I'd love to see measurements that show a difference that is significant enough to be audible. I am always sceptical of unsubstantiated claims.
Different resistors have different voltage and temperature coefficients.
I have always assumed that most 1% metal film resistors are about the same. It could be that when seeking distortion below 0.001% that resistors are a limiting factor. I'm sure someone has done a study on this somewhere. I'll have to hunt that down.
I have always assumed that most 1% metal film resistors are about the same. It could be that when seeking distortion below 0.001% that resistors are a limiting factor. I'm sure someone has done a study on this somewhere. I'll have to hunt that down.
I hear the difference between resistors, but there isn’t a test yet that describes the difference. Just because we can’t measure it with current instruments doesn’t mean it doesn’t exist, how do you describe the Mona Lisa,- as a picture of a sitting woman? If you can’t or don’t want to hear a difference save your money and buy Xicon metal films.
Last edited:
I completely agree with everything you have said here. In some situations in analogue audio resisters do make a measurable difference. The feedback loop divider of a power amplifier is likely the most extreme situation you could find. You are in the ballpark with the magnitude of the problem too. A 10c additional spend on some low TC thin film resistors in those two locations could likely be justified on engineering grounds alone, however don't think a reduction in THD from 0.001% to 0.0005% will actually be audible.
I object to the statements by Eddie and ticknpop that resistors make an audible difference. There is no study with any level of scientific rigour that will support that premise.
Last edited:
If there's a difference, there's a test for it. You just have to ask the right questions. Resistors are pretty simple. Send current through it and a voltage proportionally appears across it.
Deviation from proportionality is easy to measure and techniques certainly exist for quantifying that. Distortion can be calculated from the resulting transfer function, depending on the application. Modern instruments are certainly good enough.
I've been out of the discrete component audio game for awhile. Twenty-five years ago, when I was designing amps professionally, 0.01% distortion was considered plenty good, especially if the harmonics were low order. Any 1% metal film was good enough to deliver this performance.
Now, with modern output transistors (well, newer than 1996), and some high bandwidth drivers and pre-drivers, I can get distortion well below 0.001%. Layout parasitics and feedback resistors may be the limiting factors in how low distortion can get. To me, it's not really a question of audibility. My amplifiers with 0.02% THD sounded great. It's really just an engineering exercise of building an amp that no one can possibly blame it for the sound coming out of their speakers.
Last edited:
Of course. These resistors are very low noise, which is probably what's audible. They're very stable with regards to temperature. I buy them in batches, and they always match way better than their rated 1%.
I hope we don't have to discuss the audibility of potentiometers. Tracking is quite audible. The Blue Velvet tracks better than other potentiometers I've used and I've never had any scratchiness out of one. All of this is audible. There's cheaper volume controls, there's better volume controls, there's switched resistor arrays....I'll stick to shat I know. And I didn't do any fancy tests but I've had good luck with these resistors. They're probably overkill.
If you have a recommendation for resistors for audio circuits then I'd appreciate it. The CMF series is kind of expensive.
This will give you a perspective.
Also, don't forget that not all 1% resistors are the same. TC for instance ranges from 5ppm to 200ppm. Whether it makes an audible difference is debatable.
The feedback R in a power amp is in a class of its own - very high voltage across it (amp output voltage) and directly in the feedback loop.
Most other resistors are very uncritical, and a statement that any high-Q resistor in any position makes an audible difference is unconvincing.
And all resistors generate noise - there is no such thing as a noiseless resistor. The noise is a function of R and T. You want lower noise: lower the R and/or lower the T.
Some resistors have excess noise, like carbon resistors, but nobody uses them anymore for a long time (except in guitar amps but there they contribute to the typical non-HiFi sound).
Jan
Also, don't forget that not all 1% resistors are the same. TC for instance ranges from 5ppm to 200ppm. Whether it makes an audible difference is debatable.
The feedback R in a power amp is in a class of its own - very high voltage across it (amp output voltage) and directly in the feedback loop.
Most other resistors are very uncritical, and a statement that any high-Q resistor in any position makes an audible difference is unconvincing.
And all resistors generate noise - there is no such thing as a noiseless resistor. The noise is a function of R and T. You want lower noise: lower the R and/or lower the T.
Some resistors have excess noise, like carbon resistors, but nobody uses them anymore for a long time (except in guitar amps but there they contribute to the typical non-HiFi sound).
