AMB Laboratories DIY Audio

[judderod]

Hello all

Firstly I'd just like to say well done to all the developers of this project for creating very well received DAC (and many other devices by the looks of things)!

And secondly well done for keeping the costs realistic - keeping with one of the concepts of DIY - creating something that costs less than a professional equivalent, but hopefully performs better.

I'm looking to try out a new DAC. I'm using a high end home cinema processor at the moment to do DAC and pre-amp duties, but it's quite old, and having opened it up I have found the DAC chip is a fairly basic CS4226.

I was thinking of buying a TPA buffalo 3 (can I mention that on here?), but it is just so expensive once I add in all the extra items needed.

In keeping things as simple as possible, I'm looking for a way to drive the γ2 without the need for a γ1 by using a seperate SPDIF to I2S converter module. The only thing that is causing me some trouble is the clock generator side of things.

TPA sell an S/PDIF Transceiver Module that has a crystal on board, but I suspect that is more for the SPDIF clock than for driving the I2S output.

Can anyone recommend me a solution feed the γ2 with SPDIF, without the need for the γ1?

In the future, I'd be looking to swap out the SPDIF module for a USB-I2S module, but I'm going to wait until the hardware and drivers are more mature, with higher bitrates and multichannel decoding. Or perhaps a HDMI-I2S module if someone finds a way to get around the licencing issues.

[amb]

Why not use the γ1? It has a built-in S/PDIF-to-I2S converter (the CS8416) and supports three inputs (coax/optical/USB). The γ1 is also highly configurable (see all the possible configurations documented at the γ1 website), and then you could even have sub-configurations within those categories to tailor it to your needs. Don't need the DAC on the γ1? No problem, you don't have to populate it (and its support parts). Don't need USB, then you can skip the USB portion altogether... these are just two of many possibilities.

By using the γ1 and γ2 together, you retain the neat mate-together modularity, and perfect fitment in the Box B2-50 aluminum case, with all PCB-mounted switches and jacks with no wires whatsoever.

[DorkVader]

And the gamma1 really isn't that expensive (in my opinion). If you want it internal, the box enclosure looks really sharp, even if you have it in a case. I saw one build that had it mounted on the back, so the inputs were accessible, though passthroughs are pretty easy to wire up as well. Ofcourse, it also looks good outside. It's pretty impressive.

[linux-works]

there's a very hot new 'usb dac' that gives i2s output and a pair of analog outs. you have to hack the i2s but its easy (I'm about to do it, myself, and I'll report back how well it went). best part is that its standards based, does not need drivers (except windows, lol! isn't THAT a switch!) and goes up to 192k/32bits over usb asynch (audio class 2 stuff). you do NEED a computer since its usb based and so you'd lose spdif inputs. but if you want 'something with i2s output' this might be an option:

http://www.diyaudio.com/forums/digital- ... idget.html

[linux-works]

another option is a board like this (ebay, china, sorry)
http://www.ebay.com/itm/Multi-input-con ... 0823030994



I bought one, am using it to test/develop my own firmware, but the hardware does work and it does decode spdif either back into spdif (reclocking) or into i2s. I'm using it only for spdif-spdif but there's an option for i2s on the board and some buttons to set it.

its not open source (so I'm doing my own that will use an lcduino for control) but the hardware is easy to follow. they did some things wrong so it will need some changes but nothing major.

[judderod]

Thanks for the advice. I understand the γ2 is designed to pair with the γ1, but for various reasons I'd much rather skip out the whole γ1 altogether if I can. One of the reasons is that I have only done a little work with digital circuitry before, and as much as I'd like to learn all about what each and every component in the γ1 does before deciding which ones I can omit, I simply cannot justify the time at the moment given all my other priorities. There will almost definitely be some mistakes made, some additional components needed, and some trial and error required, and like I say as much as I'd like to do that, I can't afford the time that would be lost to other important things.

nother reason is that I am quietly skeptical that this device will sound that much better than what I already have (I know I'm being cynical), and I do not want to invest time in something that does not produce the desired end result.

