Hi ! anyone has experience with products from this company?
Welwyn Components | Resistors | Resistor Technology | Hybrid Microcircuits | TT Electronics
Welwyn Components | Resistors | Resistor Technology | Hybrid Microcircuits | TT Electronics
Thanks ! i used their metal film 0.5 and 1W in the past.
Imho they have very good q/p ratio.
https://www.mouser.it/datasheet/2/414/MFP-1528234.pdf
I have a silly question as usual ... what about linearity and noise of a resistor ?
I guess that the resistance value does not change in the audio range,
but noise can be a problem ? can it cause some kind of distortion ?
what do you use for feedback line for instance ?
Imho they have very good q/p ratio.
https://www.mouser.it/datasheet/2/414/MFP-1528234.pdf
I have a silly question as usual ... what about linearity and noise of a resistor ?
I guess that the resistance value does not change in the audio range,
but noise can be a problem ? can it cause some kind of distortion ?
what do you use for feedback line for instance ?
Thanks for the valuable advice ! ... i used only the cheap series of about 0,1 to 0,2 euro a piece ...
These instead look very serious ...
https://4donline.ihs.com/images/Vip...7-1.pdf?hkey=52A5661711E402568146F3353EA87419
looking for noise data in the datasheet i see
Noise (in a decade of frequency) µV/V 1.0 (max) 0.1 (typical)
i have no clue about the meaning
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Thanks for the valuable advice ! ... i used only the cheap series of about 0,1 to 0,2 euro a piece ...
These instead look very serious ...
https://4donline.ihs.com/images/Vip...7-1.pdf?hkey=52A5661711E402568146F3353EA87419
looking for noise data in the datasheet i see
Noise (in a decade of frequency) µV/V 1.0 (max) 0.1 (typical)
i have no clue about the meaning
Decade (log scale) - Wikipedia
looking for noise data in the datasheet i see
Noise (in a decade of frequency) µV/V 1.0 (max) 0.1 (typical)
i have no clue about the meaning
This is a specification of the "excess noise" of a resistor. Resistors produce Johnson noise because of the fact that they are resistors - all resistors produce this according to the value of resistance and the absolute temperature of the resistor. (see the example at the end of the post.)
But, depending on how the resistor is constructed, certain resistor types, and even specific resistors with a construction defect, can have "excess noise" that is greater than the required Johnson noise. This noise is developed when current flows through a resistor. If the current flow is irregular, because of defects in the resistance film, or because the resistance material (such as a carbon composition resistor) is inherently granular, noise can be generated as conduction changes the applied voltage changes.
Since this effect is caused by a voltage across the discontinuities of the resistance material, it is quoted in µV per V applied across the resistor, the specification that you found in the datasheet.
Some datasheets will quote this in decibels, or 20 * log(ratio), so your example of 0.1µV per volt would yield an excess noise spec of -140dB.
Here's a good paper about resistor noise measurement from some scientists who had to build extremely low noise electronics for their research.
https://dcc.ligo.org/public/0002/T0900200/001/current_noise.pdf
Johnson Noise:
The formula to calculate Johnson noise of a resistor R over a bandwidth B is En = sqrt(4KTRB), where
K is Boltzmann's constant (1.38 x 10-23),
T is the temperature in degrees Kelvin,
R is the resistance in ohms, and
B is the bandwidth that the noise is examined over, usually 20000 for a 20kHz audio bandwidth.
As an example, a 1kΩ resistor at room temperature (300ºK) would produce sqrt(4*1.38E-23*300*1000*20000) = 575nV of noise.
I don't think that's right. The graph on page 9 shows that the 5 ppm/ºK Welwyn PCF0805 has well above average excess noise, while the 25 ppm/ºK Phycomp TFx13 series is tied for least excess noise of the range tested.
