Thanks guys.
RG, I did mean "gain" in the technical sense, rather than the informal sense. In the example above, the resistor values in the feedback would yield a gain of 23.
I have done some more reading, and I think I know the answer. Enzo is on the right track in looking at the open loop gain differences. Although, an open loop DC gain of 200,000 vs 160,000 isn't directly the issue when you are looking at a gain of 23. Rather, the critical difference in performance between the parts is looking at the AC characteristics -- what happens when you transition from DC gain to AC signal gain.
It turns out that for DC, both parts would behave fairly comparably for modest gain levels << open loop gain levels (e.g., 23 vs 160,000). However, if you look further down the data sheet, under "AC characteristics", and look at the attenuation in the open loop gain as frequency increases in the "open loop frequency response" plots, you see that even for modest audio range frequencies (e.g., 1000Hz) the open loop gain has dropped by something in the order of 30dB compared to DC. And the critical thing is that the plot for the LM301 part is even more attenuated, by about 10dB across all the audio frequencies. So the "effective" gain of the audio signal is about doubled for the LF356 compared to the LM301!
So it's not the open loop gain DC characteristics that make the difference in this application, it's the AC characteristics.
Anyway, some tweaking of those feedback resistor values would seem to be in order if I want to go over to the LF356 part as a sub for the LM307. And at least now I have at least the beginning of understanding why that needs to be done...
BTW, just a note on RG's informal sense of "gain": On a Musicman 210 HD130, there is no "gain" in that sense. The HD130 is the amp Leo Fender built because he just thought the Twin Reverb just wasn't loud enough. This amp does not break up at any (legal) volume level. (I once tried and got the UN WMD inspectors around knocking on my door with a security council resolution telling me to shut up or I'd be in violation of several international treaties. It was still pristine "blackface" clean at those levels -- as far as I could tell with the bleeding eardrums and all. ;-)
RG, I did mean "gain" in the technical sense, rather than the informal sense. In the example above, the resistor values in the feedback would yield a gain of 23.
I have done some more reading, and I think I know the answer. Enzo is on the right track in looking at the open loop gain differences. Although, an open loop DC gain of 200,000 vs 160,000 isn't directly the issue when you are looking at a gain of 23. Rather, the critical difference in performance between the parts is looking at the AC characteristics -- what happens when you transition from DC gain to AC signal gain.
It turns out that for DC, both parts would behave fairly comparably for modest gain levels << open loop gain levels (e.g., 23 vs 160,000). However, if you look further down the data sheet, under "AC characteristics", and look at the attenuation in the open loop gain as frequency increases in the "open loop frequency response" plots, you see that even for modest audio range frequencies (e.g., 1000Hz) the open loop gain has dropped by something in the order of 30dB compared to DC. And the critical thing is that the plot for the LM301 part is even more attenuated, by about 10dB across all the audio frequencies. So the "effective" gain of the audio signal is about doubled for the LF356 compared to the LM301!
So it's not the open loop gain DC characteristics that make the difference in this application, it's the AC characteristics.
Anyway, some tweaking of those feedback resistor values would seem to be in order if I want to go over to the LF356 part as a sub for the LM307. And at least now I have at least the beginning of understanding why that needs to be done...
BTW, just a note on RG's informal sense of "gain": On a Musicman 210 HD130, there is no "gain" in that sense. The HD130 is the amp Leo Fender built because he just thought the Twin Reverb just wasn't loud enough. This amp does not break up at any (legal) volume level. (I once tried and got the UN WMD inspectors around knocking on my door with a security council resolution telling me to shut up or I'd be in violation of several international treaties. It was still pristine "blackface" clean at those levels -- as far as I could tell with the bleeding eardrums and all. ;-)