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Old 11th July 2020, 02:53 PM   #1881
barrows is offline barrows
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Default Bricasti DSD DAC

Quote:
Originally Posted by Terry Demol View Post
Bricasti are an interesting Pro Audio company that don't necessarily take the
usual approach to design. The AD1955 DAC chips are an example of this.

Their M7 digital reverb unit is absolutely superb.
They are ex-Lexicon folk, Lexicon being basically the forefather of digital audio reverb / special effects.


Does the M3's use something like a discrete resistor pulse arrray DAC for
DSD? They might well also be 'pre conditioning' the DSD data stream before
it is sent to the DAC arrays.

TCD
I cannot get them to tell me if they do anything to the incoming DSD, except they do say it always remains single bit. The DAC has an AD SHARC processor onboard, which does handle the oversampling/filtering using custom filters, for PCM input.
The discrete DSD DAC section consists of a high speed switch (IC), followed by a discrete filter circuit made up of precision resistors and film capacitors. There are four of these circuits, I presume two for each of the two (balanced) circuit paths. This looks to be similar to what Playback Designs does. I have had some experimental DSD DACs here using similar approaches, but they all had some noise issues. I like to test the noise floor by playing a file which has a 1 kHZ tone at -90 dB, one can then turn this way up, and still hear what the noise floor sounds like (my Purifi amp has so little noise the audible floor is basically that of the DAC). The Bricasti noise floor with the DSD DAC section is clear and smooth.

BTW, this same test with my (Pavel) DSC-2 is interesting, one thing it proved to me is that this DAC is performing better with DSD 256 than 512 in my set up, as the noise floor with DSD 512 starts to get a bit weird, uneven, with some static sounds sticking out. But the floor is smooth and clean with DSD 256 input. Of course this may also be related to the oversampling engine, my tests were with Roon oversampling, not with HQPlayer, yet... One can hear the results of different modulators, etc, with this test as well. Next thing to try would be to make up some non-related, low level multi tones, with some higher level tones thrown in, to then listen to the floor for modulation effects which are signal correlated.
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Old 11th July 2020, 03:39 PM   #1882
MarcelvdG is offline MarcelvdG  Netherlands
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Some noise modulation effects can be found by playing back a 1 Hz full-scale sine wave at high volume, using an analogue high-pass between the DAC and amplifier to ensure you don't trigger any DC protection or blow up any woofers.
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Old 11th July 2020, 04:21 PM   #1883
gionag is offline gionag  Italy
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Signalyst DSC1
Quote:
Originally Posted by barrows View Post
I cannot get them to tell me if they do anything to the incoming DSD, except they do say it always remains single bit. The DAC has an AD SHARC processor onboard, which does handle the oversampling/filtering using custom filters, for PCM input.
The discrete DSD DAC section consists of a high speed switch (IC), followed by a discrete filter circuit made up of precision resistors and film capacitors. There are four of these circuits, I presume two for each of the two (balanced) circuit paths. This looks to be similar to what Playback Designs does. I have had some experimental DSD DACs here using similar approaches, but they all had some noise issues. I like to test the noise floor by playing a file which has a 1 kHZ tone at -90 dB, one can then turn this way up, and still hear what the noise floor sounds like (my Purifi amp has so little noise the audible floor is basically that of the DAC). The Bricasti noise floor with the DSD DAC section is clear and smooth.

