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A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
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Old 8th April 2021, 07:30 AM   #8641
kartick is offline kartick
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Here are Vdc readings that I just took (4 boards). Also to clarify since this is being used in single ended mode, I have only connected the pos and common (nothing connected to the neg terminals).

Right Channel:
Pos-Com:2.738 mV
Neg-Com:2.714 mV
Pos-Neg: 8.3 mV

Left Channel:
Pos-Com: 2.67 mV
Neg-Com:2.691 mV
Pos-Neg: 0.1 mV
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Old 8th April 2021, 07:31 AM   #8642
kartick is offline kartick
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Thanks DD
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Old 8th April 2021, 07:40 AM   #8643
dddac is offline dddac  Germany
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A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
Quote:
Originally Posted by kartick View Post
Here are Vdc readings that I just took (4 boards). Also to clarify since this is being used in single ended mode, I have only connected the pos and common (nothing connected to the neg terminals).

Right Channel:
Pos-Com:2.738 mV
Neg-Com:2.714 mV
Pos-Neg: 8.3 mV

Left Channel:
Pos-Com: 2.67 mV
Neg-Com:2.691 mV
Pos-Neg: 0.1 mV
This is all perfectly fine and within specs Kartick....

I assumed mV in the versus Common reading is actually Volt?
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Old 8th April 2021, 07:45 AM   #8644
mbrennwa is online now mbrennwa  Switzerland
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A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
Quote:
Originally Posted by kartick View Post
the right channel seemed a tad louder than the left and the image was shifting towards the right on almost all recordings.
Simple monkey test to check where the problem is: reverse the left/right cable connections between DDDAC and (pre)amp. If the left/right problem changes to the other side, look inside your DDDAC. Otherwise, look downstream of the DDDAC.
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Old 8th April 2021, 07:47 AM   #8645
kartick is offline kartick
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Quote:
Originally Posted by dddac View Post
This is all perfectly fine and within specs Kartick....

I assumed mV in the versus Common reading is actually Volt?
My bad, indeed the readings between Pos/Com and Neg/Com are in V and not mV.

Just one more clarification DD, in the other post where I mentioned the left and right channel readings, you did mention that this difference could cause a perceivable channel imbalance and now with the fresh readings, you say all is perfectly within range. Am I not getting something right?
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Old 8th April 2021, 07:51 AM   #8646
dddac is offline dddac  Germany
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well, first you mentioned different readings, so it might had been...

now that you give new values in single end, that shows all is fine.

Just swap the transformers and see if the problem stays or not....
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Old 8th April 2021, 07:55 AM   #8647
kartick is offline kartick
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Quote:
Originally Posted by mbrennwa View Post
Simple monkey test to check where the problem is: reverse the left/right cable connections between DDDAC and (pre)amp. If the left/right problem changes to the other side, look inside your DDDAC. Otherwise, look downstream of the DDDAC.
Did that. With so much of troubleshooting through these years, these monkey tests are the first things I do. With a stereo recording, I could not make it out very clearly. I will however repeat this by playing a mono recording.

Another DIYer friend of mine suggested that if the capacitance values of the output caps are different to one another, that difference could also be the cause of the output imbalance that I am hearing. I measured the capacitance values of the 0.47uf Russian K40Y-9 PIO rated caps and the readings are as follows:

Cap1: .472uf
Cap2: .454uf

Can this be the cause of the channel imbalance?
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Old 8th April 2021, 08:00 AM   #8648
kartick is offline kartick
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Quote:
Originally Posted by mbrennwa View Post
Simple monkey test to check where the problem is: reverse the left/right cable connections between DDDAC and (pre)amp. If the left/right problem changes to the other side, look inside your DDDAC. Otherwise, look downstream of the DDDAC.
Quote:
Originally Posted by dddac View Post
well, first you mentioned different readings, so it might had been...

now that you give new values in single end, that shows all is fine.

Just swap the transformers and see if the problem stays or not....
To clarify, both sets of readings (yesterday's and today's) were taken in single ended config, i.e., with output capacitors.

If you notice, the readings between Pos and Common on both channels are pretty close between the first reading i posted yesterday and what i measured today.

First reading:
Right channel output (between POS and COMMON): 2.75 Volts
Left channel output (between POS and COMMON): 2.67 Volts

Today's reading:
Right Channel:
Pos-Com:2.738 mV
Neg-Com:2.714 mV
Pos-Neg: 8.3 mV

Left Channel:
Pos-Com: 2.67 mV
Neg-Com:2.691 mV
Pos-Neg: 0.1 mV
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Old 8th April 2021, 09:10 AM   #8649
NIXIE62 is offline NIXIE62  Serbia
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It's a little strange that the measurements don't match well.

Right channel: 2.738V-2.714V=+0.024V (+24mV). Directly measured POS-NEG: +8.3mV It should be the same (+24mV) and it is not.

Left channel: 2.67V-2.691V= -0.021V (-21mV). Directly measured POS-NEG: +0.1mV
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Old 8th April 2021, 09:22 AM   #8650
mbrennwa is online now mbrennwa  Switzerland
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Quote:
Originally Posted by kartick View Post
First reading:
Right channel output (between POS and COMMON): 2.75 Volts
Left channel output (between POS and COMMON): 2.67 Volts
kartick, we already discussed this a few times in the past. The DC bias values you reported are just that: DC. You cannot hear DC. What you hear is from the AC signals, which are independent of the DC bias point (as long as the DC bias is within the normal operating range). Slightly different DC bias between left and right channels are therefore entirely irrelevant.

What is relevant is that the POS / NEG DC bias voltages within a given channel are balanced in order to avoid saturation of the transformers.

Just read up Doedes DDDAC website and the many posts about this to remember what this all about.

Apart from this, I would not be surprised if your NOS capacitors are a bit beyond their "expiry date". Just use some modern no-nonsense capacitors that will be transparent to the audio signal.
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