discrete dac mock up

[yeo]

yes. replace both of them with 270kohm. or thereabouts. can go up till 470kohm.

[CKL]

Hi Yeo,

What is the size/package of the SMD resistors, 1206?

[yeo]

hi ck

those are 0805s but you could also replace with thru holes. just bend the legs and let them stand vertically.

yeo

[kp93300]

Hi all
I just change the resistors next to 2sk170 transistor and the the discrete dac rocks ! I replace them with 330K
It is firing on 6 cylinders compared to 2 cylinders previously . Music oozes out effortlessly from the speaker.
There is enough gain without the pre in my set up and  i think it is about the loudness of the old monica with IV resistor of 5.6 K.
CK , I am sure it  will be  better than your monica with this mod.

thanks  to Yeo for letting us know.

kp93300

[kkerwin]

i was really enjoying the discrete dac before.  i wasn't experiencing as much loss with the lower gain, but with this mod, now this dac is at another, higher level.  scary good!!!
thanks
k

[kp93300]

Hi K
I notice that it is much quieter also.
I can barely hear the hum with my 91 db / 1 w /1 m  speakers. with my ears right against the speaker.
This solve the problem of the persistent  low level  hum --i even add more cap in the power supply to my amp to try to solve it !
 
kp93300

[kkerwin]

hi kp93300
mine has always been dead silent, except when i was experimenting with using lundahl ll1660's. on the two different outputs that yeo put on the board.  the lundahls resulted in greater detail, but at a compromise to certain resonances which i think were created because of the hum presence (if that makes any sense).  my speakers are 96db.  anyway, i took the lundahls off and switched back to the original setup.  with the qa550 paused and the volume turned all the way up, they are extremely silent. and now with increased detail in all ranges, including bass which is an unanticipated pleasure.
k

[yeo]

hi kp, hi kevin

i only managed to try this tweak today. yeah! only today!

i discovered this mistake when i was building more dacs on sunday but it was too late to mod hence i posted on the forum.

i knew there would be an improvement but i'm still stumped by the quantum leap in performance!

i think it's louder than monica3. beyonce rarely goes positive db (with gain) compared to before.

boy, she's a completely different animal now. one of these days i'll try without beyonce. one less stage...

if you are keen, there is still something you could try but i'm not sure whether this tweak will improve sonics.

the board is laid out for 24 bits, hence 24 r2r resistors. however, i assembled only 20 thus making it 20 bits. it's more than enough for our systems.

most of the time, we can't even hear below 15 bits. yup, bits 15-20 most likely is as good as zero volts.

you could see i have a jumper which shorts bits 24-21. you could extend this jumper for 4 more resistors, thereby reducing the number of bits from 20 to 16 bits.

why do this? well, the ground connection is better. instead of going through so many resistors, the ground connection is better served by a hard solid wire.

anyway, this is what i think. it may not make any difference. even if there is any difference, i expect it to be minimal.

but then, i was still floored by what happened today! 

yeo

[CKL]

It is difficult for me to solder those 0805 resistors: 680 ohms & 330 kohms. The 330 kohms mod is the most significant mod. It now wins my optimized Monica3 obviously! The output level has increased a lots. Congratulations to Yeo! You had built the most affordable discrete DAC to the audio world! 

[yeo]

hi ck

welcome to the party!

glad you like it!

to other folks

i have received so many requests for the dac. i have problem building them fast enough and i have problem determining its pricing. dang, it's expensive and not to mention so bloody laborious to build! last count, 9 logic chips, and 60 0.01% resistors per channel. and i'm not even counting the regulators and caps.

cost price of components is already higher than my selling price of the monica3 module. and i haven't factored in months of r&d work plus other costs. so this will be my most expensive product now!

yeo

[kkerwin]

hi yeo,

i expect that the discrete dac may go through a few tweaks to maximize its performance, similar to monica/mojo.  what should be noted though is that this dac is performing so beautifully and it does not have custom regulator modules, v-caps, lundahls, multiple transformers, etc.  that value is already in the discrete dac performance.  by the time monica/mojo is maximized there are some significant $$$ committed that may not be needed on this dac.

k

[CKL]

Hi k,

Have you tried using Lundahl transformers replacing the Super-E?

[kkerwin]

hi ckl,
i did experiment with the lundahls. i used the "out" and the "bufout" connection points and did a comparison between the two.one was far better than the other, and i think (don't exactly remember, because i switched betweeen a few times) the "bufout" connection had the best sound.  the other was harsh and ringing.  after listening for a while, the better one still wasn't as good as yeo's original setup although it did have more detail. 

also, i do not know if eith of the connections bypass the super e blackgates.  yeo, would be able to comment on that.

interestingly, the changeout of the resistors that yeo recommeded has resulted in at least as much of a detail improvement and much better sounding.

 thanks
k

[CKL]

Hi Yeo,

Since most people are still using SPDIF, how could we connect SPDIF to the discrete DAC?

[yeo]

hi ck

i only sent you the i2s version as i know you have a capable i2s signal.

for everyone else, there is the spdif-i2s module. it is actually the spdif-eiaj module i sell but with just different settings on the dip switch to get i2s out instead of eiaj.

yeo