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How to connect balanced signals to the MOTM

How to connect balanced signals to the MOTM

2006-03-29 by chad_kettering

Hello,

I have a few MOTM filters that I plan to use to process various sounds
from my DAW. How do I connect the balanced outputs from the DAW to the
MOTM modules, and then return that signal back into the balanced
inputs of the DAW for recording?

Do I need to build cables where one side is balanced and the other is
unblanced ( the ground is lifted on the unbalanced end to avoid ground
loops )? 

Or should I use a line level transformer to change the signal back and
forth to the MOTM?

Thanks and look forward to your experience with this!!

Chad

Re: [motm] How to connect balanced signals to the MOTM

2006-03-29 by Dale Kay (Inquisitor Betrayer)

A direct box comes to mind.
active or passive, do a search and you find many that will fit your needs...
dale
dale@...
Lancaster CA
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Recent events require your assistance to your charities. Do give when able.
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Show quoted textHide quoted text
----- Original Message -----
Sent: Wednesday, March 29, 2006 7:03 AM
Subject: [motm] How to connect balanced signals to the MOTM

Hello,

I have a few MOTM filters that I plan to use to process various sounds
from my DAW. How do I connect the balanced outputs from the DAW to the
MOTM modules, and then return that signal back into the balanced
inputs of the DAW for recording?

Do I need to build cables where one side is balanced and the other is
unblanced ( the ground is lifted on the unbalanced end to avoid ground
loops )?

Or should I use a line level transformer to change the signal back and
forth to the MOTM?

Thanks and look forward to your experience with this!!

Chad

Re: [motm] How to connect balanced signals to the MOTM

2006-03-29 by Mark

You do not need a direct box or any sort of transformer adapter.

If the audio interface for your DAW uses TRS for balanced inputs and
outputs, then simply use regular unbalanced 1/4" TS cables.  I have
done this numerous times and have never had any problems.

If your audio interface uses XLR, you might have to build cables.

http://www.rane.com/note110.html

You could also buy adapter cables from numerous places, such as Markertek.

I would only consider lifting grounds, or some other alternative, if
you discover a problem.

On 3/29/06, chad_kettering put forth:
Show quoted textHide quoted text
>Hello,
>
>I have a few MOTM filters that I plan to use to process various sounds
>from my DAW. How do I connect the balanced outputs from the DAW to the
>MOTM modules, and then return that signal back into the balanced
>inputs of the DAW for recording?
>
>Do I need to build cables where one side is balanced and the other is
>unblanced ( the ground is lifted on the unbalanced end to avoid ground
>loops )?
>
>Or should I use a line level transformer to change the signal back and
>forth to the MOTM?
>
>Thanks and look forward to your experience with this!!

Re: [motm] How to connect balanced signals to the MOTM

2006-03-29 by xamboldt

Actually the Ring connector floats in MOTM jacks - it's not connected  
to anything. Some other 1/4 jacks connect the ring to ground, but not  
Switchcraft 112A.

That being said, I don't recall having any problems using TRS cables  
coming from balanced equipment to my MOTM, and vice versa.

-Chris
Show quoted textHide quoted text
On Mar 29, 2006, at 5:00 PM, Charles Stella wrote:

> In my practical experience it does not matter if the cables are  
> balanced or unbalanced. Most modern active balanced I/O's can  
> tolerate being unbalanced without a problem and usually with no  
> signal loss. The proper way to unbalance a balanced line is not to  
> drop ground but to tie Pin 3 (XLR) or the Ring (TRS) to ground.  
> When you plug a balanced TRS cable into your MOTM the Ring  
> connector is automatically grounded so there's no need to make a  
> special cable. This has worked fine for me with many different DAW  
> interfaces (Digi , Apogee, RME , Metric Halo etc. )
>
> Best, Charles.
>
>
> On Mar 29, 2006, at 7:03 AM, chad_kettering wrote:
>
>> Hello,
>>
>>  I have a few MOTM filters that I plan to use to process various  
>> sounds
>>  from my DAW. How do I connect the balanced outputs from the DAW  
>> to the
>>  MOTM modules, and then return that signal back into the balanced
>>  inputs of the DAW for recording?
>>
>>  Do I need to build cables where one side is balanced and the  
>> other is
>>  unblanced ( the ground is lifted on the unbalanced end to avoid  
>> ground
>>  loops )?
>>
>>  Or should I use a line level transformer to change the signal  
>> back and
>>  forth to the MOTM?
>>
>>  Thanks and look forward to your experience with this!!
>>
>>  Chad
>>
>>
>>
>>
>>
>> YAHOO! GROUPS LINKS
>>
>> 	▪ 	 Visit your group "motm" on the web.
>>
>> 	▪ 	 To unsubscribe from this group, send an email to:
>>  motm-unsubscribe@yahoogroups.com
>>
>> 	▪ 	 Your use of Yahoo! Groups is subject to the Yahoo! Terms of  
>> Service.
>>
>>

