PecanPi® DAC, Streamer and USB - Rev 2.0

[orchardaudio]

The PecanPi® DAC just underwent an upgrade and is now able to drive balanced headphones.
https://orchardaudio.com/pecanpi

All measurements below are for XLR outputs driving 300ohm loads, performance does not change with load and the outputs are able to drive all the way down to 32 ohms.

I will start off with bench mode as Amir likes to do.

Dynamic Range (No Weighting)

Frequency Response

Linearity

Signal to Noise Ratio (No Weighing)

THD+N Ratio Vs Level

Jitter Spectrum and Noise (256k FFT, 16 Averages)

THD+N Ratio vs Frequency

Intermodulation Distortion (IMD)

128k FFT of -20dB 1kHz Output

 

[Veri]

That 1kHz FFT looks very clean indeed. Up to par with Topping D90. Jitter is very very low, too! I wonder why SINAD isn't higher though. Some inherent noise? In any way, you seem to have squeezed the maximum out PCM1794A

Some questions though
-Any way to see what is PecanPi rev 2.0? Currently I see no indication on the site
-Could you tell us briefly about the changes from 1.0 to 2.0?

 

[orchardaudio]

I wonder why SINAD isn't higher though. Some inherent noise? In any way, you seem to have squeezed the maximum out PCM1794A

Exactly, the PCM1794A is the SINAD limiting factor.

I will answer your other questions shortly.

 

[orchardaudio]

Any way to see what is PecanPi rev 2.0? Currently I see no indication on the site

All pictures on the website are of Rev 2.0 board, except for the PecanPi USB, I have not yet updated those.
https://orchardaudio.com/pecanpi-dac -- scroll down to the photo gallery
https://orchardaudio.com/pecanpi-streamer -- scroll down to the photo gallery

Could you tell us briefly about the changes from 1.0 to 2.0?

Changes are as follows:

• DAC is now able to drive balanced headphones directly, supporting impedances down to 32-ohm.
• DAC no longer has built-in RCA connectors but comes with included custom XLR to RCA adapters.

 

[Veri]

• DAC is now able to drive balanced headphones directly, supporting impedances down to 32-ohm.
• DAC no longer has built-in RCA connectors but comes with included custom XLR to RCA adapters.

• Does this require some kind of adapter? 2x XLR 3-pin to XLR 4-pin?
• custom XLR to RCA, I suppose pin 3 is floating?

Cheers

 

[orchardaudio]

Does this require some kind of adapter? 2x XLR 3-pin to XLR 4-pin?

Yes adapter needed if your headphones do not plug into 2x 3-pin XLR

custom XLR to RCA, I suppose pin 3 is floating?

Yes, pin 3 floating.

 

[Veri]

Yes adapter needed if your headphones do not plug into 2x 3-pin XLR

Note that this is most of all headphones 2x 3-pin XLR is a pretty niche headphone cable/termination. Really.
I think pairing the XLR>RCA breakout with a RCA-headphone adapter would be a more common use case

 

[Pillars]

Well, it's kind of a DAC streamer that happens to be able to drive headphones... I don't know, for the money it's a pretty hard place to be in.

For the price I think the unit should be

Streamer, DAC w/XLR+RCA, Digital volume control (remote if possible) - just scrap the headphone ability if you don't have space. If able, just do 1/4 plug.

I really like the chip choice though.

 

[orchardaudio]

https://www.amazon.com/dp/B010NCDVIW/ref=cm_sw_r_other_apa_i_SOJEEbPVHG4V3

 

[orchardaudio]

Streamer, DAC w/XLR+RCA, Digital volume control (remote if possible) - just scrap the headphone ability if you don't have space. If able, just do 1/4 plug.

It already has all this minus the 1/4'' plug and remote...

You control the unit remotely with your smart phone...

 

[Veri]

https://www.amazon.com/dp/B010NCDVIW/ref=cm_sw_r_other_apa_i_SOJEEbPVHG4V3

Hey Orchard this terminates to 4-pin male. Balanced headphones tend to also be terminated on 4-pin male, so that won't work.
You'd need such an adapter that goes to 4-pin female, so you can plug your headphones into that.

That's why I mentioned it, this is a pretty niche/uncommon set-up. Very few headphones terminate on 3-pin xlr connectors.
XLR>RCA adapter, and RCA>headphone adapter would still be far easier to connect a headphone to..

 

[orchardaudio]

Hey Orchard this terminates to 4-pin male. Balanced headphones tend to also be terminated on 4-pin male, so that won't work.
You'd need such an adapter that goes to 4-pin female, so you can plug your headphones into that.

That's why I mentioned it, this is a pretty niche/uncommon set-up. Very few headphones terminate on 3-pin xlr connectors.
XLR>RCA adapter and RCA>headphone adapter would still be far easier to connect a headphone to..

I posted the link to wrong one sorry:
https://www.amazon.com/Female-Balanced-Adapter-Hi-end-Silver/dp/B018ZN9IXI

Also, a headphone adapter for the RCA is already sold as an option with the unit.

 

[orchardaudio]

Eye Candy for those interested...




Members of this forum get $35 off any purchase by using code: “sale35off”

 

[Veri]

http://www.ti.com/product/PCM1794A looks like you are marginally beating the datasheet's THD. That's pretty good!

I noticed a used offer for a Rev.1 Pecan Pi USB on eBay https://www.ebay.com/itm/202944795228
could you tell me if it is a ligitimate PecanPi item, and not some loaner/review unit that got pawned?

Thank you

 

[orchardaudio]

I noticed a used offer for a Rev.1 Pecan Pi USB on eBay https://www.ebay.com/itm/202944795228
could you tell me if it is a ligitimate PecanPi item, and not some loaner/review unit that got pawned?

I send you a private message.

 

[Music1969]

Hi @orchardaudio

For headphone use, I see an important measurement missing - output impedance.

Can you share the maximum output impedance of 20-20kHz ?

If it can drive 16ohm headphones I hope maximum output impedance is < 1ohm?

 

[Veri]

Hi @orchardaudio

For headphone use, I see an important measurement missing - output impedance.

Can you share the maximum output impedance of 20-20kHz ?

If it can drive 16ohm headphones I hope maximum output impedance is < 1ohm?

From the first thread:
Single ended output impedance: 0.05 ohm
So I expected Balanced XLR output impedance: 0.10 ohm

The headphone driving stage is built around parallel OPA1622s (if that is still the case in Rev 2).

 

[Music1969]

From the first thread:

Noted but this is Rev2 - just checking with the designer for latest info ;-)

Plus Rev2 now has an adapter for RCA outputs...

Also @orchardaudio - I see power input is 9Vdc but can it work with a 7.5Vdc 3A power supply?

If so, measured performance will be identical to 9Vdc power supply?

 

[orchardaudio]

Single ended output impedance: 0.05 ohm
So I expected Balanced XLR output impedance: 0.10 ohm

This is correct.

Also @orchardaudio - I see power input is 9Vdc but can it work with a 7.5Vdc 3A power supply?

It will not work with 7.5V. 8.5V is absolute lowest I would recommend.

The headphone driving stage is built around parallel OPA1622s (if that is still the case in Rev 2).

This is still correct, for balanced it is 4 parallel OPA1622 two per side.

 

[Veri]

I see power input is 9Vdc but can it work with a 7.5Vdc 3A power supply?

If so, measured performance will be identical to 9Vdc power supply?

To stay on the safe side you should go with 9V +/- 0.5V max fluctuation, otherwise you could have undervoltage or overvoltage problems.
7.5V is too little if you don't want to break down the device over time, and to prevent very unstable operation. It could randomly drop out.