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PCB Group Buy for the "DAC + headphone amp" Project

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#181
hey folks... Since my name is on the PCB, I'd like to do the modifications myself. I'm on vacation right now and I'm away from my computer and Eagle, plus I'm moving in the new year so it'll be mid-late January before I get into the changes.

My planned changes include:

definite:
- changing AVR to Mega48, saves a couple bucks
- adding a front panel power/status LED, microcontroller driven.
- Surface mount voltage regulators, TO-252 instead of TO-220, fixes case clearance and provides better heatsinking. I'll use the adjustable version and the same part # in all four places.

likely:
- Using two dual op-amps for I/V instead of a single quad op-amp.

maybe:
- having 2 oscillators instead of 1; the AD1896 will be clocked at the same 29.49, and the DAC at 49.152MHz. A 74xx393 sync counter will generate clock/FS for the DAC.

As for the 'optical loopback' thing, that's an odd feature that only a couple of people may use... but since there's room on the PCB for it and it's easily left unpopulated, I'll probably do it.
 
#182
gmarsh said:

definite:
- changing AVR to Mega48, saves a couple bucks
- adding a front panel power/status LED, microcontroller driven.
- Surface mount voltage regulators, TO-252 instead of TO-220, fixes case clearance and provides better heatsinking. I'll use the adjustable version and the same part # in all four places.

likely:
- Using two dual op-amps for I/V instead of a single quad op-amp.

maybe:
- having 2 oscillators instead of 1; the AD1896 will be clocked at the same 29.49, and the DAC at 49.152MHz. A 74xx393 sync counter will generate clock/FS for the DAC.

As for the 'optical loopback' thing, that's an odd feature that only a couple of people may use... but since there's room on the PCB for it and it's easily left unpopulated, I'll probably do it.
Click to expand...
Gary,
Those mods sound very positive......definitely worth the wait for a few weeks to get the best possible layout.
By then maybe there will be an even larger order for the group buy.
Robert
 
#191
Well, I am definitely going with two PCB's not just one.

Also, may be it would it be possible to have different hole
patterns for the electrolytic caps so one can use eventually
different caps with 3.5 mm hole spacing.

Cheers

Kay
 
#192
OK, all updated 🙂

kct - 2
tobias_svensk - 1
avarko - 2
eapavant - 1
rjkdivin - 4
ystkkmkr - 3
jormajj - 2
Mike D - 1
Apogee - 1(2)
renfrow - 1
bobgroger - 1
Ryssen - 1
genome - 1


Totals: 21 (22)
(possible in brackets)

Just a few more to go 😀

To reiterate the costs, etc.

Boards are $30.50 each. $0.50 from each board will be donated to diyAudio.com

Shipping:
I got the info on the postal increase for Small Packet Airmails, effective January 20th (around there), it's up 4%. This is affects US and overseas. For Expedited Parcel (helloooo fellow Canadians), it's up 6%.

Including the Canada Post increase, shipping will be: $7.60 or $14.61 overseas (depending on destination and qty of boards. They are HEAVY) for Small Packet Air. Lettermail to the USA isn't an option anymore, due to recent changes. Rates will be $6.20/$8.22/$12.74 (board qty dependent) for all US states and dependencies.

Canada can vary drastically by postal code, especially to Ontario. I'll use either a prepaid Xpresspost mailer or Expedited, whichever is cheaper.


Also, may be it would it be possible to have different hole
patterns for the electrolytic caps so one can use eventually
different caps with 3.5 mm hole spacing.
Click to expand...

I talked to the PCB guy and he said he needs an entire new set of Gerber's for any changes. With MLB, it's not as simple as single or double sided.

Cheers!
 
#196
Cheers guys! 🙂

kct - 2
tobias_svensk - 1
avarko - 2
eapavant - 1
rjkdivin - 4
ystkkmkr - 3
jormajj - 2
Mike D - 1
Apogee - 1(2)
renfrow - 1
bobgroger - 1
Ryssen - 1
genome - 1
gmarsh - 1
Algar_emi - 1

Totals: 19 (21)
(possible in brackets)
 
#200
Ryssen said:
Can the DAC drive a lineout direct?Would it be possible to do some line out´s on the board?
Click to expand...
Make a 1/4" stereo to dual RCA cable. 😉 I'm using the TPA6120 IC to do differential to single ended conversion, so you can't really tap a line out anywhere inside.

Rather than having a Toslink output, would anyone have use for an AES/EBU input in the same space? It won't be on a XLR connector since there's no room for one, so I'll have to use a Mini-DIN, 1/8" stereo jack or something.
 
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