Re: [motm] How to connect balanced signals to the MOTM

2006-03-29 by Dale Kay (Inquisitor Betrayer)

was reading with interest here...
microphones generally use xlr cables, they tend to have voltage levels in the microvolt range.
also some use phantom power, so that also means one needs to make sure those cables are marked so no grabs one with the wiring altered, could be bad.
going back to mikes, some send out a positive going signal and a negative going with the ground being common...

most synths that use 1/4 inch out are in millevolts

so what does the MOTM have going out it's output? microvolt, millevolts, whole volts or something larger? I am sure they must vary due to the nature of each.

what really is the impedance rating of the outs and in of a module? do they vary too?

and why is everyone not matching it, just wiring up cables to patch in? is it not critical, not a problem in the s/n area or just because you can?

going back to direct boxes, most are mindless, some are a bit more interesting in that they allow you to adjust the gain, ground lift, isolation and such
even a few channel mixer with the right in and out seems more useful than just re-wiring cables or it just doesn't matter?

I would like to hear from Paul S on this really plus a few other engineer types on this set of Modular.

dale
dale@...
Lancaster CA

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Re: How to connect balanced signals to the MOTM

2006-03-29 by ivancu@aol.com

Don't use a direct box.  Most direct boxes will take a line-level input 
and attenuate it to mic level.  You WANT a high-level line input going 
to the MOTM.

A balanced signal can drive an unbalanced input just fine, although you 
might have some signal loss depending on the balanced output topology.  
It should be minimal and not cause any problems though.

Ivan

Re: [motm] Re: How to connect balanced signals to the MOTM

2006-03-29 by Jonathan Snipes

On Mar 29, 2006, at 12:36 PM, ivancu@... wrote:

> Don't use a direct box.  Most direct boxes will take a line-level  
> input
> and attenuate it to mic level.  You WANT a high-level line input going
> to the MOTM.

I'm sorry to chime in, but this just isn't true.  DI boxes take an  
unbalanced signal and AMPLIFY it to a balanced line-level signal.   
Useful when you're plugging an unbalanced instrument in on-stage,  
then running in 200 feet back to the console, and don't want to add  
ground hum & lose signal.

Just because there's an XLR output from a DI Box, doesn't mean that  
it's mic-level.

Re: [motm] Re: How to connect balanced signals to the MOTM

2006-03-29 by Henry Till

Actually, this is factually incorrect as well.

A true passive direct box simply changes the impedance of a signal  
from low to high (or vice-versa), and does not amplify the signal in  
doing so.

An active direct box may amplify the signal as well, but this has  
absolutely nothing to do with its primary function, which is to  
change the impedance of the signal.

-Henry
Show quoted textHide quoted text
On Mar 29, 2006, at 3:46 PM, Jonathan Snipes wrote:

>
> On Mar 29, 2006, at 12:36 PM, ivancu@... wrote:
>
>> Don't use a direct box.  Most direct boxes will take a line-level
>> input
>> and attenuate it to mic level.  You WANT a high-level line input  
>> going
>> to the MOTM.
>
> I'm sorry to chime in, but this just isn't true.  DI boxes take an
> unbalanced signal and AMPLIFY it to a balanced line-level signal.
> Useful when you're plugging an unbalanced instrument in on-stage,
> then running in 200 feet back to the console, and don't want to add
> ground hum & lose signal.
>
> Just because there's an XLR output from a DI Box, doesn't mean that
> it's mic-level.
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>

RE: [motm] Re: How to connect balanced signals to the MOTM

2006-03-29 by Wheaton, Simon

Sorry, but you are wrong!
DI boxes take an instrument level signal and turn it into a mic level signal. They do not amplify a signal to line level (usually, some newer DIs do have a line level output as well)
They were originally designed to send instrument level signals from stage, through the multicore, and into the mic channels of the mixing desk, so that the instrument level signal appears at the input of the mixer as if it was a mic input.
They do not amplify the signal.
It is usual for the XLR out of a DI to be mic level, and if not then it is usually has a second output marked as line level.
Simon
Canberra
AUSTRALIA
From: motm@yahoogroups.com on behalf of Jonathan Snipes
Sent: Thu 3/30/2006 6:46 AM
On Mar 29, 2006, at 12:36 PM, ivancu@... wrote:
> Don't use a direct box. Most direct boxes will take a line-level
> input
> and attenuate it to mic level. You WANT a high-level line input going
> to the MOTM.

