Audio Analyzer worthwhile?

[jjasilli]

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=390079304869&ssPageName=STRK:MEWAX:IT

I've been watching some of these items.  Sort of the swiss Army Knife of vintage testing equipment.  They combine a signal generator, VTVM, watt meter, dummy load, etc.  Is such a thing worthwhile?  Would a 'scope be more worthwhile (though obviouly more expensive)? 

[tubesornothing]

I wouldn't bother.

You can easily build a dummy load (I suspect **you** already have one). 

I don't the the IM distortion analyzer will be of any use.  When we want to measure diustortion it is more the characteristic of it, rather than the amount.  A scope would be a better tool.

The one nice thing about analogue meters it you can easily see the needle flicker - so that might be useful.

Signal generator is good, but if you do distortion analysis make sure you get one with a very low distortion (you have to specifically look for this) otherwise you will get 2nd harmonic distortion coming from the signal generator and this will mess up your results.


Also, I am not sure, but it looks like you can only do one function at a time.  That is a total PIA.

[jjasilli]

Thanks for the info.  My test equipment is primitive.  I guess I really need to get a 'scope at some point.  My signal generator is an old Mercury 1600 tube model.  Got it cheap on eBay. So far I've just used it to check that an amp is passing clear signal at various frequencies.  Don't know how accurate it is, or if it suffers from harmonics.

Right now I'm in the middle of one of those endless regressions;  work was just finished in the basement, so I can move stuff into storage. . . blah blah. . . so I can get more room on my bench.  At least now I know there's no nead to make room for an audio analyzer.  Other boat anchors are more important!   

[tubesornothing]

As you probably know, I love scopes. Man if you can get your mits even on an old one, I think you would really enjoy them.

[jhadhar65]

What do you guys think about this one?:

http://www.tubesandmore.com/scripts/foxweb.dll/moreinfo@d:/dfs/elevclients/cemirror/ELEVATOR.FXP?item=S-MAFGEN

I've been eyeing it for a while now.

And this:

https://amptechtools.powweb.com/scope.htm

[tubesornothing]

Wow, low distortion.  .05% nice.

[jhadhar65]

I don't know how much John wants to spend, but those two are appear to be the best things I've found for the money.  I always hold out for the cheapest with the most-est.  Think these two are it?

[tubesornothing]

I bet you could do much better on ebay.  I bought a new B&K that is low distortion and has programmable sweep.  Wasn't worth the money.  PIA to set to a frequency and PIA to set up a sweep.  I think a used older style analog one that I can manually sweep would be more than good enough.  It'd be nice that the dial could sweep from 10Hz to 10kHz in a single range.

But if you really wanna cheap audio generator how about using your PC and free software?

Speaking of which, how's the bitscope working out?

[jhadhar65]

I still haven't gotten it going.  I've even gotten a few software tools, including a complete o-scope and signal generator, but haven't tried any of them yet.  I'm too paranoid to connect my laptop to an amp, I think.

jjasilli - do you want to try the signal gen program I have?

[jjasilli]

jjasilli - do you want to try the signal gen program I have?

Sure, thanks!

Re the weber scope:  it's not clear to me if it's dual trace or dual channel.  If the former you can have 2 traces on the screen at the same time.  If dual channel you can switch from one trace to the other, but can't have both at the same time.  Also there are external oscilloscope switches which effectively make any scope multi-channel.

On-line at the Oscilloscope Store completely refurbished & guaranteed tektronix SS analog scopes are available from $199+.  Dual trace from $299+ 

Looks like I'm warming-up to this.

[sluckey]

Re the weber scope:  it's not clear to me if it's dual trace or dual channel.

It's dual trace. Got all the usual modes.
Vertical mode CH1, CH2, DUAL (ALT/CHOP), ADD, CH2 INV

[jjasilli]

So what do you guys think:  weber scope; bk precision 2120B sometimes available used about $150; refurbished & guaranteed tektronix?

[tubesornothing]

I would do a refurbished tek scope any day of the week.  Here is my favorite, the 2246:

[tubesornothing]

Whats the URL for the oscilloscope store?

[sluckey]

Here is my favorite, the 2246

Hmm, that doesn't look like a 2246. The 2246 I use at work looks like this... (see pic)

I have an old 465B that I picked up on eBay for $180.00. Sharp trace, fully functional, and calibration (although expired) agrees with my work 2246. I got lucky with this one.

[jhadhar65]

Here are the software downloads:

http://www.monsterfactoryamps.com/downloads.htm

Right click and 'save as'.

[DummyLoad]

I have an old 465B that I picked up on eBay for $180.00. Sharp trace, fully functional, an

you got a good deal on a damn good scope.

[jjasilli]

Whats the URL for the oscilloscope store?

http://stores.shop.ebay.com/The-Oscilloscope-Store_Tek-Lab-Scopes_W0QQ_fsubZ156669QQ_sidZ4707027QQ_trksidZp4634Q2ec0Q2em322

or just google "oscilloscope store"

[sluckey]

you got a good deal on a damn good scope.

Yes, I know. The 465B was the industry workhorse for many, many years. FAA still uses them and keeps them in the calibration program, but as they die, they're being replaced with Fluke 199C scopemeters. I still use one at work.

I was working in PMEL during the early '70s. When I arrived one day, everyone was standing around the scope calibration area. When I walked over, I saw they were gawking over the new scope --- a 465B.

