The disappearance of analog audio signal generators

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udok

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Joined 2011
#1
I read a lot about analog signal generators in this forum...

But after looking, i did not find any new and buyable decent audio signal generator.

I mean the good quality ones with very low distortion and 20 dBu output into 50 Ohm.
With real knobs and +-0.1 dB accuracy (HP, Tek, Krohn-Hite, Bruel-Kjaer, Leader..).

Is anyone using a soundcard or a distortion analyzer nowadays for audio measurements?

How have you replaced the audio signal generator?
 
#6
Refugee1 said:
I am restoring an old Marconi one that kids you into thinking it is portable until you grab the carry handle.
Marcoin TF1101 sig gen
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Isn't the word "portable" interchangeable, and synonymous with, "equipped with handle"? At least that was the standard joke even back in the 1970's and 80's when I was lugging a lot of that test equipment around. I recently had occasion to pick up a classic HP 200C audio oscillator and was surprised by the mass of the thing. I'd guesstimate it to be 3 or 4 times the weight of my TDS1002B 'Scope, which is roughly the same cubic volume.

A lot of the better tube-based test equipment was still used through the 70's. In February, or possibly March of 1973 my college part-time job had me performing the annual proof-of-performance testing on a small-town AM radio station. At that station the last half mile to the transmitter site required either snowshoes or a snowmobile during the winter months. Getting the test equipment to the transmitter shack required two toboggan trips - and not just because the gear was especially bulky (even though some of it WAS bulky!).

I'm not sure things improved a whole lot after everything was solid state. When I did the commissioning testing for satellite earth terminals in the early 80's, the worst thing about rooftop installations was often hoisting test gear up the vertical ladders leading to the equipment penthouses.

Good luck with your restoration effort! That's a project I'd be interested in taking on, at least partly because I've admired every piece of Marconi test gear I've had the opportunity to use. Keep us abreast of your progress, and please report your results in the low-distortion audio oscillator thread that's been running for a couple of years now.

Dale
 
#9
Udok,

Your best bet is the HP8903 this is analogue and pretty common - although its only good to about 0.002% THD+N 20KHz BW (complete system).

I have a basically unused Agilent version (not HP) 8903, it had been installed in one of my racks for 8 years or so but I cannot recall if its ever been powered - its in "as new" condition...

I'd need to find it (now that I'm setting up my new lab) - I'll measure its generator on its own, I suspect the THD analyser section itself is the limitation.
 
#10
AndrewT said:
That 4gang capacitor must cost a fortune.
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Yes it is a very special part and quite rare but this time it is going to stay in the original equipment.
The Marconi was acquired from the sale of a collection of vintage kit after the original owner sadly passed away.
It cost me £7.50 (about ten bucks) plus about the same in liquid tax for the transport. British cars don't run on gas but instead run on liquid tax instead😱
I have now worked out what parts need to be replaced and then it will see some power.
The build quality just says keep it.
 
#11
Is anyone using a soundcard or a distortion analyzer nowadays for audio measurements?
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Yes, but as stated 10 KHz square waves aren't perfect even with a 192 KHz card.

I also have an old HP8903 Audio Analyzer for low distortion sine waves, an HP function generator (don't remember the number) for square waves, and a pair of 204C sine wave oscillators for IMD tones. These go from 5 Hz to 1.2 MHz with distortion in the .05% range and can often be found used for reasonable money used. Avoid the ones that have the battery option. The old Nicads have long ago corroded and usually mess up the unit.
 
#15
#16
udok said:
I mean the good quality ones with very low distortion and 20 dBu output into 50 Ohm.
With real knobs and +-0.1 dB accuracy (HP, Tek, Krohn-Hite, Bruel-Kjaer, Leader..).

Is anyone using a soundcard or a distortion analyzer nowadays for audio measurements?

How have you replaced the audio signal generator?
Click to expand...

I think the K-Hite is still sold new. Many analyzers have audio gen included so no need for a seperate one.



-RNM
 
#17
Possibly it worth finding this Kenwood generator as used.
Kenwood AG-203D Audio Signal Generator | TEquipment.NET

This item is now reproduced by a Chinese factory in the last two years.
But I did not bookmarked their website.

Personally I own something far more powerful from this analogue world.
DMM Test tools

And about budget? High quality items of analogue world never was cheap, you are buying ultimate quality engineering and not resistors and capacitors in a plastic bag.
 
#18
Another one:

Krohn-Hite 4402B Ultra-Pure Sinewave Oscillator 1Hz to 110kHz | eBay

I would start at an $200,-- offer.

Good for THD -120dBc and better after some opamp rolling.
Did it, worked out, R.N. Marsh modded his too, with good results.

But, honestly, if your not running an amp production line,
for DIY all you need is Victors oscillator, down to -140dBc,
hard to measure, not even sure an APx555 ( $ 30000,-- ) could do it.
At these levels it is distortion cancelling area ( I hear Sam Groner, yelling, 😎 )
 
#20
ghg said:
But, honestly, if your not running an amp production line,
for DIY all you need is Victors oscillator, down to -140dBc,
hard to measure, not even sure an APx555 ( $ 30000,-- ) could do it.
At these levels it is distortion cancelling area ( I hear Sam Groner, yelling, 😎 )
Click to expand...

Turns out that some folks who use both the SYS2722 and APX are reporting lower noise threshold with the SYS2722.

Victor's device is an absolute steal!
 
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