Attenuating "line out" into a mic socket

[Alex Coleman]

I have a handheld recorder which does not have a "line in" socket. The
only input it has is a "mic" socket.

The manufacturers sell a lead which is used to attenuate the "line out"
from another device into my mic socket.

I would rather make my own lead. Obviously I don't want to alter the
frequency response.

What components would I need and in what configuration would they need
to be?

 

[GregS]

In article <Xns97B890F2D6A2171F3M4@127.0.0.1>, Alex Coleman <no@no-email.com> wrote:

I have a handheld recorder which does not have a "line in" socket. The
only input it has is a "mic" socket.

The manufacturers sell a lead which is used to attenuate the "line out"
from another device into my mic socket.

I would rather make my own lead. Obviously I don't want to alter the
frequency response.

What components would I need and in what configuration would they need
to be?

Put a 470 ohm resistor across the recorder input.
Put a 10K ohm in series feeding the hot side of the input
jack fed from the line out. Other side to common
side of input jack. If the levels need changed, the ratio needs to be adjusted
between the two resistors. 10k to 27K to reduce, 10K to 5K to increase.

greg

 

[petrus bitbyter]

"Alex Coleman" <no@no-email.com> schreef in bericht
news:Xns97B890F2D6A2171F3M4@127.0.0.1...

I have a handheld recorder which does not have a "line in" socket. The
only input it has is a "mic" socket.

The manufacturers sell a lead which is used to attenuate the "line out"
from another device into my mic socket.

I would rather make my own lead. Obviously I don't want to alter the
frequency response.

What components would I need and in what configuration would they need
to be?

Specifications of mic inputs and line in- and outputs depends of the
manufacturer. One I ever found says:
mic input sensitivity 12uV max, input impedance 300-2k4
line input sensitivity 12uV min, input impedance 10k
but there are much more possibilities.
If you the specs of your recorder, you can calculate the resistor network
you need. If you can't, you can experiment with the network below.

+-----+-----+
| | |
| | R2 .-.
| |220k| |
| | | |
| | '-'
| | |
| | |
| | |
| R1 .-. .-.
-+ 12k| | | |<-----
| | | |
line out '-' '-'1k mic in
| |
-------+-----+-------
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

When the line out signal is too high, so when it is difficult to adjust the
pot in the lower part, you can rise R2 up to 1M (try some values) and lower
R1 to 10k. I don't expect the signal to be too week, but if it is you can
make both resistors 22k.

petrus bitbyter

 

[Beachcomber]

The manufacturers sell a lead which is used to attenuate the "line out"
from another device into my mic socket.

I would rather make my own lead. Obviously I don't want to alter the
frequency response.

What components would I need and in what configuration would they need
to be?


Put a 470 ohm resistor across the recorder input.
Put a 10K ohm in series feeding the hot side of the input
jack fed from the line out. Other side to common
side of input jack. If the levels need changed, the ratio needs to be adjusted
between the two resistors. 10k to 27K to reduce, 10K to 5K to increase.

A simple resistive pad is all you need. Here is a site that descibes
several options in good detail.

http://www.epanorama.net/circuits/line_to_mic.html

Frequency response should not be a problem, but noise can be. The
idea for good audio is to have as few amplifiers in the line as
possible, and with the minimum amplification necessary.

When you bring down a line level source with a resistive pad, you are
essentially bringing the original signal closer to the noise level.
Then, because you have a mic level input, you amplify the signal again
(including the noise). It's not a problem for most applications, but
then again, for a critical studio signal, it could be.

Beachcomber

 

[David Nebenzahl]

GregS spake thus:

In article <Xns97B890F2D6A2171F3M4@127.0.0.1>, Alex Coleman <no@no-email.com> wrote:

I have a handheld recorder which does not have a "line in" socket. The
only input it has is a "mic" socket.

The manufacturers sell a lead which is used to attenuate the "line out"
from another device into my mic socket.

I would rather make my own lead. Obviously I don't want to alter the
frequency response.

