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Carrie USB-Powered Headphone Amplifier
Sep 23, 2009 at 2:49 AM Post #421 of 913
Do you get that 1A inrush current if you use a switch? Where are you connecting your Fluke? You mentioned 0.222A, so I'm guessing you saw 1A at the DCP output. The differences are the DCP02 and the non-switched pot, so there is already two methods of inrush current limiting that will remain in the final version.

I'm not an expert in bench supplies, so I'm just curious: is some of that inrush current because of your power supply turning on? Does it make a difference if you apply power while it's still on versus switching it on? Also, isn't the power present in the USB port before you plug in the cable? If so, there could be a difference between your bench test and the actual plugging in of the cable in the computer.

That 70mA figure you're getting, is that quiescent current? Could you clarify what you mean there?

It seems I didn't think deeply enough into the capacitor banks, so that's something I'm gonna have to revisit.

Finally, thanks for the comments and for pushing the limits of the design. This is all useful stuff for the final version. I think I'll plugboard the power supply to see what works best.
 
Sep 23, 2009 at 2:55 AM Post #423 of 913
Quote:

Originally Posted by joneeboi /img/forum/go_quote.gif
Do you get that 1A inrush current if you use a switch? Where are you connecting your Fluke? You mentioned 0.222A, so I'm guessing you saw 1A at the DCP output. The differences are the DCP02 and the non-switched pot, so there is already two methods of inrush current limiting that will remain in the final version.


No way to put in the switch now. The 1A was going into the DCP02. By datasheet it only says it can output 0.222A

Quote:

I'm not an expert in bench supplies, so I'm just curious: is some of that inrush current because of your power supply turning on? Does it make a difference if you apply power while it's still on versus switching it on? Also, isn't the power present in the USB port before you plug in the cable? If so, there could be a difference between your bench test and the actual plugging in of the cable in the computer.


When I had the Carrie powered through the DAC, Windows would shut the port down the minute that I plugged the DAC in. Now that being said, there was still power to the DAC as the power LED was on, but it would not show up in device management.

Tried taking the power off the Carrie and putting it back on while the bench supply was on. Much more reasonable now, but still 542mA. Combine that with the startup of the DAC and it is still drawing too much.

Quote:

That 70mA figure you're getting, is that quiescent current? Could you clarify what you mean there?


Yes. I am measuring this by powering the Carrie from the bench supply and measuring current with my Fluke (an old 8024B).

Quote:

Finally, thanks for the comments and for pushing the limits of the design. This is all useful stuff for the final version. I think I'll plugboard the power supply to see what works best.


No worries, this is what prototyping is for.
 
Sep 23, 2009 at 12:11 PM Post #424 of 913
I convinced myself that cobalt mute is correct on the power supply with the caps in series. As it stands we are charging 2 banks of 6 caps to 5v, not 12 caps to 10v. Due to this we are also loosing half our reserve power. So we have caps that are way over rated in voltage that are also half the capacity of the original mini 3. the mini3 has 2 470uf caps in parallel across the rails. If cobalt is correct with his calc, even hsi 220uf bank is only charging to 600uf or so.


Capacitors in Series
 
Sep 23, 2009 at 12:53 PM Post #425 of 913
The overvoltage on the caps is a good thing.

Think about it this way - if the TLE2426 blows (which has happened), the caps see the full rail to rail voltage. That's why in my case I did 10V caps for the 9V DCP02. If you have the DCP010512 that joneeboi specs, I'd make sure that you'd have at least 16V caps.
 
Sep 23, 2009 at 9:56 PM Post #431 of 913
My Carrie lives, just need to do the end panels. I am listening to it as I type. I am using ASIO4all, Carrie with all stock parts from the BOM and Wimas in the Bantam, Sennheiser HD-515. I like the sound, plenty of authority on the bass, even mids and nice if not sparkley highs, I am not a fan of hot highs anyway. I'll let it run in for a few days and report back on the sound.
Being concerned after reading the posts about draw, I went and plugged it into 5 PCs and two laptops. I did not have an issue with the USB ports shutting down. The PCs were Dell Optiplex and the laptops Dell Latitude. I left it powered on let it discharge for a few minutes between attempts. I do not have a setup to allow me to capture the current draw.
 
Sep 24, 2009 at 6:50 PM Post #432 of 913
The Carrie PCBs have just arrived, but my Mouser order hasn't :frowning2: I just hope it arrives later today or tomorrow so I'll be able to work on the assembly during the weekend. I'll let you know when they're up and running.
 
Sep 24, 2009 at 9:37 PM Post #433 of 913
joneeboi, I think the channels may be reversed on the phone jack. AFAIK on a stereo TRS connector the tip should be the left channel, the ring should be the right channel and the sleeve should be ground. Of course I may be wrong but maybe others can check too.
 
Sep 24, 2009 at 10:16 PM Post #435 of 913
Testing on my laptop puts the channels in the correct configuration. I did not notice this before as I always set L & R through ASIO4all out of habit. But I checked using default drivers and the windows setup and configure options and it checked out. Hmmm...
 
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