# Audio Switcher Help

J

#### Jon Slaughter

Jan 1, 1970
0
I'm trying to use the MAX4571 essentially to mute some audio channels,

http://www.maxim-ic.com/quick_view2.cfm?t=qv&qv_pk=1974#Applications/Uses

I got the controller to work and it seems fine. My test was to put V+ on the
input and scope the output(with a pull down to ground for when the switch is
off). It seems to work fine. My code simply toggles the state the switches
every 1s or so.

But when I put an audio signal on the input instead I get the negative half
clipped and it is extremely attentuated(About 1/10 or more). What I did was
actually pass a sin wave generated by my computer which goes into a
mixer(for easy volume control and other things that I tend to do) then from
the mixer's headphone out into the input of the MAX4571.

Audio+ --- MAX4571 NO1

MAX4571 COM1 ---+--- Audio-
R
|
GND

(R anywhere from 500 to 3k but didn't help any and made it worse for lower
and high values)

With the scope connected to +.

Any ideas why the signal would be clipped and severly attenuated?

Its possible I ruined the device. For some reason my first PIC's I2C
channels stopped working so I might have shorted something out when I was
probing around. I replaced the pic and everything seemed to work but maybe I
screwed up the MAX4571 although it will passes the constant voltage just
fine.

First thing I need to know is if it passes AC completely(the scope says no

E

#### Eeyore

Jan 1, 1970
0
Jon said:
I'm trying to use the MAX4571 essentially to mute some audio channels,

http://www.maxim-ic.com/quick_view2.cfm?t=qv&qv_pk=1974#Applications/Uses

Just using a series switch ?

I got the controller to work

What 'controller' ?

and it seems fine. My test was to put V+ on the
input and scope the output(with a pull down to ground for when the switch is
off). It seems to work fine. My code simply toggles the state the switches
every 1s or so.

So what did you see ?

But when I put an audio signal on the input instead I get the negative half
clipped and it is extremely attentuated(About 1/10 or more).

Given an absence of a negative supply, I dare say it may have trouble passing AC
signals. What did you expect ?

The data sheet does not show any negative voltages allowable. You're using an
inappropriate part.

Graham

J

#### Jan Panteltje

Jan 1, 1970
0
I'm trying to use the MAX4571 essentially to mute some audio channels,

http://www.maxim-ic.com/quick_view2.cfm?t=qv&qv_pk=1974#Applications/Uses

It has only ground and +?
Then you must likely bias your audio at 1/2Ub, else bottom get clipped.

analog signal range is from 0 to +V!!
+V
|
R
|---------- chip input
audio in --C---|
|
R
|
///

That chip sucks in my view,
their 'no click' switching seems to be a slow 8 ms bump.

The 74HC4053 rocks, has negative supply.

Anyways, Maxim is hard to get sometimes.

J

#### Jon Slaughter

Jan 1, 1970
0
Jan Panteltje said:
It has only ground and +?
Then you must likely bias your audio at 1/2Ub, else bottom get clipped.

analog signal range is from 0 to +V!!
+V
|
R
|---------- chip input
audio in --C---|
|
R
|
///

Some of there chips allow -V on the signal. I guess they use a charge pump
to generate -V. Kinda sucsk that this one doesn't.
That chip sucks in my view,
their 'no click' switching seems to be a slow 8 ms bump.

The 74HC4053 rocks, has negative supply.

I need a very large number of switches(about 80) that uses a small space as
possible.

Having to bias it really sucks but I guess I don't have much of a choice ;/
For my application I guess the clickless switching is not all that
important. (I suppose I could do the switching myself by monitoring the
signal with the Pic and switch when needed using the high speed mode).

J

#### Jan Panteltje

Jan 1, 1970
0
I need a very large number of switches(about 80) that uses a small space as
possible.

Having to bias it really sucks but I guess I don't have much of a choice ;/
For my application I guess the clickless switching is not all that
important. (I suppose I could do the switching myself by monitoring the
signal with the Pic and switch when needed using the high speed mode).

It is an interesting subject.
For some time I wanted to make an audio switch for on my desk, that
connects all possible DVD outputs, recorder inputs, PC in and outputs,
headphones, speakers, other stuff, in a crossbar way, that can be controlled
by a simple small keyboard.
So, autonomous, not PC controlled, as PCs may be off.

