weiss

Baxandall Eq circuit, any comments?
« on: June 07, 2019, 05:46:41 PM »
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


abbey road d enfer

Re: Baxandall Eq circuit, any comments?
« Reply #1 on: June 08, 2019, 12:30:50 AM »
I thought about building this baxandall equalizer circuit.
Strictly, it's not a Baxandall; totally different topology.

Quote
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.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

weiss

Re: Baxandall Eq circuit, any comments?
« Reply #2 on: June 15, 2019, 03:26:52 PM »
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:



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

abbey road d enfer

Re: Baxandall Eq circuit, any comments?
« Reply #3 on: June 15, 2019, 03:36:21 PM »
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:



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.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

weiss

Re: Baxandall Eq circuit, any comments?
« Reply #4 on: June 15, 2019, 04:07:42 PM »
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!

Re: Baxandall Eq circuit, any comments?
« Reply #5 on: June 15, 2019, 05:08:17 PM »
Just go with LM4562 they are 1.60 at mouser, the LM 49720 seems to be the same as the 4562 but more expensive.

weiss

Re: Baxandall Eq circuit, any comments?
« Reply #6 on: June 15, 2019, 05:54:31 PM »
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, dualflip!
I already got a bunch of them here, that's why i asked.

Re: Baxandall Eq circuit, any comments?
« Reply #7 on: June 15, 2019, 06:16:19 PM »
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


abbey road d enfer

Re: Baxandall Eq circuit, any comments?
« Reply #9 on: June 16, 2019, 03:36:57 AM »
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.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


weiss

Re: Baxandall Eq circuit, any comments?
« Reply #10 on: June 16, 2019, 06:54:48 AM »
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?
« Last Edit: June 16, 2019, 08:19:14 AM by weiss »

abbey road d enfer

Re: Baxandall Eq circuit, any comments?
« Reply #11 on: June 16, 2019, 04:03:32 PM »
wouldn't that be the the principle of a baxandall?
What do you mean there?
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

weiss

Re: Baxandall Eq circuit, any comments?
« Reply #12 on: June 16, 2019, 04:22:34 PM »
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?

abbey road d enfer

Re: Baxandall Eq circuit, any comments?
« Reply #13 on: June 16, 2019, 05:30:25 PM »
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.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

weiss

Re: Baxandall Eq circuit, any comments?
« Reply #14 on: June 17, 2019, 01:18:22 PM »
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:


weiss

Re: Baxandall Eq circuit, any comments?
« Reply #15 on: June 25, 2019, 06:23:08 AM »
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
« Last Edit: June 25, 2019, 06:30:22 AM by weiss »

abbey road d enfer

Re: Baxandall Eq circuit, any comments?
« Reply #16 on: June 25, 2019, 06:37:17 AM »
So i wired up my first prototype of the Baxandall Active Tone Control
By definition, the Baxandall tone control is always active.

Quote
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.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

krabbencutter

Re: Baxandall Eq circuit, any comments?
« Reply #17 on: June 25, 2019, 07:56:30 AM »
When I was working on a Neve circuit, someone told me that tone control circuits tend to cause some DC across the pots, when built around bipolar opamps. So in case your pots start getting noisy/scratchy, swap the NE5532s for LM4562s or some Jfets
(see https://www.gearslutz.com/board/showpost.php?p=13599987&postcount=13)

weiss

Re: Baxandall Eq circuit, any comments?
« Reply #18 on: June 25, 2019, 08:49:20 AM »
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 ???
« Last Edit: June 25, 2019, 08:55:04 AM by weiss »

leitmo

Re: Baxandall Eq circuit, any comments?
« Reply #19 on: June 25, 2019, 08:57:48 AM »
Did you try it first following schematic without variable caps?


 

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