dac + smps : to noisy for headphones ?

[fillemon]

hello everybody,

i'm trying to build an quite decent headset for when i'm behind my pc.

i will have an akg 500 + ck2III. but in front of it there is a monica2 on digital out of the pc. the monica dac is powered by smps source. if you use speakers it would be fine, but i have seen a complain about noise issues for headphone. Does someone experienced this to ? or is it nor true ? if it is what have you done to overcome it ? (a lineair psu maybe?)

thanx a lot

 

[Heady]

fillemon, very interesting that today, I tried the exact same thing and found the same results, ie. noise. My equipment was CD player -> Monica2 -> PINT. Power supply for Monica2 is a SMSP. I will try to find time to test this with a regulated linear supply.

 

[fillemon]

that's nice handy (that you are on to it)

well, i haven't tested it yet, i just have red it somewhere.


i have a monica2, which i wanted to power up with smps,
but i don't have an i/v stage. They run at 12 and 18v at best they say.

so you only run the monica dac itself with an smps ?
and nog i/V stage ?

form what i have red : i thought that monica should be powered by a lineair ps, but the I/V stage could still do a smps at 18 volt. i don't know what your setup was.

i tought i had red somewhere that people tried to get rid of the noise by inserting caps, but that didn't deal with it completely, so they left the smps. (for what i remember of it).

greetings fillemon

 

[BrianDonegan]

I'm curious why you would want to use an SMPS instead of a (cheaper, quieter) linear supply? I admittedly am not completely up to speed on the latest SMPS stuff.

 

[fillemon]

well on a triptah amp they do sound better (at least that what they say, but i believe them, i have this setup and does is it very well. But you can buy smps for something like 5 euro, and you have 12v at 8 amp. no wonder that it sounds good. if you have to get a lineair psu with that kind of current supply, you gonna spent a lot more.

anyway, what kind of lineair psu are you thinking of, i was thinking of a steps or a tread for tangent (at least this design, don't know if i will order a pcb for that).

fillemon

 

[BrianDonegan]

Quote:

But you can buy smps for something like 5 euro, and you have 12v at 8 amp.

That makes sense. Perhaps all you need to do is add a bank of filter caps after the supply to tame the noise.

Shoudl note however, for most DACs you will need less than 200mA. Might be better off with a non-SMPS wall wart supply on the DAC side, might be cheaper than an SMPS even. A Tripath, being class-D, is filtered to tame switching noise.

 

[fillemon]

well some people on the forum are on to it: taming it: but i have red that it is not good enough. 1)the noise isn't gone (at least all of it) and you loose the speed because of the cap banks.

indeed for a dac you don't need a lot of current, not at all. so i think i'm going for a lineair one;

still the i/v stage has to be powered, but i can't image that i needs more than 300ma at 18v. well maybe 500ma.
i'm gonna look around for one;

 

[JadeEast]

You have to think that not every SMPS is going to be a quality one.
I've run the monica2-usb off of battery, linear and smps. One smps had
noise on one channel and another one was fine. I'm sure that the smps that
yeo sells is probably good for the application. In my experience all of the power supplies were good except for the noise in one. As well you should note that many reports of noise for the gain stage may be because of faulty leds used in the build.

 

[fillemon]

hello jadeeast, are you using the dac with a headphone or on speakers ? if you can't hear anything, well then maybe it is the smps, i have a skynet 8080; quite an overkill for 200ma; the 18v i might get out of an dell laptop adapter, again a huge overkill: 4.5 amp. but they are both cheaper then anything else.

 

[fillemon]

hello people, still reading and thougt of something.

an smps seems to have an ripple of 10mv, while a simple 317t (in a tread has 60µv, could it supply dc to a l317t and get a bit lower voltage but less ripple out of it. (it is a bit of taming, but then again not only by caps.)

what do you think,

does anyone know how much voltage you may drop over the l317t, i can supply 24v or 20 in and i need 18 and 12 volt out, so i need to drop 12v at max at 0.5 amp, will it be to hot ?

thanx a lot

 

[amb]

Quote:

Originally Posted by fillemon /img/forum/go_quote.gif does anyone know how much voltage you may drop over the l317t, i can supply 24v or 20 in and i need 18 and 12 volt out, so i need to drop 12v at max at 0.5 amp, will it be to hot ?

Do the math: 12V drop * 0.5A = 6W dissipation
You'll need one significant chunk of heatsink and good ventilation around it.

 

[BrianDonegan]

Quote:

does anyone know how much voltage you may drop over the l317t

Depending on mfg, 37-42V drop.

 

[Heady]

Quote:

Originally Posted by fillemon /img/forum/go_quote.gif i have a monica2, which i wanted to power up with smps, but i don't have an i/v stage. They run at 12 and 18v at best they say. so you only run the monica dac itself with an smps ? and nog i/V stage ?

Hi fillemon,
I am using a 15VDC SMPS to power the I/V and use a TREAD to drop the 15V to 12V for Monica2.

I will test using a linear PS for both soon, when I have the time to re-wire the DAC.

Regards.

 

[fillemon]

indeed 6 watt is quite a lot, for heating, so i should chose something as close as possible to the wanted Voltage.

heady, that is just fantastic, keep up the fine work, and shet some light on our darkness.

if your actions would not be succesfull i'll go with an sigma11. if there is still noise, i give up this hobby

 

[Heady]

fillemon,
I remembered I have an adjustable linear regulated power supply which can supply 15VDC, so no modification needed for my Monica2.

I just tried it with my PINT and I am happy to tell you, no noise. The problem is the SMPS. I normally use my Monica2 with a Amp5 which as you have noted, filters out the noise.

Looks like I have to built a power supply for my Monica2.