Strange logic. When you design stuff right straight away and test/debug the thing there is no need to upgrade. Or it must be to deliberately design mediocre and then give users a chance to "do something" which seems counterproductive.
If you care about giving laymen a chance to do something you might as well use TH parts and DIL opamps only. SMD is then a bridge too far anyway and it will result in opamp/cap rolling. It won't motivate the user to dive deeper into electronics. And... what makes your design then stand out in the vast area of mediocre/standard phono preamps?
Here a schematic of the first phono preamp I built for a friend in 1983. There are no opamps to upgrade. The friend passed away but the preamp is still in use AFAIK.
If you care about giving laymen a chance to do something you might as well use TH parts and DIL opamps only. SMD is then a bridge too far anyway and it will result in opamp/cap rolling. It won't motivate the user to dive deeper into electronics. And... what makes your design then stand out in the vast area of mediocre/standard phono preamps?
Here a schematic of the first phono preamp I built for a friend in 1983. There are no opamps to upgrade. The friend passed away but the preamp is still in use AFAIK.
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Point taken.
I will save the SMD opamps for another day and stick to TH for this project. Probably I will do a 2nd layout optimized for soic-8 for my own use at a later date.
I really don't want to rob my friend of the joy he will get from opamp rolling.
I will use SMD for regs, resistors and diodes however as it helps with the layout.
On a side note. Is there any obvious preference in SMD resistors?
Browsing through data sheets they seem broadly the same.
I don't bother with fancy parts.
I typically stick to Vishay/Dale CMF/RN series resistors. Mostly because I like the colour and being able to easily read the value.
I will save the SMD opamps for another day and stick to TH for this project. Probably I will do a 2nd layout optimized for soic-8 for my own use at a later date.
I really don't want to rob my friend of the joy he will get from opamp rolling.
I will use SMD for regs, resistors and diodes however as it helps with the layout.
On a side note. Is there any obvious preference in SMD resistors?
Browsing through data sheets they seem broadly the same.
I don't bother with fancy parts.
I typically stick to Vishay/Dale CMF/RN series resistors. Mostly because I like the colour and being able to easily read the value.
Tough to beat ne5532, it is old and cheap but also very good. You may hear a difference using a Opa2134 or other Jfet amp when using hi z inputs.
I prefer thin film, especially for the feedback circuit. The low Temp coefficient measurably reduces distortion. The difference compared to thick film is likely inaudible but comes at a low cost, so why not?
1206 is easy to hand solder or use 0805 if space is at a premium.
Good to use low excess-noise, and high linearity resistors in critical locations.
Some related info: https://dcc.ligo.org/public/0002/T0900200/001/current_noise.pdf
Depends on the application. If the application is a series resistor for an LED you can use whatever resistor you want. But for stuff that has audio going through it, you'd definitely want thin film. The Susumu RR and RG series are excellent. I tried some much fancier (read: much more expensive) ones, including the Vishay Z-foil, recently and ended up back at the RG-series.
Tom
I like Susumu RR, although last time I checked they were not recommended for new designs. Also like Yageo RT. IME, Susumu RG are another matter. They measure well in some ways, but IME they have high-ish current noise of the 1/f type. OTOH, resistors designed especially for audio use appear to be optimized for low current noise above all else. IOW, it depends. What is most important for a particular circuit will depend on its requirements. For example, I would not use Susumu RG as feedback resistors in an audio amplifier, unless maybe I wanted to add some sneaky audio signal correlated noise to hide other problems with reproduction accuracy. I would also not use Susumu RG for FIRDAC output resistors.
Moving along to metal foil resistors, they can be useful when current noise is most critical but they are costly. However, the best metal thin film resistors can come very close to metal foil, so the potential benefits of metal foil should be limited to the most sensitive cases where the absolute minimum amount of current noise can be tolerated.
Moving along to metal foil resistors, they can be useful when current noise is most critical but they are costly. However, the best metal thin film resistors can come very close to metal foil, so the potential benefits of metal foil should be limited to the most sensitive cases where the absolute minimum amount of current noise can be tolerated.
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There's no mention of current noise in the RG spec sheet. Also, the only noise types in resistors are thermal noise and excess noise. The latter is caused impurities in the materials as far as I understand. Metal film resistors tend to have very low excess noise. So I'm wondering where you get the notion of current noise from. Would you care to elaborate?
Tom
Most of Excess noise consists of current noise. End cap noise/distortion effects may be included in Excess Noise. For anyone wanting an explanation of current noise and or excess noise, IIRC The Art of Electronics has some good information.
Also, its not just impurities in the material. It depends on how the metal is deposited on the substrate, and the substrate material. IIRC, it is believed that current noise mainly arises from defects in the substrate and the metal deposition that cause current to flow around the defects. Probably, I have some more info on the details around here somewhere if there is more interest in the subject.
EDIT: Also regarding metal film resistors, there can be quite a bit of range in terms of Excess Noise. Only the best of metal film can closely approach metal foil.
Also, its not just impurities in the material. It depends on how the metal is deposited on the substrate, and the substrate material. IIRC, it is believed that current noise mainly arises from defects in the substrate and the metal deposition that cause current to flow around the defects. Probably, I have some more info on the details around here somewhere if there is more interest in the subject.
