TPA3116 / RuneAudio Project

[Downunder55]

[skrodahl]

[Downunder55]

[skrodahl]

It's really cool to see your project come together like you planned, a few reconsiderations along the way is unavoidable.

The power button stays recessed when you turn it on. It's barely noticeable from a distance. The other option is to use the momentary push-button variant, but then you'd need to make a separate circuit to keep the power on.

It definitely seems like you have a ground loop somewhere. It's difficult to see why. I would make sure none of the connectors are actually connected to the chassis.

I wouldn't worry, except for the ground loop issue, about the amperage of your PSU. I'm using a 3.5A, and it is more than sufficient to give all the power I need and then some. Under normal use, you will rarely come close to the rated wattage of the amp.

[Peter]

Some pictures of my first attempt. Plays perfectly - everything works great.

Container is a repurposed ATX power supply case, power switch is from an ATX ps, binding posts rescued from some old speakers.

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Front. Knobs are hand made from Macrocarpa, bottom strip is Oregon pine, and the red LED is to indicate power on. Aluminium detailing is just for fun.

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Inside, showing binding post, RCA and power switch connections. Power supply is a repurposed Acer 19v 3.42amp laptop power supply.

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[Peter]

Photos contd.....

Inside front. Volume pot (on the left) follows skrodahl's advice - 100k linear pot, with 10k resistors from output to ground. These are shrouded in heatshrink. The balance pot, on the right was harvested from an old National stereo. All wires are twisted to reduce interference, and cross at right angles where possible. No feedback, or hum detected.

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Birds eye view with hand painted case top. The 10k resistors mentioned in the previous post are contained in the blue heatshrink. The green pcb is cut from an old motherboard, and just used as a base for the TPA3116 board. The yellow rca cables, shown in earlier photos are home made interconnects, using cat5e solid core ethernet cable, plaited to reduce interference.

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Now for the next project...raspberry pi B+ with either hifiberry or iqaudio dac, and audiobah TPA3116 board in a single case (probably an ATX case again!)

Current pi is model B, with PiCobber i2s DAC, with RuneAudio flawlessly (to my ears) wirelessly streaming to the amp.

I guess it dates me a bit, but Kate Bush singing Wuthering Heights sounds absolutely amazing - incredibly detailed and rich sound.

Photos are a bit rubbish - I will try better next time

EDIT: I used 10k ohm resistors on the Volume pot, not 12k ohm which is what I originally said

[skrodahl]

Hi Peter,
That is one seriously cool project you've got going there. Kudos!

I hope you are happy with the volume/balance controls. One advantage with using the 12k resistors to ground is that they present a load to the amp.

At 26db gain, the input impedance of the TPA3116 is 30k. Although the rule of thumb is that the impedance of the preceding part should be 1/4, that's close enough anyway. This also may explain why you have no hum, while there are a lots of reports on various noises from many others.

[Peter]

@skrodahl: Thanks, the sound is amazing - I am now looking for some cheap (vintage) high sensitivity speakers to complement the amp

Has your Audiobah board arrived? Seems there is a long lead time for their boards. Please let us know your experience.
I have ordered the Sure board and hope to be impressed. I notice the Sure has on board RCA connections, and I hope the vias between the sockets are for additional (panel mount) RCA connectors.

@downunder55: How is the build going?

Peter

[skrodahl]

[Downunder55]

Well finally solved the SATA disk problem with a new interface card, this was the third one I tried !

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Initially had an issue with getting all the album tracks showing up in the UI, it had the all the artists, all the albums but when I went into the album folder no tracks were available, initially thought it was a problem with Alpha 3 but after much reading it didn't seem to be a reported issue so connected the disk to the laptop, all the tracks were there.....ummm .........trap for young players (yet still getting bitten) the main directory was named "Music" on the disk and I had named it within Rune as "music", a quick change long re-sync and all good !

Still have the slight grounding issue to work on and seeking help on DIYAudio

I must say it is all sounding pretty good.

Now need to have a think about the final box and all those cables, initially might start with making up a new Cat 5 cable as that is the most rigid and bulky.