tv

solved - Need equations for a circuit (see post)
« on: January 24, 2008, 01:26:08 PM »
I need equations for the noninverting tone-control circuit in FIGURE 19, pg.15 from this datasheet:

http://www.intersil.com/data/fn/fn957.pdf

it looks like some passive baxandall/james equations would be somewhere in the ballpark (for corner frequencies at least), however the 18K resistor breaks it ... (I need to get frequencies 45Hz, 4,5KHz, 5dB center-position gain). Additionally, I need to (sort-of) hipass the circuit @25Hz (with dimensioning of the 2uF elco in bass branch).

please gurus, help.

I _need_ those equations. (possibly to use lower-resistances with 5532 for stereo control - or alternatively opa2132/2604)

P.S.: I'm not sure I can get the Kaplan-Wittlinger book mentioned in the datasheet ...
If you sprinkle when you tinkle, please be neat and wipe the seat.


solved - Need equations for a circuit (see post)
« Reply #1 on: January 24, 2008, 02:39:47 PM »
Xc=

JohnRoberts

solved - Need equations for a circuit (see post)
« Reply #2 on: January 24, 2008, 03:12:00 PM »
The simple inverting opamp Baxandal was pretty well described in old National Semi Audio Application handbooks.. Try there..

JR
It's nice to be nice....

tv

solved - Need equations for a circuit (see post)
« Reply #3 on: January 24, 2008, 03:33:43 PM »
thanks BUT:

- Imho standard baxandall equations would break (I said about the offending 18k resistor in treble branch already). I would also like to tweak the circuit to pronounce some mid-register (1,2kHz ballpark) when treble is attenuated, if possible. The 18k resistors seems the key here, only if I could crack it ...

- I need equations to figure out circuit GAIN when both controls in FLAT position (5dB would be preferred versus 20dB of the datasheet version)

- I also need equations to set the corner freqs and also to figure out hi-freq rolloff (the 100pf's in treble branch)

- I also need to tweek the "low-cut" with 2uF elco ...


It MUST be the noninverting version WITH said gain. I have sh*tloads of various inverting baxandall permutations which are no-go in this case ...
If you sprinkle when you tinkle, please be neat and wipe the seat.

solved - Need equations for a circuit (see post)
« Reply #4 on: January 24, 2008, 04:02:49 PM »
For people who are too lazy to calculate there are SIMs available.

tv

solved - Need equations for a circuit (see post)
« Reply #5 on: January 24, 2008, 04:23:37 PM »
Not exactly being lazy, calculating this circuit would be a pretty tough task with virtually all components in the tone circuit interacting plus I'm no Einstein. Still seeking for some constructive input. OR a datasheet/appnote ... whatever with f.e. simplified equations similar to those for baxandall circuits.

Please? (if exists ...)
If you sprinkle when you tinkle, please be neat and wipe the seat.

solved - Need equations for a circuit (see post)
« Reply #6 on: January 24, 2008, 05:46:04 PM »
Quote from: "tv"
Not exactly being lazy, calculating this circuit would be a pretty tough task with virtually all components in the tone circuit interacting plus I'm no Einstein. Still seeking for some constructive input. OR a datasheet/appnote ... whatever with f.e. simplified equations similar to those for baxandall circuits.

Please? (if exists ...)


One more constructive input: build an equation and calculate for certain positions of potentiometers.

Or do you mean to be constructive we have to do your homework?  :roll:

One more approach: breadboard and measure.

PRR

solved - Need equations for a circuit (see post)
« Reply #7 on: January 24, 2008, 09:30:06 PM »
The Bass control must be reverse audio.

The overall gain (for reasonably flat response) is a function of the pot taper. "Audio" used to be 10% at center; 20% (or unspecified) is now common in straight-audio tapers, but a 20% reverse audio may still be hard to find.

Because this scheme combines gain and treble-boost, it really stretches an op-amp. As drawn, it tries for gain of 55 at 20KHz; with that 1969 chip, it clearly is out of NFB at the top of the audio band. It is TV quality, not studio quality. (Yeah, you can use a better chip.)

FWIW, even Kaplan and Wittlinger did NOT compute this ugly beast by hand... they used a computer.

> I'm not sure I can get the Kaplan-Wittlinger book

Not a book, a magazine. A large US university will have access; non-US universities might too.

tv

solved - Need equations for a circuit (see post)
« Reply #8 on: January 25, 2008, 04:26:34 AM »
Reverse log (ouch) ... I had a gut-feeling this one will be a ***** to figure out ... but afaik this is the only one I know of that could give gain, tone-control and could drive stereo headphones with 5532 and standard TH parts while having ~~100-150k input impendance. (a surprisingly similar circuit is used in FIGURE 7, pg.4, 12W amplifier, http://www.powerdesigners.com/InfoWeb/design_center/Appnotes_Archive/an6048.pdf, again with no formulas for tone circuit)

I'm not IEEE member, the Kaplan-Wittlinger paper seems to be here:
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4080027

if there isn't any other sources for equations, could someone with membership check the article if there is any relevant equations in it? If it's short enough, could someone post the relevant data here? (A screenshot etc ...) ?

I don't know any other source yet.

-----------------------------
EDIT: nevermind, figured it out. It's cited in an6048 "references"; an6077.
-----------------------------
If you sprinkle when you tinkle, please be neat and wipe the seat.

PRR

solved - Need equations for a circuit (see post)
« Reply #9 on: January 25, 2008, 12:50:44 PM »
Yes, AN6077 is essentially the IEEE article and Appendix B looks the same.


tv

solved - Need equations for a circuit (see post)
« Reply #10 on: January 25, 2008, 02:45:35 PM »
Yep, that's it: the intersil an6077.

Only noticed it listed in the references at the end of the an6048 when I already gave up any hope on getting these *?#"#&#% equations ...

It's going to be a ***** even to put on the perfo, I was already messing with the freeware DIY layout creator and it's a pita.

I noticed if I need only 5-6 dB "mid-position" gain, the "cut" range will have to be in the same ballpark. So I need to figure out if I can mod the circuit to give +10/-5dB control. If in the original control from the AppendixB (+/-20dB) the "mid" position is @ 91% pot-position, I can't imagine where the modded one will be.
If you sprinkle when you tinkle, please be neat and wipe the seat.


 

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