Problem with bi amping speakers


I tried to biamp my PSB Stratus Golds tonight using a Dussun V6i 150 watt SS integrated amp for the woofers and a Nobis Contigore 40 watt tube amp for the mids/highs. The contigore is similar to a Dynaco ST70. I used the preamp out on the Dussun and ran one cable to the preamp in on the Dussun and the other cable to the Nobis. Took the jumpers off the speakers and connected both amps to the respective terminals using the 8 ohm output on the Nobis.

When I turned on the amps, they both worked well for about a minute. Then I heard what sounded like feedback from a guitar amp, then ok, then feedback again, then the Dussun amp tripped. the Nobis kept playing. The feedback sound lasted for about 2 seconds each time.

Took it back apart, and both the Dussun and Nobis work fine alone. So what about my connections would cause this problem. I use a 2 male phono to a single female phono. One male end goes in the preamp out on the Dussun, the other male goes in the preamp in on the dussun, and an interconnect goes into the female end of the connector. There is one of these for each channel.

So, what am I doing wrong?
manitunc

Showing 6 responses by manitunc

yes, one set from Dussun to low, one set from Nobis to mid/hi. I was playing a vinyl record on an Oracle Delphi V which has never had an issue with feedback, so I dont think that was the problem.
yes, one set from Dussun to low, one set from Nobis to mid/hi. I was playing a vinyl record on an Oracle Delphi V which has never had an issue with feedback, so I dont think that was the problem.
The PSB Golds are set up for biamping and there are instructions for hookup in the manual which I followed.

The tube amp was sitting on the floor for this test, and the integrated was about 5 feet off the floor, directly above.

I used a y connector, two males to one female. The male ends pluged into the preamp out and power amp in on each channel and the female connector was attached to an interconnect running to the tube amp's input.

The PSB woofer does go down to 2 ohms at about 100hz, but I use the same Dussun integrated normally with these speakers without a problem. I was just trying to add the tube amp for the mid/hi to see how it worked, and maybe sweeten the sound.
Yes, the line out bypasses the preamp volume control. That is why I dont use it for this purpose.

Almarg, you get it. So, if everything is hooked up as I say with no shorts, then you say the only cause of my problem could be a connection between the woofer and the mid/high in my PSB Golds. The manual for the Golds definitely provides for biwire and bi amping the speakers just by removing the jumper between the speaker connectors and running the cable from each amp to each pair of connectors. But I will try the multimeter this weekend and see what I can see.
thanks.
I dont know how to post a diagram, but its pretty simple. From the preamp out on the SS amp I have a y connector with two male and one female ends. One male goes in the preamp out jack, the other male goes in the amp in jack and the female connector takes an interconnect cable which runs to the tube amp for that channel.

Speaker connections run from the SS amp to the woofer connection and from the tube amp to the mid/hi connection. The jumper between the two is removed. This is the way the PSB manual shows it should be hooked up, and the only way that makes sense.

I will try to reconnect it all again this weekend and see if the problem repeats.
http://www.dussun.com/english/v6.html

here is the dussun website that shows the rear of the unit and the connections