audio testing of amplifiers...espically home audio and PA...

[bsco]

I have to ask.....when checking the sound quality of audio amplifiers, I tend to use music.....and I use different types of music....suck as rock, classical, etc.....does anybody here use select ranges of freg tones? I am just curious as to what other people use and why they use it....hope I posted this in the right place and if I have not, then forgive me and correct me....
Cheers,
Bernie

[Enzo]

Oh I suppose I could use white noise or pink noise, and a spectrum analyzer and studiously check out freq response, but yes, I generally use music. I tend to use country music because it tends to be cleaner than rock. Even for guitar amps, I do my basic work with a music signal. It frees up my hands, a guitar is in the way at the bench. And it has a full range of freqs, so I can hear if the high end or bottom end are lacking, and it sounds clean or it doesn't.

[bsco]

Oh I suppose I could use white noise or pink noise, and a spectrum analyzer and studiously check out freq response, but yes, I generally use music. I tend to use country music because it tends to be cleaner than rock. Even for guitar amps, I do my basic work with a music signal. It frees up my hands, a guitar is in the way at the bench. And it has a full range of freqs, so I can hear if the high end or bottom end are lacking, and it sounds clean or it doesn't.

Thanks Enzo.....I have some country cd's here as well.....I was planning to actually make up a test cd with various types of music on there and use that.....I was just wondering why somebody would use test tones.....the music store uses them to test their PA systems....and sometimes when I get the stuff to repair and run music through it, I can't find anything wrong.....so this is whay I had asked the question.....
Cheers,
Bernie

[The Dude]

I usually just use music for final testing. I may occasionally use a guitar sample on a guitar amp so that I have both hands free to work (rather than actually playing a guitar). On rare occasion I use test tones for final testing and that's mostly when reconing speakers. Sometimes speaker issues only show up at certain frequencies. A certain tone will make something vibrate in a bad way. And, of course, you'll want to use a tone when troubleshooting/signal tracing.

[bsco]

I usually just use music for final testing. I may occasionally use a guitar sample on a guitar amp so that I have both hands free to work (rather than actually playing a guitar). On rare occasion I use test tones for final testing and that's mostly when reconing speakers. Sometimes speaker issues only show up at certain frequencies. A certain tone will make something vibrate in a bad way. And, of course, you'll want to use a tone when troubleshooting/signal tracing.

I've tried using tones but find that music is better for me...I agree about testing speakers themselves with tones....I saw a sales rep at the music store the other day and they were using tones to evaluate a book shelf speaker...the thing can only reproduce a certain band of frerq...once you go lower than that then the poor speaker unit is not going to sound good...and can probably cause the IC chips or transistors inside to drastily overheat....so now I have it here to repair so to speak.....I didn't argue with anybody....I just took it back with me....I just repaired a powered speaker cabinet....and to trouble shoot it and do final testing, I used a cd player with a cd playing......for both trouble shooting and testing after the repair was done.....not saying if something is right or wrong.....that is why I wanted to get a feel for what other people use.....not only that, I find a continious tone to be hard on the head when used for extended periods of time...doesn't really matter what the freq is....for me anyway......so I just wanted to see what other techs here on the forum used for their normal day to day repair on their bench........
Cheers......

[drewl]

I play guitar and use a mic to check as well as music.
I'll run my IPod onto it into big ass load resistors to check full power out while monitoring output with a scope.

[gbono]

HiFi/home theater can be a much more complicated to test especially if you want to see how the digital end of things are working. There are lots for demo disc out there with multichannel audio content (THX, Dolby, Crown etc). I find that human voice program is a good way to test HiFi/Home theater/PA - or at least it's a good subjective test. I found a disc of human voices that was used by a video game company to audition different "characters". Really good content to test with.

MI gear doesn't require that sophisticated of test content since you are dealing with a very subjective audio process. Sine waves are great for testing the response of the system and checking that it does produce it's rated output. Forget trying measure frequency response unless you want to see how the EQ section works. I use the appropriate instrument to do a listening test but have also used digital synths in demo mode, CDs and a player, etc.

I suggest keeping notes so you can keep track of changes, front panel settings, etc.

