CS4397 dac

[leo]

Hi Leo

I played with C25 today. I managed to find a 10 and 22uf cap in my parts bin. The 10uf cap didn't improve the bass but seemed the sharpen the sound slightly. However, the 22uf cap might have improved the bass slightly...its hard to tell. I am putting a parts order together tonight so I should have the 100uf general purpose caps in a few days.

I will report back...

Thanks for the compliment BTW




Richard

Let us know how you get on

I may build one of those transports later too!

[Naqua]

Tripmaster,

Since you are playing around with the caps on CMOUT...
In the datasheet for the DAC eveluation board there's 2 resistors of 1k to cut the 5v into 2,5v and connect it to CMOUT.

In the note's it says they are for PCM modes. I suppose its because CMOUT has to be typically (according to the datasheet) at 1/2 VA.

Maybe it's something to try also ? I havn't tried it yet.

My mod list to date is as follows:

Mod1 Standard board with coupling caps (betwee DAC and output stage) and mute chip bypassed.
Result: OK i guess, dont knw exactly

Mod 2 C20, C25, C16, C17 -> 100uF 16v OSCON
everything else rest standard as is.
Result: Bass ok good soundbalance

Mod3 C3,C18 -> 220uf 16v Philips
C19 -> 1000uf 16v general purpose
Result: Bass shy, vocals to bright

Mod4 C25 10uF 16v general purpose
C19, 100uF 16v Oscon
Result: Vocals little better, still bass shy

Mod5 30k and 150pf around opamp
Result: Not determined yet, still have offset.

Seemed Bass getting downhill with Mod 3 and after.
Let you know if i'm getting somewhere.
I have to wait for parts, got a few ELNA SILMICII and Pana FC on the way.

Stay tuned.

Naqua


PS LEO: Thanks for your suggestion, i will try matching the resistors first, then changing opamp to opa627's i have here.

[jonners]

I seem to remember reading somewhere that the CMOUT mod brings out more detail. Could be worth trying.

[leo]

I've tried the CMOUT mod, tbh I'd try it after you feel the caps etc are right

You notice people start getting problems with bass etc once they start swapping the decoupling caps
Just be patient, I think a lot of the problems is the layout and that supplied psu, its easy to results in instability

Remember this board is cheap, don't expect it give giant killing performance, it won't IMHO but what it can do is give a very good sound on the cheap

[FireFly]

General rules: use short leads, where high frequeny is present. Increase capacitor values for analog power supply lines, nothing very critical here.
For digital supply lines, big values are NO NO. It will "slow down" music, details will be lost, dynamic will suffer. Very low ESR is not always very good.

My mods (look to real PCB, not shematic):

C19: replace with 220-3300μF, low ESR. Bigger value is not always better, my choice is 470μF Sanyo green. Will try Panasonic FC 1000μF.
C1: leave SMD, bypass with 0.1μF MKP
C21: replace with 100-220μF. MUST be smaller value from C19. My choice is 100μF Oscon
C15: leave SMD, bypass with 0.1μF MKP
C14: (wrong marked as C41): leave SMD, bypass with 0.33μF MKP
C17: replace with 470μF Oscon
C10: leave SMD, bypass with 0.33μF MKP
C3: leave original, not worth replacing. Intended only for reset. Or replace with any value 10-220μF. No effect on sound.
C18: important, replace with your best cap, BG or Oscon or....., value 150-220μF. My choice is 220μF Oscon
C11: leave SMD, bypass with 0.33μF MKP
C2: replace with 100μF Oscon
C5: leave SMD, bypass with 0.33μF MKP
C20: replace with 470μF Oscon
C13: leave SMD, bypass with 0.33μF MKP

Next 5 capacitors have big impact on sound

C9: very important. Capacitor MUST have small dimensions & very short leads & very low ESR & low inductance. Use your best MKP 0.1μF or ceramic, value 10nF-100nF. Big lytic, tantalum or polyester is NO NO, sonic spectrum will be distorted, unbalanced. My choice is small ceramic 100nF (0.1μF), glued & sealed with big drop of hot melt glue or wax, to prevent microphonic effect. This is negative side of ceramic capacitor.
MKP's have no microphonic effect, but they pick up high frequency noise from receiver chip CS8416 and will remove upper part of sonic spectrum (some of high frequency will be lost & bass will have some kind of boombox effect, not very precise). Leave SMD, use ceramic or MKP as bypass (see text above).

C25, C16: very important. C25 is connected to pin FILT- and C16 is connected to pin FILT+.
Please look to datasheet
[IMG][/IMG]

C25: replace with 10μF-47μF. Bigger value=better ripple rejection, but you will loose high frequeny details & dynamic. Sound will be some kind of "slowed down"& unsharp. If you increase C25 value, you should decrease C16 value, they are correlated. It is very very difficult to find balance.
Without C25, transparency is the best, with very good details, but also bright & kind of harsh on highs.
My choice is 10-22μF, if C16 is 100μF.

C16: replace with 100-220μF. Bigger value=better ripple rejection, but you will loose high frequeny details & dynamic. Sound will be some kind of "slowed down". Same as for C25, but even bigger impact on sound. Bigger capacitor= bigger boombox My choice is 100μF, if C25 is 10-22μF.

I like open transparent system with good highs and open vocals and my bass speakers are very good in bass range (3 x bass driver). For tube amp with less bass, try to slightly increase C26 and C16. Please experiment by yourself & choose visely

C12: C12 is bypass for C25. Leave SMD, bypass with 47nF (0.047μF) MKP. Tantalum or lytic is NO NO, please no big value, it will add to capacitance of C25 and change performance.