The one I got on eBay was a good find. A scorned woman, who's hubby had disappeared with a mutual female friend, was selling all of hubby's toys.

[tubesornothing]

Hmm, that doesn't look like a 2246. The 2246 I use at work looks like this... (see pic)

Yeah that's it - I just quickly grabbed a pic off the net.

Hey jj, that scope store prices are a little expensive for way older scopes.  If you are OK with regular ebay, see if you can grab a newer model,just as long as they show a nice crisp sinewave, has tested OK and they are a seller with a good rep.  A lot of the sellers (rssurplus-xs for example) says "sold as-is" or others say "powers on fine" - those are just other words for saying "it is a piece of crap and I know it, but I ain't goinna say it".

I picked mine up for $250.  Not a steal, but a good price.

[tubesornothing]

This baby just went for $207 on ebay.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=310161604245

[PRR]

To get back to the first point:

> Sort of the swiss Army Knife of vintage testing equipment.  They combine a signal generator, VTVM, watt meter, dummy load, etc.

The "signal generator" is just the 60Hz wall-power for LOW, and a pretty cheezy 6KC oscillator for HIGH.

These test the two extremes of the audio band, simultaneously, which reveals two-tone interaction.

But it does not directly test the middle of the audio band. And a guitar-amp may well be stressed at 60CPS and 6KC yet cover the guitar range very well.

The IM test "assumes" the amplifier frequency response is "flat". Any film or hi-fi amp is flat enough. Many guitar amps are seriously un-flat... what are you really testing?

And IM readings are always mystifying. If the amp is happy, IM is what it is, and we've selected amp plans which (incidentally) have satisfactory IM. If a guitar amp is unhappy in an IM way, you don't need no silly meter to tell you it won't play two notes without a chorus of inharmonics.

The selectable impedance load meter is useful, but only up to 25 Watts. When these meters were new, 25 clean watts was a lot. The IM 2-tone signal will make less than 25W heat from a 25W amp, so you could stress somewhat larger amps. But if I put a single pure tone through my "13W" big-Champ, and crank it way up into overdrive, it will put 24W of heat in a load. So anything bigger is gonna smoke the IM-22's resistors.

The "VTVM" is only an ACVM. It will read AC voltages down to a milliVolt, below a simple AC/DC/Ohms VTVM, and well past the audio band (many DVMs won't read AC above 400Hz well).

In addition there is a filter and demodulator to recover the bent-up 6KC tone and boost it for reading.

So....

It is a very useful audio voltmeter, and often far cheaper than the nice H-P job, and maybe more reliable/fixable than my Boonton.

The internal loads are handy for -small- amps.

You can connect an external load, and if it is standard impedance (4,8,16,600) the meter will do the math for you, read directly in Power up to 150W (actually 1,500W, but that was inconceivable when this beast was sold).

It is fairly bulky.

I've owned one, rarely used it.

[jjasilli]

Yes it just doesn't seem worthwhile.  I do need a beefier dummy load than what I have now.  BUt th audio analyzer doesn't get me there.

The 'scope part of this thread has been great.  Looks like a Tek 2246 is in my future.  Looks to be quite functional in a small package and reasonably priced.

[tubesornothing]

This looks like a pretty good unit.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120459797683

He seems to sell a lot of laptops in bulk, has good reviews.

These statements hold the seller liable:

"This oscilloscope passes self test and self calibration. All four channels appear to work properly on both A and B triggers (see photos) . Although I have not checked it against all specifications, it appears to be in excellent operating condition. The screen trace is very bright with no burns. Physically, the case has very few scratches or dings."

"Terms: It will be shipped working as described. If not received that way, return it within 14 days and I will refund the bid price including the shipping cost."


You could probably get it for $250

[DummyLoad]

Yes, I know. The 465B was the industry workhorse for many years

in our camp, it still is. my dept. runs the CATV feed for our campus. we still have 4 of them.  in the late 80's, they bought replacements, tek 2235s. one the 2235's is door stop in my office.

apologies for the thread-jack...

in my opinion, a decent signal gen. (can drive down to 600ohm load) and even a "cheap" scope can't be beat. power load resistors can be had from parts-express (link below) for a fair price. a couple of 4 ohm or 8 ohm 100Wers should do for just about all but the most brutal of power amps.

http://www.parts-express.com/wizards/searchResults.cfm?FTR=load+resistor&search_type=main&WebPage_ID=3&searchFilter=load+resistor&x=0&y=0

[jjasilli]

Not a thread-jack. Well maybe techinically it is.  But this is great info for people who don't know much about scopes.

[tubesornothing]

I took a risk and picked up a 2246 for $100.  Sold "as is".  I totally lucked out.  Works just fine.

JJ did you pick something up?

[DummyLoad]

I took a risk and picked up a 2246 for $100.  Sold "as is".  I totally lucked out.  Works just fine.

JJ did you pick something up?

 :glasses9:  a bargain.

[jjasilli]

No scope yet.  Maybe for Xmas.  Meanwhnile I've been getting into pedals; and have 3 amps to fix for other people, and getting out some to jam.  Did I mention work?    I suspect a learning curve with a scope, but Im gettin there. 

[tubesornothing]

I suspect a learning curve with a scope, but Im gettin there. 

You?!?  I am sure you have it goin it no time.

If I see a real deal on a scope, I will give you a ping.