[sdiy] AS3394E: Practical power supply?

[Mike Bryant]

Before the smoothing LC I put on each output, about 10mV at 1.25MHz.  After the LC it's virtually non-existent.    

There's nothing in the audio region unless you vary the load dramatically at audio rates so that the device has to move between continuous and non-continuous modes, which is when SMPSes get a bad name.  
But when this happens it is bad design that is the problem with incorrectly specified inductors and capacitors, not the basic idea of SMPSes.   

And if you want even less noise even at high frequencies, use a SEPIC for positive and a Cuk convertor for negative voltages at the cost of a couple of extra capacitors.  These can even be combined into the same switcher if you want identical output voltages.



-----Original Message-----
From: Ben Stuyts [mailto:ben at stuyts.nl] 
Sent: 18 November 2021 17:49
To: Mike Bryant
Cc: Benjamin Tremblay; SYNTH DIY
Subject: Re: [sdiy] AS3394E: Practical power supply?

Hi Mike,

What kind of ripple/noise figures do you get with the TPS65131?

Ben


> On 18 Nov 2021, at 16:52, Mike Bryant <mbryant at futurehorizons.com> wrote:
> 
> Uh ?   A decent SMPS has far less noise on the output than most linear supplies, and all well out of audio band.
> 
> 
> -----Original Message-----
> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Ben Stuyts
> Sent: 18 November 2021 15:11
> To: Benjamin Tremblay
> Cc: SYNTH DIY
> Subject: Re: [sdiy] AS3394E: Practical power supply?
> 
> Hi Ben,
> 
> A quick glance of the datasheet warns about jitter and stability affected by both the pos and neg rails. So I would def. not use any smps for this. A pair of LM317 / LM337 would do fine of course.
> 
> (Other) Ben
> 
> 
>> On 18 Nov 2021, at 15:09, Benjamin Tremblay via Synth-diy <synth-diy at synth-diy.org> wrote:
>> 
>> Greetings,
>> 
>> I have been intrigued by the CEM3394 for a long time. I realize it’s the part of the Sequential Six Trak I like; the rest of the Six Trak leaves a lot to be desired.
>> 
>> What is a straightforward way to obtain the -6.5V negative supply? Use a 9V regulator and drop it with diodes? Use an adjustable switching supply? Add a feedback loop to a regulator? I’m assuming even a gaggle of 3394 chips won’t consume much current on the negative side.
>> 
>> I’m lazy (working 2 jobs and taking care of 2 kids and a puppy) and I won’t get much done unless I can breadboard the chip and try out some s/h ideas.
>> 
>> Thanks,
>> Ben
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at synth-diy.org
>> http://synth-diy.org/mailman/listinfo/synth-diy
>> Selling or trading? Use marketplace at synth-diy.org
>> 
> 
> 
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>