I'm sorry to chime in, but this just isn't true. DI boxes take an
unbalanced signal and AMPLIFY it to a balanced line-level signal.
Useful when you're plugging an unbalanced instrument in on-stage,
then running in 200 feet back to the console, and don't want to add
ground hum & lose signal.

Just because there's an XLR output from a DI Box, doesn't mean that
it's mic-level.

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RE: [motm] Re: How to connect balanced signals to the MOTM

2006-03-29 by Wheaton, Simon

Isn't there a module, either in production or at the design stage, that does this sort of interfacing?
Simon
Canberra
AUSTRALIA

From: motm@yahoogroups.com on behalf of ivancu@...
Sent: Thu 3/30/2006 6:36 AM
To: motm@yahoogroups.com
Subject: [motm] Re: How to connect balanced signals to the MOTM
Don't use a direct box. Most direct boxes will take a line-level input
and attenuate it to mic level. You WANT a high-level line input going
to the MOTM.

A balanced signal can drive an unbalanced input just fine, although you
might have some signal loss depending on the balanced output topology.
It should be minimal and not cause any problems though.

Ivan

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If you are not the intended recipient:

Please notify the sender and delete all copies of this transmission along with any attachments immediately.

You should not copy or use it for any purpose, nor disclose its contents to any other person.

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Re: [motm] Re: How to connect balanced signals to the MOTM

2006-03-29 by ach_gott@yahoo.com

I think you're thinking of Peter Grenader's model 18.  As for it being in MOTM format some day, I've given up hope on EAR ever releasing in large format (possibly excepting a large Milton 2).  I think developing new modules is just more exciting than expanding your install base.  Pity, that, but understandable.

Cheers,
eric f



Sent from my BlackBerry wireless handheld.
Show quoted textHide quoted text
-----Original Message-----
From: "Wheaton, Simon" <simon.wheaton@cit.act.edu.au>
Date: Thu, 30 Mar 2006 08:32:14 
To:<motm@yahoogroups.com>
Subject: RE: [motm] Re: How to connect balanced signals to the MOTM

Isn't there a module, either in production or at the design stage, that does this sort of interfacing? 
  
Simon 
Canberra
AUSTRALIA
 
 
----------------
 
From: motm@yahoogroups.com on behalf of ivancu@aol.com
Sent: Thu 3/30/2006 6:36 AM
To: motm@yahoogroups.com
Subject: [motm] Re: How to connect balanced signals to the MOTM
 
Don't use a direct box.  Most direct boxes will take a line-level input
and attenuate it to mic level.  You WANT a high-level line input going
to the MOTM.

A balanced signal can drive an unbalanced input just fine, although you
might have some signal loss depending on the balanced output topology. 
It should be minimal and not cause any problems though.

Ivan 
   
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Re: [motm] Re: How to connect balanced signals to the MOTM

2006-03-29 by Larry David

And usually a DI box will convert from unbalanced to balanced as  
well, which is why I think someone suggested using it to connect  
balanced signals to the MOTM.  I think the usual use of a basic,  
passive DI box is to convert high impedance, unbalanced signals into  
low impedance, balanced signals.  It is true that some active DIs can  
amplify/attenuate the signal, and many preamps have Hi-Z inputs and  
can function as DI boxes too.  But bringing this back around to MOTM;  
I think the answer to the original question about connecting balanced  
DAW I/O with the MOTM is that it should work fine with unbalanced TS  
(instrument) cables; i.e. just plug the TS cables from the DAW to the  
MOTM and from the MOTM back to the DAW.  Any decent DAW interface  
with balanced line ins/outs should accept a TS plug and the  
unbalanced signal it carries (and in fact have been designed to do so  
since this would be a common thing to do with most keyboards and many  
mixers, etc).  The thing to realize is that obviously you won't have  
a balanced signal, but unbalanced to and from the MOTM (even though  
the connections on the DAW ins/outs are balanced).  This should not  
be a problem unless you have really long cable runs - running through  
a long snake for example, would probably be a bad idea.  But assuming  
your DAW interface is reasonably near your modular rig (say 10 to 20  
feet; shorter is better) I think you should be fine.

