A look inside Emu 0404 USB...
May 16, 2007 at 5:23 PM Post #16 of 34
Quote:

Originally Posted by shuy /img/forum/go_quote.gif
is there an unamped line out to use my own amp?


That's what the line outputs on the back are for. Available on a single 1/8" mini TRS jack (stereo/unbalanced) or on left and right channel 1/4" TRS jacks for balanced or unbalanced use, depending on what type of plug is used.
 
May 17, 2007 at 12:54 PM Post #17 of 34
Quote:

Originally Posted by sejarzo /img/forum/go_quote.gif
That's what the line outputs on the back are for. Available on a single 1/8" mini TRS jack (stereo/unbalanced) or on left and right channel 1/4" TRS jacks for balanced or unbalanced use, depending on what type of plug is used.


will there be a diff in SQ depending on how the amp is connected? my amp has deparate L n R jacks, but my wire terminates as a single 1/8. is it worth it to mod the wire such that it's 2 separate jacks for the 0404?
 
May 18, 2007 at 5:46 PM Post #19 of 34
Quote:

Originally Posted by shuy /img/forum/go_quote.gif
will there be a diff in SQ depending on how the amp is connected? my amp has deparate L n R jacks, but my wire terminates as a single 1/8. is it worth it to mod the wire such that it's 2 separate jacks for the 0404?


I wouldn't bother. There might be a tiny difference in crosstalk, but that shouldn't be a huge issue. If you mod the cable, you would ideally terminate it with 1/4" TS phone plugs rather than RCA's--the jacks on the back of the 0404 are for phone plugs (TRS for a balanced connection, TS for consumer level/unbalanced.)
 
May 21, 2007 at 12:55 PM Post #20 of 34
Quote:

Originally Posted by sejarzo /img/forum/go_quote.gif
I wouldn't bother. There might be a tiny difference in crosstalk, but that shouldn't be a huge issue. If you mod the cable, you would ideally terminate it with 1/4" TS phone plugs rather than RCA's--the jacks on the back of the 0404 are for phone plugs (TRS for a balanced connection, TS for consumer level/unbalanced.)


Even though the 1/8" has 3 conductors and using the 1/4" jacks gives your 4?
 
May 31, 2007 at 9:10 AM Post #21 of 34
so hows the modding going guys?

Any one try a LM4562? Or had a go at the caps?

I'm running my RS-2s through it at the moment...but also use it as preamp for recording.

Any one braver than me out there?
 
Feb 11, 2008 at 7:58 AM Post #24 of 34
BUMP

I have an EMU 0404 USB and I am positive I am going to mod this thing. I've been looking at the layman's guide to hotrodding the x-fi etc and even the emu 0404 pci card which also uses an akm dac, albeit an older generation.

I want to swap the op amp for an ad8599, replace caps, decouple/short the buffers, replace the power supply wall wart with a linear regulated version, and would I even need the ERS paper etc for EMI/RFI if it's external?

I'd like some guidance on this, please. Any of those pro modders out there that has done the x-fi's and emu's please lend me some help.

Guarantee I'm doing this as I'm using it as an independent study at university, just need some more direction. I'm stuck trying to decide which caps I need to buy and replace and which to short etc. I already have 4 ad8599's coming. Also, why is there so many JRC2068s in there? are those buffers? do I remove them or what?

Thanks for all the help and I hope I get many helpful responses soon!

PS: Also for my senior project, I'm going to be creating a high powered Tripath based amp (150watts x 2) using this modded EMU 0404 USB and a pair of B&W DM601 Bookshelfs for display, I can't wait!
 
Feb 11, 2008 at 1:05 PM Post #25 of 34
If you want to know why there are so many buffers, take a look at the AK4396 datasheet for their suggested output stage. Each channel likely has two opamps to provide the balanced output, and possibly another to provide an unbalanced output, if the E-MU designers implemented something similar.

Just curious......have you studied that datasheet in detail to make sure that what you are planning will work properly?
 
Feb 13, 2008 at 2:07 PM Post #29 of 34
Are you certain that the buffers you plan to remove aren't in reality the devices necessary to drive your cables and speakers--that the DAC itself might not do it properly if you bypass the downstream circuitry?

Based on the fact that even with the existing opamps, the balanced outputs of the 0404 USB cannot drive high impedance headphones directly (I have tried)......so the output is definitely current limited. The analog output stage might also incorporate required filtering.

Also, not having opened one up and traced it out....it could be that the 0404 USB is designed to sum the inherently balanced output of the DAC to a single-ended signal, which is then fed to a chip that provides the capability to drive either balanced or single-ended outputs from the TRS jacks?

Are any of these issues a potential roadblock in your plan?
 
Feb 13, 2008 at 9:26 PM Post #30 of 34
how do you trace it out by sight? aren't pcb's multi-layered, or else you can see the pictures in the thread?

anyway, even if what you're saying is true, I can still replace crucial components like the line out and headphone op amps, as well as some of the capacitors with better ones right? I need to figure out which ones would be good for replacing, if not all lol (but that would be quite expensive I would think) and with which kinds.

The power supply is pretty simple and straight forward, I already have the parts, just need to have them soldered:

Regulated Linear Power Supply:

Jameco Electronics Power Supplies & Wall Adapters: VARIOUS : DV51AAT

Correct Sized Jack:

RadioShack.com - Cables, Parts & Connectors: Connectors & connectivity: 4.0x1.7mm Coaxial DC Power Plug (2-Pack)

and cut off the new power supply's jack off and solder the wire to the new jack and voila.

I also have 2 samples of AD8599's and 3 samples of LM4562's (maybe the LM4562's can be for the TS or Mic jacks?). This also depends on whether it's true that theres a difference in quality from the line out and the TS out.

Also would that ERS paper or something similar even be helpful for us, since it's already an external box?
 
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