiAdministrator
Since: Apr 04, 2002
Dec 01, 2006 05:46 pm Let me clear something up here. The frequency/sample rate you set your card to record at is for the sample rate at which the sound is taken. Meaning 192k gives you 192,000 samples per second of resolution. Making editing a much finer process and giving you much less data degrading as you edit your audio. Lower sample rates will give you much less resolution to edit at, meaning edits are not as finely processed and the audio will be easier to hear the degrading in. The audio itself on playback is not a huge difference in what hear. It takes a very practiced ear to hear it if at all.
Dec 03, 2006 05:14 am I'd have balanced mic inputs with gain trim pre line level inputs. Content is full band: drums, guitars, bass, keys, vocals and ambience. I'll be using condensor mics so phantom is required. I have schematics of balanced/unbalanced input gain circuits from pro consoles. The problem is knowing whether the line inputs can cope with spikes if the phantom is switched on when the system is live or if DC bias will give any grief either on the sound cards or in mixdown if the phantom is slightly offset if the resisters are unmatched or not tuneable.
I like a challenge but prefer knowing potential problems before proceeding.
I'm inclined to go for a minimum of 48k so it can be atleast compatible with DVD. If the crystal can be changed to accommodate higher resolution without hard or software problems then I'd consider that worth doing.
zekthedeadcowEat Spam before it eats YOU!!!Member
Since: May 11, 2002
Dec 04, 2006 07:08 am The main problem you're going to run into is that consumer soundcards suck. ...it's like running a neve into an answering machine.
Dec 04, 2006 07:38 pm Are there any 'consumer cards' that don't suck?
Dec 04, 2006 10:30 pm no.
Noize2uCzar of MidiAdministrator
Since: Apr 04, 2002
Dec 04, 2006 10:48 pm Not really. There are some two channel cards in the $100.00 range that don't suck though. And you can find those used for a reasonable price at some used gear stores and ebay.
Dec 05, 2006 06:04 am M-Audio makes a couple decent priced cards You can get a good card for $100 or less.
Dec 06, 2006 08:28 pm If the noise induced on sound cards is the result of switching from other devices such as drives, fans, power supply then theoretically, if these were sheilded individually and earthed to chassis (without shorts) and probably cooled then the output of the sound cards would have a better quality. I suppose this is why USB sound cards are external to overcome the noise within a PC case.
