MA-100 XLR audio adapter questions

Don Palomaki · July 21st, 2002, 06:33 PM

The circuits are based on operational amplifiers, which are connected in a way do a balanced to unbalanced conversion. The wiring specifics are hiddend in the integrated circuits, but there are a number of published circuits for this purpose. The input is balanced, so it provides the common mode rejection of a balanced input. The output is single ended (not balanced). And the unit provides about 6 dB of gain to boot.

Charles Papert · July 21st, 2002, 07:23 PM

Thank you, Don, and apologies to all for the duplicated post (I was tempted to drop it in one more time just to be really annoying).

Now, other than providing additional volume controls, what do the Beachtek or Studio 1 units do above and beyond the MA100? I have heard the Studio 1 is quieter, but being built for the mike input is not so great considering we have those RCA jacks on the XL1. And now they are apparently only making units that are intended to be worn on the built, presumably to avoid noise/interference issues.

The reason I am wondering about all this is because I am finally moving forward on making my long-threatened custom base for the XL1 that, among other things, will have power, audio and video distribution with the appropriate connectors to accomodate my film accessories. I intend to build in two XLR connectors and am wondering about how much circuitry I will need to do a good job. Looks like I will be employing an engineer to do the wiring & want to give him as much info on the audio needs as possible (they are a lot more complicated, apparently, than the power and video which just requires shielding.

Don Palomaki · July 22nd, 2002, 06:28 AM

The Beachtek and Studio One are passive devices (no possibility for gain) that use transformers for the balanced-to-unbalanced conversion. FOr this reason,they could be lower noise, but may not be in some environments, especially of the transformer is not well shielded.) They offer some options as to high/low level input and some grounding options.

The MA-100 is designed for mic-level input will clip/saturate if you give it a line-level input.

Which is better for your application? I really can't answer that.

Al Holston · July 22nd, 2002, 11:36 AM

As Don stated;

Beachtek and Studio One are passive devices, this, among other things, means, that they do NOT require an external power source, and usually employ transformers. The MA100/200and boxes like Sounddevices are active devices, and require a power source (your first hint at which type you are using). Passive devices most always (better ones anyway) and some active devices employ transformers. Active boxes can also employ the "impedance" balanced outputs using amps. To do the conversion from High Z to Lo Z, bal. to unbal. norm. used fop mics.

Balanced refers to the fact that there are two symmetrical signal lines and one ground, while unbalanced uses just one signal line in reference to ground.
The balanced input signal is then converted to an unbalanced output through an impedance matching transformer.

The following is a quote from Sounddevices:
"…the best type of topology for inputs or outputs (but especially inputs) is one which uses a high-quality transformer, as transformers provide galvanic isolation and typically provide the superior common-mode and RF rejection compared to non-transformer balanced inputs or outputs. However, when a transformer-balanced output driver is not practical, Sound Devices feels that the "impedance" balanced output is the best. ("Impedance" balanced is really a misnomer - it is simply a truly "balanced" output stage.) This topology has equal impedances from pin 2 to ground and from pin 3 to ground; however, only pin 2 is driven with signal voltage. It provides common-mode rejection of unwanted noise into a balanced output just like an "active" balanced or a transformer balanced output stage. This topology is not new at all, it has been used for years in audio equipment. It works equally well with line-level or mic-level signals - Neumann microphones are one of many examples of equipment utilizing this topology."
The advantages of the "impedance" balanced output topology are:
1. Stability issues that exist with "cross-coupled" balanced outputs are eliminated.
2. Unbalancing the output is easy- pin 3 can be either grounded or ungrounded, and it will work fine.
3. There is no 6 dB loss of signal going from balanced to unbalanced output as there is with a standard active balanced output.
4. It uses less parts and is therefore more reliable.
The only real caveat with the "impedance" balanced output is that it cannot provide inversion of the signal polarity, as pin 3 is not driven."

The common misperception is that a balanced output stage needs to have equal and opposite signals on pins 2 and 3 of the XLR connector (or tip and ring of a 1/4" connector). Actually, what defines a system as balanced is that the impedances from pin 2 to ground and from pin 3 to ground are both equal. The signal(s) appearing at the output pins has nothing to do with whether the output stage is balanced or not. Bill Whitlock, President of Jensen Transformers and a noted authority on this topic, offers an excellent overview on balanced and unbalanced systems in his paper, Interconnection of Balanced and Unbalanced Equipment.

