New PCM1794A Kit – Balanced Mode Update – Good to Fantastic Sound! - Page 8 - diyAudio
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Old 12th October 2010, 12:28 PM   #71
TC Goh is offline TC Goh  Hong Kong
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Quote:
Originally Posted by skseah View Post
Hi T C,
Finally finished my DAC...now 'burning' it in...initial sound very promising...unfortunately, one of my amp just broke down..so now have to solve the amp before I can listen to DAC. Will try to roll the caps later.
Best Regards
Hi Victor

Congrats. When I finished mine, I got quite a buzz. Hey, can you please let me know the DCV from each of the balanced signal output to ground? (ie one probe to ground and the other to each output channel). If the reading is about 2 mvdc, you can also try OCL.

I am also using a different cap at locations C45/46. Try changing these too. They have a significant impact. I am using Silmic 2 Black/Gold version now. I bought these from Thailand, where I am visiting now ha ha. The music is more mellow and bass is deeper. You will have lots of fun cap rolling. I did.

What happened to the amp? I hope it was not something serious. Is it tube or SS?

Best wishes

TC
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Old 12th October 2010, 12:38 PM   #72
skseah is offline skseah  Singapore
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Hi T C,

Thanks. The DC at the signal output is +-1 mvdc. OK. will try OCL when my amp is OK.

Hmmn..C45/46...sounds intersting....will try later. Wonder if Spencer tried too.

Oh, my amp. It is tube, and the + PS is out. Now trying to find a replacement MOSFET. The one I have seems out of production. looking at equivalent now.

Best Regards
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Old 12th October 2010, 02:31 PM   #73
TC Goh is offline TC Goh  Hong Kong
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Hi Victor

That is an excellent reading. I think Spencer designed one hell of a DAC. The previous one I had was measuring over 20 mVdc! That being the case, OCL is something definitely worth exploring too.

However, you should try cap rolling. I had hours and hours of fun doing it.

For C45/46, I tried using 470uf Silmic II (Black/Gold) initially but that didn't work as it killed the highs! I then swapped to 100uf (Black/Gold) Silmic which seemed to do the trick.

I also tried changing the seven 47uf Silmic surrounding the 1794A to 100uf Silmic B/G too. That didn't work as well too. I guess it was too much of a good thing!

I think Spencer's board doesn't like bigger value caps ha ha. I am not surprised as these were probably determined by some elaborate computations.

Are you using 100uf for the BPs? I thought of trying two 47uf instead.

I hope you fix your amp soon. What make is it?

Best wishes

TC
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Old 12th October 2010, 03:13 PM   #74
skseah is offline skseah  Singapore
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Hi T C,

Yes, I agree that Spencer designed one hell of a DAC...maybe due to his love of electronics and music.

I tried googling around about the Black/Gold Silmic..but can't seem to find much info about them. What are diff between them and the Silmic caps supplied by Spencer?

Have you tried BG?..understand they need long burn-in period.

His board is actually quite fully of components...not much space left for bigger caps. I guess he put in lots of effort on the power supply section.

I am using 2 x 50v47uf for the BPs.

Oh..my Amp..ARC mono block.

Best Regards
Victor
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Old 12th October 2010, 03:45 PM   #75
TC Goh is offline TC Goh  Hong Kong
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Ha ha...

I think these are an endangered species. I actually got them from Thailand. However, their origin remains a mystery, at least to me. Anyway, they appear to be smoother and better in bass than the Gray/White ones; not as forward.

I have tried BG but according to my untrained ears, they are not as detailed, and their bass is a little boomy. Furthermore, they cost much more than the Silmic.

Woaaaa... ARC. They were (and probably still are) what aspiring audiophiles want to own in the 70's, me included.

Best wishes

TC
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Old 12th October 2010, 04:03 PM   #76
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the Black/Gold Silmic are the new ones produced in 2010. Alot of people think these are knock offs, but if you goto there web site they announced the change. I dont think anything changed on them other then the wrapper.
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Old 13th October 2010, 01:07 AM   #77
skseah is offline skseah  Singapore
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Hi TC & nightanole,

Thanks.

Victor
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Old 24th October 2010, 12:40 PM   #78
TC Goh is offline TC Goh  Hong Kong
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Cool New Mods

Hi Victor

Sorry for not replying earlier as I was in Langkawi for some sun and R & R! Click the image to open in full size.


Did you manage to get the Silmic 2 B/G caps?

Spencer put up some mods that should improve the noise floor. I think these are to do with improving grounding. He suggested removing the ferrite bead at L5, changing capacitor at C51 to 560uf and also two additional grounding (thick) wires.

Oh, he is also suggesting (I think) using one TX instead of two, which is what I have... ah well.... so much for the 'two is better than one' theory!!!

Anyway, I just tried some of these mods. I lifted one side of L5 and also added one of two ground wires – (at C45/C46). I haven't done the cap change yet as I need to find them from my stash and the other earth connection would require taking out the boards. I will do that when I find the caps.

Although I don't have the equipment to measure the changes in noise floor, I think the bass does sound a little (just a touch) more extended. Of course, this could also be attributed to my inner ear hairs having grown 0.001mm longer last week....

So, overall verdict, go for it!

No downside and it is fun…

Best wishes

TC
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Old 25th October 2010, 01:45 AM   #79
skseah is offline skseah  Singapore
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Hi TC,

So how was Langkawi ? hope you had a good time there. You were not affected by the haze?....we had a few hazy days (with PSI over a 100 points) last week.

No, have not got the Silmic B/G caps. I am still waiting for parts to repair my amp. I hope they come quickly and also I can repair it....so currently my DAC is on R & R...ha! ha!

Will have a look at the mods suggested by Spencer.

Best Regards
Victor
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Old 1st November 2010, 11:37 PM   #80
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Hey, sorry for a noob question, but, where can we get this kit???
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