14 Apr
2008
14 Apr
'08
9:03 p.m.
I have a need to record the output of a (5150) speaker. Although I
thought that I could just alligator-clip a positive lead to one speaker
terminal and the negative to the case/ground, the output was decidedly
"buzzy" (I assumed it was too "hot" and overmodulating). I routed it
into a mixer and turned it down (speaker is 5v, not sure what line input
is) but it still didn't sound right.
I found some old directions on hooking up a PC speaker to a line input,
and was confused by the use of a capacitor -- I would have thought that
a resistor would have been more appropriate, to limit the signal
perhaps? In any case, here are the instructions, followed by my question:
Parts required:
- 6' to 12' shielded cable with RCA plug (male) on one end
- Two alligator clips
- One 4.7 uf capacitor
1. Connect one alligator clip to the shielded portion of the cable.
2. Connect the (-) minus side of the capacitor to the center conductor
of the cable and then connect the (+) side of the capacitor to the
second alligator clip.
3. Attach the clip with the capacitor to one of the wires going to your
computer's speaker. Attach the other clip to the metal case (ground)
somewhere (such as a screw or bolt connection).
4. Connect the RCA plug to the auxiliary input on your stereo system or
boom box.
While I have read the wikipedia entry on capacitors, I'm missing
something obvious. My question: Why the 4.7uf capacitor? Does it
serve to limit the signal? Reduce it's voltage? (or increase it?)
Filter the signal in some way?
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
14 Apr
14 Apr
9:47 p.m.
On Monday 14 April 2008 21:03, Jim Leonard wrote:
I have a need to record the output of a (5150)
speaker. Although I
thought that I could just alligator-clip a positive lead to one speaker
terminal and the negative to the case/ground, the output was decidedly
"buzzy" (I assumed it was too "hot" and overmodulating). I routed
it
into a mixer and turned it down (speaker is 5v, not sure what line input
is) but it still didn't sound right.
"Line input" is typically no more than a volt or so...
The output being buzzy -- do you mean while the speaker was sounding or all
the time? It's quite possible that the mixer was picking up other stuff from
inside the case. Or if it's only when sounding then you're probably
overdriving the mixer input which could have all sorts of effects depending
on the circuitry there.
I found some old directions on hooking up a PC speaker
to a line input,
and was confused by the use of a capacitor -- I would have thought that
a resistor would have been more appropriate, to limit the signal
perhaps? In any case, here are the instructions, followed by my question:
Parts required:
- 6' to 12' shielded cable with RCA plug (male) on one end
- Two alligator clips
- One 4.7 uf capacitor
1. Connect one alligator clip to the shielded portion of the cable.
2. Connect the (-) minus side of the capacitor to the center conductor
of the cable and then connect the (+) side of the capacitor to the
second alligator clip.
3. Attach the clip with the capacitor to one of the wires going to your
computer's speaker. Attach the other clip to the metal case (ground)
somewhere (such as a screw or bolt connection).
4. Connect the RCA plug to the auxiliary input on your stereo system or
boom box.
While I have read the wikipedia entry on capacitors, I'm missing
something obvious. My question: Why the 4.7uf capacitor? Does it
serve to limit the signal? Reduce it's voltage? (or increase it?)
Filter the signal in some way?
That's a rather odd way of doing things. I had thought iniially when I read
this that you were looking at perhaps blocking DC with a capacitor, which
would probably be a good thing anyhow.
I could be mistaken about this, but my recollection is that they drove that
speaker with one wire tied to +5V and the other coupled to ground through an
open-collector device such as one section of a 7405 inverter, or similar.
What I would suggest is that you use both resistance and capacitance there,
you want to attenuate that signal downwards some (probably by at least a
factor of 5-10) and you also likely want to block DC from the input of your
mixer, though there may possibly already be a DC blocking capacitor at that
input.
I'd try say a 10K resistor connected to the speaker, a 1K resistor connected
to ground, and the mixer connected to the common junction of the two. Maybe
even make that 1K a trimpot, if you want to be able to adjust the level
downward further.
Is there some reason you don't want to just use a microphone?
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
10:54 p.m.
Connect a series cap to BOTH leads, this will isolate your input from any ground fault.
