[adam79]

On 8/17/10 8:23 PM, Mike Rivers wrote:
adam79 wrote:
Scott Dorsey wrote:

I was looking up 600ohm resistors, and they come in different watts;
how many watts should the resistor be?

1/4 watt is fine. Good question, though.


I found this resistor:
http://www.ralphselectronics.com/Pro...ource=googleps

It's 1/4W 600ohms and then says "1% resistor." Is this the one I'm
looking for?

Thanks,
-Adam

[Preben Friis]

"adam79" wrote in message
...
It's 1/4W 600ohms and then says "1% resistor." Is this the one I'm looking
for?

Yes, it is.

/Preben Friis

[John Williamson]

Preben Friis wrote:
"adam79" wrote in message
...
It's 1/4W 600ohms and then says "1% resistor." Is this the one I'm
looking for?

Yes, it is.

/Preben Friis
Apart from being the wrong value at 600 *thousand* ohms......

At least that's what it shows as here.

--
Tciao for Now!

John.

[John Williamson]

adam79 wrote:
It's 1/4W 600ohms and then says "1% resistor." Is this the one I'm
looking for?


No, this is:-

http://www.ralphselectronics.com/Pro...r=PENN-1600.25

--
Tciao for Now!

John.

[PStamler]

On Aug 25, 4:00*am, John Williamson
wrote:
adam79 wrote:
It's 1/4W 600ohms and then says "1% resistor." Is this the one I'm
looking for?

No, this is:-

http://www.ralphselectronics.com/Pro...emnumber=PENN-....

What John said; the original one you found is 600k ohms, which means
600,000, which will have essentially zero effect on the loading of the
mic.

One of my students made the same mistake when he was building a Gizmo
to load an SM57. Wondered why it had no effect on the sound; I told
him to bring it in and predicted the problem was that he'd pulled a
600k (actually 681k) resistor out of the bin. I measured it on a DVM,
and my guess was right. Easy mistake to make.

Peace,
Paul

[Preben Friis]

"John Williamson" wrote in message
...
It's 1/4W 600ohms and then says "1% resistor." Is this the one I'm
looking for?

Yes, it is.

Apart from being the wrong value at 600 *thousand* ohms......

I did not check the link. I presumed that the text was taken from there. My
mistake.

/Preben Friis

[adam79]

On 8/25/10 5:00 AM, John Williamson wrote:
adam79 wrote:
It's 1/4W 600ohms and then says "1% resistor." Is this the one I'm
looking for?


No, this is:-

http://www.ralphselectronics.com/Pro...r=PENN-1600.25




When I go to that link it doesn't show the part. I took a screen shot of
the what my browser pulls up:
http://i273.photobucket.com/albums/j...ng/adapter.jpg

Could you please write the name of the adapter so I can do the search
myself?

Thanks,
-Adam

[John Williamson]

adam79 wrote:
On 8/25/10 5:00 AM, John Williamson wrote:
adam79 wrote:
It's 1/4W 600ohms and then says "1% resistor." Is this the one I'm
looking for?


No, this is:-

http://www.ralphselectronics.com/Pro...r=PENN-1600.25





When I go to that link it doesn't show the part. I took a screen shot of
the what my browser pulls up:
http://i273.photobucket.com/albums/j...ng/adapter.jpg

Could you please write the name of the adapter so I can do the search
myself?

On Ralph's website, the resistor part number is PENN-1600.25

You missed this off the end of the URL somehow.

This resistor is the one you need to solder netween pins 2 and 3 inside
the XLR connector as discussed earlier in the thread.

--
Tciao for Now!

John.

[adam79]

On 8/26/10 12:50 AM, John Williamson wrote:

On Ralph's website, the resistor part number is PENN-1600.25

You missed this off the end of the URL somehow.

This resistor is the one you need to solder netween pins 2 and 3 inside
the XLR connector as discussed earlier in the thread.


