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Thanks Leo. I've made that change.Quote:
Originally Posted by leo
I had intended to have a few boards made, but the Aussie dollar is in the toilet at the moment so It's quite expensive to have the boards done. I'm looking at other options at the moment.
Here is the final stereo board layout I ended up with. Board size is 50mm x 80mm
http://img224.imageshack.us/img224/9429/os31rn3.jpg
http://img224.imageshack.us/my.php?image=os31rn3.jpg
Hello FordGTlover.
May I suggest the next website for your pcb ?!
a quick price calculation was about 4 USD a pcb.
http://www.makepcb.com/
have fun ! and remember, i am interested in a board or 2 also
Naqua
I've just been reading through this thread, and I absolutely love the fact that we have some hardcore knowledgeable electronics engineers on here, gives the DIY section massive credibility (even if I haven't a sodding clue what you're all talking about). :lol:
I didn't expect my thread to be so popular:smoking:
I wouldn't pay too much, this was intended to be cheap;)Quote:
Originally Posted by fordgtlover
Other option is to etch your own board, you could use the layout here on page5 as its single sided http://home.quicknet.nl/qn/prive/ra..../index_en.html
You are an electrical engineer? I am in 1st year in college planning on majoring in either mechanical or electrical... then I can understand more of the complicated things you talk about lol.
I just had a quick look, and it look like a great deal. I'll do a bit more poking around, but I think you may have found me a winner.Quote:
Originally Posted by Naqua
I agree. I don't want to pay too much. I have never etched a board, and I suspect others are in the same boat. I wanted to give myself and others the opportunity to get the best out of this little DAC for a reasonable price. The place Naqua linked to looks very cheap. :)Quote:
Originally Posted by leo
I have been following this thread, and you are doing a great job.Quote:
Originally Posted by fordgtlover
When you are finally finished, let me know how much it all cost. Then I can loan you one of my DAC to compare the two...
Stan
Thanks for the words of encouragement, and the kind offer.Quote:
Originally Posted by Sensimilia
Cheers
Rob
On another note, I think I'll resize the board slightly to the same size as the DAC to allow it to be 'stacked' on top.:)
Over 19,000 views and counting. :)Quote:
Originally Posted by leo
I don't think it would better your dac Stan, it would be interesting though if the guy compared them
Just remember this thing is cheap and good option for those wanting to get into diy without having to spend much, I paid under 30 quid for the dac board:lol: seems the prices have gone up a bit though:doh:
So far I've kept it under 80 quid
will this work as an output cap?
http://www.parts-express.com/pe/psho...Number=027-222
I've never tried them, anything like that would be suitable, obviously you have to remember the high voltage film and foil type tend to be pretty large physically.Quote:
Originally Posted by JDMz
Try to keep bare leads as short as you can to help prevent any noise pick up with them being unshielded
Hello,
I have made the mod Leo suggested for the r8-r9-r14-r17 to 30k 1% and c32-c33-c34-c35 to 150pf.
I am measuring 5mV left and 23 mV right. I thought it would be closer to 0 mV. However i am measuring from pin 1 and pin 7 of the opamp to AG. This with the standard output-caps and r28 r29 still in the circuit. Does that explain the offset i'm measuring. (coupling caps between dac and opamp are bypassed)
If not, what can i do to kill the offset (apart from placing output caps).
Thanks in advance for eveyones help. It is a nice DAC indeed.
Here's my question. Alot of people buy capacitors to improve their sound. They replace their input caps from the amplifier with a better one. My amp has 3.3uf input caps stock. Do I have to remove those to add in the capacitor that I showed you? And what are the benefits of the input cap on the DAC?
Thank you leo
How long did it take for you guys to get your ebay dac board? Did anyone buy from the gigaworks guy?
Hi,
I ordered from gigaworks twice.
It's all good. Fast response, good packaging.
