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Old 20th August 2019, 06:16 PM   #1511
audiodesignguide3 is offline audiodesignguide3
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Here 3 different measurements


1) CT7302 with internal oscillator 12MHz
2) CT7302 with external oscillator 24.57MHz
3) AK4137 module with 2 on-board oscillators
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Old 20th August 2019, 07:55 PM   #1512
audiodesignguide3 is offline audiodesignguide3
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Like requested here 2 different measurements with more resolution

1) CT7302 with internal oscillator 12MHz
2) CT7302 with external oscillator 24.57MHz
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Old 21st August 2019, 09:47 AM   #1513
Vit123 is offline Vit123  Russian Federation
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Thanks, audiodesignguide3.

As audiodesignguide == Andrea Ciuffoli, who is associated with quanghao, I assume that you are using quanghao latest board for measurements.

quanghao wrote about his new design - "all ok, it is best , for last design with THD and SPL".

I'am interested in more info about DSC "THD bump" effect (THD increase with high level signal) in quanghao new design.

My measurements with DSC 2.5.2 with stock tranformers:
-0.5dB output signal - THD 0,0024%
-10dB output signal - THD 0,00025%

ppy's measurements with DSC
-0.5dB output signal - THD 0,0045%
-10dB output signal - THD 0,000354%

Your measurements:
- ARTA ~ BW 48K, ~ 0dB output - 0,0069%
- ~-5dB ouput - 0,0009%. You have very high noise floor (~ -125dB). May be you didn't do any averaging.

So I guess this effect is still here. IMO one can avoid this "THD bump":
1. by increasing the number of resistors ("taps")
2. or by using more accurate resistors (0,1% to 0,01%).
3. or by using software volume control before DSC.

The second question is why are you going to use CT7302? According to your measurements AK4137 performs a little better in THD.

As far as I remember, the only reason why AK4137 was not used with DSC is the result of subjective uncontrolled listening tests (including mine). It was concluded, that HQP is far better in PCM-DSD conversion.

Have to say, that this is a very controversial conclusion. Must be checked in DBT. Think that I personally became a victim of expectation biasing.
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Old 21st August 2019, 12:38 PM   #1514
sanji99 is offline sanji99  Croatia
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Quote:
Originally Posted by Vit123 View Post
Thanks, audiodesignguide3.

As audiodesignguide == Andrea Ciuffoli, who is associated with quanghao, I assume that you are using quanghao latest board for measurements.

quanghao wrote about his new design - "all ok, it is best , for last design with THD and SPL".

I'am interested in more info about DSC "THD bump" effect (THD increase with high level signal) in quanghao new design.

My measurements with DSC 2.5.2 with stock tranformers:
-0.5dB output signal - THD 0,0024%
-10dB output signal - THD 0,00025%

ppy's measurements with DSC
-0.5dB output signal - THD 0,0045%
-10dB output signal - THD 0,000354%

Your measurements:
- ARTA ~ BW 48K, ~ 0dB output - 0,0069%
- ~-5dB ouput - 0,0009%. You have very high noise floor (~ -125dB). May be you didn't do any averaging.

So I guess this effect is still here. IMO one can avoid this "THD bump":
1. by increasing the number of resistors ("taps")
2. or by using more accurate resistors (0,1% to 0,01%).
3. or by using software volume control before DSC.

The second question is why are you going to use CT7302? According to your measurements AK4137 performs a little better in THD.

As far as I remember, the only reason why AK4137 was not used with DSC is the result of subjective uncontrolled listening tests (including mine). It was concluded, that HQP is far better in PCM-DSD conversion.

Have to say, that this is a very controversial conclusion. Must be checked in DBT. Think that I personally became a victim of expectation biasing.
why don't we ever measure Intermodulation Distortion (IMD) that will reveal a lot more to us about audio quality ? (IMHO)
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Old 21st August 2019, 01:08 PM   #1515
audiodesignguide3 is offline audiodesignguide3
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Quote:
Originally Posted by Vit123 View Post
Thanks, audiodesignguide3.

The second question is why are you going to use CT7302? According to your measurements AK4137 performs a little better in THD.

About this question see the name of files, the order of list and of the files is inverted, so CT7302 (0.0067%) is much better than AK4137 (0.01%).
Here I have used the same DSC 2 module for all measurements and the same spdif source to eliminate I2S input cable effects.


About the first question see my last measurement with SpectraPLUS, the noise depend by the ADC resolution, analog cables length and consider that someone measure without output transformers.
I am using the Olivine 2 USB Analog To Digital Converter by Altor Audio.
Using ADC much more expensive is possible to have more resolution but this is not important for the final result.
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Old 21st August 2019, 02:14 PM   #1516
Vit123 is offline Vit123  Russian Federation
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Quote:
Originally Posted by sanji99 View Post
why don't we ever measure Intermodulation Distortion (IMD) that will reveal a lot more to us about audio quality ? (IMHO)
You can find IMD measurements (by @ppy) in the first post.
DSD ??? DSC1 ?? Signalyst

Quote:
Originally Posted by audiodesignguide3 View Post
... see the name of files, the order of list and of the files is inverted, so CT7302 (0.0067%) is much better than AK4137 (0.01%).
I see, thanks.
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Old 21st August 2019, 07:16 PM   #1517
audiodesignguide3 is offline audiodesignguide3
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Here some more measurements, probably the last, this time at DSD 8x, the CT7302 is much better than AK4137.


The external oscillators used in the CT7302 is still far from the chip so probably the two result with 11.2896MHz and 24.576Mhz will be better in the final board.


The input the 96KHz 24bit spdif and same ADC of the previous set, here input is -6dB and 0.7Vrms output.
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Old 21st August 2019, 07:18 PM   #1518
sanji99 is offline sanji99  Croatia
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[QUOTE=Vit123;5891496]You can find IMD measurements (by @ppy) in the first post.
DSD ??? DSC1 ?? Signalyst

An IMD of over 88 dB is a great result, but the graph is a combination of 19 and 20 kHz.

It would be very interesting to see that someone measured IMD by some of the other standards such as:

DIN 45403/4 Frequency f2 shall be either 4kHz or 5kHz. The amplitude ratio shall be preferably 4:1 but 10:1 is also allowed.
IEC 268/3 The frequency f2 shall be 8*f1. f1 shall be preferably 250Hz. Amplitude ratio is 4:1 SMPTE Low frequency shall be 60Hz.
High frequency either 7kHz or 8kHz. Amplitude ratio 4 : 1.

Some standards fix the high frequency to 7kHz or 8kHz. However, it may be useful to vary the high frequency over the entire frequency range.
Therefore, the A2/A2-D allows to set the high frequency freely in the range from 4kHz to 40kHz.

I measured IMDs from my DSC using a Neutrik A2 device, but the result is extremely poor so far, so I am looking for such DSC references as well.
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Old 22nd August 2019, 01:57 PM   #1519
merlin el mago is offline merlin el mago  Europe
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Quote:
Originally Posted by nautibuoy View Post
Hmmm, what's cooking?

Click the image to open in full size.
Ray could you share schematics & gerbers?

TIA & kind rgds
Felipe
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Old 22nd August 2019, 02:03 PM   #1520
merlin el mago is offline merlin el mago  Europe
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I want to use the DSC2 only as re-cloking, what are the components to be installed if I only need SE output? Can I use 22 & 24,XXX oscillators in place of 45 & 49,XXX?

TIA
Felipe

Last edited by merlin el mago; 22nd August 2019 at 02:19 PM.
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