Topic: Edirol R-44 - 4 Channel Recorder (Part Tres)

[kirk97132]

You must be a festie guy.  I have never had to worry about that for the most part.  I just label them with a silver sharpie(easier to see in low light) with a 1, 2, 3.  and then use them in chronological order.  IE if I start at 2 I go to 3 next and so on.  But I have only had to do use two cards in one night.  I just keep it in the little plastic case they come in and stick the extra in my pocket when I set up at the show.  I dump them every night, and ever since I had an HD-P2 I ALWAYS format the cards between use.  I had a couple of errors on the P2 without formatting and I have never run my cards in the R-44 without doing this and they have been flawless. 

[Gutbucket]

Similarly, I mark cards with a sharpie 1,2,3,4,5,6,..  I mark rechargeable batteries the same way.

For single events I'll just bring a spare card along as backup. For long festival type things I carry extra cards in two ziplocks, one marked 'free' the other marked 'used' so there is no confusion as to which have available space. I keep notes on what's on which along with other recording notes on a note pad.  It is very convenient to have large capacity cards for those situations, cutting down on card swapping, card tracking, and wasted space on multiple cards.

I always use the AA batteries in sequential numbered pairs or groups of 4.  Fresh batteries all point the same way in their plastic cases, discharged batteries alternate directions. Easy enough to push the button to check the lithium-ions. Works for me.

[cybergaloot]

For single events I'll just bring a spare card along as backup. For long festival type things I carry extra cards in two ziplocks, one marked 'free' the other marked 'used' so there is no confusion as to which have available space.
<snip>
Works for me.

Until you lose the baggie! Sorry, I had to toss that one in.  That had to hurt. But the "used" baggie idea sounds good!

I like the idea of putting the purchase date on the battery packs as well as giving them a identifying number.

I saw a holder system for AA batteries somewhere on the Internet and meant to go back and get it but  never did. It had plastic tubes the batteries went in, green for good, red for used. I keep hitting up the cigar smokers I know to get any of the tubes some of them come in in hopes that some may work for mics, batteries, etc. So far no luck though. What would be great is if they came in sizes that would hold four AAs at a time since that is my most common combination between the R-44 and my camera.

[Gutbucket]

Until you lose the baggie! Sorry, I had to toss that one in.  That had to hurt. But the "used" baggie idea sounds good!

Yep, lost a Ziplock with card #1 in it a couple years back at Live Oak. Had all of Friday's recordings on it. You remembered that?  I've kept a close hand on them ever since. 

[cybergaloot]

Until you lose the baggie! Sorry, I had to toss that one in.  That had to hurt. But the "used" baggie idea sounds good!

Yep, lost a Ziplock with card #1 in it a couple years back at Live Oak. Had all of Friday's recordings on it. You remembered that?  I've kept a close hand on them ever since. 

Yep, I remember all sorts of stuff that I shouldn't and can't remember a damn thing I should. 

BTW, I went by RatShack today and picked up some of the M-sized connectors to make up a power cable for the DVD battery & R-44 like you did. While I was there I noticed they had the Targas knockoff of the large Gorillapod camera tripod on sale for $7.50. I grabbed one and headed to the register. It rang up as costing $3.50 so I grabbed a second one. Pretty good deal for a versatile little tripod! 

[DSatz]

Some quick notes:

- In late February I recorded my first live concert with my new R-44 and had strange RFI problems which I reported here. Two nights ago I recorded another concert with the R-44 in the same location using a somewhat similar setup, and had no problems with RFI whatsoever. In the meantime I'd rounded up four Shure A15RF filters and had them with me "just in case," but they weren't needed.

- Apart from the great convenience while recording with three or four mikes, the R-44 is FAR more convenient than my old laptop arrangement for playing back three or four channels into a mixer. It makes a huge difference in my being able to get post-production work done within a limited time. I'm very happy about that.

- My one remaining complaint is the difficulty of seeing the exact peak levels of each channel when those levels are in the -6 to -3 dBFS range. This is forcing me to under-record somewhat, just to play it safe.

