| carlmart |
What's the best deal now for 0.1% resistors?
What are you people using on gainclones that need that precision?
Carlos |
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| leadbelly |
| The Vishay/Dale at Mouser are pretty cheap. |
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| Nuuk |
| Welwyn RC55 (from Farnell). :att'n: |
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| Upupa Epops |
| For what do you need 0.1 % resistors ? Normal 1 % ones give ( if they are used in feedback loop ) difference of gain bellow 0.1 dB... Are they only for " good feeling " ? |
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| AndrewT |
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. |
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| carlmart |
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? |
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| Cortez |
| quote: | Originally posted by Nuuk
Welwyn RC55 (from Farnell). :att'n: |
But its magnetisable, if i'am right. |
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| Upupa Epops |
| Nobody will hear difference between both value, in normal mode and in parallel or bridge too... but yes, price is low, so why not...good feeling is good feeling.... ;) |
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| carlmart |
I am not sure it's just a "good feeling" question. Pairing resistors in large quantities to such low precision can be cumbersome and expensive (in parts and time).
If a design requires 0.1% precision, I don't see how you can get away with less accuracy. |
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| Upupa Epops |
| 0.1 % resistors you need for fifth order filter for example ( as wrote Andrew ) - in other connection it is unnecessary.... more interesting is thermal coefficient... ;) |
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| Elso Kwak |
| quote: | Originally posted by Nuuk
Welwyn RC55 (from Farnell). :att'n: |
The Welwyns do sound TERRIBLE bad!!!
:att'n: :att'n: :att'n: |
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| peranders |
| quote: | Originally posted by carlmart
What's the best deal now for 0.1% resistors?
What are you people using on gainclones that need that precision? |
Plain 1% has about 0.3% tolerance in real life. 0.3% will get you 0.03-0.05dB in gain differerence as an example. Is this important or not? Deside for yourself.
Let me also point out that around 1 dB is the limit when you can clearly hear a difference. |
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| sam9 |
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. |
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| davidsrsb |
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. |
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| carlmart |
Also on a differential circuit to lower CMRR, which is the case on the examples I mentioned.
I don't think National will suggest such parts on their AN without being absolutely necessary.
Of course I would not think of using them on a plain power amp. |
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| leadbelly |
| quote: | Originally posted by carlmart
Also on a differential circuit to lower CMRR, which is the case on the examples I mentioned.
I don't think National will suggest such parts on their AN without being absolutely necessary.
Of course I would not think of using them on a plain power amp. |
Good on you! You go ahead and do what you want to do. I get so tired of these bozos who take over a thread. The topic of the thread was "where do I buy 0.1% resistors" not "do you think I need 0.1% resistors". :) |
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| Upupa Epops |
| Correct notice....:cool: |
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| carlmart |
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. |
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| leadbelly |
| 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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| carlmart |
| quote: | Originally posted by leadbelly
...I got sidetracked with tubes :) |
I know the feeling. Getting continuously sidetracked with lots of things going at the same time. |
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| eapavant |
| Why not just buy bulk and get a lcr? |
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| carlosfm |
A very good reason for matching resistors is when building a differential amp.
From Analog Devices' AN734 appnote:
"Difference amplifiers are commonly used in high accuracy circuits to improve the common-mode rejection ratio, typically known as CMRR.
For this type of application, CMRR depends upon how tightly matched resistors are used; poorly matched resis
tors result in a low value of CMRR.
...
For example, when R7 = R6 = 10 k, and R2 = R4 = 1 k, and error = 0.1%, CMRR improves to better than 80 dB.
...
Select resistors that have much tighter tolerance and accuracy. The more closely they are matched, the better the CMRR. For example, if a CMRR of 90 dB is needed, then match resistors to approximately 0.02%." |
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| neutron7 |
| quote: | Originally posted by davidsrsb
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. |
how close are the Chips themselves are they closer than 0.1% gain ? if they are not you will be rolling the dice. unless you buy a whole bunch of LM chips and make a test rig to gain match them (can you even get a to220/11 socket?
you can put the DC blocking cap right on the input so both chips will see exactly the same signal. |
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| sam9 |
| quote: | | The topic of the thread was "where do I buy 0.1% resistors" not "do you think I need 0.1% resistors". |
:ashamed:
To the original question - in addition to Mouser, I believe Michael Percy stocks such.
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When I've screened 5% resistors that come on tape the actaual variability is much less than that (+/-1-2%) and when I've screened 1% types it is sometimes difficult to even see the variation with in the limits of a typical multimeter. Extraploating from that rule, I suspect that using 0.1% results in mathing somwhat tighter than 0.1%. Looking at the app note, the prospect of keeping four LM3886's operating with nearly identical gain and current, using the closest tolerance resitors available.
I.e., not withstanding my previous comment 0.1% resitors used per the app note sound like a reasonmable precaution. |
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| safetyman |
Noob here....So what if I buy 5% resistors and match their value to exactly to each other on a normal multimeter, is that good enough or I still need the 1% or 0.1% and not having to match them.
I have thought that former would be good enough. Correct me please if I ma wrong or am not following waht has been posted especially Carlos's post. ;)
Thanks. |
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| Panelhead |
| quote: | Originally posted by safetyman
Noob here....So what if I buy 5% resistors and match their value to exactly to each other on a normal multimeter, is that good enough or I still need the 1% or 0.1% and not having to match them.
I have thought that former would be good enough. Correct me please if I ma wrong or am not following waht has been posted especially Carlos's post. ;)
Thanks. |
Most digital VOM meters are 3 1/2 digit. This is not enough resolution to match up resistors to 0.1%.
If you spring for a 4 1/2 digit meter this is no problem. I am a big believer in resistor matching. Sometimes resistors measure off from printed value. Makes me wonder if some of the projects built in the past had an off value resistor in a critical position.
Those brown bodied Dales in 0.1% are very nice resistors. If Mouser stocks that is great.
George |
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| eapavant |
| Newark is also a good choice. They seem to have better prices than Digikey or Mouser. |
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| carlmart |
| quote: | Originally posted by eapavant
Newark is also a good choice. They seem to have better prices than Digikey or Mouser. |
That might be the case on some specific part. In general you can get better deals from Mouser, except on Panasonic caps.
Is there a specific line you are talking about? |
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