For ADA4627-1, didn't offhand see anything about EMI/RFI immunity in the datasheet.
OTOH, OPA627 has info on EMIRR IN+ including a table, and this graph:
OP hasn't asked how to measure for that, particularly in situ. Certainly could be of interest in a DAC application.
OTOH, OPA627 has info on EMIRR IN+ including a table, and this graph:
OP hasn't asked how to measure for that, particularly in situ. Certainly could be of interest in a DAC application.
If you ever made a loop back measurement with your existing soundcard you knew the answer.
so, what I want to say is
Sophisticated Equipment may replace lack of knowledge - to a small extent
Knowledge may replace lack of sophisticated Equipment - to a huge extent
Sophisticated Equipment may replace lack of knowledge - to a small extent
Knowledge may replace lack of sophisticated Equipment - to a huge extent
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I can at least choose between opamps wisely, and test them in my circuits, for my application.
Also, I do not plan on using it only to measure ONLY opamps... it would be pretty dumb, to only measure opamp for the sake of just measuring opamps.
Also I did not see any measurements on the link you posted.
This looks pretty useless to me. I can't do anything with that.
So I need to be one the best engineer on the planet first, to be able to have the privilege of good measurements....
I GIVE UP GUYS... you won (probably), I am loosing my time.
I think that's a great question and one I suggest that you ask yourself. Are you willing to move along now that OP has stated that he's looking to measure harmonic distortion and not some degree of distastefulness? You've shared that out-of-context screenshot twice now in this thread alone and the thread is barely on page 3. Please accept that some of us have the desire to measure distortion, including IMD and THD, and move on. We don't all have to have the same preferences but we can still get along, right?
Tom
Understood. That's why I asked about the distortion residual. OP thinks its useless for distortion measurement. So, I guess what he really means is he is only interested in FFT measurements for HD.
@Frederico Acardi
Sadly, you're falling victim to your thread being hijacked by those who start fights and those that choose to fight vs. ignore. It's well within boundaries to flag posts and request that posts be removed.
Also, sadly, some will say that this measurement or that is irrelevant. Nonsense. You don't have to justify why you'd like to measure or compare something; at least not to me.
Mainly, you might already have everything you need once you build your uln minus some software depending on how sophisticated you want to be and/or how user friendly you want your experience to be.
If you need or choose to buy some additional gear, below may help others to be more specific in their recommendations.
However, while I'm a total beginner, I have a very small amount of beginner-level experience with below.
Have fun!
Sadly, you're falling victim to your thread being hijacked by those who start fights and those that choose to fight vs. ignore. It's well within boundaries to flag posts and request that posts be removed.
Also, sadly, some will say that this measurement or that is irrelevant. Nonsense. You don't have to justify why you'd like to measure or compare something; at least not to me.
Mainly, you might already have everything you need once you build your uln minus some software depending on how sophisticated you want to be and/or how user friendly you want your experience to be.
If you need or choose to buy some additional gear, below may help others to be more specific in their recommendations.
- What is your budget? Be specific. 'As cheap as possible' doesn't help.
- Do you want the gear you buy to be the first and last, or do you want something to get you started?
- Does buying on the used market bother you? For specific equipment, do you have the means and desire to verify calibrations, keep equipment calibrated?
- People will assume what tests THEY would run were they in your shoes. Instead, could you outline what specific measurements and a process you might follow? How are you choosing suitability for purpose?
However, while I'm a total beginner, I have a very small amount of beginner-level experience with below.
Depending on the PSU type, your oscilloscope will likely be fine. Depending on whether you want to apply any weighting to the measurements, you'd likely want some software. But for the essentials, your scope is likely just fine.
I'm assuming you mean an amplifier used to drive loudspeakers. The levels of distortion for speaker-level tube amplifiers is worlds away from op-amps I assume. For speaker-level amplifiers I've really enjoyed the QuantAsylum QA403. The REW + soundcard and other similar options are absolutely useful and IMO great suggestions. As an integrated hardware / software solution, I personally find the QA to be wonderful, and it's my current choice on the bench. For me, the learning experience was relatively 'simple'. Related to above, depending on whether you're talking about a PSU for a typical audio amplifier or extremely low noise PSUs, the QA403 and associated software is suitable for power supply noise measurements. Depending on how 'low you want to go', there could be more suitable products. The website and user forum has recommended processes posted to get started (and includes applying various weighting as needed/desired). The specifications are also clear and could help you determine suitability for your needs. Give it a look. Again, I am a total beginner. It might not be everyone's choice, but I think it's worth a look.
Have fun!
Fantastic! Measurement-based circuit design. I love it!
