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Old 27th May 2009, 09:38 PM   #1
Artie is offline Artie  United States
diyAudio Member
Join Date: Jul 2007
Location: Jax, FL
Default Help understanding tone circuit.

Hi all. Take a look at these two simple bass/treble circuits:

Click the image to open in full size.

The first one, (on the left), is from an older Pioneer reciever. The second one is from the LME49720 data sheet. The bass sides are identical, but look at the treble side. Completely different topology. The Pioneer one is in the "hot" signal path, while the 49720 one is within the feedback loop.

Is this just two different ways to accomplish the same thing, or does one have advantages over the other?

Thanks everyone.
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Old 27th May 2009, 11:30 PM   #2
Minion is offline Minion  Canada
diyAudio Member
Join Date: May 2006
Location: Cowican Bay , vancouver island
The First looks like a Passive Tone controll , No Boost , just cut ...

The second one is an active Tone controll which has Boost and Cut .....

The Values in a tone controll are determined by the Value of the Resistors and or Pots and the Capacitors and these are determined by the desired frequencies you want them to affect .....

a Passive tone controll has to take into account the impedance of the signal being fed into it and Values adjusted accordingly ....

An active Tone controll must be fed by a low impedance signal , as the input impedance affects the gain of the opamp so many times an active tone controll will have a Buffer in front of it , also most active tone controlls will alter the phaze of the signal ....

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Old 28th May 2009, 09:08 AM   #3
Artie is offline Artie  United States
diyAudio Member
Join Date: Jul 2007
Location: Jax, FL
Thanks Minion. Although, the first is active. It has both boost and cut. I didn't draw the opamp buffer that drives it just to keep the drawing simple.

But its odd that they're designed differently.
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