Hey,
I've built a few amps till now and besides my untrustworthy ears, I have no real good way to determine if the amp is working properly. I only currently own a Fluke 87-V DMM.
1) What are the few basic tests that should be measured on an amplifier? (mine are mostly headphone amps but I'm assuming its the same). Distortion, Max output power, channel imbalance etc...
2) Which equipment am I looking for that can perform these? Ideally its a single machine, and not TOO expensive (<400$ ideally).
Any recommendations to primers on the topic appreciated as well.
Thanks for the help
I've built a few amps till now and besides my untrustworthy ears, I have no real good way to determine if the amp is working properly. I only currently own a Fluke 87-V DMM.
1) What are the few basic tests that should be measured on an amplifier? (mine are mostly headphone amps but I'm assuming its the same). Distortion, Max output power, channel imbalance etc...
2) Which equipment am I looking for that can perform these? Ideally its a single machine, and not TOO expensive (<400$ ideally).
Any recommendations to primers on the topic appreciated as well.
Thanks for the help
Cheapest all in one instrument is a USB scope (if you have a PC).
This is $139. and includes probes, and has a 100kHz function generator.
Measuring distortion will cost a lot more, though.
PicoScope 2204A 10MHz 2-Ch Oscilloscope (PP906) ($139.00) : Saelig Online Store
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Get an audio analyzer, it has a ultra-low distortion audio generator, THD+N analyzer, RMS meter and other features that are needed for power amplifier building and testing in one box. No more output bias guessing when you have an audio analyzer. Some have floating outputs, balanced-input etc. that are handy for isolating ground-induced noise.
Lots of choices that have THD+N residual of -90dB/0.003% or better. Some notable examples below that are well-built and designed to last long are:
Sound Technology 1700B, 1701A, etc. (analog)
HP 339A (analog) , 8903A (digital), etc.
Booton 1120 (digital)
Tektronix SG505 audio generator (analog) + AA501 analyzer (digital)
The cheapest of the lot are the ones from Sound Technology. There are more to choose from but they have less documentation and end-users around that might be able to help you.
Stay AWAY from the cheaper and new audio analyzers from China. These are basic, low spec machines that don't use advanced methods like the ones above.
Lots of choices that have THD+N residual of -90dB/0.003% or better. Some notable examples below that are well-built and designed to last long are:
Sound Technology 1700B, 1701A, etc. (analog)
HP 339A (analog) , 8903A (digital), etc.
Booton 1120 (digital)
Tektronix SG505 audio generator (analog) + AA501 analyzer (digital)
The cheapest of the lot are the ones from Sound Technology. There are more to choose from but they have less documentation and end-users around that might be able to help you.
Stay AWAY from the cheaper and new audio analyzers from China. These are basic, low spec machines that don't use advanced methods like the ones above.
There are two tools that are invaluable. A decent soundcard (a focusrite 2i2 is a good start) to measure distortion and an oscilloscope to check for oscillations and see what's really going on with your circuit. That picoscope and the 2i2 will be well under 400$. If you start playing with higher power amplifier, an interface such as Pete Millet's for the soundcard might come in handy.
Digital scope are getting better and better but you could also consider a decent used analog scope, especially if you're getting into tubes and need high voltage inputs.
Digital scope are getting better and better but you could also consider a decent used analog scope, especially if you're getting into tubes and need high voltage inputs.
If you've got the time and patience watch your local Craigslist for a decent analog scope. I picked up a Hitachi 100MHz scope many years ago for $25 that came with a pouch full of probes and its still serving me well. Just the pouch full of probes and connectors was worth the money I spent. You may have to wait a few months before something good comes up, but it will eventually.
Combine that with a decent soundcard like those already mentioned and build a basic manually switched attenuator and you'll be at about half of your stated budget and capable of diagnosing and measuring most of your DIY projects.
The only downside is that it will not be one box like you said you wanted...
Combine that with a decent soundcard like those already mentioned and build a basic manually switched attenuator and you'll be at about half of your stated budget and capable of diagnosing and measuring most of your DIY projects.
The only downside is that it will not be one box like you said you wanted...
Its just a little over your price threshold ($450) but this is really a very capable instrument and easy to use: QA401 Audio Analyzer
– QuantAsylum
Its also getting some continuous improvement in the software. Its distortion residuals are as good or better than any of the ones listed and being FFT based it has better analytics. It won't replace a good scope or a good bench meter but you will not outgrow it very soon. And its a small fraction of the size of the older instruments.
– QuantAsylum
Its also getting some continuous improvement in the software. Its distortion residuals are as good or better than any of the ones listed and being FFT based it has better analytics. It won't replace a good scope or a good bench meter but you will not outgrow it very soon. And its a small fraction of the size of the older instruments.
Hi,
I´s assist the recommendation of the QA401 as decent audio analyzer at reasonable cost.
Another recommendation would be the Digilent AnalogDiscovery2 which is basically a complete 2-channel measuring lab beyond only the audio frequency range (impedance analyzer, network analyzer, oscilloscope, spectrum-analyzer, curve tracer, signal generator, etc. etc.)
Beeing very small and fed from USB it´s also a mobile solution.
And it fits Your budget.
It may look like a gadget at first glance, but it definitely is a serious little device.
jauu
Calvin
I´s assist the recommendation of the QA401 as decent audio analyzer at reasonable cost.