My $0.02.  Ok, now someone correct me.  :-)

Larry D.
Show quoted textHide quoted text
On Mar 29, 2006, at 4:23 PM, Henry Till wrote:

> Actually, this is factually incorrect as well.
>
> A true passive direct box simply changes the impedance of a signal
> from low to high (or vice-versa), and does not amplify the signal in
> doing so.
>
> An active direct box may amplify the signal as well, but this has
> absolutely nothing to do with its primary function, which is to
> change the impedance of the signal.
>
> -Henry
>
> On Mar 29, 2006, at 3:46 PM, Jonathan Snipes wrote:
>
>>
>> On Mar 29, 2006, at 12:36 PM, ivancu@... wrote:
>>
>>> Don't use a direct box.  Most direct boxes will take a line-level
>>> input
>>> and attenuate it to mic level.  You WANT a high-level line input
>>> going
>>> to the MOTM.
>>
>> I'm sorry to chime in, but this just isn't true.  DI boxes take an
>> unbalanced signal and AMPLIFY it to a balanced line-level signal.
>> Useful when you're plugging an unbalanced instrument in on-stage,
>> then running in 200 feet back to the console, and don't want to add
>> ground hum & lose signal.
>>
>> Just because there's an XLR output from a DI Box, doesn't mean that
>> it's mic-level.
>>
>>
>>
>>
>> Yahoo! Groups Links
>>
>>
>>
>>
>>
>>
>>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>

Re: [motm] How to connect balanced signals to the MOTM

2006-03-29 by Charles Stella

In my practical experience it does not matter if the cables are 
balanced or unbalanced. Most modern active balanced I/O's can tolerate 
being unbalanced without a problem and usually with no signal loss. The 
proper way to unbalance a balanced line is not to drop ground but to 
tie Pin 3 (XLR) or the Ring (TRS) to ground. When you plug a balanced 
TRS cable into your MOTM the Ring connector is automatically grounded 
so there's no need to make a special cable. This has worked fine for me 
with many different DAW interfaces (Digi , Apogee, RME , Metric Halo 
etc. )

Best, Charles.
Show quoted textHide quoted text
On Mar 29, 2006, at 7:03 AM, chad_kettering wrote:

> Hello,
>
>  I have a few MOTM filters that I plan to use to process various sounds
>  from my DAW. How do I connect the balanced outputs from the DAW to the
>  MOTM modules, and then return that signal back into the balanced
>  inputs of the DAW for recording?
>
>  Do I need to build cables where one side is balanced and the other is
>  unblanced ( the ground is lifted on the unbalanced end to avoid ground
>  loops )?
>
>  Or should I use a line level transformer to change the signal back and
>  forth to the MOTM?
>
>  Thanks and look forward to your experience with this!!
>
>  Chad
>
>
>
>
>
> YAHOO! GROUPS LINKS
>
> 	▪ 	 Visit your group "motm" on the web.
>  
> 	▪ 	 To unsubscribe from this group, send an email to:
>  motm-unsubscribe@yahoogroups.com
>  
> 	▪ 	 Your use of Yahoo! Groups is subject to the Yahoo! Terms of 
> Service.
>
>

Re: [motm] Re: How to connect balanced signals to the MOTM

2006-03-29 by Jonathan Snipes

Well, I'm wrong of course! Teaches me to post without doing my research :-)

I've *never* used a DI box that didn't output a +4 balanced line level signal, though. As far as I was aware, this was how they all worked.

-jonathan


On Mar 29, 2006, at 1:31 PM, Wheaton, Simon wrote:

Sorry, but you are wrong!
DI boxes take an instrument level signal and turn it into a mic level signal. They do not amplify a signal to line level (usually, some newer DIs do have a line level output as well)
They were originally designed to send instrument level signals from stage, through the multicore, and into the mic channels of the mixing desk, so that the instrument level signal appears at the input of the mixer as if it was a mic input.
They do not amplify the signal.
It is usual for the XLR out of a DI to be mic level, and if not then it is usually has a second output marked as line level.
Simon
Canberra
AUSTRALIA
From: motm@yahoogroups.com on behalf of Jonathan Snipes
Sent: Thu 3/30/2006 6:46 AM
On Mar 29, 2006, at 12:36 PM, ivancu@aol.com wrote:
> Don't use a direct box. Most direct boxes will take a line-level
> input
> and attenuate it to mic level. You WANT a high-level line input going
> to the MOTM.

