[blaken]

is there any advantage to using BUF634U over OPA551UA? Just wondering because BUF634U costs about $3 more.

 

[pegasus21]

I did ask something related just a few posts above. So I'll ask you this. Are you even going to tap the power source for your Alien DAC from another amplifier? If you are not, you don't need the BUF634.

BTW, I'm looking to implement an amplifier circuit after the DAC and the amp will be tapping power from the USB +5V and Gnd. I don't know if it'll work though. Does the analogue out from the PCM2702 reference from it's own analogue ground rather than the USB digital ground?

 

[splaz]

Bit of a dig but just thought I'd say, you guys were right, definitely get the flux.

When I was shopping around to try and get some one guy, although he didn't have it, said it was great and you can pretty much 'sweat' the solder on.

That is a pretty good description, it was a lot easier and just seemed to make a brilliant connection and faster than usual.

Same goes for a good set of tweezers, I had been using some rather awkward cheap tweezers but they get really sore to hold for a while and I often dropped things because they didn't grip all that well. That was often a write off too, if they'd fall on the floor and bounced under the desk they could be anywhere. Picked up a nice set of tweezers and the need very little force to hold things, grip them well and are just all around nicer.

Anyway, in summary you don't need flux or good tweezers but they make life a lot easier.

 

[mb3k]

Quote:

Originally Posted by splaz Bit of a dig but just thought I'd say, you guys were right, definitely get the flux. When I was shopping around to try and get some one guy, although he didn't have it, said it was great and you can pretty much 'sweat' the solder on. That is a pretty good description, it was a lot easier and just seemed to make a brilliant connection and faster than usual. Same goes for a good set of tweezers, I had been using some rather awkward cheap tweezers but they get really sore to hold for a while and I often dropped things because they didn't grip all that well. That was often a write off too, if they'd fall on the floor and bounced under the desk they could be anywhere. Picked up a nice set of tweezers and the need very little force to hold things, grip them well and are just all around nicer. Anyway, in summary you don't need flux or good tweezers but they make life a lot easier.

I'm debating between two types, no-clean and RMA.
Digikey Part numbers:
KE1803-ND
KE1804-ND
Any recommendations, or benefits of choosing one over the other?

 

[splaz]

Well I'm just using a syringe of the only stuff I could find, Interflux IF 8300.

Apaprently that doesn't require cleaning, possibly it doesn't conduct. However I still clean it off with isopropyl as it makes a bit of a mess.

So basically if you're going to clean it off you can go with either, but I suppose if you're lazy you could go the no-clean.

 

[pipp]

Anyone tried using an external xo instead of the crystal ? Yea I know implementing this require some effort

 

[t52]

Quote:

Originally Posted by pipp Anyone tried using an external xo instead of the crystal ? Yea I know implementing this require some effort

btw. anybody know a good and reasoanbly simple crystal oscillator circuit which drives the crystal in series resonance (as that mode seems to have the lowest side band noise [aka jitter])?

 

[Calroth]

So, my final shipment of Alien DAC parts arrived the other day. It was time to build.

Before this project, I was a SMD virgin. The PCM2702 was the first SMD chip that I ever soldered. Hell of a way to start. Pasted the area with flux, clipped it down, soldered. Only made two bridges on the 5V side and the 3.3v side was perfect. Cleaned up one of the bridges with braid, the other was both to ground anyway. Soldered down the other parts, hooked up the battery (it's powered by 4 AA cells), jumpered S1 so I wouldn't have to buy another switch, and powered up.

The 3.3v rail was wobbly and all over the place. Oops, the regulator pin going to ground wasn't tacked down properly. Reflowed it, now a rock-solid 3.3v rail. The 5v rail looked great. Another cursory check with the multimeter and everything seemed OK. Or so I thought.

Plugged it in to the computer. Turned it on. Computer immediately shut down and would not power on again...

This was a Calroth-special screw-up. I jumpered S1 when powering from a battery. So I was dumping 6V back into the 5V computer power rail. Needless to say, this is an utterly stupid thing to do. Don't do it. (The computer eventually came back to life after I did some Mac voodoo on it, but it was an anxious time.)

Swore, cursed, etc. Cut the S1 jumper, went over everything with a fine-tooth comb (so to speak). Tried it out on an expendable computer. Windows complained about a malfunctioning device. Went over all the solder joins again. It turns out that the bridge on PCM2702 that I thought I cleaned up wasn't. It was bridged under the pins, ugh. Used a knife and a mapping pin, scraped it out and cleaned up as best I could, and reflowed the area. No more bridge.

However, now the 5v rail was shorted to ground. Went over the solder joins yet again. And again. A few hours later, tracked it down to another solder bridge on PCM2702 that I made cleaning up the first one. Cleaned that up. Plugged into the computer, powered on. Nothing exploded, nothing happened. Pulled out the multimeter again for another round of checks. It turns out that the 3.3v side of PCM2702, the side which I thought was soldered perfectly, wasn't actually soldered down at all. I thought it was because when testing for continuity, I was pressing down on the pins, forcing contact with the PCB...

Reflowed that side. Cleaned up the bridge that I made doing it. Plugged into the computer. It detected! And (to cut the rest of the story short) it works. Now I am going to bed.

I apologise to anyone who's read this far, for making you more stupid by reading this

 

[MisterX]

lol.

 

[splaz]

Calroth, knew the name was familiar. We were talking about the pimeta over at headphonic, I go by real name over there

, still haven't got round to building it.

Sounds like one of my stories, plenty of mishaps although minus the destruction.

I made a mistake on a PINT and went postal on the pot so I am putting my Alien DAC off for a bit as the anger is still brewing, in my mind i need to finish off the PINT before I start anything anyway. My SMD work was so nice on that too.....

 

[villekille]

I'd like to build Alien Dac but I missed the group order for the PCB..if someone has one for sale I'd like to buy it.

 

[rsabo]

Quote:

Originally Posted by villekille /img/forum/go_quote.gif I'd like to build Alien Dac but I missed the group order for the PCB..if someone has one for sale I'd like to buy it.

I think alf has some spares for sale, check the group buy thread.

 

[Calroth]

I have performed RightMark Audio Analyzer testing on my Alien DAC, and posted the results.

The playback computer was a desktop PC with the following sound cards, for comparison:

1. a Sound Blaster Digital Music (a cheap USB sound card)
2. the on-board Realtek ALC850 sound card
3. the Alien DAC
4. a Chaintech AV-710, using the high-quality output

The recording computer was a MacBook Pro using its on-board SigmaTel Audio sound card. I ran the outputs from above into the MacBook Pro's line-in port without any extra load, to simulate a headphone amplifier. All playback and recording was done at 16-bit, 48kHz.

The recording computer doesn't have the greatest sound card ever, so the numbers on the report aren't absolute. However, the devices can be compared to each other.

If anyone has any questions about my testing method, or has their own RMAA tests, please post.

Edit: I updated the tests; see this post. The original results are still available here.

 

[MisterX]

Something is fishy with your results because I have got the following frequency responce "graph" with every Alien DAC I have tested in "loopback" mode without a dummy load.

 

[Calroth]

It could be due to my input device, which isn't ideal (alas, it's what I have).