1 Topic by hpw (edited by hpw 2019-03-06 19:32:53)

  • hpw
  • hpw
  • AD/DA expert
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  • From: Guacimara
  • Registered: 2007-05-27
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Topic: ADI-2 Pro Hum/Noise on Labtop on Batterie / Power

Testing the Victor LDO balanced connected (Silentswitcher powerd & USB Lithium) now on a second laptop with equal behavior sad, this means LDO (low Distortion Oscillator) is driven from battery only.

As soon Laptop (Lenovo S430) on Batteries HUM gets clearly visible. Some else did equal / similar test?

Both Laptop have 1MOhm resistor from Power Ground to Laptop DC GND...

Even using the Intona Isolater gets results even worst.

Look at the Picture..

https://download.hpw-works.com/pictures/Power-1.png

hpw's Website

  • KSTR
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Re: ADI-2 Pro Hum/Noise on Labtop on Batterie / Power

Looks like you have a general cabling or setup issue.
I have a Viktor 1kHz Oscillator board as well, and as chance would have it it's also powered from JD's silent switcher PCB via battery. Both in unbalanced and balanced connection there is absolutly *zero* hum, really nothing, no matter if the whole thing is connected to PE at ADC end (via USB to PE-connected PC) or not. The osc properly shielded and with fully shielded conncection to the ADC, of course. Only when both shield ends are directly connected to different PE locations there is a chance that the balancing current is causing R*i drops along the shield that do occur as additional signal voltage, notably in the unbalanced connections. But also the RME supply's leakage current (or that of a Class-II PSU for the LapTop) may cause some visible R*i drops along the cable shield... when a very bad cable is used, or many adapters. In balanced mode (actually impedance balanced mode, not signal symmetry which isn't required for common mode rejcection), the signal is clean unless you have a broken cable or something.

  • hpw
  • hpw
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Re: ADI-2 Pro Hum/Noise on Labtop on Batterie / Power

Thank you for your answer:D

Use Connex or Contrik Balanced wires. Wired is also getting complete different results between PC's. Just Hum signal at -120... -130dBFS just connecting a balanced with balanced 600E resistors build within a connector. But not on laptop's.
This means for me I do not know whether the cables are OK. For 50E cables exists double shielded as I use them for 50E asymmetric connections.

Victor uses a special modified balanced input with direct connection to the ADC (also using different ADC brand). Only the LDO is powered by a linear PSU. As soon he opens the shielded LDO box, hum is preset as I showed.

Also I do not know about balanced direct connections to the LDO IC's, where the oscillator loop picks-up some none pleased signals.

I will soon box the LDO and currently do not know to put the silent switcher within the same box or not. But for shure separated inside with a metal frame.

May also the input resistor of the ADI-2 Pro counts (18k), all to experiment within my puzzle ...

PS: may we share the findings on private emails... ??

Cheers

Hp

hpw's Website

  • hpw
  • hpw
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  • From: Guacimara
  • Registered: 2007-05-27
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Re: ADI-2 Pro Hum/Noise on Labtop on Batterie / Power

KSTR wrote:

Looks like you have a general cabling or setup issue.

IMHO it end's up a general grounding issue. STAR grounding, to avoid using the USB as the ADI-2 pro ground connection.

This means, used the ADI-2 in ADC/DAC mode and feed the ADC data using opto SPDIF to a second device for analysis. This required to ground the ADI-2 and the LDO box.

Poor on ADI-2 xxx is that, we do not have any ground connection pin at the most sensitive location...

For the other direct old main board hum pickup using a short balanced cable & 600E balanced termination, is currently opened.

Hp

hpw's Website