What components would I need and in what configuration would they need
to be?

Put a 470 ohm resistor across the recorder input.
Put a 10K ohm in series feeding the hot side of the input
jack fed from the line out. Other side to common
side of input jack. If the levels need changed, the ratio needs to be adjusted
between the two resistors. 10k to 27K to reduce, 10K to 5K to increase.

I don't see why you can't just put a single resistor between the line
out and mike in. Since the mike input is lower impedance than the line
output to start with, why would you need a load resistor; why not just
something to reduce the voltage?


--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"

 

[Mr.T]

"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:44593088$0$3705$822641b3@news.adtechcomputers.com...

I don't see why you can't just put a single resistor between the line
out and mike in.

Yes you could if you knew the input impedance of the mic input. Or simply
use trial and error.

Since the mike input is lower impedance than the line
output to start with,

How do you know that? In fact it is not usually the case. Line *outputs* are
often around 200 ohms or less, and mic inputs around 1k ohm or more.

why would you need a load resistor; why not just
something to reduce the voltage?

That's just what a voltage divider does no matter how many resitors you use.

In any case the performance of the mic amp on these units is usually very
poor. Be prepared to be disapponted whatever lead you use.

MrT.

 

[Arny Krueger]

"Mr.T" <MrT@home> wrote in message
news:44595a2a$0$9697$afc38c87@news.optusnet.com.au

"David Nebenzahl" <nobody@but.us.chickens> wrote in
message
news:44593088$0$3705$822641b3@news.adtechcomputers.com...
I don't see why you can't just put a single resistor
between the line out and mike in.

Yes you could if you knew the input impedance of the mic
input. Or simply use trial and error.

Since the mike input is lower impedance than the line
output to start with,

How do you know that? In fact it is not usually the case.
Line *outputs* are often around 200 ohms or less, and mic
inputs around 1k ohm or more.

why would you need a load resistor; why not just
something to reduce the voltage?

That's just what a voltage divider does no matter how
many resitors you use.

In any case the performance of the mic amp on these units
is usually very poor. Be prepared to be disapponted
whatever lead you use.

If you go the series resistor route, also you can easily end up with a
voltage divider with a high output impedance, which then exposes you to
losses at high frequencies. Not a problem when the input impedance of of the
equipment being driven is 5 K ohms, but a recipie for disaster when the
input impedance of of the equipment being driven is 500 K ohms.

 

[GregS]

In article <44593088$0$3705$822641b3@news.adtechcomputers.com>, David Nebenzahl <nobody@but.us.chickens> wrote:

GregS spake thus:

In article <Xns97B890F2D6A2171F3M4@127.0.0.1>, Alex Coleman <no@no-email.com
wrote:

I have a handheld recorder which does not have a "line in" socket. The
only input it has is a "mic" socket.

The manufacturers sell a lead which is used to attenuate the "line out"
from another device into my mic socket.

I would rather make my own lead. Obviously I don't want to alter the
frequency response.

What components would I need and in what configuration would they need
to be?

Put a 470 ohm resistor across the recorder input.
Put a 10K ohm in series feeding the hot side of the input
jack fed from the line out. Other side to common
side of input jack. If the levels need changed, the ratio needs to be
adjusted
between the two resistors. 10k to 27K to reduce, 10K to 5K to increase.

I don't see why you can't just put a single resistor between the line
out and mike in. Since the mike input is lower impedance than the line
output to start with, why would you need a load resistor; why not just
something to reduce the voltage?

It gets you off to an approximate attenuation level, not guessing.

greg

 

[David Nebenzahl]

Arny Krueger spake thus:

"Mr.T" <MrT@home> wrote in message
news:44595a2a$0$9697$afc38c87@news.optusnet.com.au

"David Nebenzahl" <nobody@but.us.chickens> wrote in
message
news:44593088$0$3705$822641b3@news.adtechcomputers.com...

I don't see why you can't just put a single resistor
between the line out and mike in.

