Yes, less resistance would be better, but what of the IC's and older tube tuners, that sound so good?
Actually, 10K is a compromise between low resistance and less optimal loading of a typical IC output stage.
I think that we can all agree that class A operation is best, and that virtually all class AB output circuits are a little irregular (at the very least) at the crossover between class A and class AB, and even if we can't easily measure much at this point, the internal correction that is necessary in order for us NOT to measure much, is working as hard as it can. Is this good? I don't think so. This is why we try to NOT load typical IC's with an external load less than 10K, EVEN if they can sometimes drive even 600 ohms, when pressed.
Of course, some output stages can do it easier than others, but even the Parasound JC-2 with 50 ma quiescent current in the output stage, will strain a little with a 600 ohm load, as was shown in the 'Stereophile' measurements of the preamp.
The other question is: What about larger resistance values?
Actually, 10K is a compromise between low resistance and less optimal loading of a typical IC output stage.
I think that we can all agree that class A operation is best, and that virtually all class AB output circuits are a little irregular (at the very least) at the crossover between class A and class AB, and even if we can't easily measure much at this point, the internal correction that is necessary in order for us NOT to measure much, is working as hard as it can. Is this good? I don't think so. This is why we try to NOT load typical IC's with an external load less than 10K, EVEN if they can sometimes drive even 600 ohms, when pressed.
Of course, some output stages can do it easier than others, but even the Parasound JC-2 with 50 ma quiescent current in the output stage, will strain a little with a 600 ohm load, as was shown in the 'Stereophile' measurements of the preamp.
The other question is: What about larger resistance values?
Well, the JC-80 was 10K, Bob Crump's CTC Blowtorch was 10K, BUT my preamp was 25K, because I owned a vacuum tube tuner. It is not good to load down an older vacuum tube circuit. In fact, I add a build out circuit to increase the input impedance for the tuner input, because of this. I lose gain, but the tuner works OK.
The old IHF standard was 10K Ohms and 10000pF I think. This was supposed to be a worst case load. Tube stuff would have definately degraded in some ways with a load like that but if you could drive it without distortion or frequency response errors you should not have problems with any commercial product.
A tube source may have reduced output and an HF rolloff but may not have an increase in distortion. An early IC (741) would probably have flat response and a significant increase in crossover distortion with that load.
A higher impedance volume control will interact with the input stage past it, with rolloff's and increased noise. A lower impedance one limits the source devices that will work well. Its all compromise.
I could not meet the 1MHz+ bandwidth spec for the DMC10 preamp with a higher than 10K pot.
Not well understood is that current recommended professional practice is not 600 Ohm source to a 600 Ohm load (discards too much signal) but a 100 Ohm source (approximating the line impedance) and a 10 K load. this precludes complex passive networks but today those are mostly digital processors or active devices at least.
I used to build pots with 29 Vishay foil resistors on Tech Labs silver contact switches. They worked real well and sounded more transparent than anything else I tried (except the Vishay trimmers) but Tech Labs is history and the work involved plus the cost was more than I could justify today.
A tube source may have reduced output and an HF rolloff but may not have an increase in distortion. An early IC (741) would probably have flat response and a significant increase in crossover distortion with that load.
A higher impedance volume control will interact with the input stage past it, with rolloff's and increased noise. A lower impedance one limits the source devices that will work well. Its all compromise.
I could not meet the 1MHz+ bandwidth spec for the DMC10 preamp with a higher than 10K pot.
Not well understood is that current recommended professional practice is not 600 Ohm source to a 600 Ohm load (discards too much signal) but a 100 Ohm source (approximating the line impedance) and a 10 K load. this precludes complex passive networks but today those are mostly digital processors or active devices at least.
I used to build pots with 29 Vishay foil resistors on Tech Labs silver contact switches. They worked real well and sounded more transparent than anything else I tried (except the Vishay trimmers) but Tech Labs is history and the work involved plus the cost was more than I could justify today.
I think qtc pills might be:
http://www.msa.ac.uk/~fraser/wiringpg/files/p001v004.pdf
I'm sticking to Shallco switches with old Holcos.
http://www.msa.ac.uk/~fraser/wiringpg/files/p001v004.pdf
I'm sticking to Shallco switches with old Holcos.
john curl said:
I think that one aspect of what you try to indicate is what hides in the reasoning behind ideal loading of an MC cartridge. The situation is less obvious in the Pot vs. loading than it is in the Cartridge vs loading.
As for my comments vs the excitation of the given reader, I prefer the idea of learning how to think effectively over rote memory skills. One or two steps further back is to me - far more valuable.
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