Damn.... I applied phantom power to my RCA-DX 77 !!
LeepinCat
(wonderful) RCA-DX 77
I keep forgetting to turn OFF the f'ing phantom power!
Any suggestions, and what is this doing to my RCA !!?? (Thankfully,
it's still working)
Thanks, -Rj
Don Pearce
wrote:
Absolutely nothing. The mic doesn't care.
d
Pearce Consulting
http://www.pearce.uk.com
Steve King
news:44291f23....@text.usenet.plus.net...
> On 27 Mar 2006 09:14:16 -0800, "LeepinCat" <nulladd...@gmail.com>
> wrote:
>
>>Switching from a phantom powered Neumann condenser to my old,
>>(wonderful) RCA-DX 77
>> I keep forgetting to turn OFF the f'ing phantom power!
>>
>>Any suggestions, and what is this doing to my RCA !!?? (Thankfully,
>>it's still working)
>>
>>Thanks, -Rj
>
> Absolutely nothing. The mic doesn't care.
Because the 77DX has an output transformer that isolates the microphone
elements including the ribbon, which might otherwise be damaged by phantom's
48 VDC.
Steve King
Don Pearce
No. It wouldn't matter if there weren't a transformer. Phantom power
is applied to both live terminals, so there is no net voltage across
them, so no current. If the ribbon were connected to ground at one
end, there would be a small current but still no damage. Remember that
each phantom connection (2 per mic) is carried via a 6.2kohm resistor.
Steve King
Tell that to a Beyer M260 I once had.
This is from the Royer site: "The ribbon elements in some vintage ribbon
microphones can be harmed or even destroyed by the presence of phantom
power. For this reason, it is commonly recommended that phantom power be
turned off when using ribbon microphones. Leaving phantom power on can
result in a stretched or completely blown ribbon. In some cases, the
microphone may still operate, but at a greatly diminished capacity."
Your comment about ribbon mics not being at risk even if the ribbon were
connected to ground at one end seems to be at odds with experience. I used
to have a large patchbay with mic lines routed through it to pre-amp inputs.
Phantom power was applied at the patch bay. Not turning off the phantom
power, when patching mics which was our practice, seemd to be what got the
Beyer. Again, here's what Royer says: If phantom power is on, ribbon
microphones can be damaged when cross-patched through a patch bay.
Here's what happens. Patch cables utilize "tip-ring-sleeve" connectors. When
a patch cable is inserted into either the upper or lower row, the phantom
power is momentarily shorted to connections that phantom power should not be
applied to. In other words, as the connector is inserted, it is, in effect,
acting (temporarily) like a miss-wired cable and applying phantom power to
the wrong leads. Ribbon mics are particularly intolerant to this because, in
the brief moment that a patch cable is being inserted into a
phantom-power-charged patch bay, phantom power is applied directly to the
ribbon element through the transformer! Each brief patching-related jolt of
phantom power across the ribbon element is equivalent to a year or more of
recordings made on the mic. A ribbon element that is designed to last ten or
fifteen years before replacement can literally be blown overnight by patch
bay mishaps."
Should phantom power blow a ribbon mic? Maybe not. Can it? Evidently, yes
under some circumstances. I prefer advising caution, or in the case of my
own shop, having a policy to double-check that Phantom power is not supplied
to ribbon microphones.
Steve King
Don Pearce
<steveSP...@stevekingSPAMBLOCK.net> wrote:
Maximum current you can get out of one branch of a phantom supply is
about 7mA. That should do no damage at all to a ribbon - certainly not
"blow it apart".
And wouldn't it be nice if the volts disappeared when you turned off
phantom, instead of having to wait half an hour while an electrolytic
discharges.
Mike Rivers
LeepinCat wrote:
> Switching from a phantom powered Neumann condenser to my old,
> (wonderful) RCA-DX 77
> I keep forgetting to turn OFF the f'ing phantom power!
You problbly haven't done any damage yet, but it's not a good idea to
plug and unplug any mic with the phantom power on. Tie a knot in the
end of the cable to remind you.
Yeah, I know, the classic vintage Neve consoles had the phantom power
on all the time, but remember that in those days, studios didn't juggle
mics nearly as much as we do now. The mics were always plugged in and
just moved to where they were needed.
