The No.1 Website for Pro Audio
ISA 428 levels to 828mk2
Old 16th July 2005
  #1
Gear Head
 

ISA 428 levels to 828mk2

Just wondering what sort of levels anyone gets out of this pre to theyre converters.

As far as the VU meters go when i track kick and snare they barely move when im getting the correct level to my 828mk2.

When tracking guitars it gets up to about halfway at maximum.

There seems to be no way to calibrate the 828 input level.

Am i doing something wrong?
Old 16th July 2005
  #2
Lives for gear
 
brianroth's Avatar
 

Several things are going on here.

First of all, one thing I dislike about MOTU interfaces is the lack of I/O analog trimmer controls. That makes them a bit of a PITA to properly interface.

Secondly, you're comparing apples to oranges between the mechanical VU meters on the Focusrite and the electronic metering on the MOTU. A mechanical meter has a comparatively slow response to fast signals with lots of transient content, such as drums. The electronic meters on the MOTU are peak responding, so they "see" fast signals that barely get a mechanical meter off the resting spot.

Third, the MOTU interfaces have inputs which appear to be too "sensitive". In every case I've seen, they appear to need to be padded to properly work with any analog signal source, be it a Studer recorder or in this case, your mic preamps.

Bri
Old 16th July 2005
  #3
Lives for gear
 
5down1up's Avatar
 

nothin more to add

vu = sloooooooooooooooow
peak = fast

when the vu goes half the way up when doing gits , guess they are distorted

Old 16th July 2005
  #4
Gear Head
 

Thanks

Do you think it would be a good idea to get some sort of pad between the outputs of the isa to the input of the motu?
Old 16th July 2005
  #5
Lives for gear
 
brianroth's Avatar
 

I'll be figuring out some sort of padding between the Studer A-80 outputs and MOTU inputs at Trent Bell's studio here.

I just wish MOTU hadn't cheaped out by eliminating analog input trim pots.

Bri
Old 16th July 2005
  #6
Gear Head
 

Yeah its a shame that they dont have them isnt it.

I may have to look into some sort of padding then, any recommendations?

Thanks

Jonny
Old 17th July 2005
  #7
Lives for gear
 
5down1up's Avatar
 

ATTY
Old 17th July 2005
  #8
Lives for gear
 
joaquin's Avatar
 

Quote:
Originally Posted by Bandit666
As far as the VU meters go when i track kick and snare they barely move when im getting the correct level to my 828mk2.
The meters on the 428 are peak...no VU!!
Old 17th July 2005
  #9
Lives for gear
 
brianroth's Avatar
 

Quote:
Originally Posted by Bandit666
Yeah its a shame that they dont have them isnt it.

I may have to look into some sort of padding then, any recommendations?

Thanks

Jonny
Will you always be coming from a balanced signal source? In Trent's case, his sources are balanced, so I'll start with around a 10 dB "U" pad. That would consist of three equal value resistors. One resistor in series with the "+" line, one in series with the "-" line and the third as a shunt on the "output side" of the two series resistors. I'll probably use 2K2 resistors.

Bri
Old 17th July 2005
  #10
Lives for gear
 
brianroth's Avatar
 

Quote:
Originally Posted by joaquin
The meters on the 428 are peak...no VU!!
Yes, that's part of the problem, but not all of it in the case of the MOTU interfaces, which are "factory set" to be just too "sensitive".

Case in point. Trent cuts a normal set of tracks on his Studer A-80 2", which is calibrated for the normal 0 VU= +4 dBu output level. The tracks from the 2" sound great, and the VU levels are kicking nicely.

When he patches repro from the Studer into his MOTU, most tracks are banging HARD into 0dBfs. Solutions are either screw up the level alignment on the Studer....or insert pads between it and the MOTU. We're moving in the latter direction.

Bri
Old 17th July 2005
  #11
Lives for gear
 

Although I didn't measure, from monitoring and listening I found the ISA 428 (analog) meters to be very accurate, one of my favorite parts of that box. I agree the problem you're having is the calibration on your converter.

Steve
Old 17th July 2005
  #12
Lives for gear
 
brianroth's Avatar
 

Quote:
Originally Posted by squeegybug
Although I didn't measure, from monitoring and listening I found the ISA 428 (analog) meters to be very accurate, one of my favorite parts of that box. I agree the problem you're having is the calibration on your converter.

Steve
Please elaborate on "calibration" of the MOTU interfaces. I never found any level trim pots, either visually, or mentioned in the documentation. Thanks!

Bri
Old 17th July 2005
  #13
Lives for gear
 

Sorry didn't mean to imply there was a way to calibrate, I do not know if there is or not.... the description from the OP appears like that's where his problem is. Your diagnosis of "too sensitive" sounded about right to me.

Steve
Old 18th July 2005
  #14
Lives for gear
 
brianroth's Avatar
 

Quote:
Originally Posted by squeegybug
Sorry didn't mean to imply there was a way to calibrate, I do not know if there is or not.... the description from the OP appears like that's where his problem is. Your diagnosis of "too sensitive" sounded about right to me.

Steve
Rats...I thought someone had discovered an overlooked solution! <g>

Until Trent added the MOTU interfaces, his room was 100% analog, with plenty of VU meters on the gear. Obviously VUs and "peak" meters are different animals.

However, as I recall (can't find my notes), a steady-state 0 VU (ie, +4 dBu) from any analog gear into the MOTU interfaces hits around -12 or -14 dBfs. That is WAY too sensitive. I prefer to set 0 VU analog to -15 to -20 dBfs...better to let the analog gear clip vs causing the digi-gear to puke with 0 dBfs overs!

Here's the "dB math". Analog 0 VU is most often +4 dBu. Clip point on any decent analog gear is at least +20 dBu, if not a lot higher. If I wanted the analog and digi-gear to clip at the same point, then 0VU analog needs to equal -16 dbfs digital. In the real world, allow some margin on the analog side, so 0VU analog should be -18 or -20 dBfs.

The PT interfaces I've used all had analog I and O trimmer pots. Maybe the Prosumer PT boxes don't, but never messed with them in this sort of situation.

So be it..I'll determine a fixed input pad into the MOTU boxes...guessing 6 to 10 dB of padding. Never had this issue with PT interfaces since they could be trimmed.

Bri
Old 18th July 2005
  #15
Lives for gear
 
orange's Avatar
 

on the 828 mkii2 you CAN change the input levels:

http://www.motu.com/techsupport/tech...733463288/view

you might have your 828 running in -10 mode ? hence overload from the isa428.

si
Old 18th July 2005
  #16
Lives for gear
 
brianroth's Avatar
 

Yes, I'm aware of those two modes. That does NOT fix the MOTU interface when working with any "normal" analog source, like a Studer recorder or similar devices.

The MOTU seems to require a 6 to 10 dB pad at the input connector since it doesn't have an input trim control.

Bri
Old 18th July 2005
  #17
Lives for gear
 
orange's Avatar
 

Additionally i've never been convinced about software switches controlling level. Its not clear if you are actually changing the gain of the amplifier or just the calibration of the A/D/A converters ?

Always happier with an knob to twiddle (!?!)

si
Old 19th July 2005
  #18
Lives for gear
 
brianroth's Avatar
 

Indeed...other devices that I'm familiar with, such as the ProTools 888 interface, provided trimmer pots to adjust the analog I and O levels.....

Bri
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump
Forum Jump