Simple tone control?

[DaveC]

I'd like to add a simple op amp-based tone control circuit to my preamp for
desktop speakers & sub that I'm modifying from stock.

This is the simplest I found:

<http://www.simplecircuitdiagram.com/2010/02/03/single-op-amp-tone-control/>

(I have +/- supplies so I will be eliminating all coupling caps and changing
Vcc/2 to ground.)

What are the positives and negatives to this design?

Better circuit (yet simple)?

Thanks.

 

[DaveC]

If you just want to change the tone (lower), not adjustable, put a

capacitor across the volume control. Start with a disc a little
smaller than a dime and work up and down from there.

I want adjustment of at least 2 bands. Not a 10-band equalizer, though... ;-)


Thanks.

 

[William Sommerwerck]

This looks a lot like the kind of tone controls mass-market
consumer-electronics equipment has been using for the past 60 years.

I don't know /exactly/ what your plans are, but the 1kHz corner frequency is
about the worst possible if you're trying to correct errors in the speakers
you're designing.

Unless you want a "tone control" that produces shrill treble and boomy bass,
you need to move the treble corner up, and the bass down.

Furthermore, it would make sense to design the speakers first, and see what
sort of correction they need. There are plenty of inexpensive drivers with
relatively flat response (if you believe the spec sheets). Neither they nor
most recordings will need much in the way of correction, so the best tone
control would be one that supplies small amounts of boost and cut at the
frequency extremes.

Unless you're looking for lots of boom and sizzle.

There are plenty of op-amps with a wider voltage range -- the 5534 and
TL-074 come to mind, but these are rather old designs. I'm sure someone will
be able to recommend something newer.

 

[DaveC]

It would really help to explain what you mean by that. 6" drivers in

wood cabs plus a 12" sub? Or 2.5" pc speakers plus a 4" sub? Very
different animals.

<
http://www.harmankardon.com/EN-
US/Products/Pages/ProductDetails.aspx?PID=SOUNDSTICKS3AM>

The video is pure marketing.

I don't have these speakers, but I do have the original SoundSticks I which
are USB input devices (no analog input). I've converted them to analog input.

Looking for an op-amp-based filter circuit. Anybody have a favorite you can
link to? Or put up an ASCII or Spice diagram?

Thanks.

 

[DaveC]

http://www.harmankardon.com/EN-
US/Products/Pages/ProductDetails.aspx?PID=SOUNDSTICKS3AM

nothing there

Yes there is. Maybe you have to copy & paste the URL, but it is valid.

 

[Phil Allison]

"DaveC"


http://www.harmankardon.com/EN-US/Products/Pages/ProductDetails.aspx?PID=SOUNDSTICKS3AM

Yes there is. Maybe you have to copy & paste the URL, but it is valid.

** The link leads to a home page and nothing else.



.... Phil

 

[Jeffrey Angus]

NT wrote...

Nothing here either.

I think the HK site redirects if it doesn't think you are in the US.

UK version here
http://uk.harmankardon.com/harman-kardon-product-detail-uk/soundsticks-
iii.html

Recommended by the News Of the World

You're links are broken/segmented.
<http://www.harmankardon.com/EN-US/Products/Pages/ProductDetails.aspx?PID=SOUNDSTICKS3AM>
Does work...

"Praised for its stunning design, the harman kardon® SoundSticks® II
speakers and subwoofer system became a milestone in harman kardon
history when it became part of the permanent collection at New York
City’s Museum of Modern Art (MoMA). Improving on its famous sibling’s
pop-culture appeal, the SoundSticks III system is all that and much
more. As a three-piece, 2.1-channel multimedia sound system, SoundSticks
III brings a new level of excitement to music, games and movies to your
home – with its exceptional sound clarity, enhanced color scheme and
bare minimum of wiring. Beyond its eye-catching appeal, SoundSticks III
continues to be incredibly capable – with 40 watts of dazzling
amplification, a down-firing powered subwoofer, eight full-range
transducers and compatibility with all sorts of multimedia devices. As
the sublime sequel to a prized performer, SoundSticks III is performance
art at its finest."

Only $169

Jeff-1.0

 

[Phil Allison]

"Jeffrey Angus"

You're links are broken/segmented.
<http://www.harmankardon.com/EN-US/Products/Pages/ProductDetails.aspx?PID=SOUNDSTICKS3AM>
Does work...

** Not from outside the USA it don't.

And the UK one is the same.

How boring of them.


.... Phil

 

[Jeffrey Angus]

"Jeffrey Angus"



** Not from outside the USA it don't.

And the UK one is the same.

Well that sucks, what's the point of that?

Jeff-1.0

 

[Don Pearce]

Well that sucks, what's the point of that?