I'm a bit curious which Analog Devices opamps that you think are better than the TI ones based on their data sheets? I'm not looking to argue. I haven't seen anything exciting from ADI in over a decade so maybe I'm missing something. It's hard to beat the OPA1611/12, OPA1642, OPA1656, etc.
The Victor oscillator is amazing value for the money and he keeps improving it. I have two of them. Along with a twin-T passive notch and your sound card you can measure harmonic distortion down below -120 dBc at 2 V RMS, 1 kHz. Maybe even lower.
The drawback of the oscillator+notch approach is that you need to take the frequency response of the notch filter into account when you read the THD. So it's not super convenient. But it's certainly good enough to evaluate Part A vs Part B.
Another approach is to use the test circuit shown in Fig. 109 of the TI LM4562 data sheet:
The key is to reduce the loop gain of the opamp so the distortion becomes measurable. Then compensate for the change in loop gain by changing the reference on the distortion plot. This does assume that the distortion doesn't change in nature/composition as the loop gain is reduced.
The Cordell Distortion Magnifier is another good approach: http://www.cordellaudio.com/instrumentation/distortion_magnifier.shtml
You don't need the 6.5 or 5.5 digits. 3.5 digits would be plenty. But the 3.5 digit meters tend to be hand-held and have a bandwidth around 1 kHz even for the better ones. If you want to calibrate your system to 20 kHz so you can take an accurate frequency response, you really need a meter with a few hundred kHz bandwidth. That's where the bench top meters come in.
I like the paint can idea ... just empty the can first. 🙂 Hammond also makes some cheap sheet metal boxes out of tin-clad steel. They can be pretty good for shielding. I bet a new clean paint can is cheaper, though. Your local paint store will be helpful there.
If you're looking to attenuate external fields you want a box made from a material with high relative permeability, µr. Steel or, better yet, mu-metal (µ-metal) is much better than aluminum. You can buy mu-metal sheets on eBay and use those to clad a steel box. That'd be a pretty nice little "screen room" for your circuits.
Tom
For noise measurements you need a 60dB LNA (low noise amplifier). There are 2 very good diy LNA alternatives here:
https://www.diyaudio.com/community/...-from-linear-audio-vol-3-spare-boards.287604/
https://www.diyaudio.com/community/...w-noise-measurement-amp-for-ikoflexer.175044/
Your soundcard is ok, but for tube amp measurements you would need an interface to scale voltages for soundcard. Something like this (probably not available anymore):
https://www.diyaudio.com/community/threads/test-measurement-interface-for-soundcard.155405/
I assume this thread could be useful as well:
https://www.diyaudio.com/community/threads/behringer-umc-202hd-for-measurements.341309/
Another aspect choosing test equipment is its versatility. A DVM, bench supplies, oscilloscope... these are quite basic, versatile instruments that are required for many measuring scenarios. What is with the victor oscillator? This is one state of the art signal source with a sinead about 150dB. It is useful for bleeding edge measurements of THD or THD+N at about 1kHz. And that's it. No IMD-measurements, other frequencies or test scenarios are possible. It excels at exact one measurement setup and is useless otherwise. This makes it nice to have at best, imho.
A reference oscillator can be useful for characterizing other test equipment so you know how much to trust them.
I fully agree. It might not be exactly what you were going after, but in addition to versatility (again from a beginner's perspective)... I'd add simplicity of use and integration.
@Frederico Acardi
By example...
The QA403 (along with the integrated software) replaced everything below for most of my amplifier measurements: Noise, THD, THD+N, Residual review, IMD, Power vs. THD, Frequency response (to a limit) etc.
Various attenuation / signal amplification devices - Autoranger, manual voltage dividers etc.
Oscillators / Signal Generators (specifically sine generators)
Software - REW and ARTA along with Excel
Some... but not all custom cabling. BNC is very nice to have for all in/out.
Stand-alone Distortion analyzer
Oscilloscope (while not ideal... the integrated software scope works, and is quite useful)
AC capable / 'proper' DMM (within the context of certain measurements it's not needed b/c it's already calibrated)
DAC / ADC / Amplifier a la Focusrite / Behringer et. al.
If you want to export data and use it for your own purposes / formats, it's a breeze. If you want to use their built in graphing functionality, it's quite nice. It also has built-in automation and test scripts. It has dual signal generators, and each can be configured independently, so IMD is a breeze etc. For more skilled users, you can write and integrate your own test scripts. The user support and forums are fabulous. Since it's still relatively 'new', upgrades / software / firmware are continually being improved. My experience with using a versatile, integrated hardware / software solution that was purpose-built vs. hardware and software that people have cleverly determined how to use for different purposes than their designers' likely originally intended was a better experience for me. Going to one group for support vs. (while wonderful) this forum or several manufacturers / software creators for support is also a benefit (to me).
