musical-fidelity-a3.24 mods

[rogerlike]

Hi again George,

Can you explain what the C36 ... C42 capacitors are in the top middle of the double-page schematic, or what they are connected to? (ground at the top... ??? at the bottom)

Thanks

 

[georgehifi]

They are all part of the power supply, decoupling smoothing caps together with the massive chokes, don't worry about them, there is no room for improvment in this area, just listen and enjoy now that you have finished all my mods.

Cheers George

 

[rogerlike]

I suppose I was asking because I was confused a little when I started looking at the board and comparing it to the schematics.

C37 has been replaced with a 29ohm R.

There is also a 100uF C straddling R26 (to the right of IC10).

Both of those changes look a bit 'ghetto' on the board, i.e. the design changes had not been made on the PCB.

(as an aside, what's a good character to use in place of 'ohm' when one cannot write omega?).

 

[rogerlike]

Might anybody know/can explain what these changes could be? Thanks

 

[erikherdian]

modification use LM4562 just fine

Hi Georgehifi,

I've read about your modification and I've done it today for my DAC,
I use LM4562 instead of AD825 because I can't find any in my city.

There's no problem found about oscillation or else and my DAC work just fine and the sound is much better.

Thank's for your article....

 

[erikherdian]

Further Modification

after last modification,
I modify the power supply, changing all diodes, each with 4 discrete hexfred HFA06TB120 and changing C1,C2,C4 with sanyo oscon. the result: sound little bit dissapointed, bit noisy and bright, then I put back C101,C201 with blackgate F 47uF and change R119 and R219 with dale metal film..
result..... very very good....

 

[georgehifi]

I've found that in the past when I've done the diodes with Shotky's or other so called better diodes, the sound became edgy or hard, and in the end went back to the normal run of the mill diodes.
Cheers George

 

[erikherdian]

hi george,
you're right..the sounds bit edgy / hard, i'm still working on that

 

[erikherdian]

Final modification

Hi again,,

here's my final mod..

I change

R119, 219 with kiwame 2W
R 220, 221, 120, 121, 103, 104, 108, 203,204, 208, with 0.5w Dale metal film,
C 208, 108, 209, 109, jamicon replaced by blackgate F type
Coupling capacitor now replaced by blackgate N type (470uF/6.3v)
C25 and C28 replaced with ROE gold capacitor
C1, C2, C4, replaced with sanyo oscon

I keep all hexfred in place and added 2x 22uF/250v SCR capacitor for smoothing analog supply,

result: better stagging, clear high, bloom mid but still neutral, smooth hight but enhanced openes and detail, dynamic enhanced, and better separation....., hardness sound also gone..

I'm really satisfy with the result..

thanks to you also George who made me start this modification..

 

[erikherdian]

Ok, this is really finale modification...

Opamp NE5332 replaced by LM4562NA

R119, 219, 203,204,103,104, 220,221,120,121 with Riken RMG 1/2W
R207,208, 107, 108, with 1/2 Dale metal film (RN60),
C 208, 108, 209, 109, 212, 112, 213, 113 replaced by blackgate F
Coupling capacitor now replaced by blackgate N type (470uF/6.3v)
C25 and C28 replaced with blackgate F,
C1, C2, C21, replaced with sanyo oscon
C110,210,111,211, replaced by BGN-HiQ 0.1uF/50v

I keep all hexfred in place and added 2x 22uF/250v SCR capacitor for smoothing analog supply, 2x 0.47/50v BGN-HiQ bypass cap on digital supply capacitors.

I also replace original output cable with Jupiter solid silver with cotton sleeves.

result:
mid and high are smoother and liquid also maintain dynamic.
sound cleaner, more musical and no hard/edgy sound. Soundstage become deeper and better separation.

note: be patient for long burn in time..

 

[tiefbassuebertr]

There are a new type of operational amplifier available (better performance as OPA627, but compatible). Please read more about the weblink
http://www.diyaudio.com/forums/showthread.php?t=150222
Perhaps of interest for the I/U converter behind the PCM1738 in this DAC.

 

[tsl0124]

Hi,
Sorry, for this is different topic from this thread. Pls excuse me, as I am new to this forum.

I need some help as my power transformer is dead, the secondary voltages of the toroid transformer is dead. Noticed the board marking indicate 3V, 9V and 13V. Checked with local dealer and the quote for replacement toroid transformer costs more than £160 after currency conversion. I not able to find a similar toroid transformer which has 3 outputs. Anyone able advise where can I get similar or lower cost transformer. An alternative transformer would be nice. My preference would be online purchase.

 

[audioquestM-40]

I know this post is so old, so incredibly old but I got an old a3.24 and thought I'd give the easy part of this mod, as was the first post of this thread. Anyway after installing the trim pots and shorting the output caps I adjusted the dc to zero, and it has no audio output. I took the jumper wire off the cap and now it works. I noticed this dac has lower output than my Yulong sabre and the board on this MF says version 3. Did they make changes or what do you think the issue might be?
I swapped the caps for 220u / set the dc and it sounds far better than it did but sure wanted to try it capless

 

[georgehifi]

As per the diagram, it worked fine for me shorted cap, now dc coupled and the 5k trimpot in place of the 2.2k resistor adjusts for dc offset.
Set the trimpot for 2.2k before you substitute it for the 2.2k resistor.
Cheers George

 

[audioquestM-40]

I get zero output with the cap shorted, but normal with it, I installed 220u film and definitely a huge improvement but could still be more transparent. The $500 D18 Yulong just kills this a3.24 in every way except maybe in the looks department.

Just noticed on your schematic it shows 470/63 the caps on my rev3 board are 470/16 did they perhaps make an output voltage change?

 

[georgehifi]

Yeah it was ok, but still Delta Sigma based.
I'm firmly sold on well implemented R2R Ladder Multibit now for Redbook PCM conversion, especially the PCM1704k. They have a jump factor (dynamics) no Delta Sigma based dacs can touch, they're sweet enough but just a yawn to listen to.

Cheers George

 

[mikerbaker]

Hi - did you have any joy with this, my transformers dead too and trying to find alternative!!

 

[mikerbaker]

transformer

Hi,
Sorry, for this is different topic from this thread. Pls excuse me, as I am new to this forum.

I need some help as my power transformer is dead, the secondary voltages of the toroid transformer is dead. Noticed the board marking indicate 3V, 9V and 13V. Checked with local dealer and the quote for replacement toroid transformer costs more than £160 after currency conversion. I not able to find a similar toroid transformer which has 3 outputs. Anyone able advise where can I get similar or lower cost transformer. An alternative transformer would be nice. My preference would be online purchase.

Hi - did you have any joy with this, my transformers dead too and trying to find alternative!! Does anyone have the current requirements for each winding and i can't see from the schematics what the 3V winding actually does. can someone explain?
thanks in advance