Line output splitting for separate backup

[David Spearritt]

Wondering what approaches you guys take towards running a completely separate backup for critical live recordings.

My mic pres have only one analog output, so if this goes to the A/D and then the laptop, is there a high enough quality line splitter out there that allows a separate feed (split at the output of the mic pres) to go to an analog mixer and second stereo recorder for a true backup. The computer can glitch and crash while not affecting this second backup.

My little customised line mixer does not have inserts on it. How are you splitting for backups? Are Y cables OK?

[macleod]

hi, i set the ins and out on the rme totalmix software on the ff800 and then flash the settings to the unit. then i take the digital outs to adats.

that way if the connection to the computer is lost or even if i pull out the firewire connection the feed to the adat still works.

I guess it would be ideal if i had a ups on the ff800.

K

[d_fu]

I split digitally... Most of my ADs have two ADAT outs (used for SMUX 96k transfer), which deliver identical signals at 44 and 48k. One set of signals goes to a recording laptop, the other to a backup medium, either a second laptop, an old DA-88, or a standalone recorder (Fostex' VR800 is a brilliant lil' machine for the purpose, even if it's only 16/44)
.
Just bought a Fostex D160 for more than 8 tracks, though.

This is a touch less redundant than splitting the mic signal, but it is 100% safe from PC crashes. Perfect redundancy would require separate mics also.



Daniel

[d_fu]

Originally Posted by macleod

that way if the connection to the computer is lost or even if i pull out the firewire connection the feed to the adat still works.

Have you actually tested this? If the host PC crashes and reboots, you may temporarily lose the connection.

[aussie_techie]

line level signals dont suffer from the same limitation as mic signals so you can just use Y-Splits (assuming everything is balanced)
it is always a good idea to have power regulation for A/D converters, especially if you are splitting digitally. power anomalies that may not be enough to knock out a computer but can easily be enough to disrupt an audio clock

[sonare]

Originally Posted by David Spearritt

Wondering what approaches you guys take towards running a completely separate backup for critical live recordings.

I feed a redundant output from my Metric Halo boxes to an HD24. If the host laptop packs it in, the MH stuff keeps outputting normally-- a great feature of MH-- not to mention the 80-bit wide record engine!

Rich

[David Spearritt]

Interesting. For those splitting digitally or taking second outputs from A/D converters, don't you worry about losing continuity in that A/D processing?

[XLR]

I'm also interested in a good line level splitter!

Just bought an used 4-channel box, SBS DA-IT, but what I'm looking for is 8 ch or more.

[noamraz]

Hey,

My usual recordings are being backuped this way:
Preamp lineouts -> HD24
HD24 ADAT Outs -> Profire lightbridge (MAudio) -> Laptop

Most of the HD24 crashes doesnt affect it's AD nor the Digital output capability so it's quite a good low-cost solution.

Best regards, Noam.

[d_fu]

Originally Posted by David Spearritt

Interesting. For those splitting digitally or taking second outputs from A/D converters, don't you worry about losing continuity in that A/D processing?

I'd answer the question if I knew what you are referring to...

[locosoundman]

For those splitting digitally or taking second outputs from A/D converters, don't you worry about losing continuity in that A/D processing?

Splitting digitally bit me in the a** once - the AES card in my AD16 jiggled loose somehow and caused intermittent dropouts on the ADAT outputs - just a complete loss of data for milliseconds at a time. I still do it, but my stomach turns continuously until the gig is over.

line level signals dont suffer from the same limitation as mic signals so you can just use Y-Splits (assuming everything is balanced)

I am curious about using Y-splits and would be interested in hearing your experience:

What if there is an impedance mismatch between the two recorders? For instance, my AD16 has an input impedance of about 50k ohms and my HD24 has an input impedance of about 12k ohms? How does this effect the loading of the mic amp?

Also, if one leg has an intermittent connection, does it effect the other ?

[LX3]

The output stages of most mic pres (or any other line level device for that matter) have a very low output impedance, so you can feed it to multiple line inputs with different input impedances (usually 10k or more) and you won't notice any level changes.

It's not like y-splitting mic outputs to multiple mic pres. Mercifully.

As someone suggested, the main problem is finding a reliable way to do a y-split. It has to be reliable, as a short on either side will result in no signal getting to the other recorder. Can be done, but requires thought and engineering effort.