I got it! I was checking my XLR mic cables and the connectors don't seem
to unscrew from the cable. There's a Philips head screw on the
connector, but when I unscrew it, I can't seem to get the connector off
the cable. Am I doing something wrong? Here's a picture of the
connector: http://members.toast.net/adam79/XLR.jpg

Also, I'm not sure if this question was already answered, but are there
XLR adapters out there that have the resistor built in (so I don't have
to permanently modify my cables)? If so, is there a name for this
particular adapter?

Thanks,
-Adam

[Mike Rivers]

adam79 wrote:

I got it! I was checking my XLR mic cables and the connectors don't seem
to unscrew from the cable. There's a Philips head screw on the
connector, but when I unscrew it, I can't seem to get the connector off
the cable.

After removing the screw, you have to push on the cable
rather than pull on the connector body. There's an insert
with the pins that slips inside the body and comes out the
"open" side.

Also, I'm not sure if this question was already answered, but are there
XLR adapters out there that have the resistor built in

Not exactly the answer you were looking for, but I answered
that there were people who will custom make one for you, but
it is not available as a commercial product. Klay Anderson
Audio (http://www.klay.com) has been providing custom
services like this for years. He may be able to accommodte
you at a price you'll be willing to pay.


--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

[John Williamson]

adam79 wrote:
On 8/26/10 12:50 AM, John Williamson wrote:

On Ralph's website, the resistor part number is PENN-1600.25

You missed this off the end of the URL somehow.

This resistor is the one you need to solder netween pins 2 and 3 inside
the XLR connector as discussed earlier in the thread.


I got it! I was checking my XLR mic cables and the connectors don't seem
to unscrew from the cable. There's a Philips head screw on the
connector, but when I unscrew it, I can't seem to get the connector off
the cable. Am I doing something wrong? Here's a picture of the
connector: http://members.toast.net/adam79/XLR.jpg

Also, I'm not sure if this question was already answered, but are there
XLR adapters out there that have the resistor built in (so I don't have
to permanently modify my cables)? If so, is there a name for this
particular adapter?

Not really. What I'd do is buy male and female XLR connectors, and use a
few inches of microphone cable to connect them pin to pin (1 to 1, 2 to
2, 3 to 3, then solder a resistor between pins 2 and 3 at one end. Kind
of like a very short extension lead.

Undoing the screw in your picture will let you push the case back along
the cable so you can get access to the connections. Don't try and pull
it off the end, it doesn't go that way.

--
Tciao for Now!

John.

[Preben Friis]

"adam79" wrote in message
net...
Also, I'm not sure if this question was already answered, but are there
XLR adapters out there that have the resistor built in (so I don't have to
permanently modify my cables)? If so, is there a name for this particular
adapter?

You can buy XLR male/female adapters made for polarity reversal and then
solder the resistor into them yourself.

http://www.adamhall.com/en/Adapter_X... _2_and_3.html
http://www.neutrik.com/fr/en/audio/2...MX_detail.aspx

/Preben Friis

[adam79]

On 8/26/10 6:42 AM, Mike Rivers wrote:

After removing the screw, you have to push on the cable rather than pull
on the connector body. There's an insert with the pins that slips inside
the body and comes out the "open" side.


Cool, I got it off! So I just use some wire cutters to strip the
covering off the wire and use a soldering iron to connect the resistor,
right? Sounds pretty simple (something even I'll be able to do)!

Thanks,
-Adam

[adam79]

On 8/26/10 6:42 AM, Mike Rivers wrote:
adam79 wrote:

Also, I'm not sure if this question was already answered, but are
there XLR adapters out there that have the resistor built in

Not exactly the answer you were looking for, but I answered that there
were people who will custom make one for you, but it is not available as
a commercial product.

I actually found a commercial product that does this:
http://www.markertek.com/Audio-Equip...ml?SES-XLR-ISO.
At $20 it's too expensive; I'm just gonna buy a pack of those resistors
and do the mod myself. Does this improve the sound quality of all mics,
or are some impartial to the mod? It can't hurt the quality, only make
it better, right?

