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DIY Audio Analyzer with AK5397/AK5394A and AK4490
DIY Audio Analyzer with AK5397/AK5394A and AK4490
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Old 11th September 2018, 08:39 AM   #2361
soongsc is offline soongsc  Taiwan
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Quote:
Originally Posted by JensH View Post
Please take a look at the document provided here:

GB for RTX6001 Audio Analyzer with AK5394A and AK4490
not in front of the machine now, but I have a feeling mine might have came with this mod. I will check when I open it up again. One unit does not have the overload issue and one does.
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Old 11th September 2018, 10:47 AM   #2362
JensH is offline JensH  Denmark
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Right, your units were actually modified, concerning the overvoltage, before shipping. I just looked it up.
Perhaps you could take a look inside and check the modification on the bad unit? It might be possible to fix it easily, so that you don't have to send it back to RTX.
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Old 21st September 2018, 12:21 PM   #2363
zfe is offline zfe
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Again annoyed by the 50Hz power-line induced artefacts in unballanced measurements using a BNC-XLR adapter (or even, to a little extend, with the recommend "no.xx" cable layout) I decided to test what would happen when the RTX is supplied with power that has "no" 50Hz content.

The following was just intended as a proof of concept with the material lying around, so far far from an optimal solution. I used 3 switched mode Laptop/Computer power supplies followed by a linear regulator to get the suitable voltage.
As the power supplies are not synced and different there is unnecessary HF noise.
The regulators were of LM317 type, thus not intended for switched mode supplies (no good HF rejection).
This causes a few spikes around 70kHz which show also up in the measurements and can be avoided with a descent supply-regulation approach.

First, as indication that there is no performance loss due to the SMPS, a balanced loopback measurement, a 1kHz test signal at -12dB (settings 0dBV out, -10dbV in). Green the original supply, red the SMPS:
1k -12db 0dbV -10dbV over.jpg

Then a unballanced loopback: BNC out to BNC cable to commercial BNC-XLR adapter. The BNC cable was not the best performing I had, but for a test this might be an advantage. First the noise floor, second a 1kHz test signal at -6dB (settings 0dBV out, -10dbV in). Green the original supply, red the SMPS:
Adapter nf0-10 over.jpg Adapter 1k-6_0-10 over.jpg

Conclusion, I would say, there is room for improvement, at least for the measurement ease of the user, in for unballanced measurements.

P.S. I give intentionally not more details on the SMPS setup as you should not duplicate it unless you know very well what you do. You can easily damage your analyzer and, of cause, warranty is voided by the attempt.
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Old 21st September 2018, 03:30 PM   #2364
mbrennwa is offline mbrennwa  Switzerland
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Quote:
Originally Posted by zfe View Post
Again annoyed by the 50Hz power-line induced artefacts in unballanced measurements using a BNC-XLR adapter (or even, to a little extend, with the recommend "no.xx" cable layout) I decided to test what would happen when the RTX is supplied with power that has "no" 50Hz content.

The following was just intended as a proof of concept with the material lying around, so far far from an optimal solution. I used 3 switched mode Laptop/Computer power supplies followed by a linear regulator to get the suitable voltage.
As the power supplies are not synced and different there is unnecessary HF noise.
The regulators were of LM317 type, thus not intended for switched mode supplies (no good HF rejection).
This causes a few spikes around 70kHz which show also up in the measurements and can be avoided with a descent supply-regulation approach.

First, as indication that there is no performance loss due to the SMPS, a balanced loopback measurement, a 1kHz test signal at -12dB (settings 0dBV out, -10dbV in). Green the original supply, red the SMPS:
Attachment 704727

Then a unballanced loopback: BNC out to BNC cable to commercial BNC-XLR adapter. The BNC cable was not the best performing I had, but for a test this might be an advantage. First the noise floor, second a 1kHz test signal at -6dB (settings 0dBV out, -10dbV in). Green the original supply, red the SMPS:
Attachment 704728 Attachment 704729

Conclusion, I would say, there is room for improvement, at least for the measurement ease of the user, in for unballanced measurements.

P.S. I give intentionally not more details on the SMPS setup as you should not duplicate it unless you know very well what you do. You can easily damage your analyzer and, of cause, warranty is voided by the attempt.
Good stuff!

I don't really know your external PSU setup, and which RTX internal sections you "skipped", but... would it make sense to think about a mod for an external DC PSU to keep the mains noise out of the RTX?
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Old 21st September 2018, 03:44 PM   #2365
zfe is offline zfe
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Originally Posted by mbrennwa View Post
Good stuff!

I don't really know your external PSU setup, and which RTX internal sections you "skipped", but... would it make sense to think about a mod for an external DC PSU to keep the mains noise out of the RTX?
I only skipped the transformer inside the RTX and used the corresponding connector as power input. Minimal invasive, but perhaps not optimal

I do not think an external supply will noticeably improve the balanced performance. But unbalanced live would become easier.

I think about battery power the RTX, but that would need a lot of batteries.
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Old 21st September 2018, 04:04 PM   #2366
mbrennwa is offline mbrennwa  Switzerland
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Originally Posted by zfe View Post

I think about battery power the RTX, but that would need a lot of batteries.


What voltage is required?
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Old 21st September 2018, 04:42 PM   #2367
anatech is offline anatech  Canada
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Using an external transformer would bring only a minimal improvement - if any at all.

-Chris
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Old 21st September 2018, 05:23 PM   #2368
mbrennwa is offline mbrennwa  Switzerland
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Originally Posted by anatech View Post
Using an external transformer would bring only a minimal improvement - if any at all.
No, not just an external transformer, but a whole DC PSU.
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Old 21st September 2018, 05:52 PM   #2369
NicMac is offline NicMac  Italy
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Quote:
Originally Posted by zfe View Post
I think about battery power the RTX, but that would need a lot of batteries.
Can't be that many batteries. Getting it completely of the grid is tempting
Did you by chance check the voltages and current draw on the different secondaries?
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Old 21st September 2018, 05:54 PM   #2370
zfe is offline zfe
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The internal transformer is 1 x 9V and 2 x 15V, 1A (AC).
A drop in DC replacement for the transformer would thus be about 1 x 12V and 2 x 21V. The margin above the voltage drop of the regulation circuitry however seems to be quite ample. Slightly less would probably do too.

I do not think it would be a good idea to bypass the internal regulation and feed the power rails directly (I have even not yet made an attempt to identify all rails). If that would be wanted then better put that on the RTX-v2 wish list with a newly designed PCB.
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