iUSB vs Server "Linear Power Supply"

[comfortably_numb]

Hello fellow nerds,

 

I am thinking about purchasing the ifi-audio iusb.

This $200 unit sits between the computer server (Mac-mini or CAPS) and the DAC or "SPDIF converter". It electronically separates the hifi-equipment by injecting its own "clean" +5V USB power, instead of the "dirty" one accompanied by the server USB output.

 

My question is this:

Would this unit do a similar job (or produce the same results) as the more expensive option of upgrading the computer power supply to a linear one?

Since the iusb is isolating the computer noise, and the SPDIF converter is taking care of jitter, seems kinda redundant to upgrade the power supply on the computer side.

 

Thanks

[4est]

Short answer, no. It is to to isolate the computer generated noise from the DAC, not the noise form the AC supply.

[comfortably_numb]

But if the Converter has its own clean power, and its digital outputs are galvanically isolated from the inputs, how does noise generated by computer AC Supply get into the Hifi equipment?

[acg]

The noise is already there in the music signal at it enters the USB cable. Many people shoot clean power into the PC (in a number of different ways) and also shoot clean power into the USB cable, the USB Converter as well as the DAC. The question you should ask is whether you need to shoot clean power into your USB cable as many USB Converters or DACs have their own power supplies and reject the USB power entirely or partially. The iUSB has benefits other than clean power, and products such as the SOtM txUSB card , the Adnaco S3B and the Empirial Audio Shortblock can also be very effective at cleaning up the signal in the USB cable.

[One and a half]

Noise Suppression guide c35e.pdf

 

Here's a paper from a manufacturer of noise clamping devices and where the noise from PCs and Macs comes from.

There are lots of places where emissions come from, the nasty ones are the conducted emissions, they are the ones that are sent down the USB cable.

 

The pdf lists a choke to filter the noise in the USB signal lines, now that could cause complications with audio quality, but the rest of the filtering looks OK.

[comfortably_numb]

I have trouble understanding this.

USB signal is digital (ie 0's and 1's) or in electrical terms, a high signal and a low signal. The risk, if the signal has noise is that a 0 is mistakenly read as 1.

But if this noise was really significant, copying files from a computer to an external HD should make the copied file different than the original. This rarely (if ever) happens...unless there is extra handshaking going on.

 

Additionally, a converter with clean power, and galvanic isolation of outputs (ie electric separation of inputs from outputs) will generate its own data signal (with its own clock) to the DAC. This means complete isolation of computer noise to the hifi-equipment.

[i2k]

Don't waste your money, does the same thing & lot cheaper : Alimentation linaires - Audiophonics KIT Isolateur USB + Alimentation