I'm sorry to chime in, but this just isn't true. DI boxes take an
unbalanced signal and AMPLIFY it to a balanced line-level signal.
Useful when you're plugging an unbalanced instrument in on-stage,
then running in 200 feet back to the console, and don't want to add
ground hum & lose signal.

Just because there's an XLR output from a DI Box, doesn't mean that
it's mic-level.
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If you are not the intended recipient:
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Re: [motm] Re: How to connect balanced signals to the MOTM

2006-03-29 by Dale Kay (Inquisitor Betrayer)

There are even DI boxes that take Speaker level and covert down to line and mike...
really do a search on DI boxes, they have all kinds...
New synth programming group for all synths.
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Show quoted textHide quoted text
----- Original Message -----
Sent: Wednesday, March 29, 2006 1:31 PM
Subject: RE: [motm] Re: How to connect balanced signals to the MOTM

Sorry, but you are wrong!
DI boxes take an instrument level signal and turn it into a mic level signal. They do not amplify a signal to line level (usually, some newer DIs do have a line level output as well)
They were originally designed to send instrument level signals from stage, through the multicore, and into the mic channels of the mixing desk, so that the instrument level signal appears at the input of the mixer as if it was a mic input.
They do not amplify the signal.
It is usual for the XLR out of a DI to be mic level, and if not then it is usually has a second output marked as line level.
Simon
Canberra
AUSTRALIA

Re: [motm] How to connect balanced signals to the MOTM

2006-03-29 by Charles Stella

Right you are Chris! Just checked I had assumed the Ring was grounded 
since I have never had any problems with either type of cable. Thanks, 
Charles.
Show quoted textHide quoted text
On Mar 29, 2006, at 11:39 AM, xamboldt wrote:

> Actually the Ring connector floats in MOTM jacks - it's not connected 
>  to anything. Some other 1/4 jacks connect the ring to ground, but not 
>  Switchcraft 112A.
>
>  That being said, I don't recall having any problems using TRS cables 
>  coming from balanced equipment to my MOTM, and vice versa.
>
>  -Chris
>
>  On Mar 29, 2006, at 5:00 PM, Charles Stella wrote:
>
>  > In my practical experience it does not matter if the cables are 
>  > balanced or unbalanced. Most modern active balanced I/O's can 
>  > tolerate being unbalanced without a problem and usually with no 
>  > signal loss. The proper way to unbalance a balanced line is not to 
>  > drop ground but to tie Pin 3 (XLR) or the Ring (TRS) to ground. 
>  > When you plug a balanced TRS cable into your MOTM the Ring 
>  > connector is automatically grounded so there's no need to make a 
>  > special cable. This has worked fine for me with many different DAW 
>  > interfaces (Digi , Apogee, RME , Metric Halo etc. )
>  >
>  > Best, Charles.
>  >
>  >
>  > On Mar 29, 2006, at 7:03 AM, chad_kettering wrote:
>  >
>  >> Hello,
>  >>
>  >>  I have a few MOTM filters that I plan to use to process various 
>  >> sounds
>  >>  from my DAW. How do I connect the balanced outputs from the DAW 
>  >> to the
>  >>  MOTM modules, and then return that signal back into the balanced
>  >>  inputs of the DAW for recording?
>  >>
>  >>  Do I need to build cables where one side is balanced and the 
>  >> other is
>  >>  unblanced ( the ground is lifted on the unbalanced end to avoid 
>  >> ground
>  >>  loops )?
>  >>
>  >>  Or should I use a line level transformer to change the signal 
>  >> back and
>  >>  forth to the MOTM?
>  >>
>  >>  Thanks and look forward to your experience with this!!
>  >>
>  >>  Chad
>  >>
>  >>
>  >>
>  >>
>  >>
>  >> YAHOO! GROUPS LINKS
>  >>
>  >>       ▪       Visit your group "motm" on the web.
>  >>
>  >>       ▪       To unsubscribe from this group, send an email to:
>  >>  motm-unsubscribe@...m
>  >>
>  >>       ▪       Your use of Yahoo! Groups is subject to the Yahoo! 
> Terms of 
>  >> Service.
>  >>
>  >>
>
>
> YAHOO! GROUPS LINKS
>
> 	▪ 	 Visit your group "motm" on the web.
>  
> 	▪ 	 To unsubscribe from this group, send an email to:
>  motm-unsubscribe@yahoogroups.com
>  
> 	▪ 	 Your use of Yahoo! Groups is subject to the Yahoo! Terms of 
> Service.
>
>

Re: How to connect balanced signals to the MOTM

2006-03-29 by chad_kettering

Wow,

My post really exploded into talks about DI boxes. I understand what a
DI box is used for. Since the MOTM jacks are constructed the way they
are, using either balanced or unbalanced seems to work just fine. The
proper grounding and line level (+4, -10) were my only concerns about
mixing formats. 

