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Mr Macaw
Guest

Sun May 08, 2016 5:47 am   



I know what a servo motor is, and that you can get servo amplifiers (or servo drives) to work with them, but what does it mean when a stereo system says it has a servo amplifier?

--
"You, you, and you ... panic. The rest of you, come with me." - U.S. Marine Corp Gunnery Sgt.

Mr Macaw
Guest

Sun May 08, 2016 8:09 pm   



On Sun, 08 May 2016 15:13:56 +0100, M Philbrook <jamie_ka1lpa_at_charter.net> wrote:

Quote:
In article <op.yg39p7rx86ebyl_at_red.lan>, no_at_spam.com says...

I know what a servo motor is, and that you can get servo amplifiers (or servo drives) to work with them, but what does it mean when a stereo system says it has a servo amplifier?

The amp is the part that actually handles the high currents in the
motor coils.

The rest of it before that is the controller that generates the
signals and monitors the motor's position vie the internal feed
back sensors of the motor.

The control could be programmed to generate signal steps per step
command or scaled, meaning that multiple steps can be generated per
step command.
One step of the motor normally is governed by the type of motor
and its feed back system..

For example, systems with internal encoders of 5k or more per
turn have step spaces of 5K or more. etc..

The amplifier can be a dummy type or it could have additional
functions for current controls for step move and control settings
for holding positions etc. Normally additional IO is set up to
trigger these options from the controller itself.

It's best to get the controller and amp together as one. Also
depending on the system of design in mind, you can op for a
master power supply to serve a rack of servo drives or get
stand alones.


Er yes.... but I have a stereo system amplifier which mentions servo. There's no motors involved.

--
How to interpret a Pregnancy Test kit:
Blue means not pregnant.
Pink means pregnant.
Brown means you had it in the wrong hole.

M Philbrook
Guest

Sun May 08, 2016 8:13 pm   



In article <op.yg39p7rx86ebyl_at_red.lan>, no_at_spam.com says...
Quote:

I know what a servo motor is, and that you can get servo amplifiers (or servo drives) to work with them, but what does it mean when a stereo system says it has a servo amplifier?


The amp is the part that actually handles the high currents in the
motor coils.

The rest of it before that is the controller that generates the
signals and monitors the motor's position vie the internal feed
back sensors of the motor.

The control could be programmed to generate signal steps per step
command or scaled, meaning that multiple steps can be generated per
step command.

One step of the motor normally is governed by the type of motor
and its feed back system..

For example, systems with internal encoders of 5k or more per
turn have step spaces of 5K or more. etc..

The amplifier can be a dummy type or it could have additional
functions for current controls for step move and control settings
for holding positions etc. Normally additional IO is set up to
trigger these options from the controller itself.

It's best to get the controller and amp together as one. Also
depending on the system of design in mind, you can op for a
master power supply to serve a rack of servo drives or get
stand alones.

Jamie

M Philbrook
Guest

Tue May 10, 2016 9:38 pm   



In article <op.yg5dmlu986ebyl_at_red.lan>, no_at_spam.com says...
Quote:

On Sun, 08 May 2016 15:13:56 +0100, M Philbrook <jamie_ka1lpa_at_charter.net> wrote:

In article <op.yg39p7rx86ebyl_at_red.lan>, no_at_spam.com says...

I know what a servo motor is, and that you can get servo amplifiers (or servo drives) to work with them, but what does it mean when a stereo system says it has a servo amplifier?

The amp is the part that actually handles the high currents in the
motor coils.

The rest of it before that is the controller that generates the
signals and monitors the motor's position vie the internal feed
back sensors of the motor.

The control could be programmed to generate signal steps per step
command or scaled, meaning that multiple steps can be generated per
step command.
One step of the motor normally is governed by the type of motor
and its feed back system..

For example, systems with internal encoders of 5k or more per
turn have step spaces of 5K or more. etc..

The amplifier can be a dummy type or it could have additional
functions for current controls for step move and control settings
for holding positions etc. Normally additional IO is set up to
trigger these options from the controller itself.