Thanks,
-Adam

[Mike Rivers]

adam79 wrote:

I actually found a commercial product that does this:
Sescom/SES-XLR-ISO

No, it doesn't do the same thing. It's a transformer, not a
load resistor. It's a problem solver, but not for this problem.

At $20 it's too expensive

For what it does, $20 is a real bargain.

I'm just gonna buy a pack of those resistors
and do the mod myself. Does this improve the sound quality of all mics,
or are some impartial to the mod? It can't hurt the quality, only make
it better, right?

Some mics will sound worse when loaded by 600 ohms. Some
won't sound any different. This particular gizmo, with the
resistor value as calculated based on the input impedance of
your preamp, is unique to the SM57. That's why the
recommendation is to make a plug-in "adapter" so you can use
it or not.


--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

[adam79]

On 8/26/10 4:42 PM, Mike Rivers wrote:
adam79 wrote:

I actually found a commercial product that does this: Sescom/SES-XLR-ISO

No, it doesn't do the same thing. It's a transformer, not a load
resistor. It's a problem solver, but not for this problem.

Some mics will sound worse when loaded by 600 ohms. Some won't sound any
different. This particular gizmo, with the resistor value as calculated
based on the input impedance of your preamp, is unique to the SM57.
That's why the recommendation is to make a plug-in "adapter" so you can
use it or not.


I'm starting to get a bit confused. My original question was about what
the mic rental guy told me: certain mics, like the RE-20, were made with
the assumption that they would be connected to a mic-pre with a
transformer. Consequently, you don't get the most out of the mic when
using it with a pre-amp absent of a transformer.

Does this "gizmo" for the SM57 relate to the topic above, or is it an
unrelated mod that makes the SM57 sound better? If it does relate to the
topic, how do you figure out what ohm resistor you need for a particular
mic? If it doesn't relate, does the Sescom/SES-XLR-ISO solve the
transformerless pre-amp issue?

Thanks,
-Adam

[Roy W. Rising[_2_]]

adam79 wrote:
On 8/26/10 4:42 PM, Mike Rivers wrote:
adam79 wrote:

I actually found a commercial product that does this:
Sescom/SES-XLR-ISO

No, it doesn't do the same thing. It's a transformer, not a load
resistor. It's a problem solver, but not for this problem.

Some mics will sound worse when loaded by 600 ohms. Some won't sound
any different. This particular gizmo, with the resistor value as
calculated based on the input impedance of your preamp, is unique to
the SM57. That's why the recommendation is to make a plug-in "adapter"
so you can use it or not.


I'm starting to get a bit confused. My original question was about what
the mic rental guy told me: certain mics, like the RE-20, were made with
the assumption that they would be connected to a mic-pre with a
transformer. Consequently, you don't get the most out of the mic when
using it with a pre-amp absent of a transformer.

Does this "gizmo" for the SM57 relate to the topic above, or is it an
unrelated mod that makes the SM57 sound better? If it does relate to the
topic, how do you figure out what ohm resistor you need for a particular
mic? If it doesn't relate, does the Sescom/SES-XLR-ISO solve the
transformerless pre-amp issue?

Thanks,
-Adam

The gizmo is for an SM57. Give me your address and I'll build one and send
it to you. I'll probably make it in the form of a short cable. Let me
know if you want it to be any particular length.

Modern "active balanced" mic pre inputs are essentially the same as those
with transformers. The EV RE20 is virtually unaffected by any of the many
kinds of inputs they might feed.

--
~ Roy
"If you notice the sound, it's wrong!"

[PStamler]

On Aug 26, 6:53*pm, adam79 wrote:
On 8/26/10 4:42 PM, Mike Rivers wrote:

adam79 wrote:

I actually found a commercial product that does this: Sescom/SES-XLR-ISO

No, it doesn't do the same thing. It's a transformer, not a load
resistor. It's a problem solver, but not for this problem.