I found one chip that did it all and it costs 135$. Doing it with 74HC4053 and the like, in DIL, takes 2 eurocards (100x160mm), Many years ago I did it for somebody else, controlled by a Z80 with CD22101 4x4 crossbar switches, and it took half a 19inch rack... (needed logic level changes). Of course it can be done mechanically too. Oh, I am only talking about a say 16 * 16 crossbar, with headphone or line drive capability, in stereo. And perhaps one for video too.... Maybe that is why I still switch connectors manually. An other thing with crossbars is that a not-connected bar will pick up noise, so you need to switch an unused bar to ground, requiring an extra bar. Using + and - supplies greatly simplifies things. crossbar, crosspoint, what is the difference? http://www.analog.com/en/prod/0,,768_832_AD8113,00.html Price about 45 USD http://www.digikey.com/scripts/DkSearch/dksus.dll?KeywordSearch Maybe one day J #### Jon Slaughter Jan 1, 1970 0 Jan Panteltje said: It is an interesting subject. For some time I wanted to make an audio switch for on my desk, that connects all possible DVD outputs, recorder inputs, PC in and outputs, headphones, speakers, other stuff, in a crossbar way, that can be controlled by a simple small keyboard. So, autonomous, not PC controlled, as PCs may be off. I found one chip that did it all and it costs 135$.
Doing it with 74HC4053 and the like, in DIL, takes 2 eurocards
(100x160mm),

Many years ago I did it for somebody else, controlled by a Z80 with
CD22101
4x4 crossbar switches, and it took half a 19inch rack... (needed logic
level
changes).
Of course it can be done mechanically too.

Oh, I am only talking about a say 16 * 16 crossbar, with headphone or line
drive
capability, in stereo.
And perhaps one for video too....
Maybe that is why I still switch connectors manually.

An other thing with crossbars is that a not-connected bar will pick up
noise,
so you need to switch an unused bar to ground, requiring an extra bar.
Using + and - supplies greatly simplifies things.

crossbar, crosspoint, what is the difference?
http://www.digikey.com/scripts/DkSearch/dksus.dll?KeywordSearch

Maybe one day

http://pdfserv.maxim-ic.com/en/an/AN638.pdf

The devices don't need any level shifting or anything. I'm going to have to
troubleshoot and see whats wrong. As far as that app note is says, it should
work the way I original thought. Might have screwed up chip(not sure how
though but I'll try another one soon).

J

#### Jan Panteltje

Jan 1, 1970
0
http://pdfserv.maxim-ic.com/en/an/AN638.pdf

The devices don't need any level shifting or anything. I'm going to have to
troubleshoot and see whats wrong. As far as that app note is says, it should
work the way I original thought. Might have screwed up chip(not sure how
though but I'll try another one soon).

YOU NEED 1/2 V BIAS FOR AUDIO.

+
|
R
|--------- chip
audio -- C --|
|
R
|
///

J

#### Jon Slaughter

Jan 1, 1970
0
Jan Panteltje said:
YOU NEED 1/2 V BIAS FOR AUDIO.

+
|
R
|--------- chip
audio -- C --|
|
R
|
///

lol, you didn't take a loot at that pdf did you?

J

#### Jan Panteltje

Jan 1, 1970
0
lol, you didn't take a loot at that pdf did you?

Actually I looked twice.
Have you tried this?

J

#### Jon Slaughter

Jan 1, 1970
0
Jan Panteltje said:
On a sunny day (Tue, 20 Nov 2007 12:16:55 -0600) it happened "Jon
Slaughter"

Actually I looked twice.
Have you tried this?

It won't solve my problem really. I guess it probably will work but
ultimately its something I need to avoid(not only more components but more
noise).

Page 1,

"Connecting an n-channel MOSFET in parallel with a p-channel MOSFET allows
signals to pass in either direction

with equal ease. Whether the n- or the p-channel device carries more signal
current depends on the ratio of

input to output voltage. Because the switch has no preferred direction for
current flow, it has no preferred input

or output.

"

Now thats telling me that it will take AC just fine such as an audio signal?
I could be wrong in interpreting it though?

On the data sheet for the 4610 it says

"Each switch handles V+ to GND analog

signal levels"

Which says it doesn't take AC ;/ So I guess I'm wrong but I can't see how
the first quote(from page 1) says AC won't work.

Doesn't Figure 1 show a circuit that lets AC go through? Note it has -V so
maybe -V = GND? But then that doesn't explain the quote that switch has no
preferred directionf or current flow. This is telling me that I could treat
the output as the input and vice versa but then that means that AC should
flow?

J

#### Jan Panteltje

Jan 1, 1970
0
On a sunny day (Tue, 20 Nov 2007 19:23:22 GMT) it happened "Jon Slaughter"
<[email protected]>:

Look at it this way:
It is a piece of silicon.
If you have Vss grounded, then driving below Vss will see diodes.
And on top of that, one of them chips has comparators that actually
switch the thing off, if the voltage is close to Vdd or Vss.