Thanks for all of the great input thus far. 

Paul, what is your take?

Chad

Re: [motm] How to connect balanced signals to the MOTM

2006-03-30 by Dale Kay

big delay in this email.. anyway, I been digging at Paul's group looking at specs...
This info on what does work will come in handy if I use any of my other outboard filters and effects, even feeding to another synth. 
I'll keep watching and piecing this thread together... It always nice to keep the audio chain as clean as possible with as little as possible in the path...

dale
dale@...
Lancaster CA

Recent events require your assistance to your charities. Do give when able.

band web pages
Inquisitor Betrayer
http://www.inquisitorbetrayer.com

Angel's Wings 
http://www.soundclick.com/angelswings

New synth programming group for all synths.
Synth_Programming-subscribe@yahoogroups.com

"without music, life would be a mistake"
Show quoted textHide quoted text
  ----- Original Message ----- 
  From: Dale Kay (Inquisitor Betrayer) 
  To: MOTM litserv 
  Sent: Wednesday, March 29, 2006 12:00 PM
  Subject: Re: [motm] How to connect balanced signals to the MOTM


  <snip>

  so what does the MOTM have going out it's output? microvolt, millevolts, whole volts or something larger? I am sure they must vary due to the nature of each.

  what really is the impedance rating of the outs and in of a module? do they vary too?

  and why is everyone not matching it, just wiring up cables to patch in? is it not critical, not a problem in the s/n area or just because you can?

  going back to direct boxes, most are mindless, some are a bit more interesting in that they allow you to adjust the gain, ground lift, isolation and such
  even a few channel mixer with the right in and out seems more useful than just re-wiring cables or it just doesn't matter?

  I would like to hear from Paul S on this really plus a few other engineer types on this set of Modular.

  dale

Re: [motm] How to connect balanced signals to the MOTM

2006-03-30 by Paul Schreiber

MOTM uses very large signals on the outputs: 10V pk-pk which is something like 
+24dBu

Most "studio" gear uses +4 dBu which I think is like 1.5V pk-pk.

Mics need balanced cables because their outputs are in *microvolts* to say 5mv 
(that's 0.005V).

Since the 'driving' signal is so small, any hum or noise is *relatively 
significant*.

Paul S.

Re: [motm] How to connect balanced signals to the MOTM

2006-03-30 by Dale Kay

are you saying that all outputs form each module is very high like this before you link to the next?
or only the final is this high?

If this was the case, I would use a DI to patch in other items then back in.

dale
Show quoted textHide quoted text
  ----- Original Message ----- 
  From: Paul Schreiber 
  To: MOTM litserv ; Dale Kay (Inquisitor Betrayer) 
  Sent: Wednesday, March 29, 2006 10:19 PM
  Subject: Re: [motm] How to connect balanced signals to the MOTM


  MOTM uses very large signals on the outputs: 10V pk-pk which is something like 
  +24dBu

  Most "studio" gear uses +4 dBu which I think is like 1.5V pk-pk.

  Mics need balanced cables because their outputs are in *microvolts* to say 5mv 
  (that's 0.005V).

  Since the 'driving' signal is so small, any hum or noise is *relatively 
  significant*.

  Paul S.

Re: How to connect balanced signals to the MOTM

2006-03-30 by coyoteous

--- In motm@yahoogroups.com, "Paul Schreiber" <synth1@...> wrote:
>
> MOTM uses very large signals on the outputs: 10V pk-pk which is something like 
> +24dBu

22.22 dBu reference: 0.775 V
20.00 dBV	 reference: 1 V
22.22 dBm reference: 1 mW at 600 ohms

(u = unloaded/m = 1 mW)
 
> Most "studio" gear uses +4 dBu which I think is like 1.5V pk-pk.

3.47 volts (p-p)
1.23 volts (RMS)

- but that is the operating level. Good gear will have 10 to 20 dB (or more) of headroom 
above that. So, the better your equipment is, the less you will probably need to pad your 
modular output, if at all. For example, this baby will take +30 dBu [that's almost 70 volts 
(p-p)]:

http://www.spl-usa.com/dmc/2490_specs.html

> Mics need balanced cables because their outputs are in *microvolts* to say 5mv 
> (that's 0.005V).

