garbled audio

[Michael Peets]

1. Managed server (Toronto) is verified as started

2. Mic and keyboard connected to Behrenger 802 mini-mixer

3. Output (1/4 " unbalanced to 1/8" stereo) from mixer connected to the Jacktrip device input

4. Headphones connected to Jacktrip device output via female to L&R RCA adapter

5. browser (iPad) connected to app.jacktrip.org and signed in

6. my Jacktrip device found as usual by the app and I connect to the server

7. speak into mic or play keyboard but audio very garbled in headphones

8. turn down volume on mixer as well as input and output on app

9. audio slightly better but very jittery and not acceptable

10. check different headphones connected to mixer and sound is perfect coming out of mixer

11. plug mic directly in to Jacktrip device with balance cable

12. Jacktrip device output better but crackling/clipping makes it still unacceptable

13. play around with volume on app, but no improvement

14. change server from stereo to mono and there is no clipping from the mic but there is a background buzz like a ground loop

15. change server back to stereo and find low-grade buzzing even with mic unplugged

15. change cables all the way around and still unacceptable output

Any ideas?

My internet is  DOWNLOAD 42.71 Mbps and UPLOAD 19.52 Mbps.

Jacktrip device is plugged directly into router.

[Michael Peets]

The mixer is not plugged into any computer. The only inputs are a good quality mic and a keyboard with stereo. The output from the Behringer is unbalanced so the cabling i used was an adapter with two 1/4” mono jacks into the mixer and one 1/8” stereo jack into the jacktrip device. I know I have to keep the output volume of the mixer very low as the jacktrip device input is mic level not line level. I start by raising the volume up slowly until it can be heard in the headphones connected to the jacktrip advice. As soon as I can hear myself at all, it is already clipping. That tells me the server can’t handle the input. When I bypassed the mixer and plugged the mic directly into the jacktrip device, it was sort of better, but still clipping at the server. But, when I switched the server to mono, I could hear myself in one ear very well.  The volume automatically was much better with no clipping. But there was a background hiss/buzz like there was a ground loop. Tomorrow, I am going to go to one of my bandmate’s place close by and connect up using his jacktrip device, the one I bought for him but he still has no clue how to use. If the clipping/garbling/hissing still exists, at least that eliminates the possibility that the problem is my device.  And I’ll find some time this week to rebuild my unbuntu server and configure jacktrip on it so I can set it up as an unmanaged server.

[Hilpoltsteiner Michael]

You are using a JackTrip device which contains a HifiBerry piggy? I guess, the output level, which is provided by Line Out is not enough for your headphones. You need to increase the input volume until clipping to be able to hear your self. Maybe it is worth to try to use your stereo mixer as an output amplifier for the headphones.

For my HifiBerry, I use a small headphone amp, which I connected to the internal outputs. Then it's fine ...

Regarding the direct connection of a XLR Mic to the mic input. There is an internal possibility to connect a differential signal directly to XLR without converting to a single ended signal - I also had similar problems when converting a XLR to a 1/8 mono jack. Check the specification of the HifiBerry to see the possibilities.

For my use case, I now use it with an electret microphone, this is the perfect solution - 10x higher output level than a dynamic mic, delivered already with a 1/8 jack  - enough headroom. But some modifications are needed to the JackTrip image to switch on bias voltage ...

[Louise Goldberg]

Michael,

I'm not sure if this applies to your situation but this is good info anyway. When using a powered mixer, you never want the volume level of the individual channels (keyboard and mic) to be set louder than the main output volume. That will cause distortion.

Hope  this helps.

- Louise

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Louise Goldberg

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[Michael Peets]

I tested the connection from the bass player's place a couple of miles from me. It was not great but it was better. We have the same internet provider; although I have a commercial high speed connection and he has a lower speed residential connection.  The difference in audio quality makes no sense, unless there is something with the internet provider's routing.  So, I went back to the studio and created a virtual server in Montreal, started it, connected to it, and voila, the sound is much better.  Toronto is 60 miles away from me in Niagara; Montreal is 250 miles away.  Hmmmm, that would seem to indicate the route from my internet provider to Montreal is configured lot different than the route to Toronto.  A ping to the server in Toronto takes an average of 18.998 ms roundtrip, while a ping to the Montreal server takes an average of 14.930 ms roundtrip. That'sodd, but not a difference big enough to make my audio terrible on the one hand and almost ok on the other hand. A traceroute from here in Niagara to the ip addresses of the Jacktrip servers Toronto or Montreal have an incredible number of hops to get there, but nothing unusual between the traceroute roundtrips. I am thinking the problem from here is more likely related to packet size and the priorities given to my packets at the various core switches along the way. I'll have to investigate this a little more, but since the sound from using the Montreal is almost ok, I'll get the guys connecting to that server until I can build a quality unmanaged server here in Niagara. Although, it would be interesting to see how the connection would be if there was a Jacktrip server just across the river in Buffalo. I wonder if the org has any plans for server(s) in Buffalo?

Thanks to the folks who provided some ideas to help me solve my problem.

[Michael Peets]

I ended up rebuilding my physical linux server, installing the latest Jacktrip stuff. I noticed a much improved version of QjackCtl with beautiful dynamic wiring diagram.  From in my studio I connected to my linux server (it is not on my home network) with the Jacktrip device using the app via my iPad. I have a mic and keyboard plugged into the mini-mixer, and the mini-mixer output connected to the Jacktrip device. I also plugged in my iMac output (via Steinberg UR44) and set one of our recordings on repeat so I could run back and forth from server room to the studio and try to hear the tune on the server and from the Jacktrip device in the studio. I then went into the server room and plugged headphones into the server. I could hear perfectly the tune playing on the iMac in the studio. Back to the studio. There was nothing in the headphones connected to the Jacktrip device. Back to the server room. After some experimentaion using the "Graph" popup (the wringing diagram) from QjackCtl, I connected the 'receive' to the 'send' and then went back to the studio and heard the tune through the headphones plugged into the Jacktrip device. Success at last. I've included herein a screen shot of the setup. I should note that while the Jacktrip device and my iMac are on the same internal router, my physical linux server is on a completely different network. The studio network and server network are close by but not interconnected. The latency is 2 ms. The big test will be getting the bass player connected, and after that, the drummer and guitarists. They are all within 30 miles so I don't anticipate much latency; although, it appears the ISP routing up here in Canada is in lets-defeat-the-musicians-mode, so we'll see what happens.