Took about a week to arrive (in the netherlands is where i live)
Naqua
Hi LeoQuote:
Originally Posted by 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
A few things could be causing the offsetQuote:
Originally Posted by Naqua
It helps to match all the resistors in the differential stage, if say the + side doesn't mirror the - side it can cause drift
If you use the supplied op-amp which I think is based on a NE5532, these are bipolar input and tend to have some dc offset on the output, you could try a jfet input stage op-amp to see if it helps
My dac measures less than 2mv's on the output, I matched all output filter resistors for the +/- output
Quote:
Originally Posted by JDMz
yes, you remove the caps to be replaced, if you leave the old ones in the new ones are then in parallel with the old ones and it will double the value
The only cap on the dacs input is for the SPDIF input which is used for blocking DC, this is a digital signal, the standard ceramic capacitor is a bit microphonic , ideally a physically small cap should be used here which is low inductance low microphonic
You don't have to change the input spdif cap, its just a bit of fine tuning, I wouldn't use anything with a bigger than 5mm leg spacing
Let us know how you get on;)Quote:
Originally Posted by Tripmaster
I may build one of those transports later too!
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.
I seem to remember reading somewhere that the CMOUT mod brings out more detail. Could be worth trying.
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
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]http://shrani.si/f/2e/Ff/4jXHB5xE/dacafter5.jpg[/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:confused: 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 :lolsign:
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) :eyebrows:
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:
http://shrani.si/f/3E/wQ/1QvwKk0J/capac.jpg
Happy modding & sorry for my English, it is not my native language
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!Quote:
Originally Posted by JDMz
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
;) http://theartofsound.net/forum/showthread.php?t=1152Quote:
Originally Posted by Tripmaster
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
NaquaQuote:
Originally Posted by 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
So I can try it bypassed and not bypassed? Is this bypassing the OPAMP or just that chip? Cus i bought a nice opamp.. lolQuote:
Originally Posted by Tripmaster
JDmz.
It's just bypassing the chip. It normally mutes the output signal when there's no lock at the pll or when powering on.
Opamp stays in place
Yes, just bypassing the chip.Quote:
Originally Posted by JDMz
Hi, I messed up the trace of C54 on the side of the right output. Do you know where I can find this? I just see a bare board... got it from using a desoldering braid
pic
http://i161.photobucket.com/albums/t...h_IMG_3784.jpg
also,did you remove r28 and r29? mine has resistors there with 104 written on it
thank you
EDIT:
I used resistance checker and the RED's have 0. So I assume I can connect the YELLOW's?
It is weird.. I always thought current moves from - to +, why is it reversed?
C54 is connected to R output
are you sure? Doesnt it go negative to positive? so the left side of C54 goes to R output?
EDIT: I fixed it by doing what I described in the picture.. why is the capacitor connected backwards? + on +
negative side of C54 is connected to R output. Positive side of C54 is connected to op-amp output.
If you bypass pads with wire, both positive and negative pads are connected to R output.
Don't understand about capacitor connected + on + or backwards :lolsign:
Signal is always traveling from higher level to lower lever. At op-amp output is higher level (source of the signal), at RCA is lower level. Capacitor is between, positive side goes to higher level, negative goes to lower level, where is problem? :eyebrows:
Anyway, using lytic or tantalum for coupling is bad idea :scratch:, but it is cheap
Hi-res shematic
http://shrani.si/t/3F/9O/2G6LodNt/boardshema.jpg
Mod update:
Mod6:
c19 pana 470uf
c21 oscon 100 uf
c3 10 uf gpo
c18 100 uf oscon
c20 470uf pana
c25 10uf pana
c16 100 uf oscon
c17 100 uf pana
Muddy bass - "air" ok "beeing there" not ok
Less detail, less dynamics
MOD7
c19 pana 470uf
c21 pana 150 uf
c3 10 uf general purpose
c18 100 uf oscon
c20 oscon 100uf
c25 10uf pana FC
c16 100 uf oscon
c17 100 uf pana FC
round bass, power dynamics, Detail and highs-ok
also tried opa21047AP was to heavy on the bass, less depth didn;t like it.
Next round -> elna SILMICII instead of Pana FC
tried all 3 types (Oscon, Panasonic FC, Elna Silmic II) during several days listening marathon :lol:
No big difference at all (the same values for all 3 types). Panasonic FC is the worst (less bass), Elna Silmic II and Oscon is equal, maybe is Oscon more stable in bass & mid region, but less details & less dynamic than Elna. Or just my imagination playing with me :lolsign:
Naqua:
Difference between your MOD6 and MOD7 is value for C20. Bigger value will "slow down" music, cause less details & muddy bass.
