OK. WTH is a pin on a DAC thats desc is "Filter connection for internal quiescent voltage"..
Its only connection is a 3.3uF cap to ground. However this cap really effects sound.
With a MUSE electrolytic the dac sounds bright and has some glare, with a poly cap the glare is gone but I think im missing some subtle detail.. I need to know what this pin does. I would like a schematic of where this pin goes internally and what it does.
Pin 26 http://www.cirrus.com/en/pubs/proDatasheet/CS4398_F1.pdf
Its only connection is a 3.3uF cap to ground. However this cap really effects sound.
With a MUSE electrolytic the dac sounds bright and has some glare, with a poly cap the glare is gone but I think im missing some subtle detail.. I need to know what this pin does. I would like a schematic of where this pin goes internally and what it does.
Pin 26 http://www.cirrus.com/en/pubs/proDatasheet/CS4398_F1.pdf
Since the DAC uses an unipolar supply, the output pins are at half supply voltage when there's no signal.
That half supply voltage internal reference has to be smoothed and that cap is external as it is too big to fit on the chip.
With a 5V supply you should measure about 2.5V there. It's really just a supply decoupling cap.
Since the max current from this node is 1uA it looks like it has a rather high value internal resistive divider across the supply of two equal resistors. The Vq cap would be between the common point of the resistors and ground, giving a low noise half-supply reference voltage.
Use whatever sounds good to you, keeping to the recommended value.
Jan
That half supply voltage internal reference has to be smoothed and that cap is external as it is too big to fit on the chip.
With a 5V supply you should measure about 2.5V there. It's really just a supply decoupling cap.
Since the max current from this node is 1uA it looks like it has a rather high value internal resistive divider across the supply of two equal resistors. The Vq cap would be between the common point of the resistors and ground, giving a low noise half-supply reference voltage.
Use whatever sounds good to you, keeping to the recommended value.
Jan
Last edited:
Yea thats what I thought it was just not clear on the datasheet..
Interesting how much it effects sound. That was surprising for me. Makes sense from its function tho.
Thanks for a quick response.
Interesting how much it effects sound. That was surprising for me. Makes sense from its function tho.
Thanks for a quick response.
OK.....
This is gonna drive me crazy... That is one critical cap for this DAC. Every cap sounds really different. The effect between different caps is hard to articulate clearly but its very obvious. With a MUSE there is a open sounding space thats a bit too bright in a digital way but it seems to convey a more accurate sense of space and seems to have excellent delineation to instruments. A WIMA MKS 2 metalized polyester the brightness is gone, it sounds very natural but is missing as good a portrayal of space, instruments are less individually defined and there seems to be less definition in the top octave.
OMG I hate deciding on caps. But this circuit is even more critical then normal.
So I put a 1uf MKS 2 across a MUSE and thats better. But still not best.
It looks like im gonna have to just try a bunch of caps and see whats best.
Any suggestions for this ?
I suppose the digital glare from using just the MUSE might be accurately reproducing glare thats really there..
Man.. using a unipolar dac has disadvantages. Or hmmm, maybe its a advantage as its creating its own mid point but I gotta find a way to tame it.
This is gonna drive me crazy... That is one critical cap for this DAC. Every cap sounds really different. The effect between different caps is hard to articulate clearly but its very obvious. With a MUSE there is a open sounding space thats a bit too bright in a digital way but it seems to convey a more accurate sense of space and seems to have excellent delineation to instruments. A WIMA MKS 2 metalized polyester the brightness is gone, it sounds very natural but is missing as good a portrayal of space, instruments are less individually defined and there seems to be less definition in the top octave.
OMG I hate deciding on caps. But this circuit is even more critical then normal.
So I put a 1uf MKS 2 across a MUSE and thats better. But still not best.
It looks like im gonna have to just try a bunch of caps and see whats best.
Any suggestions for this ?
I suppose the digital glare from using just the MUSE might be accurately reproducing glare thats really there..
Man.. using a unipolar dac has disadvantages. Or hmmm, maybe its a advantage as its creating its own mid point but I gotta find a way to tame it.
also I cant see that using a slightly larger cap could be a bad thing. Just more filtering.
Well up to the point where the inrush current causes the circuit that creates the mid point goes pop.
So rather the 3.3uF im gonna use a 10uF is gonna be my goal. Maybe 4.7. Having a dead quiet, solid, mid point is really important.
Well up to the point where the inrush current causes the circuit that creates the mid point goes pop.
So rather the 3.3uF im gonna use a 10uF is gonna be my goal. Maybe 4.7. Having a dead quiet, solid, mid point is really important.
Put a smaller cap (perhaps .1) across the large cap. You will get better high frequency filtering ... lower ESR at high frequencies. You might even want to add a .1, a .01 and a .001 cap. All in parallel with the large cap.
I just dropped in a ERO Polypropylene. Thats better. Its a 2.2uF across the 3.3uF MUSE for now.
Im gonna have to order exactly what i need. I want a 4.7 or 6.8 ERO Polypropylene. That should do it. Off to mouser..
Man... I did not expect this cap to be so critical.
Im gonna have to order exactly what i need. I want a 4.7 or 6.8 ERO Polypropylene. That should do it. Off to mouser..
Man... I did not expect this cap to be so critical.
Not good on coupling caps then you have two different caps with two different esr's working at different frqeuncies, this smears the sound at the overlaped frequencies.
De-coupling on power supplies it's OK to do this with smaller caps. But don't know how it will effect the sound in this this position.
To me I would just use a single cap of the best quality 3.3uf non electro I could find.
Cheers George
Last edited:
I would try these non polarised 3.3uf.
http://www.ebay.com/itm/Taiyo-Yuden...959?pt=LH_DefaultDomain_0&hash=item2566f80fcf
http://www.ebay.com/itm/Sprague-CH0...245?pt=LH_DefaultDomain_0&hash=item4d00b9e79d
http://www.ebay.com/itm/12-0-uf-450...mplifier_Parts_Components&hash=item2c7274af2b
Note: for Some reason they won't link to the ebay ad.
Just do an ebay search for
3.3uF Sprague,
3.3uf Taiyo Yuden (these are XR7 smd caps)
3.3uf Mundorf
Cheers George
http://www.ebay.com/itm/Taiyo-Yuden...959?pt=LH_DefaultDomain_0&hash=item2566f80fcf
http://www.ebay.com/itm/Sprague-CH0...245?pt=LH_DefaultDomain_0&hash=item4d00b9e79d
http://www.ebay.com/itm/12-0-uf-450...mplifier_Parts_Components&hash=item2c7274af2b
Note: for Some reason they won't link to the ebay ad.
Just do an ebay search for
3.3uF Sprague,
3.3uf Taiyo Yuden (these are XR7 smd caps)
3.3uf Mundorf
Cheers George
Last edited:
Yea im just gonna have to play with this. Sadly. I hate having to go thru a bunch of caps for that magical one of the specific type, brand, voltage, uF and all that.. The ERO Poly sounds good tho. I may just pull the MUSE one and leave 2 x 2.2uf ERO polys and be done with it.
Yes i know those cap you mention. The other issue is size. I need small parts.
This in a 3.3 or 4.7 uf 63V would be just the thing. But I gotta find some. http://www.vishay.com/docs/26013/mkt1813.pdf
Yes i know those cap you mention. The other issue is size. I need small parts.
This in a 3.3 or 4.7 uf 63V would be just the thing. But I gotta find some. http://www.vishay.com/docs/26013/mkt1813.pdf
- Status
- Not open for further replies.