One thing that I don't like about those graphs is that many colors look the same. I agreed that Phycomp (light green) is way down there. But I think the 5 ppm Welwyn (red) is down there next to the dark green line(Vishay SMM0204). The red line above, I think, is the Panasonic ERJ-8ENF 100ppm.
Maybe the conclusion is to get thin-film resistors 25ppm or below.
Maybe the conclusion is to get thin-film resistors 25ppm or below.
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Generally the 25 ppm metal films are the 'basic' high precision resistors. The most widely Susumu RG resistors are 0.1% and 25 ppm, and honestly, they cost less than it costs to place the part on a PCB, so I see no point in paying less, especially for DIY. I use the 25 ppm Susumu RG for pretty much everything in my projects, and then if I need something more precise, the 0.05% 10 ppm versions. They seem to perform quite well, and I've been happy with them.
The mini-MELF parts (like the SMM0204) do seem to be better overall, but they are also harder to find and I'm not crazy about the MELF package - seems too fiddly to place manually, and they're thick. Still, people who I respect do think that they perform best of all surface mount parts.
The mini-MELF parts (like the SMM0204) do seem to be better overall, but they are also harder to find and I'm not crazy about the MELF package - seems too fiddly to place manually, and they're thick. Still, people who I respect do think that they perform best of all surface mount parts.
Mouser has MELF ($0.49 each)
MMA02040D1001BB300 Vishay / Beyschlag | Mouser
a little bit more than Susumu ($0.37 each)
RG3216P-1001-B-T1 Susumu | Mouser
MMA02040D1001BB300 Vishay / Beyschlag | Mouser
a little bit more than Susumu ($0.37 each)
RG3216P-1001-B-T1 Susumu | Mouser
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The noise isn't stray connected to the ppm. Noise depends firstly on resistive material used.
For example, wired resistors have usually the lowest noise between all of the types (metal wire, metal foil, metal film, metal oxide, carbon, etc).
15 ppm and 100 ppm could be the same metal-film type, so they can have about the same noise, but can have a different noise too, because of 15 ppm resistor will be built of different materials.
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I was building Sam Groner's low noise amplifier over a year ago and had a really tough time finding any of the values needed for that amp in mini MELF. I ended up using 3216 Susumu RG which basically fit the same footprint. I just looked again though, and yes Mouser and Digikey do have stock, but sometimes the only choice is a 1% 50 ppm part, and that seems a little loose for the price compared to an RG.
At any rate, the 15 ppm 0204 MELFs seem to be pretty good performers overall, probably a good answer for critical positions if you can find them.
At any rate, the 15 ppm 0204 MELFs seem to be pretty good performers overall, probably a good answer for critical positions if you can find them.
What type of critical positions are we talking about? While this subject is fascinating (and I enjoyed reading that document), it doesn't appear to have much to do with audio.
I use a lot of Dale CMF55s. According to that document it's a very good performer with an excess noise peak of about -180dB. If I switched to the worst performer in their leaded < 1W group (Vitrom RGU 526-0), that figure would rise to -150dB. I'll admit I've never built a MC phono stage, but none of my preamps or amps have a noise floor that even remotely approaches -150dB.
I use a lot of Dale CMF55s. According to that document it's a very good performer with an excess noise peak of about -180dB. If I switched to the worst performer in their leaded < 1W group (Vitrom RGU 526-0), that figure would rise to -150dB. I'll admit I've never built a MC phono stage, but none of my preamps or amps have a noise floor that even remotely approaches -150dB.
For through hole parts, the Dale CMF are really good. I have a lot of those and the Dale ERL military version as surplus, and along with the Mepco RN series, they all work really well. For SMD, I am very happy with Susumu 2012 RG series resistors, and while I don't know how they measure re. excess noise, they seem to work well enough. I can get really good performance out of them, and they are plentiful and well stocked. I have not noticed any problems such as excess LF distortion from the smaller package, so I don't even see the need for the 3216 version, which has much poorer stock levels, takes up more PCB area, and creates more stray capacitance in a layout.