- The people here who are chiming in with "I powered four [whatever type of] microphones via the R-44 with no problems" may be missing the point somewhat. If a microphone is marginally underpowered, it may work OK or it may have decreased headroom and other possible problems, depending on the microphone's design and, of course, how far below spec the voltage actually is.

If you're using mikes that can normally handle 130 dB SPL, for example, suddenly their clip point may have dropped to 120 dB SPL. Especially for microphones with internal DC/DC converters (which is essentially every transformerless microphone in the world), the SPL limit will most likely not be proportional to the power supply voltage; the loss of headroom may be quite a bit more severe than you might expect. I have seen graphs of maximum SPL versus supply voltage for some types of condenser microphones in which there was a very rapid decline past a certain point.

Of course that loss of headroom wouldn't matter if your microphones don't need to handle very high sound pressure levels. But my guess is that most people who are posting these remarks are doing so without first checking either the voltage at the power supply or the maximum SPL that the mikes can handle when powered by that reduced voltage. And that missing information is very important.

Power supplies aren't expected to be perfect, so the IEC standard for phantom powering specifies tolerance limits. Microphones are generally designed on the assumption that the powering will be within that set of tolerances--not some other set of tolerances that the manufacturer finds more convenient. I've dealt particularly with German microphone engineers for decades now, and have found that they compartmentalize their thinking almost completely. Even though on one level they are all aware of the problems, it's as if they can't quite bring themselves to believe that another engineer would design a "professional" product that doesn't comply with the standard.

--best regards

[Gutbucket]

I posted this in the Team R44 thread so apologies to those tracking both treads.

So far I have only a few gripes with the R44-
1) No detent at the +/-0 digital level position (inner knob) for the channel input gains.
2) The red clip indicator light is missing.
3) Like others have mentioned, the metering could be better. Yet I'm rather used to the identical metering on the R09 and the R44 is identical except for the missing clip indicator light.
4) No settable delay function available as a record/playback effect, which would seem an obvious application and more useful than some of the other functions.
5) No pan function for monitoring or playback mix out, which would be another obvious application that could be handled via a record/playback effect.

The last two could conceivably be added through a future firmware update.  Any Edirol engineers lurking?

[skotdee]

- The people here who are chiming in with "I powered four [whatever type of] microphones via the R-44 with no problems" may be missing the point somewhat. If a microphone is marginally underpowered, it may work OK or it may have decreased headroom and other possible problems, depending on the microphone's design and, of course, how far below spec the voltage actually is.

If you're using mikes that can normally handle 130 dB SPL, for example, suddenly their clip point may have dropped to 120 dB SPL. Especially for microphones with internal DC/DC converters (which is essentially every transformerless microphone in the world), the SPL limit will most likely not be proportional to the power supply voltage; the loss of headroom may be quite a bit more severe than you might expect. I have seen graphs of maximum SPL versus supply voltage for some types of condenser microphones in which there was a very rapid decline past a certain point.

Of course that loss of headroom wouldn't matter if your microphones don't need to handle very high sound pressure levels. But my guess is that most people who are posting these remarks are doing so without first checking either the voltage at the power supply or the maximum SPL that the mikes can handle when powered by that reduced voltage. And that missing information is very important.

Interesting. So how can one figure if it will indeed adequately power a particular microphone? For instance, Im looking at using it to power 4 AKG480 mics. From the 480 specs, they need a supply voltage of 48v, with current consumption of <2 mA. The R-44 supplies 48 V + or - 4 V, 8 mA per 1 channel (20 mA or less in all channels), so I should be fine, no? Not sure what that "+ or -" is after 48 V though...

Am I overthinking this? If Im purchasing a 4 channel recorder I obviously want it to power 4 mics... Seems like a given that it would.

[kbergend]

- The people here who are chiming in with "I powered four [whatever type of] microphones via the R-44 with no problems" may be missing the point somewhat. If a microphone is marginally underpowered, it may work OK or it may have decreased headroom and other possible problems, depending on the microphone's design and, of course, how far below spec the voltage actually is.

