I have an LM1036 in my parts box but have yet to put it to use. This might well be something for me to remember when I put the solder to it.
I'm using the NatSemi LM1036 datasheet of January 1995 for reference. Look at page 6. There you will find info and graphs on modifying the response curves. I think what you need is shown in Figure 4 (page 7), where the treble-boost lower frequency is shifted higher. That will mean less amplification of the "hard" mids. You may have to experiment with different values of Ct to achieve the desired results. The standard circuit (which is what you're using?) uses a 0.01uF value. You may try starting with half that, ie ~4.7nF capacitor; from the graph, that looks to be about an octave higher for the low end of the treble response.
I'm using the NatSemi LM1036 datasheet of January 1995 for reference. Look at page 6. There you will find info and graphs on modifying the response curves. I think what you need is shown in Figure 4 (page 7), where the treble-boost lower frequency is shifted higher. That will mean less amplification of the "hard" mids. You may have to experiment with different values of Ct to achieve the desired results. The standard circuit (which is what you're using?) uses a 0.01uF value. You may try starting with half that, ie ~4.7nF capacitor; from the graph, that looks to be about an octave higher for the low end of the treble response.
The 4558 is an old design, not high end by today's standards, but may be fine for many. If it's high end audio I use the OPA2134's (Linkwatz uses these also). Swapping opamps in a given circuit can be misleading since the circuit may or may not be optimized for each of the opamps. Phase margin could vary a bunch and invalidate the comparison.thanks. adding 100k pot as volume control worked well. no need for volume control circuit anymore. and no need for mid range control too. i am happy with the circuit now.
i have two more simple questions
1. is 4558 is good? i have a few of them and 1558 ic.
2. will a split power supply do a much better job?
thanks
A split (bipolar) power supply means you have so little DC offset on the output of any opamps that you can avoid having the rather large output cap in most cases, and the turn-on transient that comes with the monopolar supply, due to the need to charge that large output cap. Other than that I don't see a significant difference.
With the monopolar supply you also have to tie certain opamp inputs to a half supply reference voltage, but that's pretty easy. Two 10k R's and a 1uF to ground kind of thing. If a circuit is driving a pot (output volume control for ex.), you need a DC blocking cap feeding the pot even if you have a bipolar supply, or the pot will be very noisy and can cause temporary large DC offset when turned.
In the case of a poweramp with a monopolar supply, the output cap will need to be huge due to the low impedance.
For tone controls, which I consider essential, I prefer a four section Baxandall. Lo, Lo-Mid, Hi-Mid and Hi. I combine the Lo and Hi-Mid with one opamp, and the Lo-Mid and Hi with another opamp to keep interactivity minimized. I use OPA2134 opamps and don't care if someone thinks there is a better opamp (These are good enough for Linkwitz).
I always put a passive Rf filter at the input of any circuit (3dB down around 100kHZ) so I am not asking the opamps to do something they aren't able to do well, and an R in series with the final output (100 - 200ohms) in case the output opamp may have stability issues with the reactance of the cables. Also ceramic power supply bypass caps (0.1uF or so) within an inch of every opamp. Less than any of this is not acceptable IMO.
There are those who think "shelving" is better. There may be cases where that is what you want, but they create an abrupt change in the frequency response relative to the Baxandall (variable slope), which I believe draws attention, and is therefore less desirable.
I always put a passive Rf filter at the input of any circuit (3dB down around 100kHZ) so I am not asking the opamps to do something they aren't able to do well, and an R in series with the final output (100 - 200ohms) in case the output opamp may have stability issues with the reactance of the cables. Also ceramic power supply bypass caps (0.1uF or so) within an inch of every opamp. Less than any of this is not acceptable IMO.
There are those who think "shelving" is better. There may be cases where that is what you want, but they create an abrupt change in the frequency response relative to the Baxandall (variable slope), which I believe draws attention, and is therefore less desirable.
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