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Comments for my PCM2702 DAC layout? - Page 41

post #601 of 613
Quote:
Originally Posted by tomb View Post
Sounds like you know where to look. IC1 should be producing 3.3V across C11. I can't tell you what pin to focus on, but a pic or two may help if you don't solve it.
Thanks. I think I'm gonna wait for a new iron, as getting in between IC1 and C7 is currently pretty problematic.
post #602 of 613
Yep - IC1 needed a bit more solder. The dac is now working but producing a fairly audible buzzing. Could this be attributable to interference? I haven't yet cased it.

Also, for anyone starting out, I found upgrading from the Weller SP23 to the WCL100 to be a great help

(Thanks to tomb for your assistance and the website; I've been enjoying my MM amp for quite a while now.)
post #603 of 613
Quote:
Originally Posted by Dan55 View Post
Yep - IC1 needed a bit more solder. The dac is now working but producing a fairly audible buzzing. Could this be attributable to interference? I haven't yet cased it.

Also, for anyone starting out, I found upgrading from the Weller SP23 to the WCL100 to be a great help

(Thanks to tomb for your assistance and the website; I've been enjoying my MM amp for quite a while now.)
You are welcom for the assistance and thanks for the kind comments.

I don't mean to be critical, but perhaps if your soldering was a bit dodgy on the IC1 reg, maybe you should check IC2, the PCM chip and all the other joints. The only thing I can think of is an intermittent connection or short that's causing the buzzing.

One trick many people use is to hold the board up to a very bright light or directly next to a light bulb. The fiberglass PCB is translucent enough that you can see through the solder joints for any bridges or un-soldered joints.
post #604 of 613
Quote:
One trick many people use is to hold the board up to a very bright light or directly next to a light bulb. The fiberglass PCB is translucent enough that you can see through the solder joints for any bridges or un-soldered joints.
I highly recommend this! With my poor eyesight it is the most effective method of finding poor and/or bridged joints.
post #605 of 613
A high-power LED flashlight is perfect for this. Just don't blind yourself
post #606 of 613
Thanks, guys. I tried using the way-too-bright LED I have on my Millett Max, but it required some awkward contortions. I'll have to retrieve my LED flashlight next time I'm upstate...
post #607 of 613
For those of you with great memory, it seems the issues I had with my Bantam were confined to that one computer. It must have handled USB power differently than everyone else's. That was a Toshiba L300D, but now I have an HP dm3-1020CA which I just used to listen to the Bantam for some 3 hours without the horrible screeching. At ease, gentlemen.
post #608 of 613
Well, just wanted to say thanks for a great DAC. I bought the Glass Jar Audio kit a couple of weeks ago to go along with my wonderful Millett MiniMax.

Got the kit yesterday and built it today. All in all, I was expecting to suffer with the SMD work (I confess that I ordered the PCM chip pre-soldered), but much to my surprise that took only a couple of hours; with the bulk of my suffering being the casework, just as usual.

Anyway, thanks again for this killer DAC!




cheers!
post #609 of 613
If I use a different Q1, do I size C9/C10 by the crystal's load capacitance value?

I'm looking at 559-FOXS120-LF for a substitute Q1, and this one does not have a load capacitance value. Do I simply omit C9/C10 if I use this crystal?

559-FOX120-20-LF has a 10pF load capacitance value, and is a bit tall, but I'm assuming it will work as well.
post #610 of 613
520-HCU1200-20X looks to be an alternate to the out of stock crystal.

559-FOXS120-LF has a load capacitance of 10pF (read the datasheet). You would need to change C9/C10.
post #611 of 613

RCA cable puzzles me

I was moving along pretty well putting together my first Bantam DAC and now find myself tripped up just before the end. My USB connections are straight to the board and the cable looks really nice coming out one side of the case. But, I’m not sure about the RCA 3.5mm connections. I would like both RCA cables to come of the other end of the case and terminate in male connections that I can plug directly into my MiniMAX. On the quality cables I bought for this, there is a solid silver wire in the center and many strands of thin copper wire wrapped around a sheath that surrounds the center wire. I’m assuming this is what I should use to make the ground connection. HOWEVER, when I collect all of these copper strands and twist them together into a straight piece, the result is too fat to fit into the ground connection on the DAC board. So, first of all, am I right about these copper strands being the ground? If so, how can I deal with the fact that when twisted they don’t go through the hole? Am I using the wrong cable? Can I solder a wire to this twisted strand and connect that to the ground? I would really like to avoid mounting female connectors on the side of the case and then plugging male connectors into that from the outside. Thanks in advance for any help with this.
post #612 of 613
Quote:
Originally Posted by rbarth View Post
I was moving along pretty well putting together my first Bantam DAC and now find myself tripped up just before the end. My USB connections are straight to the board and the cable looks really nice coming out one side of the case. But, I’m not sure about the RCA 3.5mm connections. I would like both RCA cables to come of the other end of the case and terminate in male connections that I can plug directly into my MiniMAX. On the quality cables I bought for this, there is a solid silver wire in the center and many strands of thin copper wire wrapped around a sheath that surrounds the center wire. I’m assuming this is what I should use to make the ground connection. HOWEVER, when I collect all of these copper strands and twist them together into a straight piece, the result is too fat to fit into the ground connection on the DAC board. So, first of all, am I right about these copper strands being the ground? If so, how can I deal with the fact that when twisted they don’t go through the hole? Am I using the wrong cable? Can I solder a wire to this twisted strand and connect that to the ground? I would really like to avoid mounting female connectors on the side of the case and then plugging male connectors into that from the outside. Thanks in advance for any help with this.
Yep - that's what I was going to suggest: solder a jumper (flex wire, not a resistor lead).

Just an FYI, but the PCB was designed for standard 22ga multi-strand flexible. All I ever use is 22ga multi-strand Teflon-insulated SPC (from John's Wire Shop on ebay).
post #613 of 613
Quote:
Originally Posted by tomb View Post
Yep - that's what I was going to suggest: solder a jumper (flex wire, not a resistor lead).

Just an FYI, but the PCB was designed for standard 22ga multi-strand flexible. All I ever use is 22ga multi-strand Teflon-insulated SPC (from John's Wire Shop on ebay).
Thanks Tom. Took your recommendation about wire when I was putting the MiniMAX together and stocked up on that from John's Wire Shop. So, time now to finish up!
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