Steve King
news:1143491840.8...@v46g2000cwv.googlegroups.com...
I was at Sound Studios in Chicago, when three of the earliest Neve consoles
in the US were delivered. Rupert flew in to schmooze the studio owners.
While he was there, we added switches for phantom power on a channel by
channel basis on the larger of the boards. We did swap microphones around a
lot.
Steve King
Predrag Trpkov
> And wouldn't it be nice if the volts disappeared when you turned off
> phantom, instead of having to wait half an hour while an electrolytic
> discharges.
What exactly is being risked if that precautionary measure is ignored?
Predrag
Paul Goelz
>about 7mA. That should do no damage at all to a ribbon - certainly not
>"blow it apart".
I had the "good fortune" to actually be watching the ribbon in my 77D
as I absent mindedly applied a VOM across the mic. The ribbon
stretched about as far as it possibly could without breaking. When I
removed the VOM the ribbon (sans corrugations) sagged horribly and was
totally unusable.
That was a while back and I obtained a new ribbon from someone at RCA
(as I recall) and managed to get it installed OK. The mic is fully
functional again, but suffice it to say that I would NEVER again apply
ANY voltage at ANY current across a ribbon mic. Not sure what the
actual current was, but I doubt it was much.
Paul
Paul Goelz
Rochester Hills, Michigan USA
Don Pearce
Which precautionary measure? Your precedent is not clear.
Scott Dorsey
>
> This is from the Royer site: "The ribbon elements in some vintage ribbon
>microphones can be harmed or even destroyed by the presence of phantom
>power. For this reason, it is commonly recommended that phantom power be
>turned off when using ribbon microphones. Leaving phantom power on can
>result in a stretched or completely blown ribbon. In some cases, the
>microphone may still operate, but at a greatly diminished capacity."
RCA built some microphones which had a grounded center tap on the transformer
secondary. The 77DX was not this way, but some 44 and 74 mikes are.
These microphones do not handle phantom power gracefully at all, because
on them, there IS a path for current to flow between the transformer secondary
and ground.
Phantom power must be avoided on these mikes. But it is not because they
are ribbon mikes, it is because they are ribbon mikes with a particular
transformer configuration that is otherwise quite rare.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Steve
If there is a momentary short say from a patch jack.
The transformer may convert the 7 mA to a pulse of around 500mA or more
at the ribbon.More than enough to do damage.
Steve
Richard Crowley
> I had the "good fortune" to actually be watching the ribbon in my 77D
> as I absent mindedly applied a VOM across the mic. The ribbon
> stretched about as far as it possibly could without breaking. When I
> removed the VOM the ribbon (sans corrugations) sagged horribly and was
> totally unusable.
Then we should all be thankful that is NOT how phantom
power is applied to microphones.
Ty Ford
(in article <e09km2$im0$1...@ss405.t-com.hr>):
As it was told to me, in certain situations, as you plug the mic in with
Phantom ON, the order in which the pins connect can, if done just a certain
way, cause the Phantom Power to zap the ribbon.
Not in every case and I don't know much more about it than to say that I have
plugged in a ribbon to a Phantom On preamp without destroying it on a number
of occasions. (not on purpose, mind you.)
Regards,
Ty Ford
-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com
Ken Winokur
about plugging mics in and out with the Phantom on. I haven't had any
obvious problems. Are there any other mics that are sensitive to this?
Is there a cumulative problem with zapping even sturdy dynamic or
condenser mics over and over?
Carey Carlan
news:g9Kdnb_7iKx5q7TZ...@comcast.com:
> As it was told to me, in certain situations, as you plug the mic in
> with Phantom ON, the order in which the pins connect can, if done just
> a certain way, cause the Phantom Power to zap the ribbon.
If one of the signal leads is faulty in the mic cable, you'll see the 48
volts between the other lead and ground. That was the warning I received
here years ago.
Don Pearce
wrote:
You ought to think about one. I dug one out of a very deep old
cupboard the other day to see what it would do. It is a Grampian GR2H,
made in the 1960's. I compared it to some modern stuff, and was very
pleasantly surprised.
