help with a biamping problem

I've been experimenting with biamping using Trends Audio TA10s and have hit a problem between two systems I've been using them on. On one setup I used two TA10s so one powered one speaker with biwiring and the other performed identical duties. It worked with no problems.

Then I went to another system to see how that sounded with the biamping arrangement and I keep getting loud buzzing/humming out of one speaker with one of the amps (is something shorting?). The setup is just like my first attempt which, as I said , worked without problems.

In a nutshell, I take the digital signal into a DAC (this is an ART Dio unmodded on the first setup and a professionally modded ART Dio (Mensa mods by bolder cables). I then use a phono adapter so the audio out can be split/doubled on both left and right channels. I don't use a pre-amp. The doubled right channel from the DAC goes to one TA10 so that I use both left and right terminals to biwire to my speakers. The left channels are connected to the other TA10 in similar fashion.

I have assumed that by biamping/biwiring as I've done, I will double the effective power going to each speaker since each amp is dedicating all it's power to one speaker, rather than two, with my setup.

I've checked all cables to ensure there are no short circuits. The TA10s work fine individually (and as I said worked fine together on my first setup).

Was hoping someone could help to sort out what is going wrong or to explain why it might not work on one system. I think the only material difference is the different DACs being used. I wondered whether something was done to the DAC in modding which would affect what I'm doing.

I haven't yet taken the modded DAC from the second system, to replace the DAC used in my first setup, which I will do with a little more time. It may be that I'm a bit premature with my post as this seems the logical next step. Just a bit frustrated with the time it has taken so far and wondered if anyone thinks I'm missing anything obvious – not being electronically minded.

Chris

 

Just to add that I have now swapped out my modded ART dio and put in the unmodded and, would you believe, the hum disappears. So, it's the modded DAC which is causing the problem. Any ideas how to resolve this?

Chris

 

you'll have to put up some pics of the internals of the dac ...but it could be any number of things...

 

I have a TA10.1 and also found when testing it out in different setups that it unexplainably hums in some setups. Im not an expert but felt that the amp is sensitive to the way cables are screened. Its a very long shot and (possibly up there with hand cream) but try turning the IC around.

 

thanks for the replies guys.

ADPully - when I changed DACs the noise disappeared so the amps work fine biamped.

Zanash - thanks for the response. I was hoping it might be something obvious from the out causing the problem - as I'm not electronically inclined. I also emailed the guy at Bolder Cables who did the original mods to the DAC. He said it could be various things, including improper earthing on one side. I may take the top off the DAC to have a look and see if there's anything obvious to this layman that has come loose. Otherwise, as the DAC works fine out of this particular biamp setup, I'll just avoid it for that purpose. Pity though as the biamped TA10's do lift the sound quality further and the modded ART Dio is such a good DAC it would have been interesting to see how it fared.

Thanks anyway

 

if you lift the lid ...take a pic of the unit and post it ...someone may spot the obvious.

but hums normally mean a grounding issue.