The question was what the spec meant on the spec sheet, so I took the nosedive into places that might not matter for audio. I'm not sure just how bad a circuit can be before it's too bad, but things like excess noise also correlate with the quality of a part's construction. And, excess noise is also generated by signal voltage, so it can also be thought of as a form of distortion, not just a benign steady state hiss. 1µV/V is -120dB, or 0.0001%, a distortion value that's not hard for modern op amps to reach. Sure, it is also 'covered up' by that same signal voltage, but in general, errors correlated directly to a signal are creepier than simple steady state noise which the ear can tune out.
So, the real meaning of why the spec is declared is for a manufacturer to say "yes, these parts aren't garbage, and they're made just as well as our competitors products." Few people expect that much out of a resistor, but for those who do, like the scientists searching for gravity waves by digging deep into the noise, these problems become significant.
Errors at this level are really tough to hear, but over time, we seem to be improving circuitry at a rate of about 20dB less distortion per decade. And, as the distortion numbers continue to drop, things do seem to be audibly improving. The "perfect" amplifiers of the 60s and 70s with 0.1% distortion don't sound as good as the best that can be done now, but at the time, the rule in the 60s was "nobody needs to have less than 1% distortion". What's that magic number that "you can't hear" for this decade? I say it'll be 20dB more than the magic number in the next decade. The -150dB and -180dB specs you quote are very low, basically near the state of the art for amplifiers these days, so yes, it's hard to practically imagine anything better. Then again, as things improve, maybe the -150dB resistors will be the dominant "problem"? We shall see.
So, if it's not too expensive, and you want to have a reliable device, I say it's fine to see which out of a range of parts behaves better and to use them. Often, performance and price are unrelated, so it makes sense to see which parts actually perform better and to use them, within budget and availability constraints.
The question was what the spec meant on the spec sheet, so I took the nosedive into places that might not matter for audio. I'm not sure just how bad a circuit can be before it's too bad, but things like excess noise also correlate with the quality of a part's construction. And, excess noise is also generated by signal voltage, so it can also be thought of as a form of distortion, not just a benign steady state hiss. 1µV/V is -120dB, or 0.0001%, a distortion value that's not hard for modern op amps to reach. Sure, it is also 'covered up' by that same signal voltage, but in general, errors correlated directly to a signal are creepier than simple steady state noise which the ear can tune out.
So, the real meaning of why the spec is declared is for a manufacturer to say "yes, these parts aren't garbage, and they're made just as well as our competitors products." Few people expect that much out of a resistor, but for those who do, like the scientists searching for gravity waves by digging deep into the noise, these problems become significant.
Errors at this level are really tough to hear, but over time, we seem to be improving circuitry at a rate of about 20dB less distortion per decade. And, as the distortion numbers continue to drop, things do seem to be audibly improving. The "perfect" amplifiers of the 60s and 70s with 0.1% distortion don't sound as good as the best that can be done now, but at the time, the rule in the 60s was "nobody needs to have less than 1% distortion". What's that magic number that "you can't hear" for this decade? I say it'll be 20dB more than the magic number in the next decade.
The -150dB and -180dB specs you quote are very low, basically near the state of the art for amplifiers these days, so yes, it's hard to practically imagine anything better. Then again, as things improve, maybe the -150dB resistors will be the dominant "problem"? We shall see.So, if it's not too expensive, and you want to have a reliable device, I say it's fine to see which out of a range of parts behaves better and to use them. Often, performance and price are unrelated, so it makes sense to see which parts actually perform better and to use them, within budget and availability constraints.
hi thanks a lot for the link. Reading better it is like 1 ppm ?
thanks for the kind and very valuable reply ! i am reading the paper ... but this is science not hifi more seriously ... can we agree that from a scientific point of view it seems like that people who are able to listen differences between cheap but good resistors and high end ones are hearing things ?