Distorting my AT4073a?

Ty Ford · June 22nd, 2006, 05:02 AM

Quote:

Originally Posted by Kevin Richard

I agree, but I have read to feed your mic to both lines as a safety for clipping and then I looked around on proper ways to do it for the sake of phantom power and everything I read acted like a straight Y was just fine. *shrug*

This is NOT a stock Marantz, this has the complete preamp section ripped out and replaced with a smoking preamp from oade brothers... they say you can run line levels into the preamp with out a concern for clipping so I'm not sure if the AT is too hot or not :(

1. Whether it's stock or not, if you are abusing the laws of impedance, you're asking for trouble, and you're asking for trouble.

2. The at4073 has one of the highest outputs among shotguns.

3. A shrug mean, "I don't know" where I come from. The right way to feed two inputs is with a mixer.

4. Good luck

Ty Ford

David Ennis · June 22nd, 2006, 09:15 AM

Kevin, the reality of sound recording is that it is often difficult to get right. Expensive equipment is subject to most of the same rules as cheap equipment. I've listened to your clip, and looked at its waveform. You have clipping as well as room reverb. I believe that because of the limitations of the situation, which was staged for novelty in the midst of the audience and not recording, you would have done as well or better with a well chosen $150 mic going into a $200 recorder.

As Steve says, the line level capability claimed by Oade Brothers is 316 mV with lots of "headroom," at term you don't normally associate with digital recording. Without more details, I'm skeptical. But even if you are getting that performance, the AT4073 is capable of 2400 mV before it clips itself, so I still think it creamed the Marantz input with the screeches from your actor. Send Oade Brothers the clip and see how they explain it.

A. J. deLange · June 22nd, 2006, 09:52 AM

If the sensitivity of the microphone is 71 mV/Pa it will drop to about 32% (square root of 10) of this or about 21 mV/Pa with a 10 dB pad installed.

Kevin Richard · June 22nd, 2006, 12:09 PM

Well, I was brickwalling the preamp... a quick email to Doug Oade cleared that up. Apparently you are supposed to have the software selectable -20db pad on at all times unless you can't get enough gain. This was contrare to the original Marantz circuit that sounded like poo if you did engage the -20db pad.

Just did some quick test and everything is perfect and I couldn't be happier again... well other than figuring out what I will do about that dialog that can't be reshot!

Kevin Richard · June 22nd, 2006, 12:13 PM

Quote:

Originally Posted by Ty Ford

1. Whether it's stock or not, if you are abusing the laws of impedance, you're asking for trouble, and you're asking for trouble.

2. The at4073 has one of the highest outputs among shotguns.

3. A shrug mean, "I don't know" where I come from. The right way to feed two inputs is with a mixer.

4. Good luck

Ty Ford

I wasn't insinuating that because it's not stock I can abuse anything... I was answering other people in the same msg (about being too hot, though I was incorrect anway). The *shrug* meant I don't understand why everything I read said to split the signal and when I read about Y's it seemed like no big deal... but this ended up not being the problem so I guess I'm "safe" doing it this way. The beauty of the marantz is not being teathered to other things, if I go with a mixer now I got more stuff strapped on me and power cords and such.

I'm all ears if you have any other suggestions or corrections to statements/assumptions I've made... I've done audio for years but it's always been band production stuff where everything is pretty straight forward... funny how 20+ mics and I'm at home but give me one mic to use and I'm screwing things up ;)

Steve House · June 22nd, 2006, 12:40 PM

Quote:

Originally Posted by Kevin Richard

I wasn't insinuating that because it's not stock I can abuse anything... I was answering other people in the same msg (about being too hot, though I was incorrect anway). The *shrug* meant I don't understand why everything I read said to split the signal and when I read about Y's it seemed like no big deal... but this ended up not being the problem so I guess I'm "safe" doing it this way. The beauty of the marantz is not being teathered to other things, if I go with a mixer now I got more stuff strapped on me and power cords and such.

I'm all ears if you have any other suggestions or corrections to statements/assumptions I've made... I've done audio for years but it's always been band production stuff where everything is pretty straight forward... funny how 20+ mics and I'm at home but give me one mic to use and I'm screwing things up ;)

Not to be putting words into Ty's mouth, but his point still stands. While you might get your "Y" cable to work, the better way is to use a mixer, especially when you're dealing with sending phantom to the mic. Something like the Sound Devices MixPre or 302 would be ideal and they are small, lightweight, and battery powered so power cords etc wouldn't be an issue. Their audio performance is very high quality, up there among the very best professional tools.

Kevin Richard · June 22nd, 2006, 01:03 PM

I'm all about doing things right or not doing them at all but at 700-1600 bucks just to split my mic into two channels of a $750 recorder what is the real harm in just using a Y?

