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γ2 with RPi network streamer

gamma2

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γ2 with RPi network streamer

Postby itsikhefez » February 12th, 2020, 7:42 pm

Hi.
I have built a streamer using RPI and piCorePlayer. PSU is s11 and everything is enclosed in a case.
Currently using HifiBerry DAC Pro HAT and looking to improve a bit (this is the primary source of my main system).

I'm thinking about incorporating the γ2 instead of the HifiBerry.

Can I power the γ2 from the same s11?
Besides needing a bigger case, are there any other issues?
Can the output be wired from the PCB to the RCA jacks ?

Thanks!

P.S I have revised the transformer wiring since. It is incorrect in this pic.
Image
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γ2 with RPi network streamer

Postby amb » February 12th, 2020, 9:30 pm

itsikhefez wrote:Can I power the γ2 from the same s11?

Functionally, yes. However, giving the γ2 its own power supply has potential benefits. It gives the γ2 a clean source of power unperturbed by the RPi.

Besides needing a bigger case, are there any other issues?

I can’t think of any.

Can the output be wired from the PCB to the RCA jacks ?

If you’re referring to panel-mount RCA jacks, yes of course. Just use isolation washers to prevent the jack bodies from grounding to the case. There should be only one thing electrically connected to the case, and that is AC ground (from the IEC inlet). In your photo this appears to be accomplished by simply mounting the metal IEC to the panel, so no explicit wire is necessary.
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Re: γ2 with RPi network streamer

Postby itsikhefez » February 12th, 2020, 10:18 pm

Thanks for the info.
I have a spare s11 and also a LM350 based regulator PCB which I could perhaps use for the RPi and designate the existing s11 to the γ2.

What about the transformer? The one in there now is 9V+9V 15VA (9V @ 1.6A).
RPi should consume max 400mA from what I read, in my case probably less since CPU is hardly working.

In your photo this appears to be accomplished by simply mounting the metal IEC to the panel, so no explicit wire is necessary.

So the wire bolted to the chassis in this case is redundant ?
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Re: γ2 with RPi network streamer

Postby amb » February 12th, 2020, 11:04 pm

itsikhefez wrote:I have a spare s11 and also a LM350 based regulator PCB which I could perhaps use for the RPi and designate the existing s11 to the γ2.

Sounds like a reasonable plan.

What about the transformer? The one in there now is 9V+9V 15VA (9V @ 1.6A).
RPi should consume max 400mA from what I read, in my case probably less since CPU is hardly working.

Sounds like it should work fine.

In your photo this appears to be accomplished by simply mounting the metal IEC to the panel, so no explicit wire is necessary.

So the wire bolted to the chassis in this case is redundant ?

Yes, but it won't hurt to have that redundancy.
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Re: γ2 with RPi network streamer

Postby itsikhefez » February 18th, 2020, 9:43 pm

I would like to avoid toggles as this will be inside the enclosure.
Can you recommend a default setting to hard wire for the 2 toggle switches?
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Re: γ2 with RPi network streamer

Postby amb » February 18th, 2020, 11:28 pm

If you're referring to the Filter and Anti-clip switches, there is no "default setting" for these, they should be set based on preference and program material. It's up to you how you want to set them. You can use panel-mount switches instead of the PCB-mount ones to make them accessible.
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Re: γ2 with RPi network streamer

Postby itsikhefez » February 21st, 2020, 3:00 am

OK thanks.... I'll figure something out.

Regarding the output caps, WIMA MKS2 10uF is larger than the recommended size but since this is not going in a case with the γ1 I'd probably be able to fit them in.
Any thoughts on using those (without C20/C26) vs the 22uF UES + 0.1uF bypass?
My current preamp has a 10K input impedance and ultimately the output will go to the a10 with 25K input impedance. In either case 10uF should be sufficient for no bass roll of.
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Re: γ2 with RPi network streamer

Postby amb » February 21st, 2020, 5:25 am

10uF into a 10KΩ load will form a high pass filter with a corner frequency of 1.6Hz. It’s low enough not to be an issue.

Whether a single film cap is better than an audio grade electrolytic paralleled with a smaller film cap is not an easy question to answer, as there are many variables. Why not experiment and see if you could hear a difference?
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Re: γ2 with RPi network streamer

Postby itsikhefez » February 28th, 2020, 2:46 am

Thanks for your reply, helpful as always.

Some progress... this is my first time soldering SMD, and while it mostly went OK, I managed to totally botch the op-amp and need to order a new one.
In the meanwhile though, I temporarily wired the unbuffered output from the DAC and it worked on the first try surprisingly.
I'm still finding the optimal piCorePlayer settings, but it actually sounds quite nice.
Nice bonus is that it all fit in the existing case.

Going back to the output coupling cap, I now realize that they can be soldered directly to the output RCA, as I temporarily have them now.
This opens up a few options as I'm not limited to the space on the board.
Is there any issue in doing this as opposed to directly to the PCB?
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Re: γ2 with RPi network streamer

Postby amb » February 28th, 2020, 3:42 am

itsikhefez wrote:Going back to the output coupling cap, I now realize that they can be soldered directly to the output RCA, as I temporarily have them now.
This opens up a few options as I'm not limited to the space on the board.
Is there any issue in doing this as opposed to directly to the PCB?

No problem with that since you are using panel-mount jacks on your own case. It is obviously not an option on a “stock” γ2 build with PCB-mount jacks.
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