Output levels of Sennheiser G3 receiver

Richard Crowley · May 5th, 2012, 09:17 AM

It is not damaging to the DR-100mkII which is supplying the phantom power. But it IS DAMAGING to the receiver. The output circuit of most audio equipment is NOT protected against phantom power voltages and you run a VERY HIGH risk of damage to the source device. You MUST NOT feed phantom voltage back into the output circuit of equipment that isn't prepared for it.

There are several ways of working around this problem. You could start at the recorder and disable (or switch) the phantom power to the inputs separately. Or you could beef up the wireless receiver with higher voltage output capacitors to withstand 48V. Or easiest (IMHO) is to simply make a DC-blocking cable to interconnect the two. It is probably easiest to do and doesn't require hacking either the recorder or receiver.

Rob Lombardi · May 5th, 2012, 04:12 PM

The DC-blocking cable is definitely the route I want to go, Richard. I've been looking all around for a place that would carry such a cable (adapter?) but can't seem to find one. Is the only option to make one? Also, does it matter that the 3.5mm to XLR cable that comes with the G3 kit (the CL 100) is unbalanced?

Rick Reineke · May 6th, 2012, 11:31 AM

If your going to modify the Sennheiser cable you'll need a 'new' XLR connector, the ones that I've seen are of a molded-on design and can't be altered. New XLR connectors are cheap though... about $ 2.50USD

Zoran Vincic · May 6th, 2012, 01:24 PM

There's no need for a special DC blocking cable.
The Sennheiser receivers, together with all modern audio devices properly DESIGNED to connect to microphone XLR inputs won't be damaged nor affected by phantom power.

However it may be damaged if it's connected to the XLR input while the phantom power is turned on. The same warning goes for the condenser mics too.

Richard Crowley · May 6th, 2012, 02:33 PM

Quote:

Originally Posted by Zoran Vincic

The Sennheiser receivers, together with all modern audio devices properly DESIGNED to connect to microphone XLR inputs won't be damaged nor affected by phantom power.

Do you have an authoritative reference source for that statement? I have heard too many horror stories of equipment that was either temporarily rendered inoperable or permanently damaged from feeding P48 back into the output that was never designed for such high voltages.

Zoran Vincic · May 6th, 2012, 06:19 PM

Reading my previous post I see that I made an error, I should have emphasized the word "properly".

I'm no Eric Cartmann but everytime a G2/G3 receiver I worked with was fed with phantom power, nothing happened. I know that it would be more exciting if I said turned the pp on and then bam, fire, smoke everywhere, run for your lives...

But it was more like oh, left the PP on again...oh well, let me turn it off and continue to work as if nothing happened...dull, isn't it?

If you wan't to be on a safe side, just read the manual first. One would think that if a device could/would be damaged by PP there would be a warning in the manual. In nice, big, bold letters with plenty of exclamation marks.

Feel free to correct me if I'm wrong but I'm pretty sure that the G3 portable receiver's manual doesn't even mention phantom power at all...

Jase Tanner · May 6th, 2012, 07:55 PM

I frequently run my G3 and an NTG-3 through a Sound Devices Mixpre. The phantom power on the mixpre is either on or off for both channels. G3 is still alive and well.

Rob Lombardi · May 6th, 2012, 09:29 PM

Quote:

Originally Posted by Zoran Vincic

But it was more like oh, left the PP on again...oh well, let me turn it off and continue to work as if nothing happened...dull, isn't it?

That's great that is doesn't explode into a million bits, but the situation I'm dealing with is that I want to use it while phantom power is on. It seems there isn't a quick "Hey, just buy this cable" kind of solution.

Zoran Vincic · May 7th, 2012, 05:25 AM

As I said earlier, you're free to use it with PP engaged and without a special cable of any kind.

Rob Lombardi · May 7th, 2012, 09:39 AM

Fair enough. But won't it introduce a bunch of "hum" and battery drain?

Paul R Johnson · May 7th, 2012, 12:14 PM

You might get the odd crack when you stick the plug in, but I've never had hum. Phantom power is current limited, so extra battery drain isn't really a problem. Some weird things can happen - some Soundcraft mixers, that maybe are providing your camera an audio feed, react oddly if phantom is present - the LEDs suddenly going up to full - but no impact on the sound.

John Willett · May 8th, 2012, 08:34 AM

Quote:

Originally Posted by Rick Reineke

NO! ... The G2/3 has an unbalanced configuration and has been known to cause excessive noise and drain the recorder's batteries faster than you can say "how come my new batteries are dead already".

Only the 100 series pocket receivers are unbalanced - the mains receivers and G1/G2 500 series and 2000 series pocket receivers are all balanced.

Quote:

Originally Posted by Richard Crowley

You can put a DC-blocking capacitor in the XLR connector to keep the P48 from back-feeding into the receiver output circuit. I would recommend also putting a clamp diode to prevent the turn-on/charging impulse current from getting through to the receiver output circuitry. I can draw you a diagram if you think that is what you want to do. It should not be too difficult to solder these components inside the XLR connector shell.

This is the best option.

John Willett · May 8th, 2012, 08:38 AM

Quote:

Originally Posted by Zoran Vincic

There's no need for a special DC blocking cable.
The Sennheiser receivers, together with all modern audio devices properly DESIGNED to connect to microphone XLR inputs won't be damaged nor affected by phantom power.

However it may be damaged if it's connected to the XLR input while the phantom power is turned on. The same warning goes for the condenser mics too.

Yes - the evolution receivers are protected against phantom power, except the first batch of G2 receivers.

But - I would not like to unbalance phantom power when you also want to use the phantom for another mic.

But - why don't you plug the receiver into a line input rather than a mic.input? It's the better option, anyway.

