AMB Laboratories DIY Audio

[orcinus]

Hi, folks!

Just popping in to say hi and share my experiences with- and photos of the γ2 build.

Finally finished the γ1 board this weekend after a lot of meddling with a few stubborn capacitors (that just wouldn't accept the solder until i've cleaned the leads and the pads for something like the 6th time). Also, the 1uF 50V AVX caps i've received ended up being 5mm instead of 2.54mm so it took me a bit of experimenting with bending the leads until i got them squeezed in. Hope they won't block anything on the γ2 board.

The SMDs were the easiest part, really. I did have some experience soldering them from before, tho, so i wasn't all that apprehensive about it. Interestingly, i was working on a much much tinier and more delicate SMT-only board a few weeks ago, with a non-regulated cheapo soldering iron and it turned out MUCH neater than this one (with a regulated iron and a finer/fresh tip this time).

However, all in all, it was a breeze. And the γ1 fired up correctly at the first attempt.
Mostly thanks to AMB's awesomely prepared and extremely detailed documentation

Some photos:









I've used three RC extension cables and some pin headers to connect the two halves for testing purposes.
So far, tried the old iPod earbuds (2nd gen) i had lying around, Stax SR-001s and Grado SR125. USB only, for now.

Sound was kinda harsh on the high-end of the spectrum with buds and Grados.
Stax was the exact opposite - bass heavy. But i don't mind any of it, since it was just a quicky test to see if things are operational or not.

Unfortunately, the γ2 board will have to wait a bit (got just the SMD's, resistors and some of the multi-layer caps on at the moment) because i'm out of 100nF Kemet caps. My order was 5 capacitors too short by accident (20 instead of 25), so i'm now missing 3 of them (C12, C14 and C27) and eagerly awaiting for the second order (via RS) to come through.

[amb]

Nice, clean job!

[DorkVader]

That's a really amazing soldering you have on the surface mount parts. It bolsters my confidence to try. You have a clean build, as Ti said, and you take excellent photographs. They are quite vibrant.

Good job all 'round.

[orcinus]

Thanks for the compliments
The soldering could've been a tad neater (perhaps some more desoldering braid work would've been a good idea), but the important thing is - it works.

I'm a bit OCD-ish when it comes to things like aligning the components on the board and reflowing the pins.

Anywho, i've hit a little snag while testing the optical in.
I can't get anything out of my Audigy 2 ZS Platinum Pro's optical out.

γ1 obviously works fine, because i get a stream from my MacBook Pro's optical out just fine.
And the Audigy's optical out also seems fine, because the γ1's switch goes green when i hook it up.
I'm assuming the problem is software-based. And probably has something to do with Creative's wonky Vista/Win7 support for older Audigy cards.

Does anyone here, by any chance, have any experience with that particular setup?

[amb]

I am not too familiar with the Audigy, but make sure your optical output is set up for PCM 2-channel stereo format rather than anything else (i.e., multi-channel surround sound).

[orcinus]

From everything i've read, it seems the only thing it can output is 2-channel PCM (unlike the coaxial which should be able to handle multichannel/Dolby stuff). Hm. Might just be an issue with Windows 7. It is an old card, after all.

Think i'll give it another go after i finish the γ2.

Oh, BTW, most of the "harshness" i've mentioned is gone at 96kHz/24bit.
Can't wait to hear what γ2 sounds like.

[orcinus]

Okay! The caps arriveth!
Gonna pick them up and probably get around finishing γ2 tonight

Oh, by the way, got some Rubycon ZLG 470 uF capacitors.
How suitable would they be for converting one of the outputs for connecting the headphones directly?

[orcinus]

γ2 assembled.
Problem popped up.

The sound coming out of the γ2 output is completely devoid of high frequencies.
I've got AD8656 on the board and 22µF caps on C20 and C26.

Any ideas on where i might start troubleshooting?

[amb]

Is U4 installed? If you're not using ASRC, then setting the filter switch to anything but the "C" position will cause severe HF rolloff if the source sampling rate is not 96KHz-192KHz. See the "Tech highlights" section of the γ2 website.

[orcinus]

ASRC is installed (SRC4192IDB).
Tried the filter switch anyways (in case the U4 is not functional), but it has no discernible effect to the sound.

Also, there appears to be no difference regardless of the input sampling rate.
However, the cutoff seems to change depending on what i hook up to the output - STAX w/ its preamp/driver unit has a sharper cutoff than cheapo earbuds (gen 2 iPod's) hooked up directly.

Edit: all the test points are reading correct voltages, except for 5V, which is about 4.9V or so.