CS4397 dac

Yes, either way.
Polyprops and other plastic types are not directional in the sense that electrolytics are.
I like to arrange things so that the start of the writing on the cap is at the input side.

Quote:

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Originally Posted by JDMz

im gonna try firefly's mod when people start confirming it is good. Yea I am confused too. Leo has 4 capacitors around the opamp when firefly removes 2 of them. And he removes the resistor mods too. Leo hasn't been on in a while, but I will do the mod once he agrees with firefly lol.

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Let's do some math:

C34 and C37 together with R11 and R15 are forming second order lowpass filter.
Fc= 1 / 2*Pi*√R11*R15*C34*C37
With values of R11=6K8, R15=22K, C34=1nF, C37=1nF is cut frequency set at 13 kHz, as proved before by Jackenhack. See post
http://theartofsound.net/forum/showp...&postcount=210

If you change value of C34 to 150pF as Leo suggested (and leave C37 at 1nf) then you will have cut frequeny at 33.6 kHz. If you change C34 value to 100pF, then is cut frequency at 41.148 kHz.

About feedback capacitors C32, C33 already Leo explained. Together with resistors R8 and R9 are forming kind of Bass Booster and decreasing gain of op-amp for high frequencies and limitting usable bandwith of op-amp.

Hello everyone,

I am still messing around to kill the offset.

So far i used 30k 0,1% resistors and measuring left 5.6mv and right -26mv
Checked and rechecked everything, used FET opamp but offset remains the same.

Measuring some voltages at the opamp i see some differences between left and right. Measurements are as follows:

Straight from the dac outputs everything 2,53v (left and right)
Left side inputs Opamp pin2: 1,448v and pin3: 1,445v
Right side input Opamp pin5: 1.434v and pin6:1.436v

Seems i am losing mvs left between dac output and left opamp inputs.
I removed the opamp and measured resistance as follows.

Left between dac output pin 19 and opamp pin2: 29,0k
Left between dac output pin20 and opamp pin3: 29,1k

Right between dac output pin24 and opamp pin6: 28,9k
Right between dac output pin23 and opamp pin5: 29,4k

Is there anyone who can help a relative noob to determine what to do to kill the offset ?

Resistors of 0,1% tolerance do not need to be matched or do they ?
They all measure 30,0k on my dmm.

Thanks in advance for your replies. !!

Naqua

@naqua
look on shematic & measure other resistors. They must match for L and R channel.
R15=R18=22K, R10=R12=6.8K, etc, etc, etc.

Today desoldered C36 and C38. On shematic, value is indicated "102", that is 1000pF or 1nF. I measured them and real value is 30pF, not 1000pF as indicated :doh:

I just removed c32,33,34,35.. I think the highs are more detailed now. With my klispch horns it seems a little bright, but clear. I don't have audiophile ears though haha.

@JDMZ

keep 2 small capacitors in spare. Some op-amps may start oscillating. In this case, solder capacitors C32 and C33 back. Very small value of 5pf will be enough.
I experienced this with some OPA op-amps.

I have a discrete opamp from audio-gd.com... Ahh crap i dont have 5pf capacitors. It still sounds pretty good though.

you need this 5pF just in case od cranky op-amp. Don't bother if everything is OK.
With Klipsch horns try this:

C34, C35: 680pF
C37, C39: 220pF
C36, C38: 680pF

experiment with C36 and C38, try values between 470pF and 1nF :eyebrows:

What do you recommend for capacitors? What type? Should I just get some ceramic ones like what I had? I bought them at digikey.com

What I see is stagnancy in this tread ;-)))
So I must show something I built.
There is an external DAC based on the CS4397 DACboard and a CD player with this DACboard built-in (Sony CDP-XA20ES). Both porojects have tube output stages instead of original opamp based stages:

http://www.audiostereo.pl/zalaczniki/1216755_1.jpg

http://www.audiostereo.pl/zalaczniki/1216755_2.jpg

http://www.audiostereo.pl/zalaczniki/1272131_1.jpg

http://www.audiostereo.pl/zalaczniki/1272131_2.jpg