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NTK

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Mainly looking to do functional and qualification testing and high level troubleshooting. As the amps are modular, will not be doing component level diagnosis or repair. Figure if I can run a decent power vs. distortion test, will cover a lot of territory. Currently just generating signals out of REW and Audigy sound card.
If you need to test for distortion, then you'll need a high resolution (24 bit) ADC. A USB interface with some voltage attenuators (to reduce the amp output voltages) should be sufficient.

Resolutions of digital scopes goes to 16 bits max and probably is insufficient for distortion measurements. However, if you need high frequency bandwidth, you may need both.
 

Instrumental

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I can recommend Visual Analyser for audio tests, freeware with lots (too many?)
features. Seems to have connections with education (University of Rome) so there are
lots of parameters in signal processing at that level. The settings mirror that but
the easier default settings go a long way.
http://www.sillanumsoft.org/

A simple but low THD oscillator (with battery supply) can be found here:
http://www.turneraudio.com.au/thd-measurement.html
I prefer a floating signal sometimes when the common ground on a sound card
gives noise or crosstalk (if analog output is used for generating test signals).

Cheap 24/96 soundcards I have tested are Steinberg CI1 and E-MU 0404 USB.
Used ones can be found for less than 50 $.

This is what the oscillator + Steinberg CI1 + Visual Analyser does.
OP-amp is NE5534 but I have some modern types to test also.
It's good enough for testing my vintage stuff.

THD-3.jpg
 

Wombat

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"You better be solderin' them leakin' water pipes agin Jethro! Don' let me catch you makin' them damn stereo thangs or you'll git anutha beat'n' "

After I finish with the SMDs. :facepalm:
 

Rick Sykora

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If you need to test for distortion, then you'll need a high resolution (24 bit) ADC. A USB interface with some voltage attenuators (to reduce the amp output voltages) should be sufficient.

Resolutions of digital scopes goes to 16 bits max and probably is insufficient for distortion measurements. However, if you need high frequency bandwidth, you may need both.

Maybe one of these?...

Siglent SSA3021X-TG Digital Spectrum Analyzer 9kHz-2.1GHz with Tracking Generator

1599654338786.png
 

NTK

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Maybe one of these?...

Siglent SSA3021X-TG Digital Spectrum Analyzer 9kHz-2.1GHz with Tracking Generator
Sorry to be blunt here. If you don't know whether you need an RF spectrum analyzer or not, you don't need one. But if you insist on getting one for yourself, get one that goes >5 GHz. At least you can use it to troubleshoot all your wireless (bluetooth/wi-fi/cell phone, no 5G though) connection problems :p.

It is arguable that you already have what you need. The required functionalities are already available in your Audigy soundcard. Its performance may be too poor, and you should be able to do a lot better with an external USB interface like a MOTU M4.
 

Rick Sykora

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Sorry to be blunt here. If you don't know whether you need an RF spectrum analyzer or not, you don't need one. But if you insist on getting one for yourself, get one that goes >5 GHz. At least you can use it to troubleshoot all your wireless (bluetooth/wi-fi/cell phone, no 5G though) connection problems :p.

It is arguable that you already have what you need. The required functionalities are already available in your Audigy soundcard. Its performance may be too poor, and you should be able to do a lot better with an external USB interface like a MOTU M4.

No prob, from the description, knew it was mainly for RF work. OTOH, just started looking and am not getting many solid recommendations. While it idles. could just be a home network monitor. ;) TBH, am a hack EE. I have worked with many over my career, but switched to software a couple of decades back, so do not have anyone I can lean on for advice. Appreciate your candidness as do not need to waste money either.

Really just started my search in earnest. I only went the SA route as it seems the main function I need and had not yet found scope that fit your earlier advice. A scope would clearly be more versatile, but better ones seem to be adding more channels and more functions than I need/want.
 

NTK

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No prob, from the description, knew it was mainly for RF work. OTOH, just started looking and am not getting many solid recommendations. While it idles. could just be a home network monitor. ;) TBH, am a hack EE. I have worked with many over my career, but switched to software a couple of decades back, so do not have anyone I can lean on for advice. Appreciate your candidness as do not need to waste money either.