I understand if it were money no object but as we all know money is an object and for example this short is being filmed on ZERO budget and actors doing it for free as long as we pay thier plane tickets. I'm the producer/grip/AC(apparently)/electritian/AD oh, and when that is all done they go "ready for sound?" and I'm like umm where is my gear at anyway as I've been having to do everyone else's job. And trust me, it's not that I WANT all those credits as I will probably only credit myself as producer and sound it's just with such a small inexperienced crew you have to wear many hats. Honestly I wish I could trust someone else to set levels and do sound so I didn't have to do that!

Unless someone can explain to me a huge short coming to the Y cable I can't justify that expense at this point.

Don't get me wrong, I am VERY greatful for the advice!

Ty Ford · June 22nd, 2006, 01:59 PM

I had to pass three FCC tests to get into radio a long time ago when you actually had to know something about electronics.

Impedance-wise, it's the wrong thing to do.
Regards,

Ty Ford

Kevin Richard · June 22nd, 2006, 02:13 PM

Quote:

Originally Posted by Ty Ford

I had to pass three FCC tests to get into radio a long time ago when you actually had to know something about electronics.

Impedance-wise, it's the wrong thing to do.
Regards,

Ty Ford

I do understand such concepts... my father is the chairman of the board for the state issued FCC liscences for working on Satellite and TV's so electrics, ohms law, and impedance matching aren't unfamiliar terms. I just don't know the specifics when it comes to mic inputs as you are making this out to be a dreadful thing.

Kevin

David Ennis · June 22nd, 2006, 03:39 PM

Quote:

Originally Posted by Kevin Richard

Well, I was brickwalling the preamp... a quick email to Doug Oade cleared that up. Apparently you are supposed to have the software selectable -20db pad on at all times unless you can't get enough gain...!

Well, I'm glad Doug was there to straighten that out--if you had listened to Dave in post #4 you might have thought you had brickwalled the preamp and needed -20 dB of attenuation ... 8>)

David Ennis · June 22nd, 2006, 03:45 PM

Quote:

Originally Posted by Ty Ford

I had to pass three FCC tests to get into radio a long time ago when you actually had to know something about electronics...

..and Morse code at 14 words per minute, right? Was that 1rst Class Radiotelephone?

Ty Ford · June 22nd, 2006, 03:49 PM

Quote:

Originally Posted by Fred Retread

..and Morse code at 14 words per minute, right? Was that 1rst Class Radiotelephone?

There was no CW test for the 1st. That was for a Ham license.

Regards,

Ty Ford

Steve House · June 22nd, 2006, 04:05 PM

Quote:

Originally Posted by Kevin Richard

I do understand such concepts... my father is the chairman of the board for the state issued FCC liscences for working on Satellite and TV's so electrics, ohms law, and impedance matching aren't unfamiliar terms. I just don't know the specifics when it comes to mic inputs as you are making this out to be a dreadful thing.

Kevin

I'm not an engineer so perhaps someone will correct me if I'm wrong but what I suspect happens is this...

The mic is the source driving a load at the inputs. Using a "Y" cable connects the two inputs in parallel. Connecting two loads in parallel halves their effective impedence when viewed from the source - ie, putting two 8-ohm speakers in parallel to an amplifier effectively puts a 4-ohm impedence load on it and doubles the output voltage it must develop. I would expect the same thing to happen with the mic - the 4073a is rated as 100 ohms and expects to work into a high impedence mic input. Driving a lower impedance means the mic's internal electronics must produce more power than they were designed to deliver, which could change its behaviour considerably.

David Ennis · June 22nd, 2006, 06:09 PM

Quote:

Originally Posted by Kevin Richard

I'm all about doing things right or not doing them at all but at 700-1600 bucks just to split my mic into two channels of a $750 recorder what is the real harm in just using a Y?...

None that I know of. I guess there is some experience of associated problems out there somewhere, and that's plausible, but I don't recall anyone reporting any specific problem around here in the past year or two. Personally, I think you'll be fine. Now that you know what your main problem was, it's worth a try. Please let us know how you make out.

Seth Bloombaum · June 22nd, 2006, 06:27 PM

Well, if both mic inputs are feeding phantom into the Y cable that could be as much as 96 volts to the mic. Or, it could be a lot less, depending on Marantz & Oade.

But it's probably way more than that little capacitor wants to see.

Does the Marantz allow you to turn off phantom individually per channel?

Lots of people record a second channel at -12 to -20db from their first for backup. No engineer I know uses a Y cable to do it. If the device doesn't do it natively (like a lot of sony cams), or no mixer, why risk good audio on both channels to impedance mismatch and double phantom to make a backup? Two bad channels is not twice as good as one good channel.