R

#### RST Engineering $$jw$$

Jan 1, 1970
0
lol, you didn't take a loot at that pdf did you?

lmfao...somebody comes in here for help, somebody else gives him the right
answer, and he comes back with a snappy retort like this.

The fellow is correct; it needs vcc/2 bias for capacitively coupled audio.
Swings above and below ground, don'cha know.

Jim

J

#### Jon Slaughter

Jan 1, 1970
0
RST Engineering (jw) said:
lmfao...somebody comes in here for help, somebody else gives him the right
answer, and he comes back with a snappy retort like this.

The fellow is correct; it needs vcc/2 bias for capacitively coupled audio.
Swings above and below ground, don'cha know.

Jim

Um if you cared to read the entire thread or even the first you would have
noticed that I never asked for a solution so the problem but asked why the
device was behaving the way it was. Obviously you don't care about that
though... I suppose your on PMS and have to find something to whine about.

Also, the app note specifically say that current can go in both directions
and my simulation of the circuit in the app note shows that it works that
way too. Either the device I'm using doesn't work that way or there -V is
ground. (there is no -V on the device though)

In any case there are other methods that are potentially better than passing
biasing... such as running a +- power supply so that I can avoid all all the
resistors an caps(which introduce noise).

Unfortunately your just a whinner that I guess has nothing better to do with

Again though, as I'm sure you completely miss what I'm saying(chances are
the device itself and how it was described in the app notes and
datasheet(i.e., no mention of biasing, example circuits not showing any
biasing, app note specifically saying "both directions", etc...)

Surely the biasing method would work but it would work even if AC could be
passed... in that case it is far from the optimal solution. If the device
I'm using will not pass AC(which it seems that way) then I need to know for
sure.

Theres a huge difference between using a method that works and a method that
works optimally. I guess your one of those people that don't give a shit

R

#### RST Engineering $$jw$$

Jan 1, 1970
0
lol, you didn't take a loot at that pdf did you?

Um, that would be look

Ooookay, if we're going to play the horse's ass game, I can play as well as
the next feller ...

That would be Um, (comma).

if you cared to read the entire thread or even the first you would have
noticed that I never asked for a solution so the problem but asked why the
device was behaving the way it was.

I've been reading the entire thread. I wanted to see how long you would
rave on about your superior knowledge of data sheets until somebody showed
you how the real world works.

Obviously you don't care about that
though... I suppose your on PMS and have to find something to whine about.

That would be "you're", and I'm way the hell too old for PMS.

Also, the app note specifically say that current can go in both directions

Yep, positive voltages at either end will be transmitted quite nicely.
Negative voltages (below the Vss rail) will turn the parasitic diodes on and
you will wind up with nothing.

and my simulation of the circuit in the app note shows that it works that
way too.

Oh, Christ, another "my simulator works just fine." Great. Pack your

Either the device I'm using doesn't work that way or there -V is
ground. (there is no -V on the device though)

That would be "their". You have no clue as to how CMOS devices work if you
say there is no V-.

In any case there are other methods that are potentially better than
passing biasing... such as running a +- power supply so that I can avoid
all all the resistors an caps(which introduce noise).

You'd rather go to the expense of a +/- supply than use a voltage divider?
Haven't marketed any products, have you? (And that would be "and".) Never
seen a capacitor yet introduce noise. That's why we use 'em, don'cha know.

Unfortunately your just a whinner that I guess has nothing better to do

That would be "whiner". I bided my time until somebody that knows what he
is talking about told you what the problem was. No sense trying to teach my
grandmother how to suck eggs.

Again though, as I'm sure you completely miss what I'm saying(chances are
you won't even read it but reply with the same BS). My first post was
about the device itself and how it was described in the app notes and
datasheet(i.e., no mention of biasing, example circuits not showing any
biasing, app note specifically saying "both directions", etc...)

So do the Motorola data books. So do the National data books. Nobody
bothers showing input biasing for an AC signal because that would defeat the
specmanship of the part. You only have to mess with an experiment for about
15 minutes and then look at the internal design of the part to figure out in
a couple of seconds why you can't force AC through this sort of device
without bias.

Surely the biasing method would work but it would work even if AC could be
passed...

That sentence fragment makes absolutely no English sense...

in that case it is far from the optimal solution.

You wouldn't know an optimal solution if it bit you in the butt.

