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Review & Measurements of Talema Relay Pre-amp

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#22
Some Chinese "engineers" save on flies. They don't even want to stick to the manufacturer's recommendations. Look at the following diagram. I put in the missing pieces and the situation improved. This is without shielding. I can't measure the noise right now. If someone does that and measures the noise, that would be great. And the copper screen is not needed. Thanks
 

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Joined
Dec 14, 2018
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#23
Some Chinese "engineers" save on flies. They don't even want to stick to the manufacturer's recommendations. Look at the following diagram. I put in the missing pieces and the situation improved. This is without shielding. I can't measure the noise right now. If someone does that and measures the noise, that would be great. And the copper screen is not needed. Thanks
I've used the TM1637 on an Arduino project I was working on.
The display manufacturer recommended a slightly different termination- 4.7k pull ups for the clock and data i/o pins, but no caps, but I did add some caps because of RF interference that it was generating.and slowing down the data and clock edges was recommended- as you noted.
Is this a similar situation? The vast majority of the noise is seemingly due to mains harmonic pick up.
Yes, the board is the same- without 100pF caps.
Have you actually measured the noise under the conditions that the review chose to evaluate?
Do you have spectral plots?
 
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#24
[
I've used the TM1637 on an Arduino project I was working on.
The display manufacturer recommended a slightly different termination- 4.7k pull ups for the clock and data i/o pins, but no caps, but I did add some caps because of RF interference that it was generating.and slowing down the data and clock edges was recommended- as you noted.
Is this a similar situation? The vast majority of the noise is seemingly due to mains harmonic pick up.
Yes, the board is the same- without 100pF caps.
Have you actually measured the noise under the conditions that the review chose to evaluate?
Do you have spectral plots?
As I wrote, I cannot now instrumentally measure noise. I connected the digital part to the case and soldered the parts as in the diagram. There's less noise by ear, but I don't know what that means.
 
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#25
[

As I wrote, I cannot now instrumentally measure noise. I connected the digital part to the case and soldered the parts as in the diagram. There's less noise by ear, but I don't know what that means.
Connecting the case and grounds makes a large difference to both the measured and audible noise, adding the shielding improves this by a significant amount. I added the caps ( pin 1 to pins 17 and 18) a few moments ago and did a quick measurement. It only seems to have a small effect on the spurs close to the max bandwidth of 96k, and makes no difference to the measured SINAD. The shielding was still in place.
 
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#26
Connecting the case and grounds makes a large difference to both the measured and audible noise, adding the shielding improves this by a significant amount. I added the caps ( pin 1 to pins 17 and 18) a few moments ago and did a quick measurement. It only seems to have a small effect on the spurs close to the max bandwidth of 96k, and makes no difference to the measured SINAD. The shielding was still in place.
You do everything very quickly! The only thing I would like to check is whether everything will be as good without shielding. I understand there are 2 options. 1) reduce the radiation of the wires by shielding them 2) reduce the amount of interference going through them. The use of two options at once may be redundant. Maybe not! Thank you very much for your work!
 
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#29
When I bought this, I was hoping it would be much better. I thought it should be completely transparent to the signal. I was very much mistaken (((((
The modifications do make it inaudible when inserted, even with a high res system.
I have a pair of AHB2s in mono driving Martin Logan Montis with an RME ADI2 PRO FS/Raspberry PI/Volumio combo as the digital source.
Prior to the changes the degradation due to the passive preamp was quite obvious. Now it is transparent.
By the way, the 1kHz harmonics and the 60Hz component in the plot above are almost entirely due to the RME DAC/ADC combo plus wiring that I'm using for source/measurement and not due to the passive preamp+active buffer that is being tested.
 
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#30
The modifications do make it inaudible when inserted, even with a high res system.
I have a pair of AHB2s in mono driving Martin Logan Montis with an RME ADI2 PRO FS/Raspberry PI/Volumio combo as the digital source.
Prior to the changes the degradation due to the passive preamp was quite obvious. Now it is transparent.
By the way, the 1kHz harmonics and the 60Hz component in the plot above are almost entirely due to the RME DAC/ADC combo plus wiring that I'm using for source/measurement and not due to the passive preamp+active buffer that is being tested.
Thank you for supporting the theme. Yes, after modifications it is not audible. I'm even without shielding the ribbon cable wires. But, I wanted to be a normal thing right after the purchase. And the, that, I soldered their hands (modification) full horror-are looking. It's very ugly, but I couldn't do better (((
CM191107-200939007.jpg
 
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