Yes you could if you knew the input impedance of the mic
input. Or simply use trial and error.

Since the mike input is lower impedance than the line
output to start with,

How do you know that? In fact it is not usually the case.
Line *outputs* are often around 200 ohms or less, and mic
inputs around 1k ohm or more.

why would you need a load resistor; why not just
something to reduce the voltage?

That's just what a voltage divider does no matter how
many resitors you use.

In any case the performance of the mic amp on these units
is usually very poor. Be prepared to be disapponted
whatever lead you use.

If you go the series resistor route, also you can easily end up with a
voltage divider with a high output impedance, which then exposes you to
losses at high frequencies. Not a problem when the input impedance of of the
equipment being driven is 5 K ohms, but a recipie for disaster when the
input impedance of of the equipment being driven is 500 K ohms.

Yes, but--2 things:

1. Isn't the input impedance of the little recorder likely to be
significantly less than 500 KΊ?

2. In any case, how would a mismatched voltage divider cause high
frequency losses? (This is a request due to ignorance.) I don't see how
a resistive network, with no L or C components, could affect frequency
response at all.


--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"

 

[Arny Krueger]

"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:445a4262$0$3681$822641b3@news.adtechcomputers.com

Arny Krueger spake thus:

"Mr.T" <MrT@home> wrote in message
news:44595a2a$0$9697$afc38c87@news.optusnet.com.au

"David Nebenzahl" <nobody@but.us.chickens> wrote in
message
news:44593088$0$3705$822641b3@news.adtechcomputers.com...

I don't see why you can't just put a single resistor
between the line out and mike in.

Yes you could if you knew the input impedance of the mic
input. Or simply use trial and error.

Since the mike input is lower impedance than the line
output to start with,

How do you know that? In fact it is not usually the
case. Line *outputs* are often around 200 ohms or less,
and mic inputs around 1k ohm or more.

why would you need a load resistor; why not just
something to reduce the voltage?

That's just what a voltage divider does no matter how
many resitors you use.

In any case the performance of the mic amp on these
units is usually very poor. Be prepared to be
disapponted whatever lead you use.

If you go the series resistor route, also you can easily
end up with a voltage divider with a high output
impedance, which then exposes you to losses at high
frequencies. Not a problem when the input impedance of
of the equipment being driven is 5 K ohms, but a recipie
for disaster when the input impedance of of the
equipment being driven is 500 K ohms.

Yes, but--2 things:

1. Isn't the input impedance of the little recorder
likely to be significantly less than 500 K??

Good design is about not taking unecessary risks.

2. In any case, how would a mismatched voltage divider
cause high frequency losses? (This is a request due to
ignorance.) I don't see how a resistive network, with no
L or C components, could affect frequency response at all.

The cable and gear downstream of the divider contributes the parallel C.

 

[David Nebenzahl]

Arny Krueger spake thus:

"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:445a4262$0$3681$822641b3@news.adtechcomputers.com

Arny Krueger spake thus:

"Mr.T" <MrT@home> wrote in message
news:44595a2a$0$9697$afc38c87@news.optusnet.com.au

"David Nebenzahl" <nobody@but.us.chickens> wrote in
message
news:44593088$0$3705$822641b3@news.adtechcomputers.com...

I don't see why you can't just put a single resistor
between the line out and mike in.

Yes you could if you knew the input impedance of the mic
input. Or simply use trial and error.

Since the mike input is lower impedance than the line
output to start with,

How do you know that? In fact it is not usually the
case. Line *outputs* are often around 200 ohms or less,
and mic inputs around 1k ohm or more.

why would you need a load resistor; why not just
something to reduce the voltage?

That's just what a voltage divider does no matter how
many resitors you use.

In any case the performance of the mic amp on these
units is usually very poor. Be prepared to be
disapponted whatever lead you use.

If you go the series resistor route, also you can easily
end up with a voltage divider with a high output
impedance, which then exposes you to losses at high
frequencies. Not a problem when the input impedance of
of the equipment being driven is 5 K ohms, but a recipie
for disaster when the input impedance of of the
equipment being driven is 500 K ohms.