Some mics will sound worse when loaded by 600 ohms. Some won't sound any
different. This particular gizmo, with the resistor value as calculated
based on the input impedance of your preamp, is unique to the SM57.
That's why the recommendation is to make a plug-in "adapter" so you can
use it or not.

I'm starting to get a bit confused. My original question was about what
the mic rental guy told me: certain mics, like the RE-20, were made with
the assumption that they would be connected to a mic-pre with a
transformer. Consequently, you don't get the most out of the mic when
using it with a pre-amp absent of a transformer.

Does this "gizmo" for the SM57 relate to the topic above, or is it an
unrelated mod that makes the SM57 sound better? If it does relate to the
topic, how do you figure out what ohm resistor you need for a particular
mic? If it doesn't relate, does the Sescom/SES-XLR-ISO solve the
transformerless pre-amp issue?

Okay, let's try to unscramble this:

1. The guy at the International House of Microphones told you that the
RE20 is sensitive to loading, and wants to be loaded with a low
impedance, preferably with a transformer-input preamp. He was wrong;
the RE20 (and its cousins the RE15 and RE16) don't much care about the
load.

2. Neither does the Sennheiser MD421.

3. On the other hand, the SM57 and its siblings the SM56 and SM58 do
care. They work best when the load is somewhere in the 500-600 ohm
range.

4. The way you figure out what resistor to use is to know two things:
the actual input impedance of the preamp, and the desired impedance.

Let's say the desired input impedance is 500 ohms, and the preamp's
actual input impedance is 2400 ohms, which I believe is the value of
some Mackie preamps. Do the following arithmetic:

Added resistor = 1/(1/desired load - 1/actual load)

Well, 1/500 = 0.002, and 1/2400 = 0.000416666...

So 0.002 - 0.00041666666... = 0.001583333333....

Take the reciprocal of that and you get 631.578 ohms; the nearest
standard 1% value is 634 ohms.

In practice you'll get decent results with anything from 600 ohms to
681 ohms.

Oh, by the way, the other mic I've found that reacts strongly to
loading is the AKG D112. Load it with 500 ohms, and the sound changes
from boomy and pilllowy to super-tight. In fact, maybe too tight; some
intermediate load might be more appropriate.

Oh, and also...most condenser mics *don't* like a lower-impedance
load. This is really something for dynamic mics, and really, mostly
for the SM57 family and the D112.

Peace,
Paul

[Mike Rivers]

adam79 wrote:

My original question was about what
the mic rental guy told me: certain mics, like the RE-20, were made with
the assumption that they would be connected to a mic-pre with a
transformer. Consequently, you don't get the most out of the mic when
using it with a pre-amp absent of a transformer.

That's a crock of baloney, but then, as I recall, he was
trying ot steer you to some other mic because he didn't have
an RE-20. But I'm confused now, too.

Does this "gizmo" for the SM57 relate to the topic above, or is it an
unrelated mod that makes the SM57 sound better?

Totally unrelated. Someone probably mentioned the SM57 as a
reasonable mic for something or other and someone else
chimed in with how you could make it sound better by loading
it with about 600 ohms rather than th 2000-2500 ohms typical
of a modern preamp (with or without a transformer).

If it does relate to the
topic, how do you figure out what ohm resistor you need for a particular
mic?

If you read Paul Stamler's article (a link was posted to it
in this thread a day or two ago) you'd know that he
determined it experimentaly, by listening with different
values of load resistor. But that load resistor applies only
to the preamp with which he tested it, or one with the same
input impedance. The article shows how to calculate the
value of the optimum load resistor for an SM57 when you know
the input impedance of the preamp to which you're connecting it.

If it doesn't relate, does the Sescom/SES-XLR-ISO solve the
transformerless pre-amp issue?

No, because there is no "transformerless preamp issue."
People design preamps with transformers. Other people design
preamps without transformers. Each one can be equally good
if it's a good design, or equally bad if it's a bad design.
Preamps like Great River or TAB Funkenwerk have very high
quality transformers and are excellent preamps. Preamps like
Millenia Media don't have transformers and are excellent
preamps. Some manufacturers stick a crappy transformer in
their preamps so they can say it has a transformer, trying
to attract business from people like you who somehow have
been led to believe that transformers make for better preamps.

