[jeffreyj]

Nice job! I was going to do the same thing to a Telex P-500 USB audio interface... until I opened one up, but that's a subject of another post.

Concerning the "gross" analogy to aos' outboard DAC/ADC, the Sonica (presume it was the regular Sonica, not the Sonica Theatre) seems to lack audio inputs! (sigh..) It was my second choice for cheap, hopefully-hackable USB audio interface. Can you please post the part numbers of the chips on the Sonica board so it can be confirmed whether it is capable of having an ADC patched in???

 

[Voodoochile]

Thanks, Jeffrey.

Here's a link to a thread regarding the parts in the Sonica.

I'm going to add a pair of RCA jacks to the rear, and just patch them directly to the amp, for use with analog sources. Why is it you wish to go A to D, then D to A in one box? Or did I miss something?

 

[jeffreyj]

Quote:

Originally posted by Voodoochile Thanks, Jeffrey. Here's a link to a thread regarding the parts in the Sonica. I'm going to add a pair of RCA jacks to the rear, and just patch them directly to the amp, for use with analog sources. Why is it you wish to go A to D, then D to A in one box? Or did I miss something?

To make an excellent spectrum analyzer for much less than $2500! It is very difficult to get meaningful results of one's amplifier designs when the sound card used to generate test signals has 0.22% THD, 40% IMD (with 11/12kHz test tones) a frequency response of -1.25/-3.57dB from 20Hz-20kHz, etc. (That would be the stellar performance of my Dell laptop's sound card, an ESS Maestro...

)

Thanks a lot for the link to that thread. I suppose I could have done that search myself...

Anyway, in the spirit of DIYing it, here's a
link to a headset evaluation board document that might help the uber-geeks among us hack this baby even more.

Just looking at the thing's datasheet, I got the impression that it could not perform full duplex audio in stereo because it only has 2 DMA channels (compared to the TAS3020A's 4), but the evaluation board document makes no reference to a half-duplex limitation... Strange. All in all, the chip looks to be very amenable to hacking. The codec used in the evaluation board is the WM9707CFT . Looks interesting, for sure.

 

[Voodoochile]

Well that makes some sense to me. I was wondering why, within the scope of a headphone amp, you'd want to do that!

Interesting.

 

[jamont]

Quote:

Originally posted by jeffreyj To make an excellent spectrum analyzer for much less than $2500!

If you come up with a way to do that, please let us know. I'd certainly be interested...

 

[Voodoochile]

Yes!
$2,350 less would be ideal.

 

[yejun]

how did you shot these pics?
I thought it was a 3d model when looking at first picture.

 

[Voodoochile]

Just a digicam. The exposure is whacky on the first two because the angle is low... and the television is behind it- and on. I should have turned it off, the extra light was affecting the meter. Low contrast. Shot on a card table that happens to be black.

The third one is at a higher angle, and is how they typically turn out. I do use a light and umbrella, as it's so much easier to deal with than trying to cut the flash way down, or bouncing it. Leftovers from my photography days, when I used to shoot a lot of b+w headshots. The umbrella is a bit of a hassle, but makes for nice soft, easy to control lighting.

 

[jeffreyj]

Quote:

Originally posted by jamont Quote: To make an excellent spectrum analyzer for much less than $2500! If you come up with a way to do that, please let us know. I'd certainly be interested...

Can't say the idea is original... any sound card + software for the job can be a spectrum analyzer. The problem is, though: is the sound card better than the device it is testing?! Obviously, if the sound card has 0.22% distortion then trying to test an amp with 0.001% distortion wil result in... results for an amp with 0.22% distortion! Ditto with frequency response, IMD, etc. However, I can't swallow paying $300+ for a boutique sound card that still might not have top-notch specs. So I'm seriously considering "upgrading" a cheap one, or maybe even building one from scratch. Though, that might get too close to aos' territory

 

[tangent]

Quote:

I can't swallow paying $300+ for a boutique sound card that still might not have top-notch specs.

The $300 level cards really don't have much better specs than the $150-200 level ones. Instead, they tend to have more outputs, be more professionally-oriented (1/4" jacks instead of RCA, etc.), external breakout boxes, etc. If you don't mind running long RCA cables to the back of the PC, an M-Audio Audiophile 2496 is every bit as good as an M-Audio Delta 44.

Or, you can help me lean on ppl to test his modded Audigy-1 (4558 -> AD8620) against his stock Audigy and publish the results.

 

[antness]

You could check out the Lynx L22 soundcard for about $650. However, the best way is probably just to have a decent $150 sound card and a good external DAC.

 

[Chipko]

Quote:

Originally posted by Voodoochile Chipko- can you get them in the US? They do look nice!

the company is american so I think so:
http://www.rose-bopla.com/pmx/rsbpwe...orFrm?OpenForm

Their homepage leaves a lot to be desired but here's the Alubos series:
http://www.rose-bopla.com/pmx/rsbpca...ocument&res3=3 use the previous/next arrows to navigate the different models.

ELFA's page of the models (swedish electronics reseller)
http://www.elfa.se/elfa/produkter/en/2021148.htm
Click the "i" for a PDF with dimensions..

I can not recommend the end pieces with 9V battery compartment, the placement of the battery is dumb to say the least. It's better to wind some tape around the battery and wedge it.

 

[jeffreyj]

Quote:

Originally posted by tangent The $300 level cards really don't have much better specs than the $150-200 level ones. Instead, they tend to have more outputs, be more professionally...

That was my point about not wanting to spend $300 or more, and not get in return what really counts (better performance, not more gee-gaws)

Quote:

an M-Audio Audiophile 2496 is every bit as good as an M-Audio Delta 44.

And still not good enough! Besides, as the excellent folks at the RightMark Audio Analyzer site point out, it seems that most sound cards trumpet the performance of their codec(s) (or separate ADC/DACs), not the unit as a whole! Obviously, this is deceptive because the level of, for example, SNR that can be achieved is much more dependent on the board layout and support components than what the codec can theoretically achieve. And putting the card inside a computer's case - especially if that case is a laptop?! - well, you can forget about getting the -120dB noise floor a 24bit codec is theoretically capable of (it's actually a bit better than -120dB, but physics precludes achieving better than -120dB more or less, ymmv.)

Also, the actual cost of components inside even the most exotic, premium sound card (even those ridiculous contraptions I've seen with tubes in the output stage?!) is minimal compared to the engineering and, probably more than anything, the perceived clout of the design. Well, I couldn't give two shakes about the perceived clout and I can deliver very adequate engineering services to myself for free. So, I'd much rather take a really cheap USB based external sound card and only keep the USB to isochronous data bridge + driver software part of it, as I'd rather give myself paper cuts on the lips than design a device driver.


Quote:

Or, you can help me lean on ppl to test his modded Audigy-1 (4558 -> AD8620) against his stock Audigy and publish the results.

Given Creative's track record (and boy did they pick the right name, at least when it comes to inventing performance metrics!), I'm inclined to think that replacing its 4558s with AD8620s would amount to little more than "casting pearls before swine"

 

[Voodoochile]

Thanks for the linkage, chipko... I'll check them out. I like the powdercoat (vs anodizing) for a change of pace.

 

[beamrider]

That's one of the best looking cases I've seen in a while, is it a standard part, or did you customize the case? If standard, link to where I can buy a few of them, please!