Disconnecting AG from Earth causes buzz, noises and radio receiving. I've connected them again through R 20 Ohm. It is now no better than it was before (see spectrum on post#1).
This is whole layout including computer, preamp and PSU.
Currently AGM is in Preamp, nearby input XLR.
Issue is buzz that starts from -100dB even when PSU is powered off by switches, but is still plugged into mains outlet. The buss exists after power on as well, and is amplified to -80dB by the preamp.
Does anybody see, how the layout can be improved?
Currently AGM is in Preamp, nearby input XLR.
Issue is buzz that starts from -100dB even when PSU is powered off by switches, but is still plugged into mains outlet. The buss exists after power on as well, and is amplified to -80dB by the preamp.
Does anybody see, how the layout can be improved?
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The TRS plugged connection between sound card and pre-amp has a PIN1 problem.
The 4 wire umbilical containing +280Vdc, +102Vdc, +90Vdc and Power Zero Volts must be maintained as a 4wire connection all the way into the tube pre-amp.
It does not stop being twisted at the chassis entry point.
I bought a 24Vdc smps a few days ago.
The output is NOT a smooth DC.
There is a very pronounced sawtooth ripple.
The up ramp of the ripple has very short charging spikes (with ringing), about 20 of them in ~2ms.
The down ramp is clean. it lasts about 8ms.
It just happens that the ripple mimics the rectified and smoothed 50Hz mains supply.
Is there a possibility that your +102Vdc +90Vdc supply passing in the buzz?
The 4 wire umbilical containing +280Vdc, +102Vdc, +90Vdc and Power Zero Volts must be maintained as a 4wire connection all the way into the tube pre-amp.
It does not stop being twisted at the chassis entry point.
I bought a 24Vdc smps a few days ago.
The output is NOT a smooth DC.
There is a very pronounced sawtooth ripple.
The up ramp of the ripple has very short charging spikes (with ringing), about 20 of them in ~2ms.
The down ramp is clean. it lasts about 8ms.
It just happens that the ripple mimics the rectified and smoothed 50Hz mains supply.
Is there a possibility that your +102Vdc +90Vdc supply passing in the buzz?
I do not know how TRS in sound card (E-MU 1212 PCI) is wired. I assumed that Sleeve is AG. I do not know if it is also Earthed.
The tube preamp is SE, not balanced, without output transformer. So I've connected Ring with Sleeve (as it was recommended here PreSonus | Articles - Balanced and Unbalanced Connections ).
It tried also to mount the TRS as connected to chassis and isolated from chassis. It does not make a difference.
What would you suggest to eliminate Pin1 problem at TRS?
Regarding SMPS.
1. I tried to turn it on and off during auditions and measurements (it has separate switch). I did not hear/see any difference. So I assume it is clean.
2. The low level buzz exists even when both the SMPS is turned off and HT is turned off. Both mains wires, the Active and the Neutral, are disconnected by power switches. Only Earth wire is not switched off because it does not go to the switch, it is bolted to chassis according with safety rules.
Will an output transformer help?
The tube preamp is SE, not balanced, without output transformer. So I've connected Ring with Sleeve (as it was recommended here PreSonus | Articles - Balanced and Unbalanced Connections ).
It tried also to mount the TRS as connected to chassis and isolated from chassis. It does not make a difference.
What would you suggest to eliminate Pin1 problem at TRS?
Regarding SMPS.
1. I tried to turn it on and off during auditions and measurements (it has separate switch). I did not hear/see any difference. So I assume it is clean.
2. The low level buzz exists even when both the SMPS is turned off and HT is turned off. Both mains wires, the Active and the Neutral, are disconnected by power switches. Only Earth wire is not switched off because it does not go to the switch, it is bolted to chassis according with safety rules.
Will an output transformer help?
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