Right, 5mV = -43.8 dBu or about half of half of half of half of half of half of half of half of 
a +4 dBu signal (1/256th? - you get the idea, my math may be off).

Barry S.
Show quoted textHide quoted text
> Since the 'driving' signal is so small, any hum or noise is *relatively 
> significant*.
> 
> Paul S.

Re: How to connect balanced signals to the MOTM

2006-03-30 by ivancu2

I stand by what I said.  A direct box converts unbalanced line-levels
to a balanced mic-level output.  That is its job.  Look up the Jensen
JT-DB-E transformer; it has 12:1 turns ratio.  Active direct boxes do
essentially the same thing.  High input impedance, ATTENUATION, low
output impedance.  And while they may work backwards, they typically
don't work WELL backwards unless designed to do so.  Active direct
boxes do not work backwards, period.

Yes, there are line interfaces that balance and unbalance line-level
signals; typically to provide interface between nominally +4dBu
balanced and -10 dBu unbalanced connections.  And yes, there are
preamplifier/direct box combinations (like the Avalon U5) that offer a
line-level preamplified output and also a mic-level "direct box" output.

As mentioned, MOTM outputs are unbalanced and substantially higher
than normal "pro" line-level outputs.  No problem for most pro gear
with line-level inputs.  But if you attenuate it to take it into
something like a guitar stomp box, then you must amplify the signal
coming out of the stomp box to come back into the MOTM.  There are
"reamping" type of boxes out there which is sort of in line with this
subject, but again they're made to deal with pro audio gear, not MOTM
signal levels.

For lots more on this general subject read up on the Jensen
Transformer and Rane website; highly recommended reading.

Ivan

--- In motm@yahoogroups.com, ivancu@... wrote:
Show quoted textHide quoted text
>
> Don't use a direct box.  Most direct boxes will take a line-level input 
> and attenuate it to mic level.  You WANT a high-level line input going 
> to the MOTM.
> 
> A balanced signal can drive an unbalanced input just fine, although you 
> might have some signal loss depending on the balanced output topology.  
> It should be minimal and not cause any problems though.
> 
> Ivan
>

IN-OUT modules

2006-03-31 by Robert Holmström

>
>Isn't there a module, either in production or at the design stage, that 
>does this sort of interfacing?
>

I am designing two very simple modules right now for this.

1. Final Output Mixer.
-Two stereo inputs and two mono inputs with pan.
-Unbalanced line and balanced line levels out (high quality chip for 
balancing).
-Two VU meters (just because they look nice, and it can give an appr 
readout)
-Hedaphone out with separate volume (pre listen before turning volume up)

2. Input module
-Two balanced in to MOTM level signals using high quality chip
-Two line level in to MOTM level signals
-Mic pre (without phantom power) to MOTM levels

I am soon about to make PCB's for these (probably within the next month), 
and if there is some interest I can order properly made boards, even though 
I won't make any money on them. I also have a "stereo synthesizer" 
(mono-stereo module)  on the way that also might be of interest.

If anybody are interested in these things please email me off list and I can 
give more info as well as an appr price if there are a few boards made.

Regards
Robert Holmstrom (UK)

[motm] Re: How to connect balanced signals to the MOTM

2006-03-31 by Mark

On 3/30/06, ivancu2 put forth:
>As mentioned, MOTM outputs are unbalanced and substantially higher
>than normal "pro" line-level outputs.

No, they aren't.

On 3/30/06, Paul Schreiber put forth:
>MOTM uses very large signals on the outputs: 10V pk-pk which is something like
>+24dBu
>
>Most "studio" gear uses +4 dBu which I think is like 1.5V pk-pk.

Actually, most studio gear is more or less 22V pk-pk, which is 20dBu.
Admittedly, the designation "+4 dBu" is a bit misleading.  MOTM is
10V pk-pk which is around 13dBu.  Which isn't as significant a
difference as one might think.  MOTM is quite compatible with most
line-level gear.

The only exception might be the MOTM-120.  I don't have one myself,
but I have read numerous complaints over the years that it isn't hot
enough.

>Mics need balanced cables because their outputs are in *microvolts* to say 5mv
>(that's 0.005V).
>
>Since the 'driving' signal is so small, any hum or noise is *relatively
>significant*.

This is true.  Imho, the advantage of using balanced interconnects
for line level over the typically short distances in most studios
isn't the common mode rejection, but that its consistent
implementation prevents ground loops and provides better level
matching.