If the device
I'm using will not pass AC(which it seems that way) then I need to know
for sure

Trust me, sonny, I've been using these things in real product design for
almost thirty years. Jan told you an inconvenient truth and you seem
unwilling to accept it.

By the way, there are several ways of low noise biasing when you've got
literally infinite input impedance but you apparently won't listen to folks
that know how to do it, so go figure it for yourself.
Theres a huge difference between using a method that works and a method
that works optimally.

I've never known an optimal design to make it in the marketplace yet. A
product is a bunch of engineering compromises flying in loose formation.

I guess your one of those people that don't give a shit

That would be "you're". I give a shit about a lot of things. One thing I
do NOT do well is suffer fools graciously.

Jim

J

#### Jon Slaughter

Jan 1, 1970
0
RST Engineering (jw) said:
Um, that would be look

Ooookay, if we're going to play the horse's ass game, I can play as well
as the next feller ...

That would be Um, (comma).

if you cared to read the entire thread or even the first you would have

I've been reading the entire thread. I wanted to see how long you would
rave on about your superior knowledge of data sheets until somebody showed
you how the real world works.

Obviously you don't care about that

That would be "you're", and I'm way the hell too old for PMS.

Yep, positive voltages at either end will be transmitted quite nicely.
Negative voltages (below the Vss rail) will turn the parasitic diodes on
and you will wind up with nothing.

Oh, Christ, another "my simulator works just fine." Great. Pack your

Either the device I'm using doesn't work that way or there -V is

That would be "their". You have no clue as to how CMOS devices work if
you say there is no V-.

You'd rather go to the expense of a +/- supply than use a voltage divider?
Haven't marketed any products, have you? (And that would be "and".) Never
seen a capacitor yet introduce noise. That's why we use 'em, don'cha
know.

That would be "whiner". I bided my time until somebody that knows what he
is talking about told you what the problem was. No sense trying to teach
my grandmother how to suck eggs.

So do the Motorola data books. So do the National data books. Nobody
bothers showing input biasing for an AC signal because that would defeat
the specmanship of the part. You only have to mess with an experiment for
about 15 minutes and then look at the internal design of the part to
figure out in a couple of seconds why you can't force AC through this sort
of device without bias.

That sentence fragment makes absolutely no English sense...

Lol, your dumber than I thought then. I would break it down for you but you
in that case it is far from the optimal solution.

You wouldn't know an optimal solution if it bit you in the butt.

If the device

Trust me, sonny, I've been using these things in real product design for
almost thirty years. Jan told you an inconvenient truth and you seem
unwilling to accept it.

Nope, sorry... are you a fucking priest or an engineer? If an engineer then
start acting like it and show me the money instead of your "Trust me, sonny"
BS.
By the way, there are several ways of low noise biasing when you've got
literally infinite input impedance but you apparently won't listen to
folks that know how to do it, so go figure it for yourself.

oh, infinite impedence huh? Sure.. I guess you think there is 0 capacitance
in there too? I don't listen to people like you who are on an ego trip. You
think just cause you've been around the block a few times that everyone is
suppose to bow down and suck your cock. It ain't going to happen. Again,
you totally missed the point of the original post and are trying to start
something that is totally irrelevant to the original post.
I've never known an optimal design to make it in the marketplace yet. A
product is a bunch of engineering compromises flying in loose formation.

Sure, cause fuckers like you always bitch about it until you get your shitty
design to replace it.
I guess your one of those people that don't give a shit

That would be "you're". I give a shit about a lot of things. One thing I
do NOT do well is suffer fools graciously.

Lovely... Keep trying to find my spelling and grammar mistakes instead of
trying to solve the real problem. You call yourself an engineer? Is that
what they taught you in schoo 140 years ago?

Your just an old coot that can't get with the times. You rather force feed
someone your puddin instead of showing them the proof. I'm sorry but like
many instances I'm not going to accept your BS until you make it logical.

Again, none of your fucking post has anythign to do with my original
question, which had nothing to do with how to get the device to work but if
the device supported ac or not. They are totaly different questions but I
guess with your limited brain cells you fail to see that(I know a bunch of
your buddies are going to jump on me and try to make it like its my fault
cause birds of a feather flock together.

Anyways, I got you on ignore now so feel free to reply ad nauseum. I'm sure
you and your buddies can reforce your ego's all you want and feed each other
ya'lls pudding.

R

#### RST Engineering $$jw$$

Jan 1, 1970
0
--
"If you think you can, or think you can't, you're right."
--Henry Ford

R

Jan 1, 1970
0
Plonk.

Jim

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