Have a listen to the comparison here. Excuse slow downloads, but I'm
experimenting with my own web server over an ADSL connection:
Steve King
I'm unfamiliar with the Grampion, but it sounds lovely. Try that mic on
brass. If I had to mic a fluglehorn, I might pull the Grampion for a try.
Steve King
Don Pearce
Great isn't it? Unfortunately no brass around at the moment, but I
know what you mean. If only more modern mics were that relaxed and
open.
Scott Dorsey
>
>Great isn't it? Unfortunately no brass around at the moment, but I
>know what you mean. If only more modern mics were that relaxed and
>open.
Some of them are! There are some really top-notch ribbon mikes being
made today, including the Coles 4040.
Don Pearce
>Don Pearce <don...@pearce.uk.com> wrote:
>>
>>Great isn't it? Unfortunately no brass around at the moment, but I
>>know what you mean. If only more modern mics were that relaxed and
>>open.
>
>Some of them are! There are some really top-notch ribbon mikes being
>made today, including the Coles 4040.
>--scott
I haven't heard the Coles, but I'm sure you're right. But the price
certainly doesn't compare. I think I paid about 15 pounds for the
Grampian. Not sure what I'd take for it now, though.
Predrag Trpkov
Oh sorry. I meant waiting for half an hour while an electrolytic discharges.
I always wait a little, maybe half a minute or a minute, before
disconnecting a condenser microphone and connecting another. Having to wait
for half an hour seems rather impractical during a session.
Predrag
Scott Dorsey
>
>I haven't heard the Coles, but I'm sure you're right. But the price
>certainly doesn't compare. I think I paid about 15 pounds for the
>Grampian. Not sure what I'd take for it now, though.
That's the thing. In the seventies and eighties, prices on ribbon mikes
were artificially low because they were unfashionable. I remember folks
trashing 77DXes because they weren't worth the $50 to replace the ribbons
on them. I still have a couple I rescued from dumpsters.
Then for a while, collectors were bidding them up, and prices were going
through the roof for nonfunctional microphones that people were just buying
to put in display cases in Japan.
Now there are folks going into production with older designs (like Wes
Dooley's replica RCA 44, which sounds and works just like the original
RCA and sells for less), as well as with newer ones (like the Coles 4040)
and there is more of an interest in some of the ribbon designs that never
did go out of production (like the Beyers and the Coles 4038). On top of
this the Asian currency crisis dropped what the Japanese collectors were
willing to pay.
As a result, I think these days the mikes are selling for about what they
are really worth. Things seem to have normallized.
Don Pearce
<predrag.t...@ri.htnet.hr> wrote:
>
>"Don Pearce" <don...@pearce.uk.com> wrote in message
>news:442e5736....@text.usenet.plus.net...
>> On Mon, 27 Mar 2006 23:15:38 +0200, "Predrag Trpkov"
>> <predrag.t...@ri.htnet.hr> wrote:
>>
>> >
>> >"Don Pearce" <don...@pearce.uk.com> wrote in message
>> >news:442d45b8....@text.usenet.plus.net...
>> >
>> >> And wouldn't it be nice if the volts disappeared when you turned off
>> >> phantom, instead of having to wait half an hour while an electrolytic
>> >> discharges.
>> >
>> >
>> >What exactly is being risked if that precautionary measure is ignored?
>> >
>> >Predrag
>> >
>>
>> Which precautionary measure? Your precedent is not clear.
>
>
>Oh sorry. I meant waiting for half an hour while an electrolytic discharges.
>I always wait a little, maybe half a minute or a minute, before
>disconnecting a condenser microphone and connecting another. Having to wait
>for half an hour seems rather impractical during a session.
>
>Predrag
>
Well, when you have a microphone connected that is actually drawing
current, the discharge happens much more quickly. A few seconds should
do it. It is only an open circuit mic input that remains powered for
ages.
Steve King
Steve King
Bob Olhsson
> RCA built some microphones which had a grounded center tap on the transformer
> secondary. The 77DX was not this way, but some 44 and 74 mikes are.
I'm sure I remember a grounded center tap remaining an optional way to
wire a 77. Remember that everybody who bought a new 77 had a shop and
soldering skills so some homework is advised before making assumptions
about how any particular 77 is wired.