Hopefully, this explanation has been a help. If you understand it all, than a job as an audio engineer may be in the wings for you!

As Don noted, which way to go -- is your choice based on what you want to accomplish. I would recommend buying componets that can be connected to meet your goal, rather than building, unless, of course, you are an audio engineer.

Charles Papert · July 22nd, 2002, 12:44 PM

Thank you so much fellas, that's a world of info and ummm--no, I don't understand it, but then again that's what audio guys are for! I will definitely pass it on to the person that makes up my box for me, though.

Chris Hurd · July 22nd, 2002, 01:13 PM

Gee whiz. This could be a Watchdog article.

Your deal too, Charles, when it's built... I want pictures.

Charles Papert · July 22nd, 2002, 01:16 PM

You'll get 'em Chris, no doubt. When I get through with this camera--hoo boy. (And then the XL2 will come out).

Jeff Donald · July 22nd, 2002, 06:46 PM

Charles,

You might want to check out these folks http://www.sounddevices.com/index.html They are the people that Al quoted above. They have two very nice products that you might be interested in. If not for purchase, ideas for your own adapter. The first is the MM-1, I've had one for about a month now and absolutly love. The specs are out of sight compared to the Studio 1 and Beachtek. The second is the MP-1, basically the same, but without the headphone monitoring.

Jeff

Al Holston · July 23rd, 2002, 10:48 AM

Jeff has a very good point. The Sounddevices MM1 is head and sholders above the others. Also check out the MixPre, a full featured 2-chan. XLR-in/XLR-out and unbal out mixer w/mic. power(unit is batt. powered) an, is not much bigger than the MM1. It has tha advantage of adding "pan" to each input and as well as headphone monitoring. It can be used both "on" and "off" the camera for seperate "soundman" operation. Prices run about $700-800 for this very ncie and rugged unit.

Andrew Leigh · August 25th, 2002, 01:02 AM

I have just started experimenting with the MA100.

With a super cartoid EV mic connected I cannot seem to get a signal past about -50dB. Have tried both inputs and the other is even worse. Is it possible that my MA-100 is faulty?

Cheers
Andrew

Don Palomaki · August 25th, 2002, 06:20 AM

Do you have the Audio1 In set for MIC level? That is the most common cause of the situation you report. You have to make the selection from the menu in addition to selecting Audio 1 from on the switch behind the door. The XL1 defaults to line level input until changed. If using 12-bit, 4-channel mode, the menu selection applies to Audio 2 In levels too.

Robert Mann Z. · September 22nd, 2002, 11:02 PM

not sure how but my ma-100 goes bad just before i'm about to mic up our guest speaker...very strange at first i thought it was the cam, but a quick audio check and everything worked..has anyone had a ma-100 go bad on them...basically the left channel has no audio...

is this thing under warrenty (i had this unit less then a year)?? well my first call into canon tomorrow if anyon ehas any advice or tips, very welcomed

Don Palomaki · September 23rd, 2002, 05:28 AM

First report of bad MA-100 I've read. If I had to make a guess, my first guess woud be the audio cable RCA plug for the left channel.

Robert Mann Z. · September 24th, 2002, 01:20 PM

fixed it myself, turned out to be bad soildering on canon's part as apposed to the right channel that was done properly, i just re-soildered it the entire process took 5 min...

November 30th, 2002, 01:38 AM

For some I can't get audio from my microphone going through the MA-100 to the XL1. I'm not sure why. I just rented it to do a quick project and I'm on a tight schedule. If someone could just give me a step by step guide to hooking it up that would be great. Thanks.

July 21st, 2002, 07:23 PM	#92
Charles Papert Wrangler Join Date: Jan 2002 Location: Los Angeles, CA Posts: 6,810	Thank you, Don, and apologies to all for the duplicated post (I was tempted to drop it in one more time just to be really annoying). Now, other than providing additional volume controls, what do the Beachtek or Studio 1 units do above and beyond the MA100? I have heard the Studio 1 is quieter, but being built for the mike input is not so great considering we have those RCA jacks on the XL1. And now they are apparently only making units that are intended to be worn on the built, presumably to avoid noise/interference issues. The reason I am wondering about all this is because I am finally moving forward on making my long-threatened custom base for the XL1 that, among other things, will have power, audio and video distribution with the appropriate connectors to accomodate my film accessories. I intend to build in two XLR connectors and am wondering about how much circuitry I will need to do a good job. Looks like I will be employing an engineer to do the wiring & want to give him as much info on the audio needs as possible (they are a lot more complicated, apparently, than the power and video which just requires shielding. __________________ Charles Papert www.charlespapert.com