Yes, but--2 things:

1. Isn't the input impedance of the little recorder
likely to be significantly less than 500 K??

Good design is about not taking unecessary risks.

For a company designing a product for sale, that would be a
consideration. For a guy trying to get a signal into an el cheapo
handheld recorder, I don't think it makes any difference.

2. In any case, how would a mismatched voltage divider
cause high frequency losses? (This is a request due to
ignorance.) I don't see how a resistive network, with no
L or C components, could affect frequency response at all.

The cable and gear downstream of the divider contributes the parallel C.

What if the single resistor was right at the microphone plug? No
significant C then, right?


--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"

 

[Mr.T]

"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:445a7207$0$3685$822641b3@news.adtechcomputers.com...

The cable and gear downstream of the divider contributes the parallel C.

What if the single resistor was right at the microphone plug? No
significant C then, right?

As Arny said, there is already some shunt capacitance in the box which you
have no control over.

MrT.

 

[Arny Krueger]

"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:445a7207$0$3685$822641b3@news.adtechcomputers.com

Arny Krueger spake thus:

"David Nebenzahl" <nobody@but.us.chickens> wrote in
message
news:445a4262$0$3681$822641b3@news.adtechcomputers.com
Arny Krueger spake thus:

"Mr.T" <MrT@home> wrote in message
news:44595a2a$0$9697$afc38c87@news.optusnet.com.au

"David Nebenzahl" <nobody@but.us.chickens> wrote in
message
news:44593088$0$3705$822641b3@news.adtechcomputers.com...

I don't see why you can't just put a single resistor
between the line out and mike in.

Yes you could if you knew the input impedance of the
mic input. Or simply use trial and error.

Since the mike input is lower impedance than the line
output to start with,

How do you know that? In fact it is not usually the
case. Line *outputs* are often around 200 ohms or
less, and mic inputs around 1k ohm or more.

why would you need a load resistor; why not just
something to reduce the voltage?

That's just what a voltage divider does no matter how
many resitors you use.

In any case the performance of the mic amp on these
units is usually very poor. Be prepared to be
disapponted whatever lead you use.

If you go the series resistor route, also you can
easily end up with a voltage divider with a high output
impedance, which then exposes you to losses at high
frequencies. Not a problem when the input impedance of
of the equipment being driven is 5 K ohms, but a
recipie for disaster when the input impedance of of the
equipment being driven is 500 K ohms.

Yes, but--2 things:

1. Isn't the input impedance of the little recorder
likely to be significantly less than 500 K??

Good design is about not taking unecessary risks.

For a company designing a product for sale, that would be
a consideration. For a guy trying to get a signal into an
el cheapo handheld recorder, I don't think it makes any
difference.

I can't believe that so much air has been warmed (figuratively speaking)
over a ten cent resistor.

2. In any case, how would a mismatched voltage divider
cause high frequency losses? (This is a request due to
ignorance.) I don't see how a resistive network, with no
L or C components, could affect frequency response at
all.

The cable and gear downstream of the divider contributes
the parallel C.

What if the single resistor was right at the microphone
plug? No significant C then, right?

Not so, even equipment that is specifically designed to have low input
capacitance like oscilliscopes and other test equipment, has input
capacitances in the range of 15-35 pF.

Equipment with high input impedance did not die with the days of the tube.
Direct boxes are very common and by definition have very high input
impedances.

 

[Tomi Holger Engdahl]

Alex Coleman <no@no-email.com> writes:

I have a handheld recorder which does not have a "line in" socket. The
only input it has is a "mic" socket.

The manufacturers sell a lead which is used to attenuate the "line out"
from another device into my mic socket.

I would rather make my own lead. Obviously I don't want to alter the
frequency response.

What components would I need and in what configuration would they need
to be?

You can find example circuits for this at
http://www.epanorama.net/circuits/line_to_mic.html

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/