It's best to get the controller and amp together as one. Also
depending on the system of design in mind, you can op for a
master power supply to serve a rack of servo drives or get
stand alones.

Er yes.... but I have a stereo system amplifier which mentions servo. There's no motors involved.


You must be referring to using a dual amp in bridge mode to drive a DC
motor for positioning an actuator ?

That being the case, you need a feed back for the position that acts as
the voltage comparator feed back signal to the control input amp.


Something in the line of RC (radio control)supplies can get you those.

Jamie

Mr Macaw
Guest

Tue May 10, 2016 10:19 pm   



On Tue, 10 May 2016 16:38:56 +0100, M Philbrook <jamie_ka1lpa_at_charter.net> wrote:

Quote:
In article <op.yg5dmlu986ebyl_at_red.lan>, no_at_spam.com says...

On Sun, 08 May 2016 15:13:56 +0100, M Philbrook <jamie_ka1lpa_at_charter.net> wrote:

In article <op.yg39p7rx86ebyl_at_red.lan>, no_at_spam.com says...

I know what a servo motor is, and that you can get servo amplifiers (or servo drives) to work with them, but what does it mean when a stereo system says it has a servo amplifier?

The amp is the part that actually handles the high currents in the
motor coils.

The rest of it before that is the controller that generates the
signals and monitors the motor's position vie the internal feed
back sensors of the motor.

The control could be programmed to generate signal steps per step
command or scaled, meaning that multiple steps can be generated per
step command.
One step of the motor normally is governed by the type of motor
and its feed back system..

For example, systems with internal encoders of 5k or more per
turn have step spaces of 5K or more. etc..

The amplifier can be a dummy type or it could have additional
functions for current controls for step move and control settings
for holding positions etc. Normally additional IO is set up to
trigger these options from the controller itself.

It's best to get the controller and amp together as one. Also
depending on the system of design in mind, you can op for a
master power supply to serve a rack of servo drives or get
stand alones.

Er yes.... but I have a stereo system amplifier which mentions servo. There's no motors involved.

You must be referring to using a dual amp in bridge mode to drive a DC
motor for positioning an actuator ?

That being the case, you need a feed back for the position that acts as
the voltage comparator feed back signal to the control input amp.


Something in the line of RC (radio control)supplies can get you those.


No, it's a stereo amp, for music through speakers. Sansui A-80.

--
Keep your nose to the grindstone, your shoulder to the wheel, your eye on the ball, and your ear to the ground. Then see how much work you get done in that position.


Guest

Fri May 13, 2016 6:24 am   



On Tue, 10 May 2016, Mr Macaw wrote:
Quote:

No, it's a stereo amp, for music through speakers. Sansui A-80.

I'm fairly sure that for an audio amp ``servo'' means the freq. response
goes all the way down to D.C.

Wayne Chirnside
Guest

Fri May 13, 2016 4:29 pm   



On Sun, 08 May 2016 00:47:57 +0100, Mr Macaw wrote:

Quote:
I know what a servo motor is, and that you can get servo amplifiers (or
servo drives) to work with them, but what does it mean when a stereo
system says it has a servo amplifier?


There is active circuitry to keep the bias at a point where the output
tracks symmetrically between positive and negative voltage excursions.

Mr Macaw
Guest

Fri May 13, 2016 6:08 pm   



On Fri, 13 May 2016 11:29:21 +0100, Wayne Chirnside <mark_at_faux.com> wrote:

Quote:
On Sun, 08 May 2016 00:47:57 +0100, Mr Macaw wrote:

I know what a servo motor is, and that you can get servo amplifiers (or
servo drives) to work with them, but what does it mean when a stereo
system says it has a servo amplifier?

There is active circuitry to keep the bias at a point where the output
tracks symmetrically between positive and negative voltage excursions.


I see. Is this to prevent unnecessary DC current through the speaker creating heat in the coil? Or does it improve sound quality by leaving the cone centred so it doesn't hit the ends of its movement?