Jeff-1.0

Just need a proxy within the USA - always useful to have one available
for every major country.

d

 

[Rich Grise]

This is the simplest I found:

<http://www.simplecircuitdiagram.com/2010/02/03/single-op-amp-tone-control/>

It looks bog-standard to me. Go ahead and use it and use your mind to go
on to greater things!

Cheers!
Rich

 

[DaveC]

Is *that* why many boomboxes and home stereos(cheap ones) have a tone

knob labeled "Bass< >Treble"?

All I notices with those is that turning it to the left made the sound
muffled and to the right made the sound more tinny/hissy. I didn't
notice that the bass was being boosted when the knob turned left or
that it was being reduced when turned right.

-CC

These pots on the circuit references aren't on a common shaft.

In other words, you can have muffled *and* tinny/hissy! ;-)

Dave

 

[Tauno Voipio]

I'd like to add a simple op amp-based tone control circuit to my preamp for
desktop speakers& sub that I'm modifying from stock.

This is the simplest I found:

<http://www.simplecircuitdiagram.com/2010/02/03/single-op-amp-tone-control/>

(I have +/- supplies so I will be eliminating all coupling caps and changing
Vcc/2 to ground.)

What are the positives and negatives to this design?

Better circuit (yet simple)?

Thanks.

This is the classic Baxandall tone control.
There is plenty of material if Googling for
'baxandall'.

 

[DaveC]

This is the classic Baxandall tone control.

There is plenty of material if Googling for
'baxandall'.
Tauno Voipio

Thanks! It really helps to know what it's called... ;-)

This page:

<http://sound.westhost.com/dwopa2.htm>

says:
"
This circuit must be driven from a low impedance, so connecting it after the
volume control (for example) is a no-no. Ideally, the output of an opamp will
be the source, thus ensuring the required low impedance.
"
The input to this circuit will be the output of a computer's sound card. I
don't know if it's an opamp driving the output or not.

What do you suggest to insure driving by low impedance? Add a buffer opamp
(gain of 1) at the input of this circuit?

Thanks.

 

[Don Pearce]

Thanks! It really helps to know what it's called... ;-)

This page:

<http://sound.westhost.com/dwopa2.htm>

says:
"
This circuit must be driven from a low impedance, so connecting it after the
volume control (for example) is a no-no. Ideally, the output of an opamp will
be the source, thus ensuring the required low impedance.
"
The input to this circuit will be the output of a computer's sound card. I
don't know if it's an opamp driving the output or not.

What do you suggest to insure driving by low impedance? Add a buffer opamp
(gain of 1) at the input of this circuit?

Thanks.

The sound card output will be fine for driving this.

d

 

[Phil Allison]

"Tauno Voipio"

This is the classic Baxandall tone control.

** It's not actually.

Seems like a ballsed up version with missing resistors that will be become
unstable at full treble.

There is plenty of material if Googling for
'baxandall'.

** And like most stuff on hobby web sites it is bunkum.

The "Baxandall" tone control design was published in Wireless World in
952 - it used valves. The network is different to the one in the link above
and produces variable turnover at both the high and low ends of the range.

http://www.novotone.be/_site/projets/Projet25/Baxandall WW.pdf



.... Phil

 

[DaveC]

A general question:

Should pots used in the audio tone filter circuits be audio (log) taper? Or
does this apply only to volume pots?

Thanks.

 

[Don Pearce]

A general question:

Should pots used in the audio tone filter circuits be audio (log) taper? Or
does this apply only to volume pots?

Thanks.

Linear

d

 

[Alex Pogossov]

I'd like to add a simple op amp-based tone control circuit to my preamp
for
desktop speakers & sub that I'm modifying from stock.

This is the simplest I found:

<http://www.simplecircuitdiagram.com/2010/02/03/single-op-amp-tone-control/>

(I have +/- supplies so I will be eliminating all coupling caps and
changing
Vcc/2 to ground.)

What are the positives and negatives to this design?

Better circuit (yet simple)?

Thanks.

This circuit, "mechanically" lifted from the tube era into op-amp
implementation, has a flaw:
If the treble control is set to maximum, then its gain is not limited at
+20dB at 10...20kHz, but keeps rising as far as the gain-bandwidth product
of the op-amp allows. Input impedance goes down accordingly. It might result
in Hf oscillations in the whole audio chain, even to burning the speakers
out if say you leave input unconnected and close to the speaker cable.

To fix the (potential) problem:
- insert 470R in series with the input 4.7uF capacitor or insert 470R
between the wiper of the treble control and the inverting input of the
op-amp;
- throw a 47pF cap from the op-amp output to the op-amp inverting input.