Another recommendation would be the Digilent AnalogDiscovery2 which is basically a complete 2-channel measuring lab beyond only the audio frequency range (impedance analyzer, network analyzer, oscilloscope, spectrum-analyzer, curve tracer, signal generator, etc. etc.)
Beeing very small and fed from USB it´s also a mobile solution.
And it fits Your budget.
It may look like a gadget at first glance, but it definitely is a serious little device.
jauu
Calvin
You need a scope because QA401 maximum input is 20Vrms or 50W in an 8 Ohm load, a PC soundcard maximum input is 1/10 this value. My audio analyzer suggestions, 200-300V or 5kW minimum. You did say you are
building power amps and want to determine maximum output power. That is not possible with a PC soundcard out of the box unless you go DIY and build an attenuator. I don't know if you want to spend more time building test equipment or power amplifiers.
PC soundcards are perfect for line level applications. QA401 is something in between and both require a PC to operate.
Clearly define your needs, do a lot of research before taking the plunge.
Thanks for the tips and recommendations.. will thoroughly look into them before making a hasty decision.
I've built mostly headphone amps which aren't very high voltage and 2 SET tube amps which are also lower powered. Although if I spend on some gear now, it better server me in the future if I do want to test higher powered amps.
For older analog scopes, are there any specific Tektronic models that are recommended?
My local craigslist is full of them, some are priced higher than others and I'm sure there are many pitfalls here.. Also, thoughts on newer Rigol like DS1054Z or DS1052E.
I've built mostly headphone amps which aren't very high voltage and 2 SET tube amps which are also lower powered. Although if I spend on some gear now, it better server me in the future if I do want to test higher powered amps.
For older analog scopes, are there any specific Tektronic models that are recommended?
My local craigslist is full of them, some are priced higher than others and I'm sure there are many pitfalls here.. Also, thoughts on newer Rigol like DS1054Z or DS1052E.
My suggestion would be an inexpensive two channel DDS signal generator, and an inexpensive DSO scope, like a Hantek, Rigol, or Siglent.
The signal generator and scope allow you to do signal tracing, and measure gain, output, imbalance, frequency response, etc., well into RF depending on the generator and scope.
You can look at IMD by injecting two tones and looking at the resulting spectrum on the FFT function. You can use a single tone and look at harmonic distortion.
The catch is that these cheap scopes ( and likely the all in one devices ) are only 8 bit, so you only see the first 45 dB or so. I think that's about one half per cent distortion.
If you are going to be building better than that, you'll need better equipment to measure it.
One exception to the all in one devices is the Red Pitaya - it is available in 10, 14, and 16 bit variants and has a 60 MHz bandwidth. The all in one things may ( or may not) be able to do tone generation and FFT at the same time, so if that is important to you, I would check their capabilities carefully.
I love old ham radio equipment, but I know how to fix it and maintain it. Personally, I do not fool with old test equipment unless it is really simple, because I can't fix and maintain the really complex stuff, and am not interested in learning how.
My $0.02
It is very depend of "what to do" - analog audio, digital audio or something else.
But, Scope - "must have"! At least nonexpensive USB or Rigol/Hantek/Owon/etc.
DVM is also "must have", but you are already have it. Fluke87 is enough for most tasks.
For distortion measurements - good SoundCard and "Victor's Generators".
If you plan to work with digital audio - the simple logic analyzer (from $8 at EBay/Ali) will be very useful.
But, Scope - "must have"! At least nonexpensive USB or Rigol/Hantek/Owon/etc.
DVM is also "must have", but you are already have it. Fluke87 is enough for most tasks.
For distortion measurements - good SoundCard and "Victor's Generators".
If you plan to work with digital audio - the simple logic analyzer (from $8 at EBay/Ali) will be very useful.
Thanks for the recommendations here, I have started setting up a test rig.
I built the Pete Millett SC interface, and ordered a used E-MU 0404 PCIe card.
That has limited driver support beyond Windows 7, so I setup a dual boot (Win10/Win7).
The Win7 will stay clean and will only serve measurement purposes.
I intend to experiment with audioTester and ARTA and purchase the one that I find easier to use.
Now, when I started this thread I wanted to tests headphone amps I have already built that are working properly (subjectively). My current tube amp project has some noise that I'm trying to identify, and it seems like an oscilloscope will be useful.
There are a few currently available on eBay, I would appreciate some feedback on which to go for.
1) Hitachi V-523 50Mhz
2) Hitachi V-660 60Mhz
3) Hitacthi V-422 40Mhz
4) Tektronix 2225 50Mhz
Also, what are reasonable prices for above scopes.
Thanks!
I built the Pete Millett SC interface, and ordered a used E-MU 0404 PCIe card.
That has limited driver support beyond Windows 7, so I setup a dual boot (Win10/Win7).
The Win7 will stay clean and will only serve measurement purposes.
I intend to experiment with audioTester and ARTA and purchase the one that I find easier to use.
Now, when I started this thread I wanted to tests headphone amps I have already built that are working properly (subjectively). My current tube amp project has some noise that I'm trying to identify, and it seems like an oscilloscope will be useful.
There are a few currently available on eBay, I would appreciate some feedback on which to go for.
1) Hitachi V-523 50Mhz
2) Hitachi V-660 60Mhz
3) Hitacthi V-422 40Mhz
4) Tektronix 2225 50Mhz
Also, what are reasonable prices for above scopes.
Thanks!
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