[ablaze]

pardon my newbieness with a multimeter.

so, I connected a 1/4"-1/4" cable (both male) to the headphone out of my amp (X-can), but when i put the ground lead of my multimeter to the corresponding ground on the male end thats not connected to the amp, and the other lead to the tip, the multimeter just reads 0mV. am I doing something wrong?

 

[Northern Oak]

ah ... ablaze, found you here. What exactly are you trying to measure? Seem to suggest that you male tip is shorted to the ground of the male...

 

[ablaze]

Hi

I think I got it. it should be AC not DC voltage right?

 

[ablaze]

oh I'm trying to figure out if it was my X-cans that killed my Sony CD3000s

 

[Northern Oak]

Firstly, you need to establish whether it's the headphone or X-can that's giving you the problem.

To check the X-Can for leakage current, the MM has to be in series, unlike how you measure voltage by putting it parallel.

X-Can left/right channel -> MM -> left/right channel of the headphones

Check for the DC leakage current, the problematic channel would show probably much higher current than the other channel.

3-Pole Plug

Another thing is to check whether you CD3K is shorted. Not too sure if measuring resistances between right channel vs gnd and left channel vs gnd would do but you can give it a try.

Just a suggestion because I don't really have the tehnical expertise to guide you...

 

[ablaze]

mm..ok. so i'm understanding
lets say if i wanna test the right channel, i place one lead of the multimeter touching the right channel of the amp, the other lead touching the right channel of the headphone's jack, and I suppose I need another wire connecting the ground of the amp output to the ground on the headphone? is that right? or am i waaay confused?

 

[Northern Oak]

Quote:

Originally posted by ablaze Hi I think I got it. it should be AC not DC voltage right?

I wonder if measuring the AC voltage would really help ... a resistivity check on your CD3K and the DC leakage test would probably tell you where the problem lies.

You should try the resistance check first before the DC leakage test on a good cheapo headphones and your faulty CD3K. ( DC leakage test on the CD3K may not help since it may already be shorted, thus showing high leakage current.)

Have you checked the connectivity and resistivity of your 1/4"-1/4" cable? Left/Right/Gnd of One end vs Left/Right/Gnd of the other?

2 Scenarios that may occur
1. Both fail DC leakage test and probably your good cheapo phones may die as well -> X-Cans at fault.

2. However, if the good cheapo headphone is okay with the DC leakage test, then it may imply that it's your CD3K that's at fault, having the internal short.

Not too sure if the high leakage current may burn the transducer causing it to short ... I have been able to burn opamps causing shorts between pins ...

Anyway, just a suggestion , (Singlish) Me not BERY TEK-nical ...

 

[Northern Oak]

Quote:

Originally posted by ablaze mm..ok. so i'm understanding lets say if i wanna test the right channel, i place one lead of the multimeter touching the right channel of the amp, the other lead touching the right channel of the headphone's jack, and I suppose I need another wire connecting the ground of the amp output to the ground on the headphone? is that right? or am i waaay confused?

Yes, you're right ... you had to have the circuit in closed loop, BTW have you checked the resistivity ?

 

[Northern Oak]

Check your PM ...

 

[ablaze]

OK. back after some testing, whilst playing a mono test tone, with the volume pot about halfway, left channel and right channels show a difference of about 0.1mA (approx 2.5mA vs 2.6mA) that looks ok right?

can't really measure resistance on my Sonys .. cos they're under repair right now

anything else I should test?

oh btw, thanks for the offer to help

 

[Northern Oak]

Doesn't seem like a DC leakage current problem, more probably an internal short in your headphone perhaps, I guess Rameish has also advised you to try out a cheapo headphone which I don't think will have any problem. More likely it's your CD3K headphone.

Hope you get it back soon and cheers!!!

 

[ablaze]

thanks Oak. looks like its not the amp. anybody else have any thoughts?

 

[rickcr42]

measuring -

you will need a audio signal generator to drive the amp input and a load on the output that simulates the headphone (load resistance/inductance)

then measure across the output load with either an audio millivolmeter or an oscilloscope

Check the links section for software versions.

while not as accurate as a hardware version they are fine for finding blatant problems or doing setup/ testing

the ouput load can be built into a stereo phone plug to match the amp output

surprising this has not come up before (or i missed it)

ALL workbenches should have input and output loading plugs (easy as hell to DIY, you should see my amp load mounted on big ass heat sinks)) , a signal source and a means to measure the output

 

[Northern Oak]

Quote:

Originally posted by ablaze thanks Oak. looks like its not the amp. anybody else have any thoughts?

With the news that one tranducer gone and the other "not quite right", I would think twice about the amp. Previously, I thought it's just one of the channels but now it seem like both are problematic ... hmmm ,,,

 

[ablaze]

I don't know if Sony's trying to rip me off by repairing the other channel as well..cos it sounded fine to me. BUT anyway..if it tests fine ie. no DC leakage, what else could it be, that would be pin-pointable to the amp?

rick: thanks for the post. I'm not really a DIY-er so much of what you're saying flies way over my head

anyway, any thoughts of how my amp might have killed my cans (IF it was the amp that is)?