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Pre-amp causing loud hiss from speakers

I have a BAT VK3i with Quicksilver Horn mono-blocks and Klipsch LaScala's. This setup is dead quiet, however when I recently hooked up Rogue Audio M-180 mono-blocks there was a loud hiss coming from the speakers well past the listening spot. This noise was constant even with the volume down to zero and occurred with either balanced or rca connectors.

When I took the BAT out of the equation there was now only a faint hiss coming from speakers but one had to put your ear to it to hear it. After disconnecting all components from the BAT and putting it back in - the noise returns. I tried a Conrad Johnson Classic and there was no noise.

So does anyone have any ideas as to why the BAK and Rogue Audios amps do not play nice together?

Thanks
deadlift
viridian's avatar
viridian
4,184 posts
 
As Newbee correctly points out the gain architecture of the system is completely wrong for the extremely high sensitivity LaScalas, which will magnify any noise upstream.

For what it's worth, IMHO the Quicksilvers are much better sounding amps than the big Rogues and will have much lower operating costs as well. Add to that the lower gain which is correct in the context of your system and it may be time to move the Rogues on.
deadlift OP
9 posts
 
I will experiment more with the IC's and binding posts, but I fear as noted the gain architecture is way off - oh well part of the journey. I do wonder if it's not inappropriate here to ask what a set of Rogues would be worth with less than 30 minutes run time?

Thanks
viridian's avatar
viridian
4,184 posts
 
Since you're in for a penny you might as well check one more thing. With the amp off, remove the interconnects from the amp. Replace them with, preferably, shorting plugs, but RCA caps would probably work as well. Turn the amp back on. What you are now hearing is the internal noise from the amp alone.

If the noise is not too bad you may be able to use line level attenuators such as those available from Parts Express between the preamp and amp and this will solve the problem without heroic efforts as Newbee suggested.

The other possibility is to call Rogue, they are most helpful and may be able to internally alter the gain of the amp.

Finally, Rogue is a hot brand and I would start at 20% off retail and probably be ready to accept 30% off retail. Just a guess here.
deadlift OP
9 posts
 
I will give it a shot nothing to lose. Those attenuators are RCA would using balanced attenuators make any really difference?

thanks again
newbee
4,093 posts
 
I can't think of any reason that the balanced attenuators would sound better, or even different. What will make a difference though is the amount of attenuation that they will provide. 10db attenuators are common (and the ones that I have used) but that might not be enough. You can also get them in 20db and perhaps anything in between. FWIW Rothwell makes a nice in-line attenuator. If the hiss is really loud I'd try the 20db ones first.
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