Jan
Last edited:
Old carbon resistors generate additional noise proportional to the applied voltage. Decades ago I had an VOX AC-30 on the bench with excessive noise - you really did not need to measure this, it was obviously audible. I replaced all anode resistors by 1% metalfilm and the noise was gone. This was the last time I experienced audible degraded sound caused by resistors.
As long as the opamp is unity gain stable, can it hurt at all? We had to stabilize an OPA1611 with nested LME49600 buffers recently. We used 100pF caps as that was the lowest value we had lying around. That should have set the cutoff frequency of the amplifier to 1.59MHz (using a 1k feedback R) if I calculated that correctly. That should not matter at all for audio frequencies AFAIK.
My comparison was between old carbon resistors and modern metal film resistors. I built my buffered volume control with resistors from old Radio Shack resistor assortments. It definitely sounded inferior to the exact same circuit with metal film resistors. $2 Bourns potentiometer vs Alps Blue Velvet potentiometer was audible too.
The CMF series resistors are overkill for audio circuits. But they work great.
I think you are right. I work with power amps mostly, and those are never unity gain stable, so I have to be careful bypassing the feedback cap. The right cap choice can add 20 degrees of phase margin. A poor choice causes pain.
It's measurable, and they claim it's not audible.
My builds may seem extravagant, but if I build something and it doesn't subjectively sound good then I consider it a failure. I wouldn't spend five times as much on resistors just because they give better measurements.
In my experience, pots have the largest potential to degrade the sound.
It makes a big difference. Price is OK. They track better than the cheap ones. I have never experienced any scratchiness from a Blue Velvet pot.
Works for me. And I'm always open to suggestions.
You'd think cheap pots having carbon film tracks would present more of an issue than they do (many many audio circuits happily use carbon pots it seems), but at essence a volume control pot is voltage divider, and to a first approximation voltage-dependent resistance effects (non-linearity) cancel out, so the track material properties are not part of the equation (literally!)
Certainly this should the case for linear-taper where the current density and voltage-gradient is constant along the track. Log/antilog tapers won't have as good cancellation though, which alas is commonly the case for audio volume circuitry. It would be interesting to see some linearity comparisons between carbon-film resistors, carbon linear pots and carbon log pots at various positions - can't seem to find any. [ alas there're are a lot of results about how linear the taper response is with angle, not wiper voltage with input voltage.. ]
The Baxandall style volume control (and tone controls of course) use linear pots and this is probably one of the reasons its a great performer. (A lot of the online pages describing the Baxandall volume circuit seem not to know the pot should be linear!).
In general avoiding carbon-track pots is good if you can, but if you do use them a linear pot circuit is likely to suffer least from carbon's shortcomings, especially if you can keep the impedances low, i.e. 1k .. 10k for the pot.
Thinking about it, one trick component manufacturers have missed is having a pot with plug-in track sections so you can swap out an old worn scratchy track section without having to buy a whole new pot body and disassemble the equipment its in... A variation on the stackable wafer switch idea I guess.
Certainly this should the case for linear-taper where the current density and voltage-gradient is constant along the track. Log/antilog tapers won't have as good cancellation though, which alas is commonly the case for audio volume circuitry. It would be interesting to see some linearity comparisons between carbon-film resistors, carbon linear pots and carbon log pots at various positions - can't seem to find any. [ alas there're are a lot of results about how linear the taper response is with angle, not wiper voltage with input voltage.. ]
The Baxandall style volume control (and tone controls of course) use linear pots and this is probably one of the reasons its a great performer. (A lot of the online pages describing the Baxandall volume circuit seem not to know the pot should be linear!).
In general avoiding carbon-track pots is good if you can, but if you do use them a linear pot circuit is likely to suffer least from carbon's shortcomings, especially if you can keep the impedances low, i.e. 1k .. 10k for the pot.
Thinking about it, one trick component manufacturers have missed is having a pot with plug-in track sections so you can swap out an old worn scratchy track section without having to buy a whole new pot body and disassemble the equipment its in... A variation on the stackable wafer switch idea I guess.
Last edited:
Also make sure not to draw any DC current out of the wiper of a carbon-track potmeter. According to an old Panasonic application note(*), this would cause anodization of the wiper.
(*) Panasonic Carbon Composition Trimmer Potentiometers Application Notes, Ev0038EK, trimmer_potentiometer.pdf; I downloaded it from internet a long time ago, but I haven't a clue from where exactly.
(*) Panasonic Carbon Composition Trimmer Potentiometers Application Notes, Ev0038EK, trimmer_potentiometer.pdf; I downloaded it from internet a long time ago, but I haven't a clue from where exactly.
Pics
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.