Connect a pot across the input to your RCA, 1K to start, if nothing happens untill you
twist to the bottom end, use a 500 ohm pot, this is your attenuator so you are not
overdriving your input
Randy
Date: Mon, 14 Apr 2008 21:47:00 -0400
From: rtellason at verizon.net
To: cctalk at classiccmp.org
Subject: Re: Beginner's capacitor question
On Monday 14 April 2008 21:03, Jim Leonard wrote:
_________________________________________________________________
Use video conversation to talk face-to-face with Windows Live Messenger.
http://www.windowslive.com/messenger/connect_your_way.html?ocid=TXT_TAGLM_W…
I have a need to record the output of a (5150)
speaker. Although I
thought that I could just alligator-clip a positive lead to one speaker
terminal and the negative to the case/ground, the output was decidedly
"buzzy" (I assumed it was too "hot" and overmodulating). I routed
it
into a mixer and turned it down (speaker is 5v, not sure what line input
is) but it still didn't sound right.
"Line input" is typically no more than a volt or so...
The output being buzzy -- do you mean while the speaker was sounding or all
the time? It's quite possible that the mixer was picking up other stuff from
inside the case. Or if it's only when sounding then you're probably
overdriving the mixer input which could have all sorts of effects depending
on the circuitry there.
I found some old directions on hooking up a PC
speaker to a line input,
and was confused by the use of a capacitor -- I would have thought that
a resistor would have been more appropriate, to limit the signal
perhaps? In any case, here are the instructions, followed by my question:
Parts required:
- 6' to 12' shielded cable with RCA plug (male) on one end
- Two alligator clips
- One 4.7 uf capacitor
1. Connect one alligator clip to the shielded portion of the cable.
2. Connect the (-) minus side of the capacitor to the center conductor
of the cable and then connect the (+) side of the capacitor to the
second alligator clip.
3. Attach the clip with the capacitor to one of the wires going to your
computer's speaker. Attach the other clip to the metal case (ground)
somewhere (such as a screw or bolt connection).
4. Connect the RCA plug to the auxiliary input on your stereo system or
boom box.
While I have read the wikipedia entry on capacitors, I'm missing
something obvious. My question: Why the 4.7uf capacitor? Does it
serve to limit the signal? Reduce it's voltage? (or increase it?)
Filter the signal in some way?
That's a rather odd way of doing things. I had thought iniially when I read
this that you were looking at perhaps blocking DC with a capacitor, which
would probably be a good thing anyhow.
I could be mistaken about this, but my recollection is that they drove that
speaker with one wire tied to +5V and the other coupled to ground through an
open-collector device such as one section of a 7405 inverter, or similar.
What I would suggest is that you use both resistance and capacitance there,
you want to attenuate that signal downwards some (probably by at least a
factor of 5-10) and you also likely want to block DC from the input of your
mixer, though there may possibly already be a DC blocking capacitor at that
input.
I'd try say a 10K resistor connected to the speaker, a 1K resistor connected
to ground, and the mixer connected to the common junction of the two. Maybe
even make that 1K a trimpot, if you want to be able to adjust the level
downward further.
Is there some reason you don't want to just use a microphone?
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
11:39 p.m.
You're recording the output of a 5150?? You mean the original IBM PC? Have
we forgotten how the PC generated audio, until real audio cards were
generated? They just toggled a line connected to the speaker-- thereby
pumped square waves at it. Squarewaves are rich in harmonics, and sound
very harsh. They were reliant on the fixed response of the speak to smooth
it out mechanically. Recording that properly will be pretty hard. You need
an RC filter to try and smooth that out, and I'm not sure what that would
look like. Probably a capacitor from the hot lead to ground, with resistor
in the hot lead before the cap. It's still going to be harsh.
It will be too "hot" certainly, and you will have to pad it down with a
series resistor followed by one to ground. But as much of the distortion is
coming from trying to record squarewaves as from overdriving the recorder's
input stage.
Series resistors or pots won't help enough. You need a T or Pi network with
a loading resistor across the speaker.
-T
At 09:54 PM 2008-04-14 -0500, Randy Dawson wrote:
Connect a series cap to BOTH leads, this will isolate
your input from any
ground fault.