Don't be a people like you.


--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

[Scott Dorsey]

adam79 wrote:

I'm starting to get a bit confused. My original question was about what
the mic rental guy told me: certain mics, like the RE-20, were made with
the assumption that they would be connected to a mic-pre with a
transformer. Consequently, you don't get the most out of the mic when
using it with a pre-amp absent of a transformer.

There are plenty of other and better ways to load the mike down without
using a transformer. One is to use a shunt resistor.

If you use a transformer then you have a different and other set of loading
issues because the _transformer_ wants to see particular loading. This is
fine if it's built into the preamp, not so good if you are trying to add it
on.

Does this "gizmo" for the SM57 relate to the topic above, or is it an
unrelated mod that makes the SM57 sound better? If it does relate to the
topic, how do you figure out what ohm resistor you need for a particular
mic? If it doesn't relate, does the Sescom/SES-XLR-ISO solve the
transformerless pre-amp issue?

It is unrelated and has nothing to do with it.

The way to find the resistor is to look at the recommended load impedance
for the mike on the mike data sheet.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[adam79]

Thanks Roy, Paul and Mike for those last three posts; I now understand
this whole issue. That guy at the mic rental place was out of his mind.
I think I went into detail on his ramblings in my first post. He
actually does have RE-20s for rental, but was strong in his conviction
that the RE20 would be boxy and unappealing when hooked up to the MBox2,
or any preamp w/o a transformer.

I went through a box of unsorted cables and found 4 short XLR cables;
they will be perfect for modification. I'm confident that I can do this
myself.

Just one quick question.. The "desired load" for a mic isn't something
that's listed in the specs, it's a value that is determined by trial and
error, right?

Thanks,
-Adam

[Mike Rivers]

adam79 wrote:

Just one quick question.. The "desired load" for a mic isn't something
that's listed in the specs, it's a value that is determined by trial and
error, right?

Right. Sometimes you'll find an "impedance" in a mic's
specification but this usually doesn't tell you anything
useful about how to get the best performance from it.

--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

[Bill Graham]

"Mike Rivers" wrote in message
...
adam79 wrote:

Just one quick question.. The "desired load" for a mic isn't something
that's listed in the specs, it's a value that is determined by trial and
error, right?

Right. Sometimes you'll find an "impedance" in a mic's specification but
this usually doesn't tell you anything useful about how to get the best
performance from it.

How about the phantom power delivered to a condenser mike? There are an
awful lot of chassis out there that only deliver 18 Volts or less to mikes
that were designed to accept up to 50 volts or so.....I often wonder how
their performance suffers from a starved phantom power supply......Any
thoughts on this?

[John Williamson]

Bill Graham wrote:
How about the phantom power delivered to a condenser mike? There are an
awful lot of chassis out there that only deliver 18 Volts or less to
mikes that were designed to accept up to 50 volts or so.....I often
wonder how their performance suffers from a starved phantom power
supply......Any thoughts on this?

Depending on the mic, anything from perfect functioning to reduced
capacity to reproduce loud sounds to a total failure to function, via an
increased self noise.

--
Tciao for Now!

John.

[Mike Rivers]

Bill Graham wrote:

How about the phantom power delivered to a condenser mike? There are an
awful lot of chassis out there that only deliver 18 Volts or less

There aren't a lot, but there are some. There's actually a
12V and 24V phantom powering voltage defined in the
standard, but the "standard" standard is 48V.

wonder how their performance suffers from a starved phantom power
supply......Any thoughts on this?

Depends on the mic. Worst case it will have less headroom,
but some condenser mics are designed to meet their
performance specifications at lower (and usually specified)
voltages. For instance, my AKG C451s are specified to work
between 9 and 52 volts.



