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Recommendation for first test equipment
Recommendation for first test equipment
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Old 13th June 2019, 05:41 AM   #11
deadpool is online now deadpool  Australia
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Philips No. 2 screwdriver

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Old 13th June 2019, 05:45 AM   #12
Calvin is online now Calvin  Germany
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Is 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 its 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.

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Old 13th June 2019, 06:28 AM   #13
ej25awd is offline ej25awd  Canada
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Originally Posted by itsikhefez View Post
Will look into this one as well.
If I were to hypothetically purchase one of these, what functions would I still need the scope for ?
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.
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Old 13th June 2019, 07:17 AM   #14
itsikhefez is offline itsikhefez  United States
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Recommendation for first test equipment
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.
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Old 13th June 2019, 02:16 PM   #15
w5jag is offline w5jag  United States
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Originally Posted by itsikhefez View Post

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).
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
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Old 13th June 2019, 04:49 PM   #16
Sheldon is offline Sheldon  United States
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Prompted by your thread, I just posted this:
Tektronix 454 and BK 3025 function generator

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Old 14th June 2019, 11:33 PM   #17
Mark Tillotson is offline Mark Tillotson
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If I were to hypothetically purchase one of these, what functions would I still need the scope for ?
General troubleshooting, being standalone is really handy too. A 'scope is your eyes for waveforms.
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Old 15th June 2019, 04:44 PM   #18
altor is offline altor  Israel
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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.
Regards, Alex
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Old 15th June 2019, 05:08 PM   #19
nigelwright7557 is online now nigelwright7557  United Kingdom
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There are some very cheap USB scopes on ebay.
Some even have FFT to measure harmonics etc.
PCBCAD51 download or CDROM 2019 version out now https://www.murtonpikesystems.co.uk
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