(and is even more of a problem now that many mic pres have their analog outs on a D-sub)

Best approach is to build a dedicated splitting box, with multiway connectors for inputs and outputs. Not cheap or straightforward.

You can also do it by using a solder-type patchbay as a glorified tag-strip.

[huub]

Well i'll tel you this: when recording nigel kennedy in poland, andy rose simply split the line level passively (same as y cable) to the main and backup recorder.. The guy who was going to mix the dvd (who works full time at abbey road) was fine with this..

I measured the loss of parrallelling once, it was about 0.1 dbu..
but I think this depends on impedance....

anyway: splitting line level is pretty safe and acceptable..

[David Spearritt]

Originally Posted by d_fu

I'd answer the question if I knew what you are referring to...

If two outputs are taken from the same A/D converter or audio interface, some people are saying this is a "backup". But what then happens if that A/D converter glitches or drops bits? Both recorders suffer.

I am hoping to use completely separate backup paths from the back of the mic amps. So two A/D converters, one multichannel in the DAW and one stereo in the second recorder (fed from analog mixer).

As Daniel has suggested, there's some interesting test results all of us could publish for mutual benefit.

While recording to your DAW, note whether the line/ADAT outputs glitch for the following:

1. Unplug the firewire connection at the audio interface
2. Shutdown the DAW off or stop it recording
3. Load up the DAW CPU, minimise/maximise windows, screensavers, browse internet, run Photoshop

[Testing123]

Originally Posted by David Spearritt

If two outputs are taken from the same A/D converter or audio interface, some people are saying this is a "backup". But what then happens if that A/D converter glitches or drops bits? Both recorders suffer.

Playing devil's advocate here - what if the mic preamp fails? What if a microphone fails? I guess we're assuming any problems will be in the digital domain for backup purposes. Probably true a large percentage of the time.

[macleod]

Originally Posted by d_fu

Have you actually tested this? If the host PC crashes and reboots, you may temporarily lose the connection.

hi, yes. if you flash the settings to the rme it retains the settings in stand alone mode so there is no errors etc. works very nice for me.

K

[David Spearritt]

Originally Posted by macleod

hi, yes. if you flash the settings to the rme it retains the settings in stand alone mode so there is no errors etc. works very nice for me.

K

But have you deliebrately taken the DAW down or unplugged the firewire cable DURING record? Are there any dopped bits or glitches in the changeover to stand alone mode>

[David Spearritt]

Originally Posted by Testing123

Playing devil's advocate here - what if the mic preamp fails? What if a microphone fails? I guess we're assuming any problems will be in the digital domain for backup purposes. Probably true a large percentage of the time.

Yes, the reason for the backup, is to cover the digital side of things. Mic amps and mics are so reliable its not necessary to back them up.

If millions of dollars are at stake like in the Three Tenors concerts, then you run parallel mics as well.

[sonare]

Originally Posted by David Spearritt

Interesting. For those splitting digitally or taking second outputs from A/D converters, don't you worry about losing continuity in that A/D processing?

For me the answer is no. The box is completely separate in every way and talks to the laptop/ext HDs via optical (no, not ADAT).

If the box feeding the HD24 packs it in that is a different and utterly tragic exception, but the probability is so low that I will address it only if there is budget for redundant mics etc.

Rich

[d_fu]

Originally Posted by David Spearritt

If two outputs are taken from the same A/D converter or audio interface, some people are saying this is a "backup". But what then happens if that A/D converter glitches or drops bits? Both recorders suffer.

I've never seen a standalone AD converter glitch or drop samples... An audio interface like the FF800 is a different subject. I wouldn't take my digital backup from an audio interface if real redundancy is required.

I am hoping to use completely separate backup paths from the back of the mic amps. So two A/D converters, one multichannel in the DAW and one stereo in the second recorder (fed from analog mixer).

An AD converter (or combined preamp/ADC) with parallel digital outputs should be just as good..

As Daniel has suggested, there's some interesting test results all of us could publish for mutual benefit.

Not quite what I was referring to. The point where I split is completely detached from the PC (as Rich pointed out, too). I'd also make sure to have the ADC run as Clock Master.

Originally Posted by macleod

hi, yes. if you flash the settings to the rme it retains the settings in stand alone mode so there is no errors etc. works very nice for me.

