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Linear PSU for Raspberry Pi 3, which one? Confused.
Linear PSU for Raspberry Pi 3, which one? Confused.
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Old 4th November 2017, 11:13 PM   #61
drtebi is offline drtebi  United States
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Join Date: Jul 2013
Location: San Francisco
Quote:
Originally Posted by ktham View Post
Here are some thoughts for your design consideration.

The Allo Boss has power pins to allow you to separately power it from the RPi. This will require another 5V regulator board should you choose to examine/test this configuration. Accordingly you will then have to re-lay your PCB for separate secondary windings instead of paralleling them to get two 8VAC outputs for your regulator. Lay it out so that the windings can be paralleled by a jumper on the board.

You can hard wire/solder power leads to the Rpi and the Allo Boss instead of using connectors/plugs. Use 22 or 24 ga wire.
Are those power pins the ones referred to in the Allo Boss manual to as 5V battery power connectors? Reading the manual, it appears that the Allo Boss should do a great job of "cleaning" the power that comes from the Pi, they even mention no need to contact extra power source to BOSS DAC[...].
I don't know... is it really worth the trouble to separately power Pi and DAC? I also don't feel too comfortable about de-soldering the R826 resistor on the DAC... the same goes for the Raspberry—while I could solder on the power wires directly, it would also make it more difficult to remove the Pi at a later point. I prefer the idea of having everything "pluggable", or connected with screw-terminals.

Quote:
Originally Posted by ktham View Post
I have some audio cable, 2 conductor shielded, 3.5mm black which I can send you for your build. It is new on a roll and I can take off 10ft. and send it to you. Send me a PM with your address.
Thank you, very generous! I do have a whole lot of wire at home though, from 12 gauge 30AMP power cables to CAT6 ethernet and Mogami RCA/ Canare coax and lots of bits and pieces in between. I am sure I will find something suitable in that big box.

Quote:
Originally Posted by linuxfan View Post
I agree with ktham; your project is currently so extensive that it would be a shame not to go just a bit further and accommodate a second 5V supply for the DAC-hat.
The DAC-hat deserves a high quality, low noise, such as the LT3042, ADM7150, or TPS7A4700 ...
but I see the BOSS DAC's onboard regulators are LT3042 - OK, in that case I would exclude LT3042 from your choice of pre-regulators, because by combining two different regulator types your get to reduce two different noise bandwidths.
ADM7150 and TPS7A4700 regulator kits can be found at diyinhk. You could also try eBay and AliExpress, with some price versus quality considerations.

Regarding the transformer, sure, you could split your Triad's secondaries to supply two regulators, but it seems to me that you have plenty of space in your enclosure, so I would use a second (smaller) transformer for the DAC-hat. Something like this Hammond -
229A16 - Hammond Mfg.
8VAC 700mA 48x40x22mm

or if you're more comfortable with a higher current rating, the next size up is
229B16 - Hammond Mfg.
8VAC 1.4A 64x51x27mm
See my comments above... I am just wondering if it's all worth it; after all, the Allo Boss was designed to filter the power as good as possible so that a separate PSU would not be possible, at least that's what they claim, isn't it?

One idea that was brought to my attention is, why go through the trouble designing an "AC board", but then using a separate regulator board. I could as well just design one board for both... it would be more challenging, but I like the idea. I already have the regulator parts, so in theory I would only need to put them onto my AC board design... oh well... maybe everything is becoming more complicated than it has to be?
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Old 5th November 2017, 01:52 AM   #62
linuxfan is offline linuxfan  Australia
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Join Date: Dec 2007
Well ALLO has a good reputation for power filtration, but I can't help thinking that a dedicated high quality power supply to the DAC is best practice, especially since you are already going to a lot of effort with transformers, regulators, chassis etc.
If I was doing this project, I would maybe go even further and bypass the DAC's input power filters, inserting my own clean 5V power further downstream! Of course, this means brandishing a solder iron to the BOSS DAC, with corresponding risks.

The question at stake is does a separate power feed to the DAC-hat have an audible benefit? Only someone who has tried this will know - ktham might be able to say?

Quote:
Originally Posted by drtebi View Post
why go through the trouble designing an "AC board", but then using a separate regulator board. I could as well just design one board for both.
Yes, but the regulator board you have chosen is a commercial product. Will you copy its layout? Or will you design your own LD1085-based regulator circuit?

Here's a complete solution for you - LT3083 regulator with onboard transformer (the 12 watt Version is 2A @ 5VDC)
K&K Audio | Other kits
This regulator has better specs than the LD/LT/LM1085 regulators.
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Old 5th November 2017, 02:54 AM   #63
ktham is offline ktham  Canada
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Join Date: Feb 2010
New DAC from Allo ess9028q2m for RPI

Check out this Allo news item on their existing Boss and the replacement. Maybe you should wait for this new model and see how it will integrate with your current design objectives/build. I will be ordering one when available.

I use Molex connector pins on my power leads so disconnecting is not an issue for me. I do not have faith in the Rpi power connectors. On all my builds I will over engineer those areas I think will be problematic based on my experience.

Try and build as much flexibility into your design because as you evaluate your build during listening tests you can be sure the tweak itch is going to bite you as you look for that ultimate sound that is unique to you.