Zoran Vincic · May 8th, 2012, 08:59 AM

It's actually better to connect it to a mic input as the receiver doesn't really output a line level signal even when the output is boosted to + 12dB.

Steve House · May 8th, 2012, 10:11 AM

If it's not outputting a high enough signal to drive a line-level input properly when the output adjustment is on one of the top settings, you're probably under-modulating at the transmitter. Set the transmitter's audio input sensitivity higher.

May 5th, 2012, 09:17 AM	#46
Richard Crowley Trustee Join Date: Aug 2007 Location: Portland, Oregon Posts: 1,238	Re: Output levels of Sennheiser G3 receiver It is not damaging to the DR-100mkII which is supplying the phantom power. But it IS DAMAGING to the receiver. The output circuit of most audio equipment is NOT protected against phantom power voltages and you run a VERY HIGH risk of damage to the source device. You MUST NOT feed phantom voltage back into the output circuit of equipment that isn't prepared for it. There are several ways of working around this problem. You could start at the recorder and disable (or switch) the phantom power to the inputs separately. Or you could beef up the wireless receiver with higher voltage output capacitors to withstand 48V. Or easiest (IMHO) is to simply make a DC-blocking cable to interconnect the two. It is probably easiest to do and doesn't require hacking either the recorder or receiver.

May 5th, 2012, 04:12 PM	#47
Rob Lombardi New Boot Join Date: May 2012 Location: Dubuque, Iowa Posts: 5	Re: Output levels of Sennheiser G3 receiver The DC-blocking cable is definitely the route I want to go, Richard. I've been looking all around for a place that would carry such a cable (adapter?) but can't seem to find one. Is the only option to make one? Also, does it matter that the 3.5mm to XLR cable that comes with the G3 kit (the CL 100) is unbalanced?

May 6th, 2012, 11:31 AM	#48
Rick Reineke Inner Circle Join Date: Aug 2008 Location: New York Posts: 2,039	Re: Output levels of Sennheiser G3 receiver If your going to modify the Sennheiser cable you'll need a 'new' XLR connector, the ones that I've seen are of a molded-on design and can't be altered. New XLR connectors are cheap though... about $ 2.50USD

May 6th, 2012, 01:24 PM	#49
Zoran Vincic Regular Crew Join Date: Jul 2010 Location: Split, Croatia Posts: 189	Re: Output levels of Sennheiser G3 receiver There's no need for a special DC blocking cable. The Sennheiser receivers, together with all modern audio devices properly DESIGNED to connect to microphone XLR inputs won't be damaged nor affected by phantom power. However it may be damaged if it's connected to the XLR input while the phantom power is turned on. The same warning goes for the condenser mics too.

May 6th, 2012, 06:19 PM	#51
Zoran Vincic Regular Crew Join Date: Jul 2010 Location: Split, Croatia Posts: 189	Re: Output levels of Sennheiser G3 receiver Reading my previous post I see that I made an error, I should have emphasized the word "properly". I'm no Eric Cartmann but everytime a G2/G3 receiver I worked with was fed with phantom power, nothing happened. I know that it would be more exciting if I said turned the pp on and then bam, fire, smoke everywhere, run for your lives... But it was more like oh, left the PP on again...oh well, let me turn it off and continue to work as if nothing happened...dull, isn't it? If you wan't to be on a safe side, just read the manual first. One would think that if a device could/would be damaged by PP there would be a warning in the manual. In nice, big, bold letters with plenty of exclamation marks. Feel free to correct me if I'm wrong but I'm pretty sure that the G3 portable receiver's manual doesn't even mention phantom power at all...

May 6th, 2012, 07:55 PM	#52
Jase Tanner Major Player Join Date: Feb 2007 Location: Vancouver, Canada Posts: 346	Re: Output levels of Sennheiser G3 receiver I frequently run my G3 and an NTG-3 through a Sound Devices Mixpre. The phantom power on the mixpre is either on or off for both channels. G3 is still alive and well.

May 7th, 2012, 05:25 AM	#54
Zoran Vincic Regular Crew Join Date: Jul 2010 Location: Split, Croatia Posts: 189	Re: Output levels of Sennheiser G3 receiver As I said earlier, you're free to use it with PP engaged and without a special cable of any kind.

May 7th, 2012, 09:39 AM	#55
Rob Lombardi New Boot Join Date: May 2012 Location: Dubuque, Iowa Posts: 5	Re: Output levels of Sennheiser G3 receiver Fair enough. But won't it introduce a bunch of "hum" and battery drain?

May 7th, 2012, 12:14 PM	#56
Paul R Johnson Inner Circle Join Date: Nov 2005 Location: Lowestoft - UK Posts: 4,044	Re: Output levels of Sennheiser G3 receiver You might get the odd crack when you stick the plug in, but I've never had hum. Phantom power is current limited, so extra battery drain isn't really a problem. Some weird things can happen - some Soundcraft mixers, that maybe are providing your camera an audio feed, react oddly if phantom is present - the LEDs suddenly going up to full - but no impact on the sound.

May 8th, 2012, 08:59 AM	#59
Zoran Vincic Regular Crew Join Date: Jul 2010 Location: Split, Croatia Posts: 189	Re: Output levels of Sennheiser G3 receiver It's actually better to connect it to a mic input as the receiver doesn't really output a line level signal even when the output is boosted to + 12dB.

May 8th, 2012, 10:11 AM	#60
Steve House Inner Circle Join Date: Mar 2005 Location: Hamilton, Ontario, Canada Posts: 5,742	Re: Output levels of Sennheiser G3 receiver If it's not outputting a high enough signal to drive a line-level input properly when the output adjustment is on one of the top settings, you're probably under-modulating at the transmitter. Set the transmitter's audio input sensitivity higher. __________________ Good news, Cousins! This week's chocolate ration is 15 grams!