--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

[Scott Dorsey]

adam79 wrote:
Thanks Roy, Paul and Mike for those last three posts; I now understand
this whole issue. That guy at the mic rental place was out of his mind.
I think I went into detail on his ramblings in my first post. He
actually does have RE-20s for rental, but was strong in his conviction
that the RE20 would be boxy and unappealing when hooked up to the MBox2,
or any preamp w/o a transformer.

The RE-20 is almost totally immune to loading. It will sound good into
just about anything. Unfortunately, the low coupling that makes it immune
to loading also means the output level is pretty low.

Just one quick question.. The "desired load" for a mic isn't something
that's listed in the specs, it's a value that is determined by trial and
error, right?

It should be mentioned on the spec sheet if it's from a legitimate
manufacturer, although a lot of manufacturers are dumbing things down.
Rated impedance on the SM-58 is 150 ohms for use into a 300 ohm load.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Bill Graham wrote:

How about the phantom power delivered to a condenser mike? There are an
awful lot of chassis out there that only deliver 18 Volts or less to mikes
that were designed to accept up to 50 volts or so.....I often wonder how
their performance suffers from a starved phantom power supply......Any
thoughts on this?

There is an AES standard for reporting this on the datasheet, which most
manufacturers ignore.

Some mikes will work fine at 12V. Some won't work at all. The KMS105
goes into oscillation if the phantom drops too much. The datasheet should
say whether the mike can perform properly at reduced phantom but usually does
not any more.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Roy W. Rising[_2_]]

adam79 wrote:
Thanks Roy, Paul and Mike for those last three posts; I now understand
this whole issue. That guy at the mic rental place was out of his mind.
I think I went into detail on his ramblings in my first post. He
actually does have RE-20s for rental, but was strong in his conviction
that the RE20 would be boxy and unappealing when hooked up to the MBox2,
or any preamp w/o a transformer.

I went through a box of unsorted cables and found 4 short XLR cables;
they will be perfect for modification. I'm confident that I can do this
myself.

Just one quick question.. The "desired load" for a mic isn't something
that's listed in the specs, it's a value that is determined by trial and
error, right?

Thanks,
-Adam

For many years, the "rule of thumb" for mic preamps' *actual* input
impedance has been "2000 ohms or greater", largely to *avoid loading*
ribbon mics. Most other mics perform very well "unloaded" per this rule.
It's almost a fluke that the SM57 is helped by 600 ohm loading. So, your
question might be answered "Most mics don't have a *desired* load".
Rather, they "desire" to be unloaded.

P.S. ~ Somewhere in this thread there was mention of 1% resistors. That
precision is not needed for the SM57 "gizmo". Phantom power current
limiting resistors should be matched to a tolerance of 1% or better.

--
~ Roy
"If you notice the sound, it's wrong!"

[Bill Graham]

"Mike Rivers" wrote in message
...
Bill Graham wrote:

How about the phantom power delivered to a condenser mike? There are an
awful lot of chassis out there that only deliver 18 Volts or less

There aren't a lot, but there are some. There's actually a 12V and 24V
phantom powering voltage defined in the standard, but the "standard"
standard is 48V.

wonder how their performance suffers from a starved phantom power
supply......Any thoughts on this?

Depends on the mic. Worst case it will have less headroom, but some
condenser mics are designed to meet their performance specifications at
lower (and usually specified) voltages. For instance, my AKG C451s are
specified to work between 9 and 52 volts.

Well, one advantage of the reduced voltage is that it doesn't seem to hurt
dynamic mikes if you plug them into a reduced voltage condenser mike
jack.....My Behringer 45 Watt keyboard amp has a permanent 15 VDC phantom
power on the XLR channel 1 input all the time, and they say it won't hurt to
plug a dynamic mike into it. - That being the case, I'd still prefer a
switchable 48 volt phantom power......

[Bill Graham]

"Scott Dorsey" wrote in message
...
Bill Graham wrote:

How about the phantom power delivered to a condenser mike? There are an
awful lot of chassis out there that only deliver 18 Volts or less to mikes
that were designed to accept up to 50 volts or so.....I often wonder how
their performance suffers from a starved phantom power supply......Any
thoughts on this?