Really just started my search in earnest. I only went the SA route as it seems the main function I need and had not yet found scope that fit your earlier advice. A scope would clearly be more versatile, but better ones seem to be adding more channels and more functions than I need/want.
For audio uses, we don't usually need dedicated spectrum analyzers. We just run FFT on the signals captured by the sound card or USB interfaces, and that is our spectrum analyzer. There are many free software for that, @ Instrumental has mentioned a few. And of course, REW is a popular one here.

If you are interested in a "turn key" product, and don't mind spending a little bit more, you may want to take a look at the QuantAsylum QA401 (reviewed here). The product web page (scroll down to "More Reading" section) has a lot of good information and examples on how to measure power amps.

Amir only uses his APx555 for his measurements and no scope. The APx555 can measure at 24 bits all the way up to 1 MHz. I couldn't find the maximum upper bandwidth for the QA401, but as its maximum sampling rate is 192 kHz, it must be be somewhere between 20-96 kHz. The advantage of oscilloscopes are their much higher bandwidths, but at the expense of much lower resolution (often only 8 bits). For example, it is nice to have a scope so we can look at the residual switching noise at the amp outputs -- and for that we shouldn't need high resolution. It is also informative to look at square wave responses (but we'll also need a waveform generator for a nice and sharp square wave source for the input signal). Practically all digital scopes can perform FFT and will function as spectrum analyzers too.
 

Instrumental

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The green eye-pattern from the Siglent is well-known from telecom as an example
of phase modulation that is common in satellite and terrestial systems, 16PSK in the
picture. It's used in all (GSM and up) mobile phone systems and is "somewhat demanding" to
get to grips with. Nasty combination of maths, hardware and signal theory. Not much
DIY going on there. I do the satellite DX-ing as a hobby but it's a different world from
audio, 20 GHz does not have much in common with 20 kHz. One thing is a bit similar
though, no one has ever seen a radio wave but many have strong opinions anyway.
 

JP

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When I was very little my dad built a visible V-8 engine kit. That one had an electric motor for the starter along with spark plugs that were miniature bulbs and a functional distributor that ‘fired’ them.
 

GeorgeWalk

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When I was very little my dad built a visible V-8 engine kit. That one had an electric motor for the starter along with spark plugs that were miniature bulbs and a functional distributor that ‘fired’ them.

I built that same kit with my father. It took us weeks to finish it. That was fun.
 

Digital Mastering System

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I've inhaled more solder fumes than fresh air on some days...
As a matter of speech...
My tech at work would sometimes put in tants backwards so they'd blow and she could hear me swear clear across the lab! They really make a POP!
 

Helicopter

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I have been cleaning up a pile consumer grade panasonic and realistic labs units with rca speaker outs with and without integrated 8 track players. Also restoring 8 track tapes so they are playable again.
 

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restorer-john

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I love restoring old calculators. Here's an early LED scientific from Commodore circa 1976. (44 years old!)

commodore (2) (Medium).jpeg
commodore (3) (Medium).jpeg
commodore (1) (Medium).jpeg


1976 fabricated ITT display driver
IMG_3833 (Medium).jpeg


1975 MOS MPS7529 VLSI introduced in 1976/7 .
IMG_3834 (Medium).jpeg


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National Semiconductor 7 segment LED array.
IMG_3835 (Medium).jpeg

IMG_3836 (Medium).jpeg
 

dfuller

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More guitar amps. This time, a Peavey 5150 II in for some serious mods.
 
OP
pma

pma

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OK, not the worbench, but lab bench. Acoustic spectrum of a plasmatron running at 110kW power. Almost ideal omni-directional sound source, the spectrum is almost the same everywhere, even behind the door and wall :). The cut-off near 20kHz is a video bandwidth.

plazmatron_spektrum_s.png


vyfuk.jpg
 
OP
pma

pma

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Sure, the smaller the better.
 
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