[francisdemarte]

Searching the thread a lot of people see little or no difference with an external power source over USB. I didn't notice any differences between using external power and usb power from my desktop.

People who do have issues tend to be on laptops with noisy power supplies.

 

[thoppa]

Quote:

Originally Posted by francisdemarte /img/forum/go_quote.gif Searching the thread a lot of people see little or no difference with an external power source over USB. I didn't notice any differences between using external power and usb power from my desktop. People who do have issues tend to be on laptops with noisy power supplies.

Yeah, I can only hear very slight changes, so slight in fact that I think USB power wins if you need convenience. But if not, then using a battery or a very good linear regulated supply is the way to go. Maybe the 'best' thing is to use a good reg chip like an LT1084 ?

I've been trying various filters to see if I can improve the USB but so far I've not had any great success. I want a physically small filter that will fit in the case, but most small chokes with reasonably high Henries have too much dc resistance and so reduce the input voltage.

The other option is to use large value capacitors with low esr, like Sanyo oscon, together with the existing ferrite beads, so I'm going to look into this next. But to be honest, I'm just having fun, I'm not really gaining much, if any, real performance increase.

 

[MisterX]

Quote:

The other option is to use large value capacitors with low esr, like Sanyo oscon, together with the existing ferrite beads, so I'm going to look into this next. But to be honest, I'm just having fun, I'm not really gaining much, if any, real performance increase.

Been there tried that and found there was very little to be gained there but don't let me discourage you from having some fun.

 

[thoppa]

Yeah, I think the chips and circuit design are so good the performance is confined to a very narrow envelope, with very little room for tweaking. In a word, excellent.

But then part of the fun of diy is discovering circuit behaviour and playing with it.....right ?

So far, my 'best' tweak is filtering the usb power with a pi filter of 1uF x7r - 100uH 5amp toroid - 1uF X7R. This has a corner frequency of around 15Khz so it seems to work where the onboard regs are less effective and provide a bit of a cleaner supply way up into the Mhz region.

One thing I'm wondering about on the y1 usb board, would be the effect, if any of swapping the position of c10u and r4u. If I did this then it would be easier to implement the pi filter. R4u would become a 1uF ceramic and vbus could be connected to VCC via the toroid and the second 1uF ceramic could go across VCC to gnd.

What do you reckon ?

BTW, I'm pairing the Y1 usb as the i2s source for a y2.

EDIT : the change would make L2u and r4u into an lr low pass filter - 3.2x10^-11 H and 47k R = no effect, but would it affect U2U or the host pin ? I assume not....

 

[MisterX]

Quote:

But then part of the fun of diy is discovering circuit behaviour and playing with it.....right ?

Absolutely.

If you are using the the USB board as an I2S source what are you doing with the DAC portion of the Y1 board?
I am thinking with all of the unused holes in that section and with the way the power is routed you could mount the filter parts over there (where the theoretical EMI is less likely to effect the analog output?) and it would give you a real easy way to jumper it in and out of the circuit for comparative testing?

 

[thoppa]

Quote:

Originally Posted by MisterX /img/forum/go_quote.gif Absolutely. If you are using the the USB board as an I2S source what are you doing with the DAC portion of the Y1 board? I am thinking with all of the unused holes in that section and with the way the power is routed you could mount the filter parts over there (where the theoretical EMI is less likely to effect the analog output?) and it would give you a real easy way to jumper it in and out of the circuit for comparative testing?

Yep, that's exactly what I'm planning - on y2, the toroid will connect vbus to vcc through J5 and locate near the jp2 jumpers. The second 1uF X7R will go across vcc and gnd on J5. on the y1 usb board, I might replace C10U with an oscon and move c10u so it shunts vbus and gnd near J2U, or put it near J5 on y2.

I will probably completely remove the y1 dac board for another project.

EDIT : I tried two Oscons 47uF as the caps for the pi filter with a 100uH and it blew the regulators on the y2. oops. I changed the 3.3v no problem but pin 3's solder pad for the 4.75V reg came off the board. umm. So I soldered on a bridge wire between pins 1 and 3...... and she's fine.... enough fun for one day I think....

Here's the final filter : 100uH coil connecting Vbus and VCC and Sanyo 100uF across VCC and Gnd. It has a significant effect on noise, and doesn't introduce any emi. However, the USB earth is still very polluted and this is now the limiting factor for everything. Anyone know how to filter an earth line effectively ?

Here are scope photos showing the noise on the usb power line before the filter and the noise after the filter, which is the same as the noise on the earth.

 

[amb]

For those sourcing parts for γ2, AD8656ARZ and OPA2365AID are both out of stock at Mouser, Digikey and Newark, Digikey shows that they are restocking AD8656ARZ in just a few days (3/3/2010). Mouser has some OPA2365AID coming in in early April, and you can buy from Newark's Farnell-UK direct-ship and receive them in 7 business days (a flat service fee of $20 applies, look at their part number 61M8029).

FYI.

 

[mace1337]

Aww damn, just when I wanted to order parts.

I see that Mouser is also out of the TI SRC and Crystek OSC for the y2

 

[amb]

mace1337, since you're in Holland, maybe your best bet is to source as much parts as possible from Farnell.

 

[MisterX]

The OPA2365AID is available from Avnet or Arrow, either of which are cheaper for US buyers then the Farnell export service.

 

[mace1337]

Quote:

Originally Posted by amb /img/forum/go_quote.gif mace1337, since you're in Holland, maybe your best bet is to source as much parts as possible from Farnell.

Yeah, but Mouser or Digi-key aren't bad either, since they have free shipping over an X amount, and Mouser takes care of import taxes as well. With Digi-key you have to pay the UPS man at the door.

Both Mouser and Digi-key ship fast, Mouser uses Fedex and Digi-key UPS, potayto potahto.

 

[slowpogo]

I'm looking at building the σ25 + σ24 to power the y2. I did the calculations on the σ25 page, and it seems for the y2 you would need a 9VAC secondary transformer, at least 3.3VA, to meet the 5VDC/300ma requirement of the y2.

Of course, after going through the data sheets on amb's site for part numbers, it appears that neither Mouser, Digikey, Farnell, or Allied stock any EI30 transformers that meet these requirements. In the event that I might be able to sneak by on 3.2VA, I checked for those, but none of those are in stock either.

Am I missing something or is it not possible to build a σ25 + σ24 to power the y2 at this time?

 

[MisterX]

Where are you located?
If it was me I would snag one of those $12 Multicomp toroids from Newark (# MCFM70/09) but they are much more expensive for people in other countries.



http://www.head-fi.org/forums/f6/gam...ml#post6169217

 

[Volkum]

Quote:

Originally Posted by slowpogo /img/forum/go_quote.gif Am I missing something or is it not possible to build a σ25 + σ24 to power the y2 at this time?

I ran into the same thing. I have 567-1040-5-ND on intergalactic backorder with Digikey (estimate is 6/9). I figure I'll just use USB power until I get it later this year or get a toroid if I feel the need.

 

[ShinyFalcon]

1k or so units will arrive on June... for the time being, use a wallwart or another transformer... Many to choose from.