July 22nd, 2002, 11:36 AM	#94
Al Holston Regular Crew Join Date: Jun 2002 Location: San Francisco Posts: 51	As Don stated; Beachtek and Studio One are passive devices, this, among other things, means, that they do NOT require an external power source, and usually employ transformers. The MA100/200and boxes like Sounddevices are active devices, and require a power source (your first hint at which type you are using). Passive devices most always (better ones anyway) and some active devices employ transformers. Active boxes can also employ the "impedance" balanced outputs using amps. To do the conversion from High Z to Lo Z, bal. to unbal. norm. used fop mics. Balanced refers to the fact that there are two symmetrical signal lines and one ground, while unbalanced uses just one signal line in reference to ground. The balanced input signal is then converted to an unbalanced output through an impedance matching transformer. The following is a quote from Sounddevices: "…the best type of topology for inputs or outputs (but especially inputs) is one which uses a high-quality transformer, as transformers provide galvanic isolation and typically provide the superior common-mode and RF rejection compared to non-transformer balanced inputs or outputs. However, when a transformer-balanced output driver is not practical, Sound Devices feels that the "impedance" balanced output is the best. ("Impedance" balanced is really a misnomer - it is simply a truly "balanced" output stage.) This topology has equal impedances from pin 2 to ground and from pin 3 to ground; however, only pin 2 is driven with signal voltage. It provides common-mode rejection of unwanted noise into a balanced output just like an "active" balanced or a transformer balanced output stage. This topology is not new at all, it has been used for years in audio equipment. It works equally well with line-level or mic-level signals - Neumann microphones are one of many examples of equipment utilizing this topology." The advantages of the "impedance" balanced output topology are: 1. Stability issues that exist with "cross-coupled" balanced outputs are eliminated. 2. Unbalancing the output is easy- pin 3 can be either grounded or ungrounded, and it will work fine. 3. There is no 6 dB loss of signal going from balanced to unbalanced output as there is with a standard active balanced output. 4. It uses less parts and is therefore more reliable. The only real caveat with the "impedance" balanced output is that it cannot provide inversion of the signal polarity, as pin 3 is not driven." The common misperception is that a balanced output stage needs to have equal and opposite signals on pins 2 and 3 of the XLR connector (or tip and ring of a 1/4" connector). Actually, what defines a system as balanced is that the impedances from pin 2 to ground and from pin 3 to ground are both equal. The signal(s) appearing at the output pins has nothing to do with whether the output stage is balanced or not. Bill Whitlock, President of Jensen Transformers and a noted authority on this topic, offers an excellent overview on balanced and unbalanced systems in his paper, Interconnection of Balanced and Unbalanced Equipment. Hopefully, this explanation has been a help. If you understand it all, than a job as an audio engineer may be in the wings for you! As Don noted, which way to go -- is your choice based on what you want to accomplish. I would recommend buying componets that can be connected to meet your goal, rather than building, unless, of course, you are an audio engineer. __________________ Al

July 22nd, 2002, 12:44 PM	#95
Charles Papert Wrangler Join Date: Jan 2002 Location: Los Angeles, CA Posts: 6,810	Thank you so much fellas, that's a world of info and ummm--no, I don't understand it, but then again that's what audio guys are for! I will definitely pass it on to the person that makes up my box for me, though. __________________ Charles Papert www.charlespapert.com

July 22nd, 2002, 01:13 PM	#96
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,368 Images: 513	Gee whiz. This could be a Watchdog article. Your deal too, Charles, when it's built... I want pictures. __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

July 22nd, 2002, 01:16 PM	#97
Charles Papert Wrangler Join Date: Jan 2002 Location: Los Angeles, CA Posts: 6,810	You'll get 'em Chris, no doubt. When I get through with this camera--hoo boy. (And then the XL2 will come out). __________________ Charles Papert www.charlespapert.com

July 21st, 2002, 06:33 PM	#91
Don Palomaki Wrangler Join Date: Sep 2001 Location: Northern VA Posts: 4,489	The circuits are based on operational amplifiers, which are connected in a way do a balanced to unbalanced conversion. The wiring specifics are hiddend in the integrated circuits, but there are a number of published circuits for this purpose. The input is balanced, so it provides the common mode rejection of a balanced input. The output is single ended (not balanced). And the unit provides about 6 dB of gain to boot.

