Intona User Forum

I have purchased a 7055-C for use with an Audio Precision APx555 and am having some trouble.

When trying to connect via USB 3.0, the connection is immensely unstable. Frequently I cannot even get the software to fully load before the device connection is lost.
Sometimes I can get it to load, but it will lose connection to the device either entirely (device drops from the PC entirely) or partially (software still sees the device and I can still control the analyzer, but FFT graphs etc are not updating, seemingly no receiving data.).

Connecting via USB 2.0 seems to be more reliable although it still disconnects after some time, usually longer than if using USB 3.0.
Providing aux power makes no difference.

I've tried using two different PCs, various USB cables including some deliberately very short ones. But cannot seem to get the analyzer to maintain a solid USB 3.0 connection at all through the intona.
If it helps, when the analyzer disconnects fully, the LED on the intona goes green. Then back to blue after a short while when the device reconnects.


Connecting directly works without any issue. And connecting via an ifi iGalvanic 3.0 which is an alternative USB isolator (one that I'd purchased the intona to replace as the iGalvanic is transformer isolated, not optical, meaning it could potentially still pass some AC noise), works fine for shorter connections but is somewhat unreliable for longer ones.


Has anyone else had a similar issue or have any suggestions I could try? At the moment I'm really struggling to find any solution to fully isolate the analyzer as the intona cannot maintain a connection.

The APx series is known to be a bit flimsy when it comes to analog coupled, redriven 3.0 wires. This is what the 7055-C does.
I suggest that you replace your isolator by the 7055-D model. This has true digital, optical, protocol-aware isolation.

Another quick solution is to use the USB 2.0 portion only (as I do in my AP). You can try this by exchanging your cabling by USB 2.0 ones.

Daniel (Intona) wrote: ↑September 4th, 2021, 8:52 am The APx series is known to be a bit flimsy when it comes to analog coupled, redriven 3.0 wires. This is what the 7055-C does.
I suggest that you replace your isolator by the 7055-D model. This has true digital, optical, protocol-aware isolation.

Another quick solution is to use the USB 2.0 portion only (as I do in my AP). You can try this by exchanging your cabling by USB 2.0 ones.

Thank you very much Daniel.
I'll need to see about upgrading. Hopefully it'll sort the issue.

In terms of 7055-C vs 7055-D, other than the max isolation, is there any difference in the level of AC noise that is isolated?
One of the reasons I'm looking to move away from the ifi iGalvanic is because it's transformer isolated and so I'm concerned that AC noise could still be passed.
Is this the case for either of the intona models? I'm having a bit of trouble understanding what the differences are between the 7055-D and 7055-C in terms of how they work.

I noticed on the spec sheet here for example: [External Link Removed for Guests] ... 055-D.html
That the 7055-C does not list AC isolation

Thank you very much for your help!

First, the USB 2.0 portion is the same in all 7055 models: isolation voltage is 5kV RMS and there is no intentional capacitive coupling. Isolation is granted between DC and GHz range (limited by the parasitic capacitance that is everywhere in nature and defined by clearance and air gap which is industries-best here).
AC noise (which I consider as random frequencies in the kHz range to GHz range) is NOT going to be passed here.

The USB 3.0 portion is completely different in 7055-C and 7055-D models.

In the -C version, it is an analog-only circuit, that basically consists of a receiver -> equalizer -> capacitive galvanic isolation -> equalizer -> redriver (this is *very* high speed, not to confuse with audio-like circurity). This topology limits the isolation from DC to about some tens of MHz. Above those MHz range, it is going to couple by intention. This is indeed desirable because it guarantees a common shielding especially in the ground system. Unfortunately, this is not very popular in audiophile speak because of rather esoteric reasons. Neither ADCs nor DACs (and even much less Audio Precision hardware) can alias those high frequencies into the audible or measured range.

The -D version has a completely different circuit for the 3.0 portion. It consists of a receiver -> DSP -> laser diode -> gap -> optical receiver -> DSP -> transmitter. This guarantees not only zero BER* but has also no intentional capacitive coupling. AC isolation can be considered the same here as for the 2.0 portion.

I hope, it's a bit clearer now.

*BER: bit error rate. This is clearly allowed in a certain amount by the USB 3.0+ standard and inevitable with long cabling. But some devices are designed in a wrong way here (which I call: flimsy) and cannot handle subsequent CRC errors. Such applications are clearly violating the standard and should be fixed by the developers.

Daniel (Intona) wrote: ↑September 6th, 2021, 8:33 am
The -D version has a completely different circuit for the 3.0 portion. It consists of a receiver -> DSP -> laser diode -> gap -> optical receiver -> DSP -> transmitter. This guarantees not only zero BER* but has also no intentional capacitive coupling. AC isolation can be considered the same here as for the 2.0 portion.

Hi Daniel

How is USB ground isolated with the -D version? Or USB ground is isolated optically/air gap also?

Also how is AUX input galvanically isolated with the -D version?

Thanks!

The ground is completely isolated and has an air gap to extend the creepage distance even beyond the necessary.
AUX is coupled tightly to the isolated side. This is for pushing more current to the device where the DC/DC isolation would be too weak. Any quality branded standard PSU has usually a very good isolation. Use a medical grade power supply to maintain highest isolation from ground.

Thanks Daniel.