Hi psemeraro,
I'm new to audio world. I just got my Gigaworks and I would like to mod it as what you've done.
step 1 - do you mean remove the caps next to c71 and c72 and short it ?
step 4 - If I want to mod this, I can skip step 2 & step 3 right? And can you show me the connection for this step. A graph will be much helpful.
Thank in advance.
I'm new to audio world. I just got my Gigaworks and I would like to mod it as what you've done.
step 1 - do you mean remove the caps next to c71 and c72 and short it ?
step 4 - If I want to mod this, I can skip step 2 & step 3 right? And can you show me the connection for this step. A graph will be much helpful.
Thank in advance.
Bill F.,
I've been reading this plus the epic DIY DAC thread and I notice that you used the 10K:10K Jensen. There have been a bunch of people using 600:600 transformers, apparently with pretty good success. Jensen has a app note up that recommends a 600:600 transformer with a RC filter.
I'm planning on calling Jensen to order a couple of transformers on Monday after they reopen after the holidays. As an old hand at this stuff, what would you order? I was planning on buying the [FONT=Verdana, Arial]JT-11-EMCF [/FONT][FONT=Verdana, Arial]600:600 and copying the circuit in the app note, but now I'm waffling[/FONT][FONT=Verdana, Arial].[/FONT]
Opinions from the experts here that have been hacking these DACs would be greatly appreciated.
Thanks,
Jim
I've been reading this plus the epic DIY DAC thread and I notice that you used the 10K:10K Jensen. There have been a bunch of people using 600:600 transformers, apparently with pretty good success. Jensen has a app note up that recommends a 600:600 transformer with a RC filter.
I'm planning on calling Jensen to order a couple of transformers on Monday after they reopen after the holidays. As an old hand at this stuff, what would you order? I was planning on buying the [FONT=Verdana, Arial]JT-11-EMCF [/FONT][FONT=Verdana, Arial]600:600 and copying the circuit in the app note, but now I'm waffling[/FONT][FONT=Verdana, Arial].[/FONT]
Opinions from the experts here that have been hacking these DACs would be greatly appreciated.
Thanks,
Jim
Actually, I use JT 11-DMCF 600/600, i've never tried 10k/10k. I'm no expert by any stretch, but the 10Ks could be problematic with capacitance issues and drive capabilities. BudP is the trafo man and he has come to the conclusion that around 1.5-2K would be the ideal target, but the inductance is probably the more important number. There is a low freq rolloff when you start to run out of inductance at low freq, depending on the source impedance that the trafo sees. You can see it in Jensen's response graphs with different source impedances. Generally, the bigger the trafo physically, the less problematic they are. The 11-EMs are slightly smaller than the 11-DMs but should be fine for this app., and they are really great trafos. I got mine used, for a song, off of Ebay, should have bought all that the seller had. I use them purely passively with nothing else but the RC filters, and you don't need the offset balancing arrangement shown. The 4398 chips don't have that problem. I wouldn't hesitate to buy the 11-EMs.
Read Bill Whitlocks article on audio trafos in the white papers section of the Jensen website, it's a gold mine of info.
Best, Bill
Read Bill Whitlocks article on audio trafos in the white papers section of the Jensen website, it's a gold mine of info.
Best, Bill
Glad I could help. Resist any temptation to hook anything to the primary center taps, it would be inviting disaster for the dac chip.
The 250 ohm primary series resistance should be fine with a .001 cap across the primaries, and the secondary RC circuit is also fine. If you can hear the filters doing anything the caps are too big. Their f3 is around 150khz.
The 250 ohm primary series resistance should be fine with a .001 cap across the primaries, and the secondary RC circuit is also fine. If you can hear the filters doing anything the caps are too big. Their f3 is around 150khz.
After I get the transformers installed in the DAC, I'm planning on checking the frequency response to make sure it is flat and running a bunch of square waves through it to make sure they come out relatively square. And looking for high frequency "junk". I can't imagine there's too much more that can be done to "tune" a transformer setup.
thanks again,
Jim
thanks again,
Jim
I'm pretty sure the USB input is synchronous. I don't think there's any way to get the DAC+Computer into async mode.
I added a M2Tech USB->SPDIF interface from my computer which adds an bitperfect async USB driver and it made a huge difference. The DAC didn't get listened to much except as background filler with the direct computer USB connection.
Jim
I added a M2Tech USB->SPDIF interface from my computer which adds an bitperfect async USB driver and it made a huge difference. The DAC didn't get listened to much except as background filler with the direct computer USB connection.
Jim
130mm wide
175mm long
37mm high
look on ebay for typical R-core transformer dimensions.
Modushop Maggiorato 230 x 280mm case is perfect for this DAC:
modushop.biz
Nice case, and not too expensive ($32).
Too bad the shipping charges to North America are so high.....
$61 for non-traceable 3-week delivery???
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