BTW, this same test with my (Pavel) DSC-2 is interesting, one thing it proved to me is that this DAC is performing better with DSD 256 than 512 in my set up, as the noise floor with DSD 512 starts to get a bit weird, uneven, with some static sounds sticking out. But the floor is smooth and clean with DSD 256 input. Of course this may also be related to the oversampling engine, my tests were with Roon oversampling, not with HQPlayer, yet... One can hear the results of different modulators, etc, with this test as well. Next thing to try would be to make up some non-related, low level multi tones, with some higher level tones thrown in, to then listen to the floor for modulation effects which are signal correlated.
i have also noticed the very same dsd-512 behaviour on my past dsc-2.
then i switched to mcfifo+dsc 2.6.2 and the noise went away.

with the St!cks, same thing. DSD512 all day and never had some "strange" noise issues.

i must confess that i always suspected that trace layout on the dsc2 was a little bit clumsy, nor impedance matched in any way (neither on the 2.6.2, but there was much larger clearences) and i think the increase in frequency lends more opportunity to trigger noise along the path in case traces was not carefully layed down.
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Old 11th July 2020, 04:49 PM   #1884
lindamar is offline lindamar  Spain
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Quote:
Originally Posted by gionag View Post
... the stick's attaches to the McFifo / McDualXO combo from IanCanada.

on the DualXo i am using the adpater to mount the NDK SDA 45.xxx and 49.xxx

nothing fancy here
well, funcy enough the McFifo ... I've got one too, I did not recall by your picture, but I have it. So I might end up replicating your project if you do not mind.
thanks mate

The output trafos from bisesik right ?. I got a pair a while ago, they are fantastic. My trafos are 1:5, we found out that it was the best output ratio for the DSC.
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Old 12th July 2020, 05:49 PM   #1885
gionag is offline gionag  Italy
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Signalyst DSC1
Quote:
Originally Posted by lindamar View Post
well, funcy enough the McFifo ... I've got one too, I did not recall by your picture, but I have it. So I might end up replicating your project if you do not mind.
thanks mate

The output trafos from bisesik right ?. I got a pair a while ago, they are fantastic. My trafos are 1:5, we found out that it was the best output ratio for the DSC.
surely i don't mind at all...
on the contrary, I encourage you to do it, they sound amazing (to my ears... of course)

BTW the otp xfrmr are biseik nonetheless, in ratio 1:5 (old version) as yours.

I just need time and willing to finalize all the docs (schematic, component placement, gerbers, bom ecc.. ecc...)

and also, i don't want to speak too soon, but maybe there's something going on with ian and the mcfifo for the dsc applications...
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Old 20th July 2020, 08:12 AM   #1886
nguyentanvu90 is offline nguyentanvu90
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I think here it is an layout error.
Click the image to open in full size.
Click the image to open in full size.
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Old 20th July 2020, 08:28 AM   #1887
nguyentanvu90 is offline nguyentanvu90
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My PCB ). Thank you ppy.
Click the image to open in full size.
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Old 21st July 2020, 11:33 AM   #1888
Brzzl is offline Brzzl  Europe
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Signalyst DSC1
Quote:
Originally Posted by nguyentanvu90 View Post
I think here it is an layout error.

Cool. Where can I get my hands on those gerber files or do you maybe by any chance have some leftover PCB's?
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Old 21st July 2020, 12:08 PM   #1889
ppy is offline ppy  Russian Federation
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For Ivan's transformers with a large coefficient, the question arose again with the quality of the mute signal.

Slightly changed the mute signal in the firmware for the BeagleBone.
New mute signal on P9/28. This pin needs to be connected to +3.3V via 4.7K.
The old signal is retained at P9/27.

The new signal analyzes the state of Alsa and Roon, HQP players. Works better than Botic driver signal. Ideally, you need to mute the OE registers. But current PCB do not allow this.

sd_botic7.img (2).gz — Yandex.Disk

In the new firmware, after Linux is fully loaded, all LEDs are turned off. The system boots in about 2 seconds.

Last edited by ppy; 21st July 2020 at 12:36 PM.
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Old 21st July 2020, 12:53 PM   #1890
ppy is offline ppy  Russian Federation
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Quote:
Originally Posted by gionag View Post
I encourage you to do it, they sound amazing (to my ears... of course)

BTW the otp xfrmr are biseik nonetheless, in ratio 1:5 (old version) as yours.
Newer versions of transformers sound very good. And their measurements are also very good. This is practically the limit for my E-MU 0204.
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