XL6009 based DC/DC Converter for sensitive audio voltages like e.g. phantom power?

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Stick a 100uF Cap and a 10mH/10Ohm choke there, after the PCB.

To lower noise on the input side, 3,300uF/100uH/0.1Ohm/3,300uF will isolate the incoming voltage from switching noise.
Thanks, I have ordered a couple of suitable chokes. Yesterday, a test with my new tube microphone preamp using an ordinary RC filter yielded positive results. There is certainly still room for improvement, but overall the whole thing was promising.
The switching frequency is 400kHz, not 400Hz.
This PCB, you are quite sure? And you are sure the bodged up 34063 works nice and stable without subharmonic oscillation?

It's not what I see on the 'scope shot in the back of the pic, BWTFDIK.
Among other things, I actually "measured" something around 400Hz, which irritated me. As I said, my approach could be improved and it could also be due to the upstream power supply, possibly interference?1000053006.jpg
I am trying to understand the function of the small board in detail with this test, I am currently researching on the web. I'm beginning to understand better how it works.

The journey continues.
 
Among other things, I actually "measured" something around 400Hz, which irritated me.

The circuit was designed to power nixies. Absolute stability and noise were not a relevant consideration.

In typical China fashion, it was then copied badly and applied badly.

As I said, my approach could be improved and it could also be due to the upstream power supply, possibly interference?View attachment 144241

Hard to say, these days SMPS typically use either 67kHz, 132kHz fixed, much higher frequencies or variable (resonant and quasi resonant) switching frequencies, QRP/RP style valley/zero switching supplies are normally targeted at 23kHz minimum frequency under maximum load and ~80khz at idle.

I am trying to understand the function of the small board in detail with this test

What we typically see is this:

1737879530218.png
Normally a linear regulator for heaters & this for the HT. Switching frequency will be below 20kHz

An alternate schematic in common use on china boards (and a bit better in theory) is this:

1737879635080.png

This should switch at ~ 30khz.

By comparison, using a suitable MOSFET as cascode on a modern Switcher IC is a much better choice:

1737880077541.png
This circuit uses a SPOT-23-6 6Pin SMT IC with 400mA maximum current and compact MOSFET with minimal additional parts and switches at 1MHz. It can be very stable and low noise (around like an adjustable 3-pin regukator).

Of course, this actually needs DESIGN WORK, not just copy/pasta, so you will not find it on china aliexpress and e-bay boards.

I have used this with the Richtek RT9297 with ~ 3.8A switch current and 1.2MHz switching frequency to generate high voltages with many Watts of power. Using a USB-C Brick supplying 20V/5A (100W) we can easily get 4A Heaters at any voltage > 18V you like and around 25W HT, using two IC's, one mosfet, one USB-C trigger chip and a few small size passive parts.

Thor
 
Thanks, that helps a lot.
17379031021898776677567871369705.jpg

Here two boards I got to make a HT and heater for a 5670 based circuit.

HT uses SG3525 which is a proper SMPS controller, works up to 400kHz (no idea what is actually used here, have to check) with a push-pull switching stage and bridge rectifier.

Rest is left to the user - no filtering whatsoever integrated.

LT is (fake) LM2596HV with generic elcaps that need replacing with Solid electrolyte types.

So these are a cut above the usual AliExpress junk.

Thor
 
Using a USB-C Brick supplying 20V/5A (100W)

I have seen more music equipment (e.g. controller keyboards) running from USB power these days. Any concern about the very light friction fit of most USB connectors? It helps to not break your power adapter when you accidentally pick up your phone or laptop when forgetting to unplug, but studio and stage equipment usually needs a more secure power connection.
 
I have seen more music equipment (e.g. controller keyboards) running from USB power these days. Any concern about the very light friction fit of most USB connectors?

There are one's with a latch or other lock:

1737999750377.png1737999761503.png

It helps to not break your power adapter when you accidentally pick up your phone or laptop when forgetting to unplug

Actually, it doesn't.

I use USB-C charging cable with a magnetic coupling precisely for that reason.

I can pick up most USB Battery banks (and mine are chunky) by picking up the phone and the usb-c cable carries the weight of the power bank.

The magnetic coupling gives way, normal USB-C cables not so easily.

but studio and stage equipment usually needs a more secure power connection.

Well, I see 2.1mm DC a lot. That is less secure than USB-C IF YOU ASK ME.

Thor
 
There are one's with a latch or other lock

Interesting, I had not seen those. Nice to see that it is standardized (for example some HDMI cables have a similar locking screw, but I don't think it is standardized in the HDMI spec, so a bit hit or miss how you get the right latching cables or whether the equipment has threaded hole needed).

I see 2.1mm DC a lot. That is less secure than USB-C

Agreed. Sometimes equipment will have a clip of some kind to hold the cable so that if the power cable gets tugged it just pulls on the clip, not the barrel connector, but still not ideal.

Using a USB-C Brick supplying 20V/5A

To get anything other than 5V you need a microcontroller to negotiate the handshake, correct? That makes it a little more difficult for a lot of DIY cases. Maybe someone makes a turnkey device you can drop in, I haven't researched it yet.
 
Agreed. Sometimes equipment will have a clip of some kind to hold the cable so that if the power cable gets tugged it just pulls on the clip, not the barrel connector, but still not ideal.

And of course a similar clip will work the same for USB-C.

To get anything other than 5V you need a microcontroller to negotiate the handshake, correct?

There are many stand-alone IC's where you set the desired voltage with pin strapping to ground, usually jumper.

Readymade PCB's off the shelf.

That makes it a little more difficult for a lot of DIY cases.

Nope, what makes it difficult are all the people looking for reasons why it must be a bad thing.

Maybe someone makes a turnkey device you can drop in, I haven't researched it yet.

Maybe Scheena?

The catchphrase is USB PD Trigger PCB.



Thor
 
Thanks, had a short crash course in USB PD today. Looks like a great way to get decent power supplies at commodity prices.

One angle I take is that agency compliance (electrical safety, EMC, Mains harmonics) for small scale production and DIY is a huge PITA.

A 100W GaN USB power brick will pass all of it, for a fairly nominal account.

Once we have 20V @ 5A to work with, that's a decent amount of power for a wide range of project.

The 48V @ 5A (240W) variant is standardised, but not yet widely supported.

Some "bricks" on sale now offer dual "lane" 20V@5A for 200W continuous power.

With a suitable strategy (large local power storage) and if we accept that AES2 2012 applies not just to speakers but also the amplifiers driving them, 100W or 200W continuous input power allows 1600W peak Audio Power under AES2 2012.

So, USB-C has a lot of potential for audio.

Thor
 
Even at the risk of repeating myself. I would very much welcome it if this idea becomes reality. I have no idea how I can help, but I hope more people jump on this bandwagon.

Think about how a clever solution could make life easier. You set what you need and take care of the (amp) circuit instead of building a dedicated power supply for the umpteenth time.
I would jump on this bandwagon, such a great idea. Just finished another power supply for the umpteenth time and am tired of it. Count me in, not sure how I can help but am quite willing to contribute.

Thanks for a very educational thread. I have lurked for many years, learned a lot, posted infrequently but wanted to applaud this one.
 

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