If you're using mikes that can normally handle 130 dB SPL, for example, suddenly their clip point may have dropped to 120 dB SPL. Especially for microphones with internal DC/DC converters (which is essentially every transformerless microphone in the world), the SPL limit will most likely not be proportional to the power supply voltage; the loss of headroom may be quite a bit more severe than you might expect. I have seen graphs of maximum SPL versus supply voltage for some types of condenser microphones in which there was a very rapid decline past a certain point.

Missing the point entirely, as a matter of fact!  In my own case, I was recording at very modest SPL levels.  Thanks for the clarification -- now I'm thinking I should go out and record some jackhammers with 4 vs. 2 mics connected to see how well they hold up.  I think all the condensers I use have nominal requirements of 48V ±4.

Am I correct in assuming that the voltage/current of the power source to the R-44 has no direct relation to the ability of the unit to power the mics, as long as the power source is within Edirol's specs?

[skotdee]

Just got this response from Oade:

The R44 has 20 mils of current for all 4 channels, most mics draw 2 to 4 mils each. Only a very few, like EarthWorks mics need more,. You can run 4 C480s ( or 4 of most any  mic) without any trouble.
I hope this helps...Doug

[kbergend]

Interesting. So how can one figure if it will indeed adequately power a particular microphone? For instance, Im looking at using it to power 4 AKG480 mics. From the 480 specs, they need a supply voltage of 48v, with current consumption of <2 mA. The R-44 supplies 48 V + or - 4 V, 8 mA per 1 channel (20 mA or less in all channels), so I should be fine, no? Not sure what that "+ or -" is after 48 V though...

The "+ or -" means the actual voltage should be between 44 and 52 volts, but if I understand DSatz's test measurements, that's not necessarily the case for certain mics with four of them drawing power.

I'm also planning on using four 480s with the R-44, so I'm somewhat reassured to read Doug's assessment. 

[DSatz]

skotdee, if your R-44 is like mine, then based on what I measured, I think you'll have no problem at all with it powering four of your AKG microphones. Doug Oade's summary is a bit too warm and fuzzy--quite a few microphones draw more than 4 mA, not just a few rare types--but if your microphones draw less than 3 mA apiece then there really is no problem.

kbergend, perhaps the issue is open-circuit voltage versus voltage under load. For 48-Volt phantom powering the specified tolerance is ±4 Volts, but that's open-circuit voltage--what you would measure at an XLR socket that has no microphone connected to it. The usual circuit feeds the DC to each microphone through a matched pair of resistors specified at 6.8 kOhms each for 48-Volt powering. When a microphone is connected, half of its supply current flows through each of those resistors--and the more current that flows through any resistor, the more the voltage drops across that resistor. So the voltage actually delivered to the microphone is less, in proportion to the current drawn.

If a microphone draws 2 mA, then 1 mA is flowing through each of the 6.8 kOhm resistors, causing a voltage drop of 6.8 Volts across each resistor. Thus if the open-circuit voltage was 48 Volts to begin with (and if the supply itself is perfect and doesn't sag at all under load), then the voltage actually reaching the microphone will be 48 - 6.8 Volts, or 41.2 Volts. That is completely in accord with the standard; only the open-circuit voltage is specified, and the actual voltage reaching the microphone is supposed to be lower in proportion to the current being drawn. The microphone designers know this and work with it.

If a microphone draws ca. 7 mA then it is really receiving only about 24 Volts. To draw more than 7 mA is actually to pass the point of diminishing returns as far as power is concerned--at 10 mA (Earthworks), the drop across each resistor is 5 x 6.8 = 34 Volts so the great majority of the power is being expended in the feed resistors, not the microphone circuitry; it is simply wasted as heat.

Now as it happens, the supply in the R-44 isn't quite perfect, and it does sag as more current is drawn--if you connect 1, 2, or 3 microphones at 4.5 mA apiece and measure the open-circuit voltage at the fourth, unused socket, it keeps getting lower as more and more current is drawn from the other sockets. Ideally that should not be the case, but as long as the equivalent open-circuit voltage stays in the 44 - 52 Volt range and the recorder isn't harmed by being pushed up to its limit, then everything should work fine.