EDIT: Also regarding metal film resistors, there can be quite a bit of range in terms of Excess Noise. Only the best of metal film can closely approach metal foil.
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So you're saying that the Susumu RG resistors have high excess noise? That should be somewhat easy to measure. Are you aware of measurements?
I spent a good chunk of my summer looking at various resistor types in a low-noise, low-THD amp. I don't recall seeing any significant differences in the noise of the total circuit with the different resistor types. I did notice a difference in THD between different types. That seems to be mostly related to the temperature coefficient and voltage coefficient of the resistor material, but LF THD can also be impacted by how the resistor material is bonded to the substrate. Bruce Hofer has a good presentation on that.
Tom
I spent a good chunk of my summer looking at various resistor types in a low-noise, low-THD amp. I don't recall seeing any significant differences in the noise of the total circuit with the different resistor types. I did notice a difference in THD between different types. That seems to be mostly related to the temperature coefficient and voltage coefficient of the resistor material, but LF THD can also be impacted by how the resistor material is bonded to the substrate. Bruce Hofer has a good presentation on that.
Tom
What I did was try some different well known, well respected resistor types as FIRDAC output resistors. Susumu RG were the worst of any tried by far. Sound was badly and strangely blurred as compared to the best metal film resistors tried. I know Susumu RR are good because they can work very well in @MarcelvdG RTZ dac. Also, Yageo RT were good in another similar FIRDAC.
Look, I have nothing against Susumu. They make a line of audio resistors that they only claim are especially low noise. To me it seems obvious that they are not kidding. Low current noise can matter for audio.
Also, this is entirely different from THD (which is arguably not that useful). If one measures for THD and not for Excess noise, then one will probably go with low THD over anything else. The problem is that THD is too easy to measure and excess noise isn't as easy (that's where human bias comes in). In fact, it can be rather difficult to measure current noise quantitatively if the noise is highly correlated with the audio signal. It can end up as noise skirts on a hi-res FFT.
Look, I have nothing against Susumu. They make a line of audio resistors that they only claim are especially low noise. To me it seems obvious that they are not kidding. Low current noise can matter for audio.
Also, this is entirely different from THD (which is arguably not that useful). If one measures for THD and not for Excess noise, then one will probably go with low THD over anything else. The problem is that THD is too easy to measure and excess noise isn't as easy (that's where human bias comes in). In fact, it can be rather difficult to measure current noise quantitatively if the noise is highly correlated with the audio signal. It can end up as noise skirts on a hi-res FFT.
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Excess noise in resistors is also known as current noise, as the noise only shows up when there is current flowing through the resistors. It is most unfortunate that people call it that, as current noise is also short for equivalent input current noise, which is something completely different.
With the same logic they might as well call it voltage noise, as the noise only shows up when there is voltage dropping across the resistor, but thank goodness no one calls it that.
The L78xx datasheet in my old SGS-Thomson databook shows that same recommendation, but the L79xx datasheet demands a 2.2 uF solid tantalum or 22 uF aluminium electrolytic input decoupling capacitor if the regulator is placed far from the smoothing capacitor. In my experience, both the 78xx and the 79xx work fine with a 22 uF run-of-the-mill aluminium electrolytic decoupling capacitor at the input.
I once had to repair a studio mixing console that had started to make soft beeping sounds. It turned out to be due to the manufacturer using 10 uF electrolytic input decoupling capacitors for the 7815 and 7915 regulators that were on each of the few dozen modules. When new, that just worked, but with a bit of capacitance loss, it didn't. The resulting ultrasonic oscillations gave audible mixing products. I changed all the capacitors to 22 uF and it never beeped again.
That has changed with recent (= post 2000) 78xx/79xx and 78Lxx/79Lxx. Just as their lower noise numbers and also lower dropout voltage. Sometimes at some types at some manufacturers dropout voltage is typical 1.3V which could today be called LDO... Please check current datasheets of TI, On Semi etc.
About 78Lxx/79Lxx 100 mA regulators: old 79Lxx also were notorious for being unstable without load. They were also less reliable compared to 78Lxx and sometimes latched up. A reason to keep using the cheap TO220 1A versions. Then, not today.
About 78Lxx/79Lxx 100 mA regulators: old 79Lxx also were notorious for being unstable without load. They were also less reliable compared to 78Lxx and sometimes latched up. A reason to keep using the cheap TO220 1A versions. Then, not today.
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The ones from ST are still the same, see page 11 of the pdf on https://www.st.com/en/power-management/l79.html
Input cap 2.2 µF, output cap 1 µF, dropout voltage 1.4V typical..... Even 1.1V (!) for the 12V version. They seem to be a lot more noisy with 100 µV typical than those by competitors. Not recommended. I have seen 7905 with less than 40 µV of noise.
So they are not at all the same as the ancient ones except their unchanged datasheet higher input/output capacitor requirements which are unusual today. Besides that exceptions confirm the rule 🙂
78xx/79xx have evolved to a better version of themselves in time. From noisy LEGO like common parts to pretty good regulators. Point today is which one to pick from what brand as they differ.
So they are not at all the same as the ancient ones except their unchanged datasheet higher input/output capacitor requirements which are unusual today. Besides that exceptions confirm the rule 🙂
78xx/79xx have evolved to a better version of themselves in time. From noisy LEGO like common parts to pretty good regulators. Point today is which one to pick from what brand as they differ.
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