There is an AES standard for reporting this on the datasheet, which most
manufacturers ignore.

Some mikes will work fine at 12V. Some won't work at all. The KMS105
goes into oscillation if the phantom drops too much. The datasheet should
say whether the mike can perform properly at reduced phantom but usually
does
not any more.
--scott

Well, if you are using $700 microphones, you'll probably be working with
equipment that provides a full 48 volts phantom power, but that's good to
know.....Especially if the spec sheet doesn't tell you.......

[PStamler]

On Aug 26, 10:59*pm, "Bill Graham" wrote:

How about the phantom power delivered to a condenser mike? There are an
awful lot of chassis out there that only deliver 18 Volts or less to mikes
that were designed to accept up to 50 volts or so.....I often wonder how
their performance suffers from a starved phantom power supply......Any
thoughts on this?

It completely depends on the mic. I have some mics (Oktava MC012,
Shure SM81) that'll work on just about any phantom voltage. Then I
have some (Neumann FET-80 series) which won't work at all if the
voltage is less than 44V -- not just have too much self noise, they in
fact have no signal at all. Look at the spec sheet.

Except that one pair of mics I have is from Microtech Gefell; they
swear that the mics won't work on 24V. But they do just fine. Might
have a little less headroom, but 2 feet from a clarinet I'll never
hear it.

Oh, and the point of the 1% resistor isn't to get super-precision;
it's that 1% resistors are metal film, and those are good-quality
resistors.

Peace,
Paul

[Scott Dorsey]

Bill Graham wrote:
Well, one advantage of the reduced voltage is that it doesn't seem to hurt
dynamic mikes if you plug them into a reduced voltage condenser mike
jack.....My Behringer 45 Watt keyboard amp has a permanent 15 VDC phantom
power on the XLR channel 1 input all the time, and they say it won't hurt to
plug a dynamic mike into it. - That being the case, I'd still prefer a
switchable 48 volt phantom power......

That's not a consequence of the reduced voltage, that's a consequence of
it being common-mode power and not differential. The voltage is between
the signal pins and ground, so if there is no connection between the signal
pins and ground (because they are just connected to a coil of wire), then
no current will flow. You could put hundreds of volts there and it wouldn't
hurt the mike.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Bill Graham]

"PStamler" wrote in message
...
On Aug 26, 10:59 pm, "Bill Graham" wrote:

How about the phantom power delivered to a condenser mike? There are an
awful lot of chassis out there that only deliver 18 Volts or less to mikes
that were designed to accept up to 50 volts or so.....I often wonder how
their performance suffers from a starved phantom power supply......Any
thoughts on this?

It completely depends on the mic. I have some mics (Oktava MC012,
Shure SM81) that'll work on just about any phantom voltage. Then I
have some (Neumann FET-80 series) which won't work at all if the
voltage is less than 44V -- not just have too much self noise, they in
fact have no signal at all. Look at the spec sheet.

Except that one pair of mics I have is from Microtech Gefell; they
swear that the mics won't work on 24V. But they do just fine......

I think that sometimes specifications are written by their lawyers, rather
than their engineers......:^)

[Bill Graham]

"Scott Dorsey" wrote in message
...
Bill Graham wrote:
Well, one advantage of the reduced voltage is that it doesn't seem to hurt
dynamic mikes if you plug them into a reduced voltage condenser mike
jack.....My Behringer 45 Watt keyboard amp has a permanent 15 VDC phantom
power on the XLR channel 1 input all the time, and they say it won't hurt
to
plug a dynamic mike into it. - That being the case, I'd still prefer a
switchable 48 volt phantom power......

That's not a consequence of the reduced voltage, that's a consequence of
it being common-mode power and not differential. The voltage is between
the signal pins and ground, so if there is no connection between the
signal
pins and ground (because they are just connected to a coil of wire), then
no current will flow. You could put hundreds of volts there and it
wouldn't
hurt the mike.