@DorkVader Cost isn't really an issue, I just want the best sound possible for little initial time and effort. If I like it, I will prioritise some time to develop it. Maybe I've got it the wrong way round but it's that or stick with what I've got at the moment. The other thing is won't use the standard case. I think I'll need a larger one as I want to include an IR receiver so it can be switched on and off remotely, and I also want to include analog line inputs for pass-through when the device is off, but switched over to the γ2 with a DPDT relay when it is on and has digital sync. This is so I can continue to use my processor for day to day duties, yet only have to press a button on my remote to switch over to the γ2.

@linux-works I've seen that thread and have been reading it. It seems the USB-I2C module cannot be bought seperately, and even if it could, I would still need an external clock. The other problem is I'm set with Windows 7 x64.

As I'm writing I see you've posted about the ebay china module... Now that looks interesting. I guess that should be pretty much plug and play with the γ2? Do you know if it works with windows 7 x64?

[judderod]

Any further thoughts guys?

linux-works I've contacted the seller of that board about it being an I2S master and am waiting to hear back...

they did some things wrong so it will need some changes but nothing major.

Would you mind sharing your experiences?

[linux-works]

the maker of that board followed the datasheet *too* literally (lol). example: he has 75ohm R's across inputs to the chip pins when the 'sender' is a few inches away! no need for that. when you have a local cmos or ttl signal version of spdif you don't need to cap-block it and 75ohm shunt it. you might have to level match, though (this chip takes either .5v input or 5v input style and I think it defaults to .5v 'coax format' style in hw mode and only in software mode can you set it to TTL level).

I'm not sure the board maker did the 5v clock can to 3.3v level matching properly. I'd have used a v-divider instead of just a series R.

I would use pulse trafos for coax in and out. the data sheet and the vendor don't do that. the vendor should have even if the data sheet didn't list it.

I'd have to refresh my memory what else I didn't like. but at any rate, I'm going to do my own (quite a bit more than this, too!) and so this was just a demo board to get some direct experience with this chip.

there is a hole pattern for the i2s connector but he does not give a connector and it may even be possible that the firmware does NOT work for i2s! I have not tried. and with all china goods, there is NEVER support or updates. ever. and so don't plan on this being any kind of supportable board. I love the chip but I'm not in love with how this vendor implemented it.

the ebay module uses cm102 cmedia usb chip. very good chip and very standard. like all the main ones, it stops at 48k/16bit. needs no drivers at all for any os (well, maybe DOS needs a driver, lol).

[judderod]

Very informative - some great info there, thanks

So far it's linux-works 1, ebay seller 0! I still haven't heard back. I wonder if they think I'm talking gibberish, asking about I2S.

All too often I see boards on ebay that are just copies of IC evaluation kits. This one doesn't seem too different. At least you're knowledgable enough to know what to do to improve it. I'll certainly look to do those mods if I end up getting one.

So I'm still none the wiser with regards to directly driving the γ2 with SPDIF... It's starting to look like building and learning about the γ1 is my only option :S

Searching ebay for 'cm102' brings up a few cheap china DAC's. Perhaps I could piggy back the γ2 off one of those. Then again the SPDIF and USB side of things could be badly implemented and cause poor results. Hmmmm

[linux-works]

the cm102 is spdif-out only. there's another cmdia chip that does have i2s but its probably not a great i2s chip.

what does happen is the cm102 goes to the wm8805 and THAT's the magic dejitter chip. anything that comes out of that is 40ps of jitter or in that range. that's often a lower number than what comes out of any spdif source.

the y1 does a proper job of taking in spdif and putting out i2s. its KNOWN to work and needs no firmware. the chinese thing is not proven for i2s (its proven for spdif but you don't need that). the y1 is not too expensive and the pcb quality is top notch. the pcb quality on the china board is as bad as it can be (they all are, sigh).

if you are not hacking the wm8805, I would not buy this board. get the y1 and use that for i2s. its what I would suggest, really. again, its known to work and that counts for a lot