[Enzo]

It all depends on what you are trying to do. I largely use music, it is easier to listen to than a tone. 1kHz is REAL annoying. 100Hz I can listen to a long time. But in general music tells me a lot about the amp. On the other hand, if there is some distortion, other than clipping, it is hard to see on a scope. A sine wave through an amp gives me a known waveform that I can look at and see where it no longer looks right. And yes, if there is a speaker or cabinet buzz, then a sweep with a sine generator lets me home in on the exact frequency that is sensitive. I don't have to hope my music hits the magic note often enough to be useful.

[trem]

Regards "pumping" music into a guitar amp......could I use the Headphone Out jack from my Windows computer.?
What would I do, just take one side of the TRS plug and solder it onto a 1/4" connector...run it the front of the amp.....or maybe there are all kinds of adapters that would take me from that size stereo plug to a Mono 1/4" plug.?
Thank You

[Enzo]

I have a cheap Technics stereo receiver on my bench riser. I can listen to the FM or a CD if I want. There are outputs from it on my speaker patch panel, so I can drive either the bench speakers or other speakers under test. But on the rear panel is the typical RECORD OUT jacks, and I simply have a cord plugged into one of those and trialing around front where I can use it. You got a stereo? For that matter a plain old CD player has outputs, as do cassette decks.

[DrGonz78]

Regards "pumping" music into a guitar amp......could I use the Headphone Out jack from my Windows computer.?
What would I do, just take one side of the TRS plug and solder it onto a 1/4" connector...run it the front of the amp.....or maybe there are all kinds of adapters that would take me from that size stereo plug to a Mono 1/4" plug.?
Thank You

Yeah I do this all the time. I have just a mono cable 1/8inch plug on one end and 1/4 inch on the other. There is a way to just plug the 1/8 inch side in the output of the computer headphone output where it is not fully inserted. So you get the tip making contact with just the ring contact of the jack(right channel). As I recall when I plug in the entire plug it grounds out the output. Now it's a bit ghetto but it works for me just fine. Sure a stereo 1/8inch plug on one end and then if you made your own version of the mono 1/4inch on the other side, that would work too.

[trem]

10-4
Thanks.....

[Leo_Gnardo]

Regards "pumping" music into a guitar amp......could I use the Headphone Out jack from my Windows computer.?
What would I do, just take one side of the TRS plug and solder it onto a 1/4" connector.

That's one good solution.

maybe there are all kinds of adapters that would take me from that size stereo plug to a Mono 1/4" plug.?
Thank You

Definitely, if you still have a Radio Shack open nearby. I've had to get a couple of mini TRS to dual RCA, then an RCA to quarter-inch, always a bunch of those around, then into the amp. You'll hear one side of the stereo which in most cases sounds just fine. No point in trying to "mono" with a wire jumper, your headphone driver chip may object to that and let you know by going up in smoke.

[bsco]

I have a cheap Technics stereo receiver on my bench riser. I can listen to the FM or a CD if I want. There are outputs from it on my speaker patch panel, so I can drive either the bench speakers or other speakers under test. But on the rear panel is the typical RECORD OUT jacks, and I simply have a cord plugged into one of those and trialing around front where I can use it. You got a stereo? For that matter a plain old CD player has outputs, as do cassette decks.

I have a Sanyo stereo from 1974......I use that as a signal source as well....plus I have a small portable cd player with a line out and a headphone out...I use that alot for testing PA systems.....and powered speakers............Then a Fender Strat and Les Paul for testing guitar amps...for bass amps I use a Fender Precision Bass...early 80"s......

[trem]

That's one good solution.



Definitely, if you still have a Radio Shack open nearby. I've had to get a couple of mini TRS to dual RCA, then an RCA to quarter-inch, always a bunch of those around, then into the amp. You'll hear one side of the stereo which in most cases sounds just fine. No point in trying to "mono" with a wire jumper, your headphone driver chip may object to that and let you know by going up in smoke.

Yeah.....I may actually have the parts to do this very thing. Bought a bunch of adapters from Parts Express a few years ago...forgot I had them.....but all that kind of stuff, yes.
Thanks For Reminding Me