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Variation in voltages measured during cold start of DAC. Expected?

Pdxwayne

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#1
In a few months span, I bought 3 DAC so far due to ASR. : )

After I got my Gustard x16, I decided to measure it's RCA output voltages over a range of frequencies. I found the results kind of odd. X16 has the lowest measured output via REW at -16db as compared to KTB and E30. Due to that, I decided to measure E30 again just to make sure.

What I found is that on cold start (plug in E30 power supply after it is off power for a while), E30 voltages are not stable for the bass freqs I measured. It would move up and down slightly. Maybe after 10 to 20 minutes later, it's output voltages started to stabilize.

Is this expected?
 
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Blumlein 88

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#2
No, I've measured at least a handful of DACs on turn vs a few minutes vs an hour later. Never seen any do something like this. Whether it is normal for the E30 only some E30 owners can say or maybe @JohnYang1997 can answer the question for you as he is with Topping.
 
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Pdxwayne

Pdxwayne

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Thread Starter #4
What did you measure with?
Just a low cost multi meter that is not accurate, but consistent. Klein Tools MM200.

X16 (which was powered on for a day when I measured) was very stable. No variation in voltages for all freq I measured, other than very small change when measured at 20 Hz.
 

voodooless

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#5
I would not really trust a DDM for measuring various frequencies reliably. But over time a single frequency should be at least stable. I would not expect the E30 to not be stable. What was the latitude of the deviation?
 
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Pdxwayne

Pdxwayne

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Thread Starter #6
I would not really trust a DDM for measuring various frequencies reliably. But over time a single frequency should be at least stable. I would not expect the E30 to not be stable. What was the latitude of the deviation?
I measured with REW output setup at -16db to be consistent with my other measurements. It seems at cold start, 120 Hz got the most variations.

e30_voltage_variation_cool_start.PNG
 
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mansr

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#7
No, I've measured at least a handful of DACs on turn vs a few minutes vs an hour later. Never seen any do something like this. Whether it is normal for the E30 only some E30 owners can say or maybe @JohnYang1997 can answer the question for you as he is with Topping.
Some slight variation while parts reach stable temperatures is normal. That's why lab instruments always specify 30 minutes or so of warm-up time. Of course, it's not likely to make any audible difference.
 

Blumlein 88

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#8
I measured with REW output setup at -16db to be consistent with my other measurements. It seems at cold start, 120 Hz got the most variations.

View attachment 110424
Okay variations that small yes. You have like .03 db there. I thought you were talking significant levels. That is nothing to worry about.
 
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Pdxwayne

Pdxwayne

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Thread Starter #9
Okay variations that small yes. You have like .03 db there. I thought you were talking significant levels. That is nothing to worry about.
Good! It was just a bit inconvenience when I was trying to get a solid number for each freq I measured. At that low level, small changes in voltage matters when I am trying to compare DAC.
: )
 

Blumlein 88

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#10
There was once a thread on whether distortion lowered with warm up for DACs. I had I think three DACs on hand and measured them. Measurement gear had been on for a week. I turned on and immediately measured each DAC, and then did so at 30 minutes, each hour until 4 hours and every 6 hours after that. You could say it didn't change or you could say it improved for about 2 hrs on each DAC. The improvement was from something like .0039 % distortion just turned on to like .0030 % over 2 hrs. After which it stayed stable for 2 days. That was true I think of those with lowest distortion. One with slightly higher distortion like .05% didn't change after the 30 minute measurement. In all cases I'd consider that nothing to even think about.
 
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Pdxwayne

Pdxwayne

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Thread Starter #12
I think the variations are so small they are within the error range of the multi meter.
Yeah, I suspect that when measure at different time, the number might be different by 0.001V, due to error range of multi meter. But, I expect the number to stay stable when doing measurements.
It was interesting to note that a E30 could not stay stable for a while when cold boot. X16 was very stable (powered on for a full day before measurements).
 
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Pdxwayne

Pdxwayne

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Thread Starter #13
Okay variations that small yes. You have like .03 db there. I thought you were talking significant levels. That is nothing to worry about.
In my case, such small voltage differences between DAC was noticeable. I started doing the measurements because I noticed that E30 has a bit more "sparkles" when playing electronica type music as compared to X16.

My measurements indeed found E30 have higher voltages from >5Khz and up. Interesting that such small differences (of cause, my multi meter is not accurate anyway, so the real difference in > 5Khz could be larger) was noticeable.

KTB_E30_X16_capture.PNG
 

Blumlein 88

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#14
In my case, such small voltage differences between DAC was noticeable. I started doing the measurements because I noticed that E30 has a bit more "sparkles" when playing electronica type music as compared to X16.

My measurements indeed found E30 have higher voltages from >5Khz and up. Interesting that such small differences (of cause, my multi meter is not accurate anyway, so the real difference in > 5Khz could be larger) was noticeable.

View attachment 110558
Those are borderline audible. A couple or three tenths of a db over an octave.
 
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Pdxwayne

Pdxwayne

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Thread Starter #15
Those are borderline audible. A couple or three tenths of a db over an octave.
Yeah, and my measurements stopped at 10Khz. Who knows what else going on over 10Khz....I am too lazy to do more measurements and my multi meter is not up to the task anyway as freq going up.
 
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Pdxwayne

Pdxwayne

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Thread Starter #17
Multimeters are totalt inaccurate and inadequate for measuring Frequency responses.
I agree with you. The numbers clearly indicated inaccuracies.

However, it is consistent. I can measure multiple times and the numbers would be pretty much the same, like maybe sometimes showing 0.001V differences.

It can also show stable reading or changing reading. Like I mentioned in my OP, x16 very stable. I measured 120 Hz and the reading stays the same, no variations, and not even 0.001V movement. E30 was not stable during cold boot. Voltage reading can varies 0.007V for 120Hz.
 

Blumlein 88

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#20
OOOOooooooh!!!! More than a .01 db increase after only 3 hrs.
 
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