Re: Audio test generator and measurement - can anyone suggest a good set?

Dave Daniel

The Tek TM500 and TM5000 series instruments are highly useful. It is important to note, though, that if you are going to target particular plug-ins, you need to make sure that you have the correct mainframe (500 or 5000), as not all plug-ins work in both. Some do, some don't I'm still trying to sort this out (I just bought a TM5006 and have had a TM506 for a few years). The distortion analyzer mentioned below (AA5010) only works in the 5000-series frames.

There is also a "canned" set of Tek plug-ins that were basically (I think) modified versions of the plug-ins put together in a frame to make a high-performance distortion set, consisting of  TM504A Mod WQ frame, SG-505 Mod WQ, FG-503 Mod WR and AA-501A Mod WQ plug-ins. The instrument manual refers to the collection as "F7523A1 Mod WQ Distortion Test Set". The manual is available on the web, but I forget from what web site I downloaded it. I don't have any experience with this set up, but it looks intriguing. Maybe someone else owns one and can elucidate.


On 4/22/2013 12:52 PM, David wrote:

--- In TekScopes@..., "cheater00 ." wrote:
> Hi guys,
> De-lurking as I've been doing some measurement equipment related shopping :)
> I'm slowly building up my workbench, and was wondering if anyone could
> suggest what gear to get.
> After getting a Tek 7704 I now need a good sinewave generator for some
> work. I thought to myself, why buy just a sinewave generator, when I
> could get a distortion meter? Those have sinewave and square built in,
> are of variable frequency, and it's better to have one large box than
> two large boxes.
> Could someone suggest a good distortion analyzer that can be had
> relatively inexpensively? I'm probably looking at vintage equipment at
> this point because it can be had fairly cheaply. Something around 100
> Euro would be a good start, but it's only a very roughly estimated
> price range.. maybe those things can be had for much less -- or only
> for much more? Note - doesn't necessarily have to be tektronix...
> although I'll be perfectly happy if it is.
> Also: are distortion analyzers always limited to 20 Hz - 20 kHz, or
> are there not-too-unusual ones that go below 1Hz and high above?
> What is the 'workhorse' distortion analyzer? Is there one or a few
> that were very good and very popular? It's important to me not to buy
> something relatively unknown, so that when it breaks I can find
> replacements, schematics, and people who know how to repair them.
> What other tools - other than a distortion analyzer - could I see
> myself using when building filters, mixers, amplifiers, etc? In the
> future I'd also like to work a bit on tube circuits, but this is not
> currently a major focus.
> My plan is to get a distortion analyser (with integrated square and
> sine wave oscillators), and I already have a frequency counter for the
> Tek 7000 coming in. I'd probably get a curve tracer at some point too,
> and maybe a precision current and voltage source or precision
> amplifier. Still need an esr/LC meter, I saw some boxes online. To
> round this off I'd probably get an isolation transformer and possibly
> variac (or both in one box). Currently not planning for a tube tester
> or for anything that can measure transformers. Am I missing something
> as far as the most basic measurement equipment goes?
> Thanks,
> D.

I've not heard of a distortion analyzer that contains a square wave generator, however, the HP 339A will certainly handle the oscillator and distortion analysis criteria. The frequency range is 10Hz to 110Hz for both functions.
The HP 334A has a wider frequency range (5Hz to 600KHz, and also has an AM detector to allow distortion analysis on AM signals), but contains no oscillator output.
Both are frequently available on eBay.

You might investigate the Tektronix TM500 series of modular equipment. The series contains oscillators, function generators, scopes, counters, pulse generators, etc. The modules plug into a mainframe/power supply. This flexibility means that you can build an instrument containing all the instruments that you need for frequency response, distortion, etc., into a single package. If your aim is for scope repair and calibration, you can assemble all the needed equipment into a single package, interchanging the modules as you wish.
Most are on eBay frequently. These modules are somewhat more costly than conventionally packaged bench test equipment, but their small size and interchangeability are great benefits.

All that said, the equipemnt that you should target is highly dependent on the type of equipment that you will be servicing. Give us an example of the types and quality of the equipment to be serviced and we can offer more pertinent suggestions.

Dave M

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