Unfortunately what I found is that my R-44 can't actually deliver even 16-18 mA without the voltage sagging below the tolerance limit. Thus I avoid connecting four Schoeps CMC-series 48-Volt mikes at the same time, simply because the recorder is at or slightly past its actual limit then, and I'm averse to operating equipment that way. I have seen a phantom power supply literally burn itself out; it smells funny, it can be expensive to repair, and it spoils the recording, which kind of defeats the purpose of my being there.

[MaxJames]

skotdee, if your R-44 is like mine, then based on what I measured, I think you'll have no problem at all with it powering four of your AKG microphones. Doug Oade's summary is a bit too warm and fuzzy--quite a few microphones draw more than 4 mA, not just a few rare types--but if your microphones draw less than 3 mA apiece then there really is no problem.

kbergend, perhaps the issue is open-circuit voltage versus voltage under load. For 48-Volt phantom powering the specified tolerance is ±4 Volts, but that's open-circuit voltage--what you would measure at an XLR socket that has no microphone connected to it. The usual circuit feeds the DC to each microphone through a matched pair of resistors specified at 6.8 kOhms each for 48-Volt powering. When a microphone is connected, half of its supply current flows through each of those resistors--and the more current flows through any resistor, the more the voltage drops across that resistor. So the voltage actually delivered to the microphone is less, in proportion to the current drawn.

If a microphone draws 2 mA, then 1 mA is flowing through each of the 6.8 kOhm resistors, for a voltage drop of 6.8 Volts across each resistor. Thus if the open-circuit voltage was 48 Volts to begin with (and if the supply itself is perfect and doesn't sag at all), then the voltage actually reaching the microphone will be 48 - 6.8 Volts, or 41.2 Volts. That is completely in accord with the standard; only the open-circuit voltage is specified, and the actual voltage reaching the microphone is supposed to be lower in proportion to the current being drawn. The microphone designers know this and work with it.

If a microphone draws ca. 7 mA then it is really receiving only about 24 Volts. To draw more than 7 mA is actually to pass the point of diminishing returns as far as power is concerned--at 10 mA (Earthworks), the drop across each resistor is 5 x 6.8 = 34 Volts so the great majority of the power is being expended in the feed resistors, not the microphone circuitry; it is simply wasted as heat.

Now as it happens, the supply in the R-44 isn't quite perfect, and it does sag as more current is drawn--if you connect 1, 2, or 3 microphones at 4.5 mA apiece and measure the open-circuit voltage at the fourth, unused socket, it keeps getting lower as more and more current is drawn from the other sockets. Ideally that should not be the case, but as long as the equivalent open-circuit voltage stays in the 44 - 52 Volt range and the recorder isn't harmed by being pushed up to its limit, then everything should work fine.

Unfortunately what I found is that the recorder can't actually deliver even 16-18 mA without the voltage sagging below the equivalent of the 44-Volt tolerance limit. Thus the reason I avoid connecting four Schoeps CMC-series 48-Volt mikes at the same time is simply that the recorder is at or slightly past its actual limit then, and I'm averse to operating equipment that way. I have seen a phantom power supply literally burn itself out; it smells funny, it can be expensive to repair, and it spoils the recording, which kind of defeats the purpose of my being there.

The above is completely untrue. Have just tested my R-44: Open circuit phantom is 47.9V. With one microphone connected drawing 5 mA, the phantom drops to 47.75V, two mics connected eaching drawing 5 mA, the phantom drops to 47.6V...With four mics connected eaching drawing 5 mA (total 20 mA), the phantom drops to 47.4V, well within the specs. End of story. You can test yours to confirm or to get the exact voltage, but please do not mix speculations with facts. 

 

[Ozpeter]

Your test says one thing, his another - I don't see where 'speculation' comes into it.  Presumably you were using the same model of mic as in his test?  Otherwise your test as a check on his would appear to be invalid.

[MaxJames]

Your test says one thing, his another - I don't see where 'speculation' comes into it.  Presumably you were using the same model of mic as in his test?  Otherwise your test as a check on his would appear to be invalid.

The "speculation" is his "calculations" indicating that currents drawn in one XLR connector will affect the phantom supply voltage in other XLR connectors, because of the 6.8 K ohm. This is simply not true, a conclusion obviously not based on measurements.