I increased C19 from 470μF to 1000μF. Changed C20 from 470μF to 220μF OSCON and changed C17 from 470μF OSCON to 100μF Elna Silmic II.
How come leo's board did not come with R28 and R29? I have resistors there. Should i remove those since I added in 30k resistors?
Hello, again.
I tried Leo's mod for the r's and c's around the opamp. (R's 30k C's 15-pf). But i am still getting about 25mv on each side (left +27mv and right -23mv).
tried matching the resistors: resistors went down from about 30,2k to about 29,9k dc output went up from about 25mv to 30mv. Fet based opamp also had no result.
Maybe it's the way i am measuring ?!
Ouput caps and r's are still in place and i measure between pin s1 and 7 from the opamp to ground (middle) pin on the output connector. The DAC is not connected to an amp. Opamp is JRC5532.
Is this the correct way to measure the DC on the output or do i have to remove output caps and resistors first to get correct measurement ? Or do i have to connect the dac to an amp ?!
I would be pleased to hear from someone who knows and can help me eliminate the offset.
Thanks in advance !
Naqua
@Naqua
your measurement is correct. Pin 1 and 7 from op-amp to ground. I am using 30 K resistor (matched set) and my offset is 1 mV left side and 2 mV right side.
Use matched set od 4 resistors. You need to buy 10 or 20 resistors & use your multimeter to match 4 of them. If you are using coupling capacitor, capacitor will block DC, no need to worry about some DC offset left. And C's are not 15pF, they are 150pF.
Resistors are responsible for DC offset, no capacitors. Capacitors+resistor are RC filter.
@JDMZ
why to remove R28 and R29? Look again on board shematic I posted, what will you accomplish with this action?
Thanks Firefly! I'm glad somebody else can help answer questions , I think the manufacturers of this dac should be paying us:lol:
I've noticed a few of the dac boards had R28/28 missing, maybe they just forgot to fit them on some batches
Thanks Firefly,
To resume i understand correctly:
I'll try to macht 4 resistors of 30k. My multimeter just has 1 digit after the decimal point. Will that be enough to match ??
Also my Resisitors are matched as follows:
30.0k 29.9k for left channel
29.8k 29.8k for right channel
I assume this is not matched enough then ?!
Is it better to have precision resistors of 0.5% or 0,1% tolerance or do i have to match them also.
Is it ok to raise the resistor value if it helps to eliminate the offset? (ie to 31k or 33k)
Thanks again
@Naqua
30.0K vs. 29.8K, is this matched? For me this is NOT matched. Maybe you can use 27K resistor and 5K multiturn trimmer in series to set offset to 0 mV :eyebrows:
If you change resistors, you will have to change capacitors values too. Stay with 30K resistors and capacitors 120-180pF.
Pic of multiturn is bellow
http://shrani.si/f/t/YV/3wOuhRIJ/multiturn.jpg
@leo
thanks, will try to help, but credits for major work goes to you :)
Thanks Firefly (and of course Leo) :)
Will try 0,1% 30k resistors first.
Then will try your multiturn option.
Thanks again (and again and again etc) :)
My opa hdam opamp has a ground wire. Can I hoook this to AG ground? between the two outputs? or one of those other grounds?
The output caps i used.. does not show polarity. Is this normal/ok?
Thank you
Some new things about op-amp output stage.
Look to shematic I posted on page 28
http://theartofsound.net/forum/showp...&postcount=288
Capacitors C32 and C33 are connected as negative feedback. This is very very bad practice, to put capacitors as negative feedback, they are destroying trebles & fine high details. It is asking for trouble or like giving pacient a medicine, after he is already death :lolsign:
They must go out. I cut them from the my board.
And resistors R8 and R9 are also negative feedback. Too much negative feedback is poison for sound, like hitting a pacient with hammer to sedate him :lolsign:
Values must go higher, do decrease neg. feedback, I will make some tests & calculation and post results.
Capacitors C37 and C39 are part of RC lowpass filter for L and R channel, They have too big values, will make some calculations & tests and post results.
Also capacitors C44 and C51, near wide white power connector, with original values of 100μF. Values should NOT be increased, they should be decreased something like 47μF, to give sound more air. But this depends on your ears :lol:
So you are saying I should just desolder those two capacitors? Anyone know where the ground of my opamp can go? AG or the other ground?(or however many types there are)
Looking forward to your results!