Baxandall Eq circuit, any comments?

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weiss

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Jun 16, 2014
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I thought about building this baxandall equalizer circuit. Found it interesting that the corner frequency doesn't change with the cut/boost setting.
Any comments are welcome.

thanks
 

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weiss said:
I thought about building this baxandall equalizer circuit.
Strictly, it's not a Baxandall; totally different topology.

Found it interesting that the corner frequency doesn't change with the cut/boost setting.
Does it really matter? Is it actually true? What's the "corner frequency" in an EQ? Doesn't it actually depend also on the amount of Boost/Cut?
Build it and judge by yourself if it really makes a significant difference...
IMO the only difference is that it makes variable frequency easier.
 
Alright, i'm also not sure if it makes a difference.. anyway i searched a little more and i'm gonna build this circuit only with stepped frequency selections:

eq-f5.gif


Now i ask myself, what would be the most useful op amp for this circuit?
Do you guys know what Dangerous uses in their bax?

I got these here..

NE5532
TL072
THAT 1206
LME49270
LM4562
 
weiss said:
Alright, i'm also not sure if it makes a difference.. anyway i searched a little more and i'm gonna build this circuit only with stepped frequency selections:

eq-f5.gif


Now i ask myself, what would be the most useful op amp for this circuit?
Do you guys know what Dangerous uses in their bax?

I got these here..

NE5532
TL072
THAT 1206
LME49270
LM4562
THAT1206 is not an opamp; can't be used in this position.
All the others can be used; some may disagree, but I think you would be hard pressed to hear a difference between all the others in this configuration.
 
abbey road d enfer said:
THAT1206 is not an opamp; can't be used in this position.
All the others can be used; some may disagree, but I think you would be hard pressed to hear a difference between all the others in this configuration.

Alright thank you!
I am just gonna try and see  :)

Quick question, am i correct, for modifying the frequency i gotta change R3 and C2 ?

thank you!
 
Just go with LM4562 they are 1.60 at mouser, the LM 49720 seems to be the same as the 4562 but more expensive.
 
user 37518 said:
Just go with LM4562 they are 1.60 at mouser, the LM 49720 seems to be the same as the 4562 but more expensive.
Thanks for the input, user 37518!
I already got a bunch of them here, that's why i asked.
 
weiss said:
Alright thank you!
I am just gonna try and see  :)

Quick question, am i correct, for modifying the frequency i gotta change R3 and C2 ?

thank you!

C1 and C2
 
weiss said:
Alright thank you!
I am just gonna try and see  :)

Quick question, am i correct, for modifying the frequency i gotta change R3 and C2 ?

thank you!
Actually, the HF corner frequency can be altered by changing either R3 and/or C2. However, there's also interaction with the values of R1, R2 and VR1. With the actual values, the HF corner frequency varies with the amount of LF boost/cut.
In order to make the shift more predictible, I would increase R3 to about 10k, and scale C2 accordingly.
 
abbey road d enfer said:
Actually, the HF corner frequency can be altered by changing either R3 and/or C2. However, there's also interaction with the values of R1, R2 and VR1. With the actual values, the HF corner frequency varies with the amount of LF boost/cut.
In order to make the shift more predictible, I would increase R3 to about 10k, and scale C2 accordingly.

oh okay! i am gonna try that. but wouldn't that be the the principle of a baxandall?
 
abbey road d enfer said:
What do you mean there?

that the corner freq changes when adjusting gain? i mean, for example increasing gain from 1db to 5db, won't the freq naturally increase then?
 
weiss said:
that the corner freq changes when adjusting gain? i mean, for example increasing gain from 1db to 5db, won't the freq naturally increase then?
Actually there is no set definition of the corner frequency - the usual -3dB point just doesn't work for EQ's- but it is quite possible to determine graphically a pivotal frequency, and it can be shown that it does not vary significantly with the amount of boost/cut, as long as certain constraints are observed. The math analysis is too complex for this thread.
 
Thanks for the comments!

Do i need to keep attention to something when wiring the Op amps? Do i need a buffer schematic?

Or can i just use this scheme:

 

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So i wired up my first prototype of the Baxandall Active Tone Control using the NE5532 +/-15V.
I followed this schematic:




The thing is, with the potentiometers and the switched capacitors i get no change in tone.
The only difference i hear when i take them out of the circuit is that the overall loudness decreases..  ???

Would be really grateful if someone could help me out here !

thanks
Ansgar
 
weiss said:
So i wired up my first prototype of the Baxandall Active Tone Control
By definition, the Baxandall tone control is always active.

The thing is, with the potentiometers and the switched capacitors i get no change in tone.
The only difference i hear when i take them out of the circuit is that the overall loudness decreases..  ???
Then there is something wrong with your circuit.
Well, I see you have only two wires coming from the PSU! You should have 3, one for positive voltage, one for negative and one for zero-volt ("ground")! That means the circuit is not powered correctly.
 
thank you guys,

the pots are not making noise or anything. i bought them new, they should be fine.
i wired the 0v connection to pos. input of the opamp (pin 3) but nothing changed.
i replaced the NE5532 with a LM4562 but no change.

There is also no difference if i disconnect power ???
 
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