Connect a pot across the input to your RCA, 1K to start, if nothing
happens untill you twist to the bottom end, use a 500 ohm pot, this is
your attenuator so you are not overdriving your input
Randy
read
-----
36. [Philosophy] Consistency is the last refuge of the unimaginative. --Oscar
Wilde
--... ...-- -.. . -. ----. --.- --.- -...
tpeters at nospam.mixcom.com (remove "nospam") N9QQB (amateur radio)
"HEY YOU" (loud shouting) WEB: http://www.mixweb.com/tpeters
43? 7' 17.2" N by 88? 6' 28.9" W, Elevation 815', Grid Square
EN53wc
WAN/LAN/Telcom Analyst, Tech Writer, MCP, CCNA, Registered Linux User 385531
Date: Mon, 14 Apr 2008 21:47:00 -0400
From: rtellason at verizon.net
To: cctalk at classiccmp.org
Subject: Re: Beginner's capacitor question
On Monday 14 April 2008 21:03, Jim Leonard wrote:
all
I have a need to record the output of a (5150)
speaker. Although I
thought that I could just alligator-clip a positive lead to one speaker
terminal and the negative to the case/ground, the output was decidedly
"buzzy" (I assumed it was too "hot" and overmodulating). I routed
it
into a mixer and turned it down (speaker is 5v, not sure what line input
is) but it still didn't sound right.
"Line input" is typically no more than a volt or so...
The output being buzzy -- do you mean while the speaker was sounding or the time? It's quite possible that the mixer
was picking up other
stuff from
inside the case. Or if it's only when
sounding then you're probably
overdriving the mixer input which could have all sorts of effects
depending
on the circuitry there.
> I found some old directions on hooking up a PC speaker to a line input,
> and was confused by the use of a capacitor -- I would have thought that
> a resistor would have been more appropriate, to limit the signal
> perhaps? In any case, here are the instructions, followed by my
question:
Parts required:
- 6' to 12' shielded cable with RCA plug (male) on one end
- Two alligator clips
- One 4.7 uf capacitor
1. Connect one alligator clip to the shielded portion of the cable.
2. Connect the (-) minus side of the capacitor to the center conductor
of the cable and then connect the (+) side of the capacitor to the
second alligator clip.
3. Attach the clip with the capacitor to one of the wires going to your
computer's speaker. Attach the other clip to the metal case (ground)
somewhere (such as a screw or bolt connection).
4. Connect the RCA plug to the auxiliary input on your stereo system or
boom box.
While I have read the wikipedia entry on capacitors, I'm missing
something obvious. My question: Why the 4.7uf capacitor? Does it
serve to limit the signal? Reduce it's voltage? (or increase it?)
Filter the signal in some way?
That's a rather odd way of doing things. I had thought iniially when I this that you were looking at perhaps blocking DC
with a capacitor, which
would probably be a good thing anyhow.
I could be mistaken about this, but my recollection is that they drove
that
speaker with one wire tied to +5V and the other
coupled to ground
through an
open-collector device such as one section of a
7405 inverter, or
similar.
What I would suggest is that you use both
resistance and capacitance
there,
you want to attenuate that signal downwards some
(probably by at least a
factor of 5-10) and you also likely want to block DC from the input of
your
mixer, though there may possibly already be a DC
blocking capacitor at
that
input.
I'd try say a 10K resistor connected to the speaker, a 1K resistor
connected
to ground, and the mixer connected to the common
junction of the
two. Maybe
even make that 1K a trimpot, if you want to be
able to adjust the level
downward further.
Is there some reason you don't want to just use a microphone?
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies.
--James
M Dakin
_________________________________________________________________
Use video conversation to talk face-to-face with Windows Live Messenger.
http://www.windowslive.com/messenger/connect_your_way.html?ocid=TXT_TAGLM_W…
15 Apr
15 Apr
3:15 a.m.
On Mon, 2008-04-14 at 22:39 -0500, Tom Peters wrote:
You're recording the output of a 5150?? You mean
the original IBM PC? Have
we forgotten how the PC generated audio, until real audio cards were
generated? They just toggled a line connected to the speaker-- thereby
pumped square waves at it. Squarewaves are rich in harmonics, and sound
very harsh. They were reliant on the fixed response of the speak to smooth
it out mechanically. Recording that properly will be pretty hard. You need
an RC filter to try and smooth that out, and I'm not sure what that would
look like. Probably a capacitor from the hot lead to ground, with resistor
in the hot lead before the cap. It's still going to be harsh.