I can't believe I'm using these words, but "It just works". For me, a novice with no experience in audio, it took me <1/10th the time to learn to use it effectively vs. the listed separate components and software above. In addition, for a newer person, it minimized my errors. My testing process is now repeatable and reliable, in part due to the lower complexity / automation of the testing system itself.
Also, if speed/efficiency is part of your equation... my time to complete a set of measurements and have my report completed is 1/20th or less than with the "separates".
Is it the 'most capable' product? I doubt it; but if another integrated solution exists anywhere near this price category, I haven't found it. They also have a slew of other auxiliary products for more specialized and/or more automated needs.
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Frederico,
If you have truly left, I feel badly about that. You asked for some realistic advice and asked legitimate questions. I hope you get some somewhere.
In case you still can't help yourself from sneaking a peek here, I'll explain my strategy for test gear.
I wanted to be able to measure audio gear I built. That implies measuring components, too. In addition, this is not a full time activity, so I wanted to purchase gear that didn't take up a lot of space or cost a ton. 99.96% of the time my test equipment sits on a shelf in the closet not taking up space on my work table.
Here's my list of what I bought, my reasoning, and what I found:
DMM - I've owned a Fluke 87 mark something or other for more than 30 years. It still works great.
Oscilloscope & more - I purchased a Diligent Analog Discovery 2 a few years back. For as often as I use a scope, it works great. The software lets me do a lot. I can perform square wave testing on an amplifier circuit. It allows me to make amplitude response measurements far beyond the audio band. It also provides a spectrum analyzer good up to maybe 10 MHz or so. I can measure passive components at various frequencies. I've built some accessory pieces that allow me to measure the closed loop gain and phase margin for amplifiers. Easily programmed, too.
If I was using a scope as a central tool for repairs, I'd probably purchase one of the very new Rigol scopes. That is a faster tool to use because it takes no set-up - just turn it on, set a couple knobs, and probe. Less flexible than the Analog Discovery 2, but wider bandwidth. So far, I haven't found a justification for one of those, although I've tried. 🙂
Regardless of the scope you choose, it's good to have both a differential probe system and a current probe. Sadly, neither of the ones I bought and just linked to are available any longer. (If anybody knows of some reasonable alternatives, I'd be very interested.) It's amazing to see what currents are flowing where when you have a current probe to look at that. It makes you realize some of the imperfections that you don't easily observe in SPICE simulations unless you really make the effort to create realistic simulation circuits. Basic stuff that is basically ignored.
Basic LCR meter - DE-5000 I bought this before I bought the Analog Discovery 2 and a lot of the measurement capabilities overlap. But, the DE-5000 allows for really fast measurements.
Semiconductor tester - For sorting semiconductors, this is really useful: DCA75. You can do a lot of the same with the Analog Discovery, but the Peak device is really simple and fast. You can sort JFETs for Idss in seconds.
Distortion testing - When they were first available, I bought a QuantAsylum QA401. The newer QA40x devices have much better distortion measuring capabilities because of the better DAC and ADC parts available now. But, I haven't tried those. (More on that in a bit.) The QA401 is great for lots of measurements, like noise, frequency response, and so on. It just is limited for distortion testing. I bought a QA480 to supplement the basic QA401 and it works great and does get me to -150 dBC harmonic measurement of a 1 KHz tone.
During the great component shortage, QuantAsylum was forced to redesign their products and were held back in production for lots of months. During that time, a company called E1DA arrived with some new products: Cosmos Audio Test Gear. You pretty much know about those. With a Victor Oscillator as a test source, I can now reliably make simple harmonic distortion measurements at much better than -150 dBC when using the APU and the rest. That level of test resolution really pretty much allows you to get a good understanding of the components you use and the circuits you build. Without the APU in line, the distortion limits of my ADCiso and Scaler combination are close to -140 dBC using the Victor oscillator as the source. That's still really great and is 30 or more dB better than I could get with the unaugmented QA401.
If you want to go beyond testing a single tone as from the Victor oscillator, like for various multitone IMD tests, you need a DAC as a source. This article caught my eye: PMA Test System. So, I purchased a Topping D10s. It performed exactly as described in the article. Based on a different review, I then purchased a Topping E50 because it has both unbalanced and balanced outputs and promised better performance. Indeed, the noise performance of the E50 is about 10 dB better than with the D10s. The distortion performance is variable - it takes some adjustments of the software to make it approach what the reviews describe. (I think this shows some of the ups and downs of distortion compensation.) Both of these DACs will do the job. The E50 I have gets to better than -135 dBc for each harmonic and the D10s gets to about -125 dBc. But, if E1DA releases the Cosmos DAC, I'll probably purchase one.
I tend to use two pieces of software for distortion testing. REW is the prime one and works across Windows, macOS, and Linux. It really does everything and works very well indeed. I also use Multitone.
