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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
apachef1
164 posts
 
Thanks Al I got it now. I had to look at the picture again of the Dussun
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almarg
9,670 posts
 
Let me ask you this, if the jumpers are removed this disconnects the integrateds amplifier power output so hence the need for the "Y" cable
Yes. If no jumper and no y-cable were present, no signal would be going into the power amp section of the Dussun. Presumably the purpose of having a removable jumper between preamp out and power amp in is to allow the Dussun to be used just as a power amp, in conjunction with a separate preamp or other front-end component.

Best regards,
-- Al
manitunc OP
795 posts
 
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.
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almarg
9,670 posts
 
12-21-11: Manitunc
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.
More precisely, it's the only one I can think of :-)

Best regards,
-- Al
hifihvn
943 posts
 
Almarg's choice seems to want to get rid of the risk, of having these two amps outputs, that may be tied together in the speaker some way. If this is happening, it could be a recipe for disaster. Checking with the meter should answer that easy enough.

Another possibility I'm thinking, is mechanical feedback. This would be similar to a guitar, or a microphone picking up the vibration from the speakers, and causing that feedback. The same happens with records. I've had this problem over the years (all size rooms) with vinyl. If the speakers are close enough to the speakers, the record will get the vibration. The result, feedback. I remember this happening is a big Disco, and it sounded like that large building was going to fall apart, until they turned the volume down.

So, the OP has a lot more bass now (higher power solid state), and most likely less treble and midrange (low powered tube), with this new mis-matched level combination. If you don't hear enough highs and mids, you turn it up, and also receive more bass. This is a possibility that I'm thinking might be happening. Try a CD at your risk, to see if this is the problem.

Then another possibility. I'm assuming both of these amps are using feedback. This is taken off at the speaker output area. This output is signal is then fed back into the front end (input area) of an amp.

If either of these amps is doing something a little strange (odd), it may handle that (odd signal) in its own feedback loop, and play fine by itself.

Now if one of these amps is doing something a little odd itself, and that odd signal (that doesn't bother the amp with it) is being fed right back to its input tied right to the RCA area. And, bonding this amp with a different one may give that little odd (feedback) signal to the other amp, that its (RCA) inputs are tied to.

So, if this is happening, that little odd signal in the one amp (that doesn't mind it), can be driving the other crazy, so to speak. And, these two amps may not ever work together, if one these amps is wired this way, and being the problem.
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