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Problem: distortions with xlr dac / sub connection

joker, modified 7 Years ago.

Problem: distortions with xlr dac / sub connection

Youngling Posts: 7 Join Date: 6/24/14 Recent Posts
Hi,

my setup is a F2 sub with two G3 connected via XLR, then I use a 9091a wired volume control. I use a TEAC UD-501 DAC directly connected to the F2 with inputs from a cd player and a squeezebox streamer. As XLR cable I use Cordial CXM 5 Encore 5 meter.

Using RCA connections, it is great. Using XLR connections though, there are medium to high frequency distortion noises overlaying the music, especially when there peaks. Even when the sub's volume control knob is turned to zero. The Teac is configured to use the Pin 2 as hot. No difference when swiching to Pin 3 as hot.

Any idea what is wrong with my configuration? or where do such kind of distortions might have its origin?

Thanks and regards,
Joker
joker, modified 7 Years ago.

Re: Problem: distortions with xlr dac / sub connection

Youngling Posts: 7 Join Date: 6/24/14 Recent Posts
....meanwhile it is obvious that the subwoofer is just defect and will be sent to repair.
Bye, Joker
ilkka-rissanen, modified 7 Years ago.

Re: Problem: distortions with xlr dac / sub connection

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts
Hi,

The subwoofer is not defective. Distortion is due to overloading of the system volume circuit inside the subwoofer. Maximum allowed input voltage for both XLR and RCA inputs is about 2.3 volts. If the maximum output of the DAC is more than this, clipping and distortion will be present.

http://www.teac.com/product/ud-501/specifications/

By looking at the specs, TEAC is rated at 4.0 volts through XLR outputs and 2.0 volts through RCA outputs. So the solution to the problem is to use RCA outputs instead of XLR.

What do you mean by "9091a wired volume control"? We have 9000A model, do you mean this? If you have it connected after the DAC, you can use it to attenuate the output level.
joker, modified 7 Years ago.

Re: Problem: distortions with xlr dac / sub connection

Youngling Posts: 7 Join Date: 6/24/14 Recent Posts
Hi Ilkka,

now thanks for the reply, that explains it, but is surprising to me. Why I said that the sub was defective is because my dealer tried out the sub and also had these distortions, with a different DAC, but might have beeen another DAC product with also too high output. Using RCA instead is not really what I wanted, as the xlr connection seems to have advantages when it comes to longer cables, and I need somewhat 5m for optimal positioning. The fact that xlr does not cope with higher input than RCA disappoints me, as far as I know the xlr typically are about double as RCA (e.g. Oppo HA1, Cambridge Audio DAC Magic, Essence HDMI DAC, they all have some 4 Volt output on xlr, and 2,x on RCA). So why is the Genelec DAC not capable of dealing with such standard DAC outputs, that does not seem up to date for such a configuration that might become quite usual.

Remote: yes, was my fault, the model is a different one. I was using a remote control knob from a 5040, but the distortions are the same, as this remote works quite the same way as the wireless remot. So, that does not help either, because then the input level is still too high, or did I miss a thing?

Any other idea? What about attenuators, with -10db level? Any recommendation?

Regards, and thanks for helping,
Jochen
ilkka-rissanen, modified 7 Years ago.

Re: Problem: distortions with xlr dac / sub connection

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts

Remote: yes, was my fault, the model is a different one. I was using a remote control knob from a 5040, but the distortions are the same, as this remote works quite the same way as the wireless remot. So, that does not help either, because then the input level is still too high, or did I miss a thing?

Correct, using the system volume controller doesn't help because it doesn't attenuate the signal before the volume chip.


Any other idea? What about attenuators, with -10db level? Any recommendation?

Regards, and thanks for helping,
Jochen

An in-line XLR attenuator pad of 10 dB would work great.

http://www.studiocare.com/neutrik-in-li ... 3-pin.html
http://www.schoeps.de/en/products/mdz
joker, modified 7 Years ago.

Re: Problem: distortions with xlr dac / sub connection

Youngling Posts: 7 Join Date: 6/24/14 Recent Posts
Hi Ilka,
meanwhile I got attenuators with -10db, better now but sometimes still distorted. So now I try out -15 db or -20db?
Or, could you please give me more details about the technical data of the F2 subwoofer input level? On wich dbu/dbv level does it work?
Regards,
Jochen
ilkka-rissanen, modified 7 Years ago.

Re: Problem: distortions with xlr dac / sub connection

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts
Please see this post: viewtopic.php?f=4&t=1369#p4459

2.3 volts equals to ~9.5 dBu
joker, modified 7 Years ago.

Re: Problem: distortions with xlr dac / sub connection

Youngling Posts: 7 Join Date: 6/24/14 Recent Posts
Thanks Ilkka, but following the link it brings me back to the same thread?

Ok, then the max. input level of the F2 is 9,5 db, and my DAC delivers 4 Vrms which is 14,3 dbu. So an attenuator with -10 db should solve it, right? But it doesn't. Feeding in xlr with attenuation still sounds louder than RCA input.

My conclusion: either the attenuator doesn't really take 10 db off, or there might be some other aspect. Btw, I set the +10 db dip switch on my F2 and the G3 to on as the manual suggests, does that have any impact?

Thanks for you thoughts,
Jochen
ilkka-rissanen, modified 7 Years ago.

Re: Problem: distortions with xlr dac / sub connection

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts
Hi Jochen,

Your conclusions are correct. If you take 10 dB out of 14.3 dBu, you get 4.3 dBu which equals to 1.2Vrms which is well within the operating range of the subwoofer. So either the attenuator isn't really 10 dB or the DAC puts out higher level than 4 Vrms. Of course it is also possible that the subwoofer itself is indeed defective and needs to be serviced.

+10 dB sensitivity dip does not have any effect to this as it is placed after the volume control chip inside the electronic signal path.