With this test set-up, I can make measurements almost as good as what can be done with an Audio Precision test set. In some ways, even better. Yeah, it took a few hours to learn some of the subtleties, like which drivers to use and the various settings, but that's also true when you first start using an AP system. I think something similar to my system would do what you want. I also suspect that the QA403/404 would as well. I just can't speak to that because I haven't tried it, so I don't know what the new software capabilities are. But, QuantAsylum makes very well engineered and thoroughly thought out products. Having everything in one box with test software specifically designed for its use is a great advantage in some ways.
Beyond - I also have a few other pieces that are mostly used for RF testing, but also are helpful with audio projects, too. Just not that often. Here's a list:
tinySA
NanoVNA
Signal Generator
VFO/Signal Generator
OK, that's a lot. Of course, you don't need all that stuff. In fact, I don't need all that stuff. At least a third of that is redundant and essentially has been replaced with newer, better gear, as I described. (I just need to figure out what to do with the surplus.) But, it all still fits on a single shelf in the closet.
Hope that helps you or somebody. I'm no expert, but I pretty much know what has worked for me and what hasn't.
Oh - one other thing. Experimenting with this kind of thing is what gets you to be one of the best engineers on the planet.
Usual disclaimer: I have no, zero, zip connection with any of the companies mentioned above. None. I have purchased whatever I have from them at normal retail prices like everybody else. I think I may have saved a few bucks once or twice when a piece was on sale for some reason. The people at those companies wouldn't know me if I knocked on their door and was wearing a name badge.
If we go back to the start of this ther eis a bit of futility in the requested measurements. A properly operating opamp will have virtually unmeasurable distortion (even with APX555) in a normal circuit. A distortion measurement is really useful to spot a problem (bad power supply, overloaded circuit, damaged device) so it can be useful even if the numbers don't correlate with listening. Measuring opamp noise is very challenging but manageable. However not a lot to be learned that's not in the datasheets. Transistors are a different story. Measuring resistor excess noise requires very specialized equipment. So does passive component linearity. I have a bench with all those specialized instruments. I use them occasionally, usually to confirm the obvious.
For a meter the old Fluke 8060A covers most of what anyone would need for audio. A QA403 (or earlier models) again does most of what anyone would need. A cheap digital scope with 100 MHz bandwidth should be enough to see any problem. I would push for a battery powered scope to eliminate ground issues. A function generator with a fast rise square wave would cover the frequency range beyond a QA403 well enough to make sure nothing bad is happening.
For a meter the old Fluke 8060A covers most of what anyone would need for audio. A QA403 (or earlier models) again does most of what anyone would need. A cheap digital scope with 100 MHz bandwidth should be enough to see any problem. I would push for a battery powered scope to eliminate ground issues. A function generator with a fast rise square wave would cover the frequency range beyond a QA403 well enough to make sure nothing bad is happening.
OP quit...
Shall we vote for thread closure?
His target was useless, the measurements would have to be interpreted.
For example, I measure a rod, micrometer says 6.33 mm....unless I know this is within or out of tolerance, what use is the measurement?
You want a setup, fine, but do you have the ability to judge and act on those measurements?
He does not seem to a have even a multimeter...
Like a bicycle mechanic trying to tune a V8...out of his depth.
Shall we vote for thread closure?
His target was useless, the measurements would have to be interpreted.
For example, I measure a rod, micrometer says 6.33 mm....unless I know this is within or out of tolerance, what use is the measurement?
You want a setup, fine, but do you have the ability to judge and act on those measurements?
He does not seem to a have even a multimeter...
Like a bicycle mechanic trying to tune a V8...out of his depth.
I personally vote to leave DIYAudio altogether. The positive helpfulness here is far too overwhelming for me to handle.
Cheers!
Cheers!
@CG Suppose the OP came here and expressed an interest in acquiring some $20,000 cables so his system could sound better. Would the right thing to do be to suggest some $20,000 cables he might like? I mean, would or wouldn't that be excellent helpfulness?
Just answer the man's question, some might say. Don't try to teach or give advice. That's wasn't what was requested. Just be helpful and answer the question.
Well, I for one would disagree. Whether someone is asking an ill-informed question about cables, or whether asking newbie questions about test gear to buy, on what basis is a line drawn to say when it is or isn't appropriate to offer information and advice in relation to the stated end goal versus the OP's presumption of what should be purchased?
Just answer the man's question, some might say. Don't try to teach or give advice. That's wasn't what was requested. Just be helpful and answer the question.
Well, I for one would disagree. Whether someone is asking an ill-informed question about cables, or whether asking newbie questions about test gear to buy, on what basis is a line drawn to say when it is or isn't appropriate to offer information and advice in relation to the stated end goal versus the OP's presumption of what should be purchased?