I don't know about harsh, but it won't sound like a PC speaker. If you
want it to sound exactly right you're going to have to mike it in a
quiet room.
It will be too "hot" certainly, and you will
have to pad it down with a
series resistor followed by one to ground. But as much of the distortion is
coming from trying to record squarewaves as from overdriving the recorder's
input stage.
You know that most synthesizers produce squarewaves, and they can be
recorded without any problems at all, right?
Jim: try this - 4.7k resistor onto the hot side of the speaker, 1k
resistor from the "free" end of the 4.7k resistor to ground, 1uF cap
from the junction of the two resistors to the line in
on your desk (and
obviously ground to ground on the desk). You may need to fiddle
with
the EQ to get a nice sound.
Gordon
4:16 p.m.
On Mon, 14 Apr 2008 20:03:17 -0500
Jim Leonard <trixter at oldskool.org> wrote:
While I have read the wikipedia entry on capacitors,
I'm missing
something obvious. My question: Why the 4.7uf capacitor? Does it
serve to limit the signal? Reduce it's voltage? (or increase it?)
Filter the signal in some way?
The capacitor simply eliminates the DC offset on the
signal. Most likely
the speaker is connected to a digital (totem-pole) output that switches
between 0 V and 5 V. So you get a squere wave signal from 0 V to 5 V.
I.e. a squere wave signal with 5 V amplitude peek-to-peek with 2.5 V DC
offset. A large DC offset can drive a line input out of range.
Therefore you add a capacitor in series to filter out any DC on the
signal. Also: If your amplifier chain is completely DC coupled you will
end up with considerable DC current on your speakers. This can damage
the speakers. (Overheat, drive the moving parts to there extreme
positions.)
--
tsch??,
Jochen
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
4:57 p.m.
On Tuesday 15 April 2008 16:16, Jochen Kunz wrote:
On Mon, 14 Apr 2008 20:03:17 -0500
Jim Leonard <trixter at oldskool.org> wrote:
Not the way he described it being connected, across the speaker. If it'd
been between the speaker and whatever was processing the signal subsequently,
I'd have to agree, but that's not what was described.
While I have read the wikipedia entry on
capacitors, I'm missing
something obvious. My question: Why the 4.7uf capacitor? Does it
serve to limit the signal? Reduce it's voltage? (or increase it?)
Filter the signal in some way?
The capacitor simply eliminates the DC offset on the signal. Most likely the speaker is connected to a digital
(totem-pole) output that
switches between 0 V and 5 V. So you get a squere wave signal from 0 V to 5
V. I.e. a squere wave signal with 5 V amplitude peek-to-peek with 2.5 V DC
offset. A large DC offset can drive a line input out of range. Therefore you
add a capacitor in series to filter out any DC on the signal. Also: If your
amplifier chain is completely DC coupled you will end up with considerable
DC current on your speakers. This can damage the speakers. (Overheat, drive
the moving parts to there extreme positions.)
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
16 Apr
16 Apr
1:34 a.m.
On Tue, 15 Apr 2008 16:57:31 -0400
"Roy J. Tellason" <rtellason at verizon.net> wrote:
Correct. I missread the original post.
This is just a guess: If there is some series resistor (for current
limiting) in line with the speaker, this resistor and the capacitor
should construct some sort of low pass filter. I.e.: The speaker is
driven with a square wave voltage that has many harmonics. The low pass
filter can cut off may of the harmonics making a better "sound". The
speaker, as beeing an inert mechanical system, has a low pass filter
"build in".
--
tsch??,
Jochen
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
The capacitor
simply eliminates the DC offset on the signal.
Not the way he described it being
connected, across the speaker.
9:18 a.m.
On Wednesday 16 April 2008 01:34, Jochen Kunz wrote:
On Tue, 15 Apr 2008 16:57:31 -0400
"Roy J. Tellason" <rtellason at verizon.net> wrote:
Correct. I missread the original post.
This is just a guess: If there is some series resistor (for current
limiting) in line with the speaker, this resistor and the capacitor
should construct some sort of low pass filter. I.e.: The speaker is
driven with a square wave voltage that has many harmonics. The low pass
filter can cut off may of the harmonics making a better "sound". The
speaker, as beeing an inert mechanical system, has a low pass filter
"build in".
That makes some sense to me...
