Test equipment question,please.

30Weight

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#1
I've been busy bringing a Technics SE-A3 amp and Technics SU-A4 preamp combo back from the sonically dead.In the SE-A3 shop manual it says to use a distortion analyser between the o'scope and VTVM on the speaker jacks (while monitoring a 20khz signal from input to output,dummy load in circuit) to adjust Icq and clamp voltage.I'm missing one of those.I just hooked the o'scope and my dmm (repairing an old Simpson VOM,not done yet).I ran the output volume pot gain up to 28.28vac,as specified.Monitored both input and output.Nice clean signal all the way thru,no distortion and good gain.The vu meter showed about 150W.Got the voltage regulator set to 85.5 vdc and dc balance set to 0.00mvdc each channel,as specified.I was happy,adjusted nothing after that.Considered everything within spec.

My question revolves around the distortion analyser.I've found that with tools if I need it once,I'll need it again sometime.Some comments and recommendations please from those of you familiar with this piece of test gear.I've never used one before,seems like a handy thing to know about and use.I know they aren't cheap.I'm thinking about something used from one of the test equipment surplus dealers on the web.Something in the affordable/hobbyist range.Will I need to get one? Suggestions as to which one,please? Some info regarding their use would be appreciated also.

Thanks,
Lee

P1010185.jpg
 

laatsch55

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#2
Had that same question myself a couple years ago...being involved in the WOPL conversions I was getting a lot of the same questions from customers. Output is not that hard to do, get a good load cell and an RMS voltmeter and your set. But it was all the other; THD & N, phaselag/lead, residual noise, signal-to-noise tation, rise time/slew rate, crosstalk etc. I looked at used HP units as both Nav and Gepetto( Joe) had them , but man a lot of calculation still involved, and no printout capability.

So I stumbled on Audio Precision's website. It was pretty apparent I wasn't going to buy a new AP analyzer, bit did happen upon a used
ATS-1DD on e-bay. Knowing it was still a gamble I bit the bullet and sent this guy 4100.00, my ass was pretty tight till it arrived and i got to use it. What a phenomenal piece of equipment. Not only does it do all the above, it ptints it out in graph or table form. Simply a delightful piece of test gear....

Through other means I also acquired one of the Phase Linear factories RIAA cirve tracers built inhouse and one of their BPI 2,000 watt load cells. A Tektronix digital storage scopes to replace my old analog Leader LBO-308S and I was on the way....

A Fluke 179, a Fluke 355, and Simpson 260 (3) round out the test gear...
 

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laatsch55

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#4
Not anymore.....OH THE OTHER WHITE LEE!!! DAYAM...gonna take some getting used too...
 

30Weight

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#6
You guys crack me up.Easy way to tell us apart,I'll be the one askin'.................he'll be the one answerin' :)

I'll check their site out Lee,thanks.A bit overkill for me,but I like the part where it does the computation and documentation,challenged and lazy there.I know what you mean about sweating things thru all the way,regarding that price range.Pretty slick device there,Bob.Seems popular with the car install crowd......heard more than a few cruizin' by the shack that sure could use it.Price seems reasonable too.I'd much rather test the waters with a small amount of $ 1st before buying the stuff that require$ calibration$.Thanks
 

eminence1963

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#7
You guys crack me up.Easy way to tell us apart,I'll be the one askin'.................he'll be the one answerin' :)

I'll check their site out Lee,thanks.A bit overkill for me,but I like the part where it does the computation and documentation,challenged and lazy there.I know what you mean about sweating things thru all the way,regarding that price range.Pretty slick device there,Bob.Seems popular with the car install crowd......heard more than a few cruizin' by the shack that sure could use it.Price seems reasonable too.I'd much rather test the waters with a small amount of $ 1st before buying the stuff that require$ calibration$.Thanks
I know how this hobby can break the bank especially us hobbiest :clown:
 

gadget73

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I have an older HP 333a distortion analyzer. It can be something of a finicky thing to use since it involves a number of adjustments and tweaking to get it to read. You have to re-do all of that if you change the test frequency too. I need a good audio generator to pair with it. The one I have rings out at something like 2.5% THD, which is not at all usable if you want to test an amplifier's distortion levels to lower than that.

The HP doubles as a nice RMS voltmeter, so at least it will cut one piece of gear out of the chain. You can pick up the pieces to assemble a test rig for not a ton if you don't mind some manual work. Just keep in mind that the newer and easier to use it is, the more expensive it gets. My 333a I think was made in the early 1980s. Same with my 8640b RF generator. I think the only test gear I own that is newer than me by any degree is my digital voltmeter, and I've had that thing for 15 years.
 
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