Changing volume in a power amp

[Dave Ryman]

Is there an easy way to change the volume of an IC-based power amp without
building a whole preamp stage? For example, changing the voltage level
supplied to the IC.

--
Regards,
Dave

[email protected]
http://welcome.to/daves.website
http://travel.to/formula.one

 

[Kalman Rubinson]

Is there an easy way to change the volume of an IC-based power amp without
building a whole preamp stage? For example, changing the voltage level
supplied to the IC.

Even that may not work if the chip is putting out all it can. There
are many ways to change output and gain but most require more specific
information in order to be of any use.

Kal

 

[Mac]

Is there an easy way to change the volume of an IC-based power amp without
building a whole preamp stage? For example, changing the voltage level
supplied to the IC.

You could attach a potentiometer (pot) to the input. Like this:


IN------------\
/
\<-------TO AMP
/
\
/
|
|
GND

"IN" is from the CD player (or other signal source). "TO AMP" is to the
power amp IC. They make dual pots that can control two channels at the
same time. That's probably what you want, unless you are designing a mono
amplifier.

I would guess that anywhere from 20k to 100k would be a good amount of
total resistance in your potentiometer. Look for one that advertises an
audio taper, and make sure you hook it up so that turning the knob
clockwise makes it louder. ;-)

regards,
Mac

 

[Ban]

Dave Ryman wrote:
|| Is there an easy way to change the volume of an IC-based power amp
|| without building a whole preamp stage? For example, changing the
|| voltage level supplied to the IC.
||
|| --
|| Regards,
|| Dave
||

Dave,
depends what you want to do:
1. In-/decrease the gain (fixed)--usually possible by inceasing/decreasing
the feedback resistor from the output. You have to look into the datasheet
of the IC to find the appropriate connection and identify the resistor. Some
compensation caps might be needed to tweek to prevent instability.
If gain is only to be lowered, you can put an attenuating network(1 or 2
resistors) at the input.

2. Make gain variable-- easy with a pot on the input eventually combined
with a gain increase as in point1.
If your amp has balanced inputs like most professional amps do, you can do
that at the output of the balanced to unbalanced stage.

The supply voltage has nothing to do with the gain (because of the above
mentioned feedback), only with the maximal achievable output voltage.

Please define the problem better, so our advice can be more specific.

 

[Dave Ryman]

(snip)

You could attach a potentiometer (pot) to the input. Like this:


IN------------\
/
\<-------TO AMP
/
\
/
|
|
GND

"IN" is from the CD player (or other signal source). "TO AMP" is to
the power amp IC. They make dual pots that can control two channels at
the same time. That's probably what you want, unless you are designing
a mono amplifier.

I would guess that anywhere from 20k to 100k would be a good amount of
total resistance in your potentiometer. Look for one that advertises
an audio taper, and make sure you hook it up so that turning the knob
clockwise makes it louder. ;-)

regards,
Mac

Sounds good, thanks

--
Regards,
Dave

[email protected]
http://welcome.to/daves.website
http://travel.to/formula.one

 

[Dave Ryman]

Thanks for that

--
Regards,
Dave

[email protected]
http://welcome.to/daves.website
http://travel.to/formula.one

 

[YD]

Is there an easy way to change the volume of an IC-based power amp without
building a whole preamp stage? For example, changing the voltage level
supplied to the IC.

Up or down?

If down try a potentiometer or voltage divider (for fixed output
level) between the input jack and and amp input. No need for a
complete preamp stage.

If up take a look at the specs and see if you can give it a boost from
current configuration. If it's already at the max you're SOL. If the
volume's low it may be that the signal is insufficient and you'll need
a preamp.

- YD.

 

[John Fields]

Is there an easy way to change the volume of an IC-based power amp without
building a whole preamp stage? For example, changing the voltage level
supplied to the IC.

---
If your input signal has no DC on it and your amp's input is referenced
to GND:

CW
IN>--------[POT]---------+
| |
| |
+-----|-\ |
| >--+---->OUT
+-----|+/
|
GND>---------+---------------->GND

You'll get a gain of -1 with the pot at mid-point, a gain of zero with
the pot fully CCW and infinite gain with the pot fully CW so you'll need
to get a pot with a resistance high enough so that it doesn't load your
signal source too much as you turn it CW. You may also want to limit
the range of the pot like this:

CW
IN>--[R]---[POT]---[R]---+
| |
| |
+-----|-\ |
| >--+---->OUT
+-----|+/
|
GND>---------+---------------->GND

You may also have to do some compensation to keep the thing from
oscillating, but what the hell, it's worth a try. ???

 

[Paul Hovnanian P.E.]

You could attach a potentiometer (pot) to the input. Like this:

IN------------\
/
\<-------TO AMP
/
\
/
|
|
GND

"IN" is from the CD player (or other signal source). "TO AMP" is to the
power amp IC. They make dual pots that can control two channels at the
same time. That's probably what you want, unless you are designing a mono
amplifier.

I would guess that anywhere from 20k to 100k would be a good amount of
total resistance in your potentiometer. Look for one that advertises an
audio taper, and make sure you hook it up so that turning the knob
clockwise makes it louder. ;-)

You could use one of these (make sure you're sitting down before you
scroll to the bottom of the page):

http://www.referenceaudiomods.com/M...reen=CTGY&Store_Code=RAM&Category_Code=VOLUME

 

[Mac]

You could use one of these (make sure you're sitting down before you
scroll to the bottom of the page):

http://www.referenceaudiomods.com/M...reen=CTGY&Store_Code=RAM&Category_Code=VOLUME

Thanks for the tip. At that price, I figure the best bet is to buy two and
breed 'em. ;-)

Mac

 

[Dave Ryman]

(snip)

Thanks for the tip. At that price, I figure the best bet is to buy two
and breed 'em. ;-)

Mac

LOL - a little over the top for my project!

--
Regards,
Dave

[email protected]
http://welcome.to/daves.website
http://travel.to/formula.one