Problem with bi amping speakers

why not just go with preamp out of the Dussan to the tube amp's in puts?

Guys, the Dussun normally has a jumper connecting the rca output jack of its preamp section to the rca input jack of its power amp section, for each channel. What Manitunc has done is to replace that jumper with a y-adapter. That maintains the connection that is normally provided between those jacks by the jumper, while also allowing the inputs of the other amp to be connected to the preamp out signals. All of that is correct.

My guess, assuming that no shorts were introduced by any of the cables or connections, and despite the fact that the speaker supposedly can be biamped, is that the low frequency and mid/hi frequency parts of the crossover are not completely separate, and a path between the outputs of the two amps somehow exists through the speaker. Which is why I suggested the multimeter measurements in my earlier post.

Regards,
-- Al

I'll give 8:3 Al is right.

Al

I seem to think with this type of connection Manitunc has made introduces the impedance of the tube amps input stage into Dussun loop through the Dussun preamp section. This would seem to be the source of the overload to the Dussun preamp stage.

Is this a recommended connection for the Dussun-"Y" cables?
What is the point of pre/power RCA jumper threw if you need to use the "Y" cable?

I would think the correct connection is to use a male to male jumper across the pre/power RCA's and connect the tube amp to the line out RCA's. My speculation is that this would allow the line out RCA connections to attenuate the tube amp he wants to connect to the mid/high section on the PSB

All the speaker connections are correct. Also his PSB speakers are bi-amp capable.

I did ask Manitunc about the line out RCA's being attenuated from the volume control or if they only feed a constant signal. I was waiting to hear back before I made this recommendation

No manual was a available from the website so all this is trouble shooting for him.

Ed

I seem to think with this type of connection Manitunc has made introduces the impedance of the tube amps input stage into Dussun loop through the Dussun preamp section. This would seem to be the source of the overload to the Dussun preamp stage.

Hi Ed,

Typically tube amps have high input impedances, so its presence most likely does not result in a significant load on the preamp out signals from the Dussun. Even if it did, it would most likely just result in a small effect on sound quality, not an overload that would result in oscillation or shutdown. Depending on the output impedance and other aspects of the design of the circuit that drives the preamp outputs, even a dead short on that point is unlikely to cause those effects (although it would reduce the volume of what is heard to zero or close to it).

What is the point of pre/power RCA jumper threw if you need to use the "Y" cable?

The y-adapter allows the tube amp to be connected to the preamp out signals at the same time as the preamp out signals are routed into the power amp section of the Dussun. When the Dussun is the only amp being used, the jumpers that are normally in place (instead of the y-adapters) allow the preamp out signals to be routed into its power amp section.

I did ask Manitunc about the line out RCA's being attenuated from the volume control or if they only feed a constant signal.

I would feel pretty certain that the volume at the "line out" jacks is not varied by the volume control, while the volume at the "preamp out" jacks is varied by the volume control. The "line out" jacks are probably the same as what are sometimes referred to as "tape out" jacks.

Best regards,
-- Al