The BOSS is sitting on an Ian Isolator-Pi
Thanks Greg for the in depth reply, it was helpful.
It is very small margins I guess at this point. Interestingly I had to use a linear supply with the Boss 1.2 to beat a naked ChromeCast Audio - well to my ears anyway. I figure unless you have two identical setups a comparison would be awkward and I'm never going to have dual linear supplies to do any worthwhile A/B testing with and without the Isolator.
My hunch is to go with the Allo Isolator and then remove it if I think it's masking anything.
I am using Alsa equalizer and Bass preset to increase the bass.
Not sure whether this is the right thread to ask my question. But it seems like there is some expertise on powering Allo Boss here.
I am building a dual linear psu for my rpi + allo dac.
One supply is for pi the other for the dac. All should go into (reasonably) nice box with a 2 lines LCD display (box not tall enough for mire lines) to show played song.
I would like to feed 5V directly to the boards, bypassing the usb connectors.
I understand the I can feed Boss through GPIO 1-15. Is pin 1 connected to pi's 5V line when the jumper separating dac's and pi's power lines is OFF? Probably not, but I want to make sure.
Is there any way of accessing Rpi's 5V line with the dac hat on?
Normally one can feed the Rpi throught its pins 2,4(5V) and 6(GND).
Maybe I can use one contact of the jumper which controls whether the devices are feed from one PSU of separately. As the jumper is now OFF, maybe one pin of the jumper is Pi's 5V and the other DAC's 5V?
IMHO, directly accessing the 5V for both the RPi and the Boss 1.2 AND bypassing the micro-USB and USB-C is a good idea. For the RPi micro-USB, while I've not tried it myself, I've seen reports of that being an improvement from others. That's why I went to that type of connection when I first started using RPis. AND I did bypass the USB-C on my Boss 1.2 and found it a mild upgrade.
For the Boss, accessing the RPi and Boss 1.2 5V is pretty easy using pins on the Boss J25 and J19:
- For powering the Boss DAC, the pin of the J25 jumper closest to the edge of the board is the Boss 5V. I just soldered a connector directly to that pin and the ground side of the connector to the shell of the USB-C connector (see picture).
- For powering the RPi, the other pin of the jumper, the one towards the center of the board, is the RPi 5V. You can access that there. Also you can use the ground and 5V pins on the J19 header. They are directly connected to the RPi 5V and ground and with the J25 jumper off they are NOT connected to the Boss 5V.
Some of this is covered in the Boss 1.2 Tech Manual, but not all.
Sorry for the slow response, I had lent out the Boss 1.2 I have here and knew it was coming back. I wanted to have it in my hands and be able to confirm everything before I posted.
Also, in my experience, the Boss 1.2 works ok if both the DAC and RPi supplies both come up at the same time.
I hope that all helps!
Greg in Mississippi
P.S. As I've posted here and on other forums I was and am really impressed with the Boss 1.2. It is IMHO the best implementation of a PCM51x2-based RPi DAC, especially powered well and using an Isolator board. After the original Boss came out, I was similarly impressed with it and found it beating my highly-modified HiFiBerry DAC+Pro. So I got another original Boss with the intention of modifying it for even better SQ. THEN before I got to that project, Allo introduced the 1.2 version. It was sufficiently good that I dropped any intention of trying to make it better! In my experience, you have to get to a DAC board with separate output stages which are separately powered (or good transformers) to better this.