On 3/29/06, Charles Stella put forth:
>The proper way to unbalance a balanced line is not to drop ground
>but to tie Pin 3 (XLR) or the Ring (TRS) to ground.

Which is what generally happens when one uses a TS cable with
balanced TRS jacks, however there are instances (eg. you are using a
one-conductor cable with equipment with mismatched grounds) where it
is preferable to float the ring even though it causes a 6dB loss in
signal.  The ideal solution in going from TRS to TS would be to use a
2-conductor cable where the signal ground (the ring) is connected to
the the sleeve of the TS, and the TRS sleeve is connected to the cable
shield but is left unconnected at the TS end.  Although that usually
isn't necessary.

>When you plug a balanced TRS cable into your MOTM the Ring connector
>is automatically grounded so there's no need to make a special cable.

I do not think that is true.  Although, with good equipment the
sleeve is still grounded (to the chassis) at both ends so it should
still work, even though it is not the best way since you are ignoring
the signal ground.

However, be warned, there is equipment out there with floating
unbalanced TRS jacks where the sleeve is not connected.  While these
sort of bullshit balanced connectors will work if you use a TRS cable
to connect to a TRS jack that does have its ring and sleeve
connected, and will also work if you use a TS cable, they will not
work properly if you use a TRS cable to connect to a TS jack such as
MOTM.  (Oddly enough, it doesn't seem to occur to the manufacturers
that the shield remains completely unconnected when using TRS cable
to connect these pseudo-balanced TRS connections together!!)

Almost all equipment with TRS jacks is made with the expectation that
someone will stick a regular TS plug into it at some time or another.
So I strongly recommend using regular TS cables to connect MOTM to balanced
TRS, and only trying other options if noise or other problems occur.

Re: [motm] Re: How to connect balanced signals to the MOTM

2006-03-31 by Oakley Sound

> Almost all equipment with TRS jacks is made with the expectation that
someone will stick a regular TS plug into it at some time or another.

But one notable exception to this rule is Digidesign, although there are 
others.

Digi hardware did [and may still do] have the ring connection tied to an 
active op-amp output. Short that out and the op-amp will probably 
survive, but the current consumption will go up and the little guy will 
get hot.

However, Digi and most other manufacturers provide all the information 
you need in the relevant User Guide. The one thing to remember that 
there is no standard.

Tony

www.oakleysound.com

Re: How to connect balanced signals to the MOTM

2006-03-31 by coyoteous

Oops! I think dat wrong.

It's been a long time, but we need RMS first, right?

So, 10V peak to peak is 5V peak, then 5V x .7071 (square root of 2 over 2) = 3.536V RMS

dBu = 20log(V1/V2) where V2 = .775V

20log(3.536/.775)= 13.18 dBu

Barry S.

--- In motm@yahoogroups.com, "coyoteous" <antithesist@...> wrote:
Show quoted textHide quoted text
>
> --- In motm@yahoogroups.com, "Paul Schreiber" <synth1@> wrote:
> >
> > MOTM uses very large signals on the outputs: 10V pk-pk which is something like 
> > +24dBu
> 
> 22.22 dBu reference: 0.775 V
> 20.00 dBV reference: 1 V
> 22.22 dBm reference: 1 mW at 600 ohms

Re: How to connect balanced signals to the MOTM

2006-03-31 by ivancu2

I stand corrected!  I had thought that MOTM had a nominal output level
of 10VRMS but I hadn't noticed Paul's statement of 10V pk-pk (which is
 actually around 13dB).

By the way, this is a VERY handy spreadsheet for those of you doing
these calculations:

http://www.benchmarkmedia.com/caig/caigla.xls

Ivan


--- In motm@yahoogroups.com, Mark <yahoogroups@...> wrote:
>
> On 3/30/06, ivancu2 put forth:
> >As mentioned, MOTM outputs are unbalanced and substantially higher
> >than normal "pro" line-level outputs.
> 
> No, they aren't.
> 
> On 3/30/06, Paul Schreiber put forth:
> >MOTM uses very large signals on the outputs: 10V pk-pk which is
something like
Show quoted textHide quoted text
> >+24dBu
> >
> >Most "studio" gear uses +4 dBu which I think is like 1.5V pk-pk.
> 
> Actually, most studio gear is more or less 22V pk-pk, which is 20dBu.
> Admittedly, the designation "+4 dBu" is a bit misleading.  MOTM is
> 10V pk-pk which is around 13dBu.  Which isn't as significant a
> difference as one might think.  MOTM is quite compatible with most
> line-level gear.

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