Thanks.....that explains why I have never heard of anyone wrecking his
dynamic mike by accidently plugging it into a phantom powered mike input
jack.....This in the face of the usual rule....."If something can screw up,
it will"....:^)

[PStamler]

On Aug 27, 8:28*pm, "Bill Graham" wrote:

Except that one pair of mics I have is from Microtech Gefell; they
swear that the mics won't work on 24V. But they do just fine......

I think that sometimes specifications are written by their lawyers, rather
than their engineers......:^)

Naw, one of their engineers actually told me on the phone that the mic
couldn't possibly work on 24V phantom. I told him it did, and he
repeated that it couldn't. I'm glad it does.

Peace,
Paul

[Mike Rivers]

Bill Graham wrote:
Well, one advantage of the reduced voltage is that it doesn't seem to
hurt dynamic mikes if you plug them into a reduced voltage condenser
mike jack.....My Behringer 45 Watt keyboard amp has a permanent 15 VDC
phantom power on the XLR channel 1 input all the time, and they say it
won't hurt to plug a dynamic mike into it.

The reason why you won't hurt a dynamic mic when plugging
one into a powered mic input is not because of the low
voltage, it's because of the design of the phantom powering
circuit - which is the same for any voltage. If you were to
connect a dynamic mic using a cable that had a short between
the shield (pin 1) and one of the other pins, you could do
as much damage to the mic with 15V phantom power as with 48V
phantom power. Same thing if you have a dynamic mic that's
been wired with an unbalanced 1/4" phone plug instead of an
XLR, and you use an XLR-TS adapter to connect it.


--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

[Mike Rivers]

Bill Graham wrote:

Thanks.....that explains why I have never heard of anyone wrecking his
dynamic mike by accidently plugging it into a phantom powered mike input
jack.....This in the face of the usual rule....."If something can screw
up, it will"....:^)

The usual warning is to not "power" a ribbon mic. This is
based on the way the input transformer of a particular model
RCA mic from about 50 years ago was wired. But today, it's
not a problem (and on those mics, either they've been
destroyed by people who didn't know better or they've been
modified to be "phantom safe."

Still, it's good practice to have phantom power turned off
before connecting or disconnecting the mic. Then, it's safe
to turn power on after it's been plugged in or unplugged.
There are a couple of reasons for this. One, pretty rare, is
that if the connector gets misaligned and pins 1-2 or 1-3
mate before all three pins are mated, current can flow where
it shouldn't. The other is that connecting or disconnecting
a mic with phantom power applied can cause a voltage spike
that the input to the mic preamp stage sees. Today most mic
preamps are made idiot-resistant with the use of clamping
diodes on the input to keep the spike from getting higher
than the power supply voltage. But some people believe that
those diodes affect the sound so they're not present in some
designs and I suppose that some have been removed.


--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

[adam79]

On 8/27/10 9:16 PM, PStamler wrote:

Oh, and the point of the 1% resistor isn't to get super-precision;
it's that 1% resistors are metal film, and those are good-quality
resistors.

Peace,
Paul

I read your article on the SM57 article; cool stuff. The link to the
recommended resistor in the article (at mouser.com) is out of stock, but
they have this one:
http://www.mouser.com/search/Product...x?R=270-698-RC which seems
to have the same specs. This is the correct resistor, right?

Thanks,
-Adam

[adam79[_3_]]

I was just over at Radio Shack and they had a 680 ohm, 1/2 watt, 5%
tolerance resistor. Will this one work just as well, or is the wattage/
tolerance too high?

Thanks,
-Adam

[Scott Dorsey]

In article ,
adam79 wrote:
I was just over at Radio Shack and they had a 680 ohm, 1/2 watt, 5%
tolerance resistor. Will this one work just as well, or is the wattage/
tolerance too high?

That's just fine. It'll be physically larger than the 1/4W one, so it may
take a big more poking and prodding to fit in there, but it'll fit.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."