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Luxman uses ROHM Semiconductor MUS-IC BD34301EKV dac
Luxman uses ROHM Semiconductor MUS-IC BD34301EKV dac
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Old 11th May 2021, 08:28 PM   #101
syn08 is offline syn08  Canada
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Quote:
Originally Posted by peufeu View Post
Well considering the layout, I'm not sure it can be further massacred, lol.
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Markw4 will find a way, wanna bet?
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Originally Posted by Markw4 View Post
A little more progress. I/V opamps at this point are OPA1612 still on adapters. Jumpered the XLR output coupling caps. Routing the output with it's roughly -3v offset into a class-A MOSFET buffer setup to remove DC offset using some pretty good big film caps. The buffer box has been powered down for a few days and the particular film caps in it are ones that can take a couple weeks to fully 'open up.'
Peufeu, you lost big time .
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Old 11th May 2021, 08:49 PM   #102
Markw4 is offline Markw4  United States
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For the record, four 30ga wires, each about 1/4" long were soldered across capacitor legs, the PCB was not touched. The MOSFET buffer is external to the eval board.

Last edited by Markw4; 11th May 2021 at 08:53 PM.
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Old 11th May 2021, 09:43 PM   #103
chris719 is online now chris719  United States
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Luxman uses ROHM Semiconductor MUS-IC BD34301EKV dac
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Originally Posted by Markw4 View Post
For the record, four 30ga wires, each about 1/4" long were soldered across capacitor legs, the PCB was not touched. The MOSFET buffer is external to the eval board.
If nothing else, I admire your persistence and enthusiasm.
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Old 12th May 2021, 10:07 AM   #104
Terry Demol is offline Terry Demol  Australia
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Since the current discussion is around PS decoupling and also noting that there is a bit of disdain here for audiophile electronic designers, I thought the job on
my bench was ironic. I'm looking at various channel strips of an English mix console, I guess you could call it a semi-pro, 32 ch -> 8 sub grp -> 2 master
section in for upgrade.

Inspecting the subgroup card, all 9 opamps are JRC TL072's. Looking for PS decoupling caps there is total of *1 per rail, 22 uF - that's it.
These cards include a 12-LED level meter driven by 3 x LM339 comparators powered off the +-17V audio supplies.
Those 2 caps are in the LED switching section and there are no PS caps anywhere to be seen near the OPA's

So... lot's of work to do.


TCD
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Old 12th May 2021, 10:22 AM   #105
peufeu is online now peufeu  France
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TL072 has 3MHz GBW

Ironically it will probably perform better with less caps to inject power supply noise into the ground traces...
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Old 12th May 2021, 12:33 PM   #106
Terry Demol is offline Terry Demol  Australia
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Originally Posted by peufeu View Post
TL072 has 3MHz GBW

Ironically it will probably perform better with less caps to inject power supply noise into the ground traces...
You may think so but that is not the case, it just has to be done carefully.

All under control.

TCD
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Old 12th May 2021, 04:20 PM   #107
Evenharmonics is offline Evenharmonics  United States
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Originally Posted by chris719 View Post
If nothing else, I admire your persistence and enthusiasm.
When a business is factored in, that's a given. As the saying goes, business is business.
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Old 12th May 2021, 06:55 PM   #108
Markw4 is offline Markw4  United States
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^^^
Speaking of persistence...
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Old 20th May 2021, 11:36 AM   #109
Markw4 is offline Markw4  United States
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Been thinking some more about BD34301EKV and the eval board design.

Interesting that there are so many different pins, or sets pins, labeled with AVCC in the name. Why? Since the dac is segmented architecture maybe the three most significant bits are thermometer coded, and the lower order bits are binary coded (something like that anyway).

https://www.analog.com/media/cn/trai...als/MT-016.pdf

https://www.lumerink.com/courses/ece...hitectures.pdf

In such a case, all the AVCC signals would need to be at the same nominal DC voltage, but at least they could be bypassed separately so that switching transient currents of the few highest order bits do not excessively glitch, distort, or otherwise disturb the lower order bits.

If something more or less like the above were true, then the recommended AVCC decoupling and or possibly the odd PCB layout might make a certain type of sense.

Okay with me so far, but here is a concern: I listened to aluminum polymer and tantalum polymer electrolytics for AK4499 AVCC. They were located at the dac chip AVCC pins. To me they made sort of a low level 'gritty' or 'popping' type of noise. It was different that Panasonic FM (which have their own characteristic noise sound). Other electrolytics such as Silmac don't have that noise effect to me, but they have dynamically flat sound sort of like an audio compressor (lots of good app notes on compressor design at That Corp, if anyone is interested). As said in other posts and threads, to me good film caps are the most benign sounding, but they are bulky and expensive (which brings its own set of problems).

What I have been leading up to is this: Now wondering if the sound of this dac will be limited by the sound of the AVCC bypass caps in a way that might be very difficult to avoid.

Time will tell, I guess.

Last edited by Markw4; 20th May 2021 at 11:38 AM.
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Old 20th May 2021, 01:39 PM   #110
altor is offline altor  Israel
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Yes!
I made eval board by myself and run it a few weeks ago.
It is too early to say something, but it works, at least PCM.

Last week I was very busy at my main job, also the next week will be the same. But after I will try to run also DSD.
Last weekend I was able to return back to my board. But unfortunately, I made a mistake connecting the power supplies.
The result was a loss of ~100 dollar chip, and what is the most important - the time, since I had only one
I have to think well before spending another $100, but in any case BD34301 is not available now. Digikey and others said - in August.

P.S. During the previous session, I did not have time for documented measurements, and also the listening time was rather short to make any conclusions.
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