Don't be too sure. Stand alone mode is for switching the unit on without the PC attached to begin with. Unexpected loss of connection during PC-based operation may leave the unit in an undefined state and if and when the computer reboots, driver initialization may also cause short interruptions. Try it out before you trust an important recording to it.

Originally Posted by David Spearritt

If millions of dollars are at stake like in the Three Tenors concerts, then you run parallel mics as well.

And if there's an electricity "dropout", even that won't help...

Daniel

[David Spearritt]

Originally Posted by d_fu

Not quite what I was referring to. The point where I split is completely detached from the PC (as Rich pointed out, too). I'd also make sure to have the ADC run as Clock Master.

What device do you use Daniel?

[Plush]

There are several ways to do it. Mind you, we don't use laptop computers here for recording.

Digital console---Out AES and Out SPDIF to two separate recorders. Also Analog out of the digital board.

Analog console--analog Y cable is perfectly acceptable if made correctly. This goes to two recorders or two a/d's.

I've never seen or heard an a/d converter that is running on internal clock skip a beat.
With that in mind, don't most of your converters have provisions for sending out more than one signal?

The only time I've ever lost a program (a long time ago) was due to poorly set-up digital clock issues. It was pilot error and a learning experience.

(not counting eaten dat tapes of course) Who remembers DIC[K] dat?

[locosoundman]

I've never seen a standalone AD converter glitch or drop samples...

I've never seen or heard an a/d converter that is running on internal clock skip a beat.

See my post above - it refers to an Apogee AD16 running on internal clock. An improperly seated AES card was the culprit. Whether the card was not properly installed in the first place or it just jiggled loose after years of travel I do not know. I do know it worked fine for a long time and then randomly began having dropouts.

Mic amps and mics are so reliable its not necessary to back them up.

I have had channels on mic amps go bad - but thankfully not in the middle of something important. As far as mic's go - anyone ever have an M50 sizzle out?

And if there's an electricity "dropout", even that won't help...

But a UPS can save your assets.

The fact of the matter is something can go wrong at ANY point in the chain. It is a matter of minimising as much of the risk as you can and introducing redundancy just before the point you think is the most likely for something to go wrong. I continue to split from the Apogee for reasons of convenience (and possibly stubbornness).

Then I say a prayer...

[d_fu]

Originally Posted by locosoundman

I have had channels on mic amps go bad - but thankfully not in the middle of something important. As far as mic's go - anyone ever have an M50 sizzle out?

A 8-channel ADC of mine died minutes before a concert - luckily, I had a second unit (combined preamp/ADC) with me that I was able to hook up just in time. I don't recall a mic dying during show, though.

Daniel

[7rojo7]

I use a half normalled tt patch bay as a line splitter.

[Don S]

I've had success with the FireFace800. It sends any input (or mix of inputs) to any output. Both ADAT or analog signals get backed via the ADAT outputs. It has the advantage, as most pro gear, that it keeps a signal flowing as a stand alone unit. The computer can crash completely and your backup will be uneffected.

[macleod]

Originally Posted by David Spearritt

But have you deliebrately taken the DAW down or unplugged the firewire cable DURING record? Are there any dopped bits or glitches in the changeover to stand alone mode>

Hi Yes there is no difference when the firewire is pulled out or if the computer crashes.

I would not restart the computer during a recording when it has crashed as there is a risk it would mess things up for the backup.

K

[yrplace]

We have three systems, the first uses Aphex pres which have two separate analog output as well as multiple digital outs so feeding multiple machines is easy. We use a pair of Edak 90 pin connectors for each analog feed and the digital is converted to madi for long runs via fiberoptic cable.

The other two systems (ATI and OSA pres) have only a single out from the pres and we have simply multed those to the same pairs of EDAK 90 pin connectors so our cabling is the same. Works great with no noticeable degradation of the signal and without any risk that if one record deck fails we lose audio to the 2nd.

Mark

[oshearer]

This may be a silly question, but when referring to Y-cable splitting, what is the distinction between a "well engineered" Y-cable, and a poorly done one? How would one make sure that their split would be reliable and long-lasting? Thanks.

[aussie_techie]

same as with any cable make sure who ever is making it is doing a good job and useing decent cable and connectors.