And it's likely that there is a series resistor in there, typical speaker
impedances being on the low side and a bit much in terms of loading for the
output of a TTL gate...
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
The
capacitor simply eliminates the DC offset on the signal.
Not the way he described it being connected, across the speaker.
20 Apr
20 Apr
5:57 p.m.
New subject: Recording the PC Speaker
Roy J. Tellason wrote:
And it's likely that there is a series resistor in
there, typical speaker
impedances being on the low side and a bit much in terms of loading for the
output of a TTL gate...
BTW I wanted to thank everyone who gave a response last week; I
collected most responses into an article here:
http://www.oldskool.org/guides/speakerrecording/
Thanks again!
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
7:39 p.m.
New subject: Recording the PC Speaker
At 04:57 PM 2008-04-20 -0500, you wrote:
Roy J. Tellason wrote:
Nice! Got it all collected in one place. Appreciate being cited too.
"Peek to peek" should probably be "peak-to-peak" however, if you want
to be
correct about it. You got it right in one other place.
-Tom
-----
449. [Humor] I remember when the candle shop burned down. Everyone stood
around
singing "Happy Birthday". --Steven Wright
--... ...-- -.. . -. ----. --.- --.- -...
tpeters at nospam.mixcom.com (remove "nospam") N9QQB (amateur radio)
"HEY YOU" (loud shouting) WEB: http://www.mixweb.com/tpeters
43? 7' 17.2" N by 88? 6' 28.9" W, Elevation 815', Grid Square
EN53wc
WAN/LAN/Telcom Analyst, Tech Writer, MCP, CCNA, Registered Linux User 385531
And it's likely that there is a series
resistor in there, typical
speaker impedances being on the low side and a bit much in terms of
loading for the output of a TTL gate...
BTW I wanted to thank everyone who gave a response last week; I collected
most responses into an article here:
http://www.oldskool.org/guides/speakerrecording/ 
15 Apr
15 Apr
5:06 p.m.
I found some old directions on hooking up a PC speaker
to a line input,
and was confused by the use of a capacitor -- I would have thought that
a resistor would have been more appropriate, to limit the signal
perhaps? In any case, here are the instructions, followed by my
question:
Parts required:
- 6' to 12' shielded cable with RCA plug (male) on one end
- Two alligator clips
- One 4.7 uf capacitor
Others have pointed out that an electrical connection isn't going to
achieve what you want, but some background on the capacitor:
It will, of course, block DC. If I'm not mistaken, mathematically, it's
a high pass filter, with a half-power (3dB down) cutoff frequency of
1/(2*pi*R*C), where R is the impedance of the load (speaker, mixer,
whatever) and C is the value of the capacitor in Farads. You would have
to work out the impedance, select the desired 3db point, and turn the
crank to calculate the needed cap value. You would want to keep in mind
that the graph of the filter effect has a shoulder, so that response
won't be flat toward the low end of the passband. Their capacitor value
would make sense for an 8 ohm speaker and a 4 Hz cutoff. My
recollection is that the basic interpreter didn't let you go below about
16 Hz, so that would give you two octaves of "footroom" if you will.
Since the signal is apparently 0-5V, based on other posts, you would
need to pad it down, but you'd probably want to try to more or less
match the impedance the driver circuit expects. That sort of thing is
accomplished with a resistor voltage divider. Line inputs are usually 1
V peak-to-peak.
Again, I think others have this right: put the machine in one room,
extend the speaker into a quiet recording space, mic it. Or just mic
machine and all, since its noise was part of the original experience. ;)
De
6:50 p.m.
On Tue, 2008-04-15 at 17:06 -0400, Dennis Boone wrote:
Again, I think others have this right: put the machine
in one room,
extend the speaker into a quiet recording space, mic it. Or just mic
machine and all, since its noise was part of the original experience. ;)
Oh yeah, make it sound easy, why don't you?
To properly capture it, you're going to need a decent mike near the
speaker. Of course this is going to catch a certain amount of hard disk
noise too, but to get the noise of the floppies right, you're going to
want another mike there too. These should be panned left and right,
about 40% each way.
The fan is a significant noise, so you're going to want a good condenser
mike with a popshield somewhat off-axis - this will probably catch the
satisfying *clunk* of the Big Orange Switch.