Just do a good job on the first channel. Use the mic like it was designed to be used. In my opinion that's appropriate risk management. Most people who stick with audio professionally develop a "best practices" sort of approach. Using a Y increases risk. Not having a backup channel? That risk can be managed by good engineering.

June 22nd, 2006, 09:15 AM	#17
David Ennis Fred Retread Join Date: Jul 2004 Location: Hartford, CT Posts: 1,227	Kevin, the reality of sound recording is that it is often difficult to get right. Expensive equipment is subject to most of the same rules as cheap equipment. I've listened to your clip, and looked at its waveform. You have clipping as well as room reverb. I believe that because of the limitations of the situation, which was staged for novelty in the midst of the audience and not recording, you would have done as well or better with a well chosen $150 mic going into a $200 recorder. As Steve says, the line level capability claimed by Oade Brothers is 316 mV with lots of "headroom," at term you don't normally associate with digital recording. Without more details, I'm skeptical. But even if you are getting that performance, the AT4073 is capable of 2400 mV before it clips itself, so I still think it creamed the Marantz input with the screeches from your actor. Send Oade Brothers the clip and see how they explain it. __________________ "Nothing in the world can take the place of persistence..." - Calvin Coolidge "My brain is wired to want to know how other things are wired." - Me

June 22nd, 2006, 01:59 PM	#23
Ty Ford Inner Circle Join Date: Nov 2004 Location: Baltimore, MD USA Posts: 2,337	I had to pass three FCC tests to get into radio a long time ago when you actually had to know something about electronics. Impedance-wise, it's the wrong thing to do. Regards, Ty Ford __________________ Ty Ford's Audio Bootcamp Field Guide Ty Ford's Audio Video Blog Last edited by Douglas Spotted Eagle; June 22nd, 2006 at 02:26 PM. Reason: edited by moderator

June 22nd, 2006, 09:52 AM	#18
A. J. deLange Major Player Join Date: Jun 2004 Location: McLean, VA United States Posts: 749	If the sensitivity of the microphone is 71 mV/Pa it will drop to about 32% (square root of 10) of this or about 21 mV/Pa with a 10 dB pad installed.

June 22nd, 2006, 12:09 PM	#19
Kevin Richard Major Player Join Date: Mar 2005 Location: Lafayette, LA Posts: 270	Well, I was brickwalling the preamp... a quick email to Doug Oade cleared that up. Apparently you are supposed to have the software selectable -20db pad on at all times unless you can't get enough gain. This was contrare to the original Marantz circuit that sounded like poo if you did engage the -20db pad. Just did some quick test and everything is perfect and I couldn't be happier again... well other than figuring out what I will do about that dialog that can't be reshot!

June 22nd, 2006, 01:03 PM	#22
Kevin Richard Major Player Join Date: Mar 2005 Location: Lafayette, LA Posts: 270	I'm all about doing things right or not doing them at all but at 700-1600 bucks just to split my mic into two channels of a $750 recorder what is the real harm in just using a Y? I understand if it were money no object but as we all know money is an object and for example this short is being filmed on ZERO budget and actors doing it for free as long as we pay thier plane tickets. I'm the producer/grip/AC(apparently)/electritian/AD oh, and when that is all done they go "ready for sound?" and I'm like umm where is my gear at anyway as I've been having to do everyone else's job. And trust me, it's not that I WANT all those credits as I will probably only credit myself as producer and sound it's just with such a small inexperienced crew you have to wear many hats. Honestly I wish I could trust someone else to set levels and do sound so I didn't have to do that! Unless someone can explain to me a huge short coming to the Y cable I can't justify that expense at this point. Don't get me wrong, I am VERY greatful for the advice!

June 22nd, 2006, 06:27 PM	#30
Seth Bloombaum Inner Circle Join Date: Sep 2003 Location: Portland, Oregon Posts: 3,420	Well, if both mic inputs are feeding phantom into the Y cable that could be as much as 96 volts to the mic. Or, it could be a lot less, depending on Marantz & Oade. But it's probably way more than that little capacitor wants to see. Does the Marantz allow you to turn off phantom individually per channel? Lots of people record a second channel at -12 to -20db from their first for backup. No engineer I know uses a Y cable to do it. If the device doesn't do it natively (like a lot of sony cams), or no mixer, why risk good audio on both channels to impedance mismatch and double phantom to make a backup? Two bad channels is not twice as good as one good channel. Just do a good job on the first channel. Use the mic like it was designed to be used. In my opinion that's appropriate risk management. Most people who stick with audio professionally develop a "best practices" sort of approach. Using a Y increases risk. Not having a backup channel? That risk can be managed by good engineering.