--
What is it when a man talks nasty to a woman?
Sexual Harassment.
What is it when a woman talks nasty to a man?
3.99 a minute.

Mr Macaw
Guest

Fri May 13, 2016 8:46 pm   



On Fri, 13 May 2016 01:24:02 +0100, <colonel_hack_at_yahoo.com> wrote:

Quote:
On Tue, 10 May 2016, Mr Macaw wrote:

No, it's a stereo amp, for music through speakers. Sansui A-80.

I'm fairly sure that for an audio amp ``servo'' means the freq. response
goes all the way down to D.C.


What purpose would that be for? You can't hear anything that low.

--
Murphy says to Paddy, "What ya talkin into an envelope for?" "I'm sending a voicemail ya thick sod!"

Ian Field
Guest

Sat May 14, 2016 2:32 am   



"Mr Macaw" <no_at_spam.com> wrote in message news:op.yhehc4it86ebyl_at_red.lan...
Quote:
On Fri, 13 May 2016 11:29:21 +0100, Wayne Chirnside <mark_at_faux.com> wrote:

On Sun, 08 May 2016 00:47:57 +0100, Mr Macaw wrote:

I know what a servo motor is, and that you can get servo amplifiers (or
servo drives) to work with them, but what does it mean when a stereo
system says it has a servo amplifier?

There is active circuitry to keep the bias at a point where the output
tracks symmetrically between positive and negative voltage excursions.

I see. Is this to prevent unnecessary DC current through the speaker
creating heat in the coil? Or does it improve sound quality by leaving
the cone centred so it doesn't hit the ends of its movement?


That's more difficult in a direct coupled amplifier - drift is always a
problem.

There's no way out of incorporating loads of DC only nfb. That has to be
decoupled against the AC signal, the capacitors tend to be bigger than you'd
use for AC coupling.

That means aluminium electrolytics, probably about as bad as it gets for
colouring the audio signal.

Wayne Chirnside
Guest

Sat May 14, 2016 7:30 am   



On Fri, 13 May 2016 13:08:54 +0100, Mr Macaw wrote:

Quote:
On Fri, 13 May 2016 11:29:21 +0100, Wayne Chirnside <mark_at_faux.com
wrote:

On Sun, 08 May 2016 00:47:57 +0100, Mr Macaw wrote:

I know what a servo motor is, and that you can get servo amplifiers
(or servo drives) to work with them, but what does it mean when a
stereo system says it has a servo amplifier?

There is active circuitry to keep the bias at a point where the output
tracks symmetrically between positive and negative voltage excursions.

I see. Is this to prevent unnecessary DC current through the speaker
creating heat in the coil? Or does it improve sound quality by leaving
the cone centred so it doesn't hit the ends of its movement?


Prevents DC current as well as eliminates the need for capacitors which
always introduce phase shift that annoys purists.

It also eliminates drift but getting the design just right AND fail safe
requires exceptionally careful and thoughtful design.

Very few got it right but when they did it was terrific.
Very few tried because blowing out customers speakers makes for bad
business, all too easy with that design.

Now the new gainclones take all the perfect design out and make it dead
easy to employ DC servo circuitry and all the paralleled chips designs
incorporate this in the design.

However...
They also introduce their own circuit protection and thermal shutdown
that can very easily color and prevent perfect reproduction of loud
transients.

The only way around that is three or four chips servo slaved together
such that they have such an overabundance of headroom they never come
close to the limiting circuitry.

Planning my own gainclone based on the TDA7293 right now AAMOF.
As well as ordering another cheap Chinese digital amplifier having had
the best of luck with the last.
But only after adding my own DC protection circuit should a failure occur.
Quad matched Technics speakers with 12 inch woofers are not to risk!

Believe it or not they sound just great running at 2 ohms off a 25 dollar
Parts Express Lepai digital amplifier up to about 1/2 volume, after that
it's all down hill but for a small room being digital it's more than I
ever need.
YMMV as I've heard the quality of these amps isn't exactly uniform but
mines been running two years w/o an issue.

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