[Sathimas]

Hello,

I just finished my Mini³ and I'm going through the initial checks.

But when measuring the quiescent current draw as shown on AMBs site, I get 15mA instead of 10mA.

I'm kind of worried since the difference is very high.

Where could the problem be?
Up to that point there where no problems.

Thank you
Sathimas

 

[fordgtlover]

You will probably find the answer at the support thread over at
HeadWize: DIY Workshop > Mini³ v2: A portable headphone amplifier

Those guys have seen and heard it all on that build.

 

[n_maher]

What kind of DMM are you using to measure the current draw? I'm wondering if at current levels that low if it's really all that accurate. Also, if you're not seeing the current draw rise (i.e. it stays stable at 15mA) that might point to the fact that there really isn't problem. I think if it were oscillating you'd see the level rise with time.

Also, I second the above advice, post in one of the build threads so that the answer can be used by other builders easily.

 

[Sathimas]

I asked over at head-wize as you told me and - It's alive now!

My only problem is, that the background noise (white noise) is very loud.
Louder than on my Cowon D2 (I'm using Westone UM1).

I don't think thats normal, since the Amp was designed for mobile use ...

 

[bigcat39]

Quote:

Originally Posted by n_maher /img/forum/go_quote.gif What kind of DMM are you using to measure the current draw? I'm wondering if at current levels that low if it's really all that accurate. Also, if you're not seeing the current draw rise (i.e. it stays stable at 15mA) that might point to the fact that there really isn't problem. I think if it were oscillating you'd see the level rise with time. Also, I second the above advice, post in one of the build threads so that the answer can be used by other builders easily.

I most heartily agree with Nate. I'm a metrologist, and I'm here to tell ya, you get what you pay for with cheap DMM's People, these things are cheap for a REASON. Actually a bunch of reasons.

 

[xmokshax]

Quote:

Originally Posted by bigcat39 /img/forum/go_quote.gif I most heartily agree with Nate. I'm a metrologist, and I'm here to tell ya, you get what you pay for with cheap DMM's People, these things are cheap for a REASON. Actually a bunch of reasons.

so for measurements on the order of 10mA, a cheap DMM can actually be >= 50% off? does this hold true for ~50mA? i built a PIMETA a couple of months ago for which the quiescent current draw was about 10mA higher than the expected 40 or so. is this within the margin of error for a <$20 DMM?

P.S.: do you work for Fluke?

 

[NelsonVandal]

The noise level should be very low in this amp. It might be the cause of the excessive current draw. That kind of errors is not expected even from cheap DMMs. If the noise is eqaully strong in both channels, look closer at the ground channel opamp for bad solder joints, and go through all components to see you put everything where it belongs.

 

[Sathimas]

The current draw is OK according to AMB (wrote this on Headwize).

All parts are in correct place.

I'll have a look at the ground OPA and resolder the pins.