Are you going to connect your RPi using WiFi or Ethernet to your music server? You will need to address this in your case layout.
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Old 5th November 2017, 05:09 AM   #64
drtebi is offline drtebi  United States
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Join Date: Jul 2013
Location: San Francisco
Quote:
Originally Posted by linuxfan View Post
[...] Yes, but the regulator board you have chosen is a commercial product. Will you copy its layout? Or will you design your own LD1085-based regulator circuit?
I don't know yet... I already have the GlassWare regulator, so if I don't use the board that came with it (which looks really nice, by the way), I could potentially copy the design to a board that includes the transformer. Since this is for my own personal project, I don't think I'd be in trouble doing that (I bought it after all... just changing the color of the car...)

Quote:
Originally Posted by linuxfan View Post
Here's a complete solution for you - LT3083 regulator with onboard
transformer (the 12 watt Version is 2A @ 5VDC)
K&K Audio | Other kits
This regulator has better specs than the LD/LT/LM1085 regulators.
Looks good; I remember K&K from when I explored SUT kits. But as I said, I already have the GlassWare regulator; in fact, I also already have the transformer etc. for the AC part of the PSU.

Quote:
Originally Posted by ktham View Post
New DAC from Allo ess9028q2m for RPI

Check out this Allo news item on their existing Boss and the replacement. Maybe you should wait for this new model and see how it will integrate with your current design objectives/build. I will be ordering one when available.
Hmmm.... just ordered the Allo Boss yesterday!

Quote:
Originally Posted by ktham View Post
Try and build as much flexibility into your design because as you evaluate your build during listening tests you can be sure the tweak itch is going to bite you as you look for that ultimate sound that is unique to you.
I think that is the key to this project. I will definitely leave it as flexible as possible, so that I can change the DAC or power supply etc. if I decide to later on. Thankfully I am going to use a huge case...

Quote:
Originally Posted by ktham View Post
Are you going to connect your RPi using WiFi or Ethernet to your music server? You will need to address this in your case layout.
Ethernet. I got a nice RJ45 connector from Switchcraft, just arrived today. Along with a couple of Canare RCA panel mounts.

For the most part I am ready to start putting the electronics together. I will spend some time on the case design, and try to make up my mind what exactly to do with the PSU part.

On a side note: I build a PCB board holder today, came out pretty nice, no wobbling, everything sits tight, up to 9" in width. All made from recycled parts (old printer, keyboard mount, wood).

I'll keep you posted!
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Old 10th November 2017, 03:15 PM   #65
wcwc is offline wcwc  United States
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Join Date: Oct 2011
Would the Glassware LV-regulator work with a transformer set up with dual secondaries as long as the supplied voltage and current are correct?
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Old 10th November 2017, 06:23 PM   #66
ktham is offline ktham  Canada
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Join Date: Feb 2010
Quote:
Originally Posted by wcwc View Post
Would the Glassware LV-regulator work with a transformer set up with dual secondaries as long as the supplied voltage and current are correct?
My response assumes that you are asking about dual secondaries in parallel and identical in voltage to feed the LV regulator. Short answer is yes.

The designer's recommendation is that the output current be no more than 2A so your transformer need not be oversized. You can size the transformer accordingly by paralleling the outputs. Just be careful how you parallel the secondaries when connecting them as there is definite protocol to observe. The transformer manufacture will have identified this in their documentation and on the transformer itself.

There is enough flexibility in the board layout for those who want to do some tweaking for their own specific build needs. Some information is covered in part in the User Guide supplied with the kit. Remember the warranty.
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Old 10th November 2017, 07:44 PM   #67
wcwc is offline wcwc  United States
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Join Date: Oct 2011
Well for the 5V LV-Regulator I could get the same one that drtebi got to power an Odroid C2. I was looking at an LV-Regulator for 12V power for a preamp board and an arduino which should together be around 2A. I have another 7V to 8V regulated supply (salas SSLV) to power which will be powering the isolated side of Ian's Isolator Pi, Kali reclocker board, and the isolated side of a Dam-1021 DAC. Since I need a 15Vac for the Salas SSLV, and most likely 15VAC for the Lv-Regulator could I use a dual 15VAC transformer to power both? Or would it be better to just get two smaller transformers and parallel the secondaries. Just trying to eliminate a transformer, since if I split them I have 4 transformers in the enclosure.
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Old 10th November 2017, 09:46 PM   #68
ktham is offline ktham  Canada
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Yes you can use a dual output 15VAC to power the LV Regulator and the Salas where each one is an individual/independent circuit as stated. You can get the same effect by using two smaller transformers. Just remember to specify the output voltage desired when you order the LV Regulator as this will require different a resistor value and capacitor voltage value from the supplier. I am not familiar with the Salas.

If you look at the thumbnail in Post 59 I use three dual winding transformers for powering 6 different devices. Two are for my Pi/HAT/DAC/Kali combos and one is for +/- 15VDC. My builds use common elements wherever possible for flexibility and redundancy. Buy once and reuse as required.
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Old 11th November 2017, 05:19 AM   #69
drtebi is offline drtebi  United States
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Join Date: Jul 2013
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Quote:
Originally Posted by wcwc View Post
Well for the 5V LV-Regulator I could get the same one that drtebi got to power an Odroid C2.
The transformer I chose is a PCB mounted transformer, so you need a PCB to go with it. Just wanted to point that out.

I only chose that particular one because I needed something very flat... since my case is only 2.25 inches high on the inside.

You shouldn't have a problem finding a transformer with the same specs but without the need to mount to a PCB. Unless, of course, that is what you want...
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Old 14th November 2017, 06:33 PM   #70
wcwc is offline wcwc  United States
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A41-25-16 Bel Signal Transformer | Mouser


How does this work for a chassis mount version of the one drtebi used?
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