July 22nd, 2002, 06:28 AM	#93
Don Palomaki Wrangler Join Date: Sep 2001 Location: Northern VA Posts: 4,489	The Beachtek and Studio One are passive devices (no possibility for gain) that use transformers for the balanced-to-unbalanced conversion. FOr this reason,they could be lower noise, but may not be in some environments, especially of the transformer is not well shielded.) They offer some options as to high/low level input and some grounding options. The MA-100 is designed for mic-level input will clip/saturate if you give it a line-level input. Which is better for your application? I really can't answer that.

July 22nd, 2002, 06:46 PM	#98
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	Charles, You might want to check out these folks http://www.sounddevices.com/index.html They are the people that Al quoted above. They have two very nice products that you might be interested in. If not for purchase, ideas for your own adapter. The first is the MM-1, I've had one for about a month now and absolutly love. The specs are out of sight compared to the Studio 1 and Beachtek. The second is the MP-1, basically the same, but without the headphone monitoring. Jeff

July 23rd, 2002, 10:48 AM	#99
Al Holston Regular Crew Join Date: Jun 2002 Location: San Francisco Posts: 51	Jeff has a very good point. The Sounddevices MM1 is head and sholders above the others. Also check out the MixPre, a full featured 2-chan. XLR-in/XLR-out and unbal out mixer w/mic. power(unit is batt. powered) an, is not much bigger than the MM1. It has tha advantage of adding "pan" to each input and as well as headphone monitoring. It can be used both "on" and "off" the camera for seperate "soundman" operation. Prices run about $700-800 for this very ncie and rugged unit. __________________ Al

August 25th, 2002, 01:02 AM	#100
Andrew Leigh Major Player Join Date: Oct 2001 Location: Johannesburg, South Africa Posts: 220	MA100 - Audio levels very low I have just started experimenting with the MA100. With a super cartoid EV mic connected I cannot seem to get a signal past about -50dB. Have tried both inputs and the other is even worse. Is it possible that my MA-100 is faulty? Cheers Andrew __________________ PAL XL-1, DV Raptor, Premiere TOTAL AMATEUR - DOING IT FOR THE FUN

August 25th, 2002, 06:20 AM	#101
Don Palomaki Wrangler Join Date: Sep 2001 Location: Northern VA Posts: 4,489	Do you have the Audio1 In set for MIC level? That is the most common cause of the situation you report. You have to make the selection from the menu in addition to selecting Audio 1 from on the switch behind the door. The XL1 defaults to line level input until changed. If using 12-bit, 4-channel mode, the menu selection applies to Audio 2 In levels too.

September 22nd, 2002, 11:02 PM	#102
Robert Mann Z. Skyonic New York Join Date: Nov 2001 Location: NYC Posts: 614	Ma-100 gone bad not sure how but my ma-100 goes bad just before i'm about to mic up our guest speaker...very strange at first i thought it was the cam, but a quick audio check and everything worked..has anyone had a ma-100 go bad on them...basically the left channel has no audio... is this thing under warrenty (i had this unit less then a year)?? well my first call into canon tomorrow if anyon ehas any advice or tips, very welcomed

September 23rd, 2002, 05:28 AM	#103
Don Palomaki Wrangler Join Date: Sep 2001 Location: Northern VA Posts: 4,489	First report of bad MA-100 I've read. If I had to make a guess, my first guess woud be the audio cable RCA plug for the left channel.

September 24th, 2002, 01:20 PM	#104
Robert Mann Z. Skyonic New York Join Date: Nov 2001 Location: NYC Posts: 614	fixed it myself, turned out to be bad soildering on canon's part as apposed to the right channel that was done properly, i just re-soildered it the entire process took 5 min...

November 30th, 2002, 01:38 AM	#105
Matt Carlson Posts: n/a	Help. Need MA-100 help For some I can't get audio from my microphone going through the MA-100 to the XL1. I'm not sure why. I just rented it to do a quick project and I'm on a tight schedule. If someone could just give me a step by step guide to hooking it up that would be great. Thanks.