C8: C8 is bypass for C16. Leave SMD, bypass with 47nF (0.047μF) MKP. Tantalum or lytic is NO NO, please no big value, it will add to capacitance of C16 and change performance.

Op-amp mods (already described before by Leo)

R8, R9, R14, R17: replace with 30K matched resistors, to remove DC on op-amp pin 1 and 7.
C32, C33, C34, C35: replace with 100-220pF polystyrene (styroflex) capacitors. It is tricky here to find right balance
C32, C33: 100pf = great details, but bright sound. 220 pf = less details, muffled sound. My choice is 180pF.
C34, C35: replace with 100pF

C27, C28, C30, C31: remove capacitors and bypass pins with wire (already described before)
C6, C54: remove capacitors and bypass pins with wire (already described before)

Another trick: If you like vocals, please try to add some capacitance to C36 and C38. Leave SMD, bypass with 220pF-560pF polystyrene (styroflex) capacitor. My choice is 440pF (2x220pF in parallel)

With these mods, DAC will sound very analitic, with very good bass and highs, exceptionaly good mids, very musical, a lot od details. Maybe a little on bright side.

Some info on caps:





Happy modding & sorry for my English, it is not my native language

[JDMz]

leo, on your instructions for modding, you bridged the chip below the board. What does this do?

[Tripmaster]

leo, on your instructions for modding, you bridged the chip below the board. What does this do?

It bypasses the chip. Leo thinks the DAC sounds better without. I removed the chip completely as a last resort. If you do add a blob of solder to those points make sure you lightly scratch the surface so you get a good solder joint. I didn’t and ended up burning off the pad!

[Tripmaster]

Wow! thanks for those comprehensive lists.


I removed all of the Oscons and Tants and replaced with general purpose caps, but now the LED doesn't light up! I have checked the PS and I am still getting the correct output.

I am going to check the board for continuity in my lunch break and see if I can find the fault(s). The trouble is I have soldered and re-soldered so many times resulting in a lifted a solder pad or three! I have always managed to find the track by scratching away the black coating.

An ill fated project from the start

I am debating whether to buy another board or try something else.

Does anyone have a spare DAC PCB they would like to sell?

Leo, you mentioned you may be planning another DAC project...any news?

Richard

[leo]

Leo, you mentioned you may be planning another DAC project...any news?

Richard

http://theartofsound.net/forum/showthread.php?t=1152

I think best thing to do with the cheapo CS4397 would be to do the output filter mod (30k + 150pf) bypass the smd chip bottom of board and sort the output coupling DC blocker caps first and see how it sounds.
I'd then try updating the PLL filter to the correct values (1N/3k/22N)

Maybe then try a better op-amp, obviously one that won't go unstable in this circuit

Then try the decoupling caps in stages so its easy to revert parts back if you don't like it.
Problem with passive parts like capacitors is that people have their own references , they can alter the tone of the sound and sometimes have undesirable effects in both sound and stability to the circuit

[fordgtlover]

Tripmaster,

Since you are playing around with the caps on CMOUT...
In the datasheet for the DAC eveluation board there's 2 resistors of 1k to cut the 5v into 2,5v and connect it to CMOUT.

In the note's it says they are for PCM modes. I suppose its because CMOUT has to be typically (according to the datasheet) at 1/2 VA.

Maybe it's something to try also ? I havn't tried it yet.

My mod list to date is as follows:

Mod1 Standard board with coupling caps (betwee DAC and output stage) and mute chip bypassed.
Result: OK i guess, dont knw exactly

Mod 2 C20, C25, C16, C17 -> 100uF 16v OSCON
everything else rest standard as is.
Result: Bass ok good soundbalance

Mod3 C3,C18 -> 220uf 16v Philips
C19 -> 1000uf 16v general purpose
Result: Bass shy, vocals to bright

Mod4 C25 10uF 16v general purpose
C19, 100uF 16v Oscon
Result: Vocals little better, still bass shy

Mod5 30k and 150pf around opamp
Result: Not determined yet, still have offset.

Seemed Bass getting downhill with Mod 3 and after.
Let you know if i'm getting somewhere.
I have to wait for parts, got a few ELNA SILMICII and Pana FC on the way.

Stay tuned.

Naqua


PS LEO: Thanks for your suggestion, i will try matching the resistors first, then changing opamp to opa627's i have here.

Naqua

Mine is similarly modded to your except for the following (possibly significant) differences C25 -> 10uf Oscon, C20 -> 330uf Oscon, C19 -> 1500uf MBZ and C21 -> 470uf pana FM. I am also running an OPA2107 opamp. I don't consider mine to be bass shy at all. I actually think it is pretty well rounded. Apart from the output stage that I am working on, I don't think I'll be making any other changes.

Here is my current configuration:
R2 3K
C3 10uF 10V Oscon
C8 .1uf Polypro
C9 .1uf Polypro
C10 .1uf Polypro
C11 .22uf MKT EPCOS
C12 .1uf Polypro
C13 .22uf MKT EPCOS
C16 100uF 16V Oscon
C17 100uF 16V Oscon
C18 100uF 16V Oscon
C19 Rubycon MBZ 1500uF
C20 330uF 6.3V Oscon
C21 470uF Panasonic FM
C22 22nF
C23 1nF
C25 10uF 10V Oscon

R8, R9, R14, R17 30K
C32, C33, C34, C35 150pF

Opamp OPA2107

Leo's bypass mod
C27,C28,C30,C31,C6,C54 Bypassed
L & R out C 2uF Obbligato PIO
L & R out R 51 Ohm Kiwame