CS4397 dac

[paradox]

I'm also looking for somewhere to draw power for some LEDs to indicate which input is being used. I'm using a rotary switch to select between coax and optical, and could do with an external LED indicator.

[jonners]

Leo, do you have a link to a schematic of this amp?

A schematic can be found here (scroll down to near bottom of page) : http://lampizator.eu/LAMPIZATOR/LAMP...ampizator.html

As Leo said, the part numbers are different from those on the board.

[Tripmaster]

I tested the dac before fitting parts and it worked fine.

The story so far...

Stage 1

Changed LM4562 OPAMP Sound: ok

---------

Stage 2

Removed and bypassed PS caps (C30, C31, C28, C27 & C54, C6) with thin wire. connected coupling caps and R68 resistors on RCA output, soldered two blobs to bypass chip on the base of board.

Sound: Treble is OK but bass really muffled and distorted - Sounds really bad.

----------

Stage 3

Change all other caps. Sound: Still sounds the same, but it still works!

I have not removed any of the smd caps, just bypassed with vishay

I have not changed any resistors.


Do you have any clues?

[alb]

Aaaaaarrrrgh! CAPACITOR OVERKILL!!!!!

I think you may have made things difficult for yourself, with the choice of caps. Not easy to see whats what.
Probably best to retrace your steps and find out where it went pear-shaped.
Even put it back to std board and use it for a few days, till its all nicely run in. Then you'll know better what to expect.

I don't use opamps in mine so difficult to comment.
It should when upgraded(and before), sound very clear and dynamic.
Good luck.

[leo]

A few problems I can see

WAY too many Oscons there I'm afraid, the ESR will be too low, you need to check for possible instability on a scope, Oscons also have a tendency to kill bass if you use too many of these which will give very soft signature
Those film caps are too big physically, their inductance will be too high

A mistake I've seen a lot is people tend to think low ESR capacitors are the best for all apps, infact it can cause a lot of problems with regulation regarding stability

If you have to use this many Oscons and after say a few days it still sounds bad try adding a low value resistor in series with those caps to add some impedance and help cure any possible ringing

[leo]

Also I noticed you used Sonicaps, these are reported to need some burning in , also the LM4562 tends to be poor at driving capacitive loads, I tried this chip but removed it, it needs care before it sounds half decent IMO

[Tripmaster]

Hi

I think I may have got little carried away!


The bass is in fact very heavy. It sounds like strumming a loose bass guitar string

I started by just changing the opamp and it didn't sound any worse than the stock card.

I then proceeded to remove only C30, C31, C28, C27, C54, C6 and added two SCR coupling caps and 68R resistors. It was at this point the sound took a turn for the worse. I changed to the Sonicaps because I thought the SCRs may have dried up as they are quite old (18years)

In my parts bin I have the following items

10x 47uf 16v Tant beads
5x WIMA 150pf
10x Panasonic FC 470uf

Would I be better off replacing some of the components with these items, And if so at which points?

Thanks for your help

Richard

[Tripmaster]

The oscons are 150uf SA

Grey Vishay MKP 0.22uf

Blue Vishay MKP 0.1uf

The Vishays are bypassing the SMDs

[alb]

Richard.

Sorry for the poor photo but this will show you how mine looks with the upgraded caps.



C19 is 1000uf Pana FC.
C21 is 150uf Pana FC.
You can use your 470uf at C19. C21 should be smaller.

C9 is Vishay mkp1837 0.1uf. This was the best i found after trying twelve different caps here. Big ones don't work properly and generally mess up the sound, sometimes in a big way.
C9 is in my opinion one of the most important caps on the board. This also the only surface mount that i removed.

C16,17,20 and 25 are Oscon 150uf 16v. Probably enough Oscons.
C3,C18 are 220uf Samwha caps(gold), but any decent quality cap suitable for purpose would perhaps do.

C8,11,12,13 are 3.3uf Tants.

All lytics are bypassed by 0.1uf film caps.
I think blue Vishays are preferable to Wima, anywhere on this pcb.

This DAC works very well. Hope this is helpful.

[Tripmaster]

Whilst listening to the DAC last night one of the solder connections attaching the right channel lead to the coupling cap broke away.

I re-soldered the lead and at the same time decided to remove the two blobs of solder from the chip on the base of the board (These blobs bypass the chip). I fired it up it up again and only the left channel works. All of the connections seem fine and both channels operate via the DACMAGIC.

I re-soldered the two blobs to the chip and now the output is very quite and distorted.

This is not a good way to finish the evening!

HELP!!!!