All first generation Phantom power was global. There's a good reason we
insisted that the next generation not be. I found plugging my 77DX into
active phantom powering produces a pop from the mike which can't be very
good for it. It certainly had a lot more top-end after replacing the ribbon.
Hopefully the folks dispensing advice that there's no problem are
willing to pay for any repairs people incur as a result of following
that advice.
--
Bob Olhsson Audio Mastery, Nashville TN
Mastering, Audio for Picture, Mix Evaluation and Quality Control
Over 40 years making people sound better than they ever imagined!
615.385.8051 http://www.hyperback.com
Mike Cleaver
concur with Bob.
Better safe than sorry.
A miswired cable can also cause problems.
I have seen ribbons destroyed when plugged into preamps and boards
with phantom power on.
On Wed, 29 Mar 2006 12:16:44 -0600, Bob Olhsson <o...@hyperback.com>
wrote:
>Scott Dorsey wrote:
>
>> RCA built some microphones which had a grounded center tap on the transformer
>> secondary. The 77DX was not this way, but some 44 and 74 mikes are.
>
>I'm sure I remember a grounded center tap remaining an optional way to
>wire a 77. Remember that everybody who bought a new 77 had a shop and
>soldering skills so some homework is advised before making assumptions
>about how any particular 77 is wired.
>
>All first generation Phantom power was global. There's a good reason we
>insisted that the next generation not be. I found plugging my 77DX into
>active phantom powering produces a pop from the mike which can't be very
>good for it. It certainly had a lot more top-end after replacing the ribbon.
>
>Hopefully the folks dispensing advice that there's no problem are
>willing to pay for any repairs people incur as a result of following
>that advice.
Mike Cleaver Broadcast Services
Voice-overs, Newscaster, Engineering and Consulting
Vancouver, BC, Canada
radiov...@hotmail.com
Bob Cain
Remember that that 48 volts is divided between 6800 ohms and the rather
small resistance of a ribbon or transformer. It is sorta difficult to
understand how 7 mV (max phantom current) could damage either. The
maximum power in mW that the ribbon or transformer would have to
dissipate is .0049 times its resistance.
Bob
--
"Things should be described as simply as possible, but no simpler."
A. Einstein
Mike Rivers
Bob Cain wrote:
> Remember that that 48 volts is divided between 6800 ohms and the rather
> small resistance of a ribbon or transformer. It is sorta difficult to
> understand how 7 mV (max phantom current) could damage either. The
> maximum power in mW that the ribbon or transformer would have to
> dissipate is .0049 times its resistance.
Tell that to someone who has damaged a ribbon as a result of connecting
the mic to a phantom powered input. The simple answer is that
microphone ribbons aren't designed to serve as loudspeaker cones.
They'll take a little energy, but not a lot, and sometimes a transient,
particularly when multiplied by the inductance of the transformer, can
cross the line and damage the ribbon.
Scott Dorsey
>
>Remember that that 48 volts is divided between 6800 ohms and the rather
>small resistance of a ribbon or transformer. It is sorta difficult to
>understand how 7 mV (max phantom current) could damage either. The
>maximum power in mW that the ribbon or transformer would have to
>dissipate is .0049 times its resistance.
It's not the heating, it's the physical movement. The ribbon slams forward
or back very quickly and tears itself up. It doesn't take much.
Mike Cleaver
The internal microphone wiring may make the ribbon liable to self
destruct if it sees 48v.
It would also be an incorrectly wired mic cord.
Don't take chances.
Re-ribboning starts at 100 dollars US and goes up from there.
Plus there are fewer and fewer ribbon experts available to do the job.
The best are well into their retirement years already.
On 5 Apr 2006 09:23:26 -0400, klu...@panix.com (Scott Dorsey) wrote:
>Bob Cain <arc...@arcanemethods.com> wrote:
>>
>>Remember that that 48 volts is divided between 6800 ohms and the rather
>>small resistance of a ribbon or transformer. It is sorta difficult to
>>understand how 7 mV (max phantom current) could damage either. The
>>maximum power in mW that the ribbon or transformer would have to
>>dissipate is .0049 times its resistance.
>
>It's not the heating, it's the physical movement. The ribbon slams forward
>or back very quickly and tears itself up. It doesn't take much.
>--scott
Mike Cleaver Broadcast Services