Hi,
0.1% tolerance is normally reserved for super matching eg. multipole active filters, test instruments, or where another characteristic follows from that super spec eg. temperature coef.
1% are very cheap now and do for almost all nomal audio uses. but even 5% are acceptable in many locations.
0.1% tolerance is normally reserved for super matching eg. multipole active filters, test instruments, or where another characteristic follows from that super spec eg. temperature coef.
1% are very cheap now and do for almost all nomal audio uses. but even 5% are acceptable in many locations.
Why 0.1% precision?
To name just a few applications for these chips that demand 0.1% resistors are Mauro Penasa's Ref design and when you want to bridge and/or parallel gainclones, like National itself puts on their application notes.
Of course you can match resistors to get very close to that value, but prices are going down on 0.1% parts, so why bother?
To name just a few applications for these chips that demand 0.1% resistors are Mauro Penasa's Ref design and when you want to bridge and/or parallel gainclones, like National itself puts on their application notes.
Of course you can match resistors to get very close to that value, but prices are going down on 0.1% parts, so why bother?
From curiosity, I once built 2 versions of the same amp using 1% and 5% resistors. I could hear no difference. There may have been measurable difference that I could have seen with better test equipment. Oddly the 5% version had a lower DC offset, the place I expected to see a benefit from 1% due to better matching in the LTP input.
My conclusion for now is that variatoions (wityhin spec) in active components and constyruction technique (solder and wiring skills) have more of an impact than resistor tolerances.
My conclusion for now is that variatoions (wityhin spec) in active components and constyruction technique (solder and wiring skills) have more of an impact than resistor tolerances.
Bridge amp are not too critical, but the parallel output recommended for National chip amps is.
I simulated a paralleled opamp arrangement, basically a dual LM3886 circuit scaled by a factor of 10.
blue and khaki are with 1% error in gain
red and green are with 0.1%.
The National PA100 application note emphasises minimising dc offset, going as far as using servos, but the gain error is the major problem.
I wonder how safe the paralleled circuit is at both low frequencies where the dc block electrolytic would be hard to match and at high frequencies where the device bandwidth spread will start to become significant.
When errors of just 0.1% become important, even the thermal layout of the power amp pcb becomes critical.
I simulated a paralleled opamp arrangement, basically a dual LM3886 circuit scaled by a factor of 10.
blue and khaki are with 1% error in gain
red and green are with 0.1%.
The National PA100 application note emphasises minimising dc offset, going as far as using servos, but the gain error is the major problem.
I wonder how safe the paralleled circuit is at both low frequencies where the dc block electrolytic would be hard to match and at high frequencies where the device bandwidth spread will start to become significant.
When errors of just 0.1% become important, even the thermal layout of the power amp pcb becomes critical.
Thanks for your comments, Leadbelly.
But I didn't feel cast aside with the comments I got. I took them more like coming from friends trying to find out what I was getting into.
Perhaps I should have hinted that I rather knew what I was doing, as in the past I also argued here why using such expensive parts when you could assemble with what you had available.
But I didn't feel cast aside with the comments I got. I took them more like coming from friends trying to find out what I was getting into.
Perhaps I should have hinted that I rather knew what I was doing, as in the past I also argued here why using such expensive parts when you could assemble with what you had available.
That's good carlmart. It's true that there can be a dotted line between encouraging words, discouraging words, and a reality check. Personally, I think it's great when somebody wants to go whole hog, no holds barred and shun "collective wisdom", especially the collective wisdom of a forum, where there can be a lot of regurgitation of the same opinions turning into "truth". Anyways, I bought a bunch of Vishay/Dale 0.1% from Mouser back in the good old days when they offered cheaper shipping to Canada, but haven't built the parallel GC they are intended for yet, I got sidetracked with tubes 
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