Case resonances make up a huge part of the sound - what's the case lid,
but a little reverb plate? So, you're going to want a couple of
overheads on that panned hard left and right, and maybe a PZM stuck
right to the case to bring out some of the warmth.
You're only looking at six channels there, but it should mix down into a
nice clean recording of the *real* sound of an IBM 5150.
Gordon
7:17 p.m.
On Tuesday 15 April 2008 18:50, Gordon JC Pearce wrote:
You're only looking at six channels there, but it
should mix down into a
nice clean recording of the *real* sound of an IBM 5150.
:-)
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
5:53 p.m.
I have a need to record the output of a (5150) speaker. Although I
I would think the characteristics of the (small, low quality) speaker in
a 5150 would affect the sound, and that if you want the result to sound
like a 5150, you should proably record the sound produced by said speaker
using a microphone. But that leads to all sorts of other problems
thought that I could just alligator-clip a positive
lead to one speaker
terminal and the negative to the case/ground, the output was decidedly
"buzzy" (I assumed it was too "hot" and overmodulating). I routed it
into a mixer and turned it down (speaker is 5v, not sure what line input
is) but it still didn't sound right.
Line input is about 0.75V to 1V RMS IIRC.
The 5150 speaker, IIRC, is connected between the +5V line and an
open-collector output.
While I have read the wikipedia entry on capacitors,
I'm missing
something obvious. My question: Why the 4.7uf capacitor? Does it
serve to limit the signal? Reduce it's voltage? (or increase it?)
Filter the signal in some way?
One property of a capacitor is that it'll pass AC (the changes in a
signal) while 'locking' DC (the steady, average, voltage of the signal).
And I think that's the main use here, to remove that 5V standing voltage.
I think I would try the following circuit if I wanted to record my PC
speaker output :
1uF
+
|| | 10k
o------|| |----------/\/\/----+----- Output 'hot' (centre of RCA plug)
Hot || | |
Side of PC |
Speaker /
\ 1k
/
\
|
o------------------------------+------ Output ground
PC ground
Where the hot side of the PC speaker is the terminal _not_ connected to
+5V. If youy get that wrong, you'll get no sound, but it shouldn't do any
damage.
-tony
7:15 p.m.
On Tuesday 15 April 2008 17:53, Tony Duell wrote:
I thought I'd remember that as being the case, nice to have my vague
recollection confirmed. :-)
That's pretty close to what I came up with.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
I have a need
to record the output of a (5150) speaker. Although I
I would think the characteristics of the (small, low quality) speaker in
a 5150 would affect the sound, and that if you want the result to sound
like a 5150, you should proably record the sound produced by said speaker
using a microphone. But that leads to all sorts of other problems
thought that I could just alligator-clip a
positive lead to one speaker
terminal and the negative to the case/ground, the output was decidedly
"buzzy" (I assumed it was too "hot" and overmodulating). I routed
it
into a mixer and turned it down (speaker is 5v, not sure what line input
is) but it still didn't sound right.
Line input is about 0.75V to 1V RMS IIRC.
The 5150 speaker, IIRC, is connected between the +5V line and an
open-collector output. While I have
read the wikipedia entry on capacitors, I'm missing
something obvious. My question: Why the 4.7uf capacitor? Does it
serve to limit the signal? Reduce it's voltage? (or increase it?)
Filter the signal in some way?
One property of a capacitor is that it'll pass AC (the changes in a
signal) while 'locking' DC (the steady, average, voltage of the signal).
And I think that's the main use here, to remove that 5V standing voltage.
I think I would try the following circuit if I wanted to record my PC
speaker output :
1uF
+
|| | 10k
o------|| |----------/\/\/----+----- Output 'hot' (centre of RCA plug)
Hot || | |
Side of PC |
Speaker /
\ 1k
/
\
o------------------------------+------ Output ground
PC ground
Where the hot side of the PC speaker is the terminal _not_ connected to
+5V. If youy get that wrong, you'll get no sound, but it shouldn't do any
damage.
5971
days inactive
5976
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15 comments
8 participants
participants (8)
-
ard＠p850ug1.demon.co.uk -
drb＠msu.edu -
gordonjcp＠gjcp.net -
jkunz＠unixag-kl.fh-kl.de -
rdawson16＠hotmail.com -
rtellason＠verizon.net -
tpeters＠mixcom.com -
trixter＠oldskool.org