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Parasound JC-1 variations

I installed the 3rd JC-1 yesterday. It drives the center channel, and the sound of the 8 Ω KEF R600C now matches that of the 4 Ω 107/2s quite well. But this JC-1 seems different form the pair I’m using to drive the 107/2s. In high bias mode it runs hot to the touch, whereas the LR pair are just warm to the touch. If I set the bias of the new JC-1 to low, it is also just warm to the touch. Reviews and a couple of posts at AVS have noted that the amps run hot, but I thought the 107/2s might be an especially easy load coupled with the moderate levels of music I prefer may have accounted for the mild warmth. Now I wonder if the pair of amps I bought to drive the 107/2s may be running in low bias mode even though the switch is set to high bias. But those amps sound great driving the 107/2s. Would I notice any difference in sound between high and low bias at moderate levels?

Also, the blue light of the new amp is much brighter than that of the other two amps and is bright whether powered up or not — red lights of all the amps follow the same pattern of being bright when on and going to dim when off.
Ag insider logo xs@2xdbphd
7 responses Add your response
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dbphd OP
1,628 posts
 
The amps were bought used, the pair that tuns cool from one party and the third that runs hot from another. Given that I think they sound so good running on low bias, I plan to use them that way for the time being. At some point I may send them to Parasound for service, but I'm really don't want three amps running as hot as the third amp does when the bias is set to high.

Each of the amps driving the KEF 107/2s uses two Clear Day cables for biwiring; a second Clear Day cable is on its way for the amp driving the R600C so it can be biwired as well. I suspect that's irrelevant to the issue.
db
pryso
1,927 posts
 
Coli, $300-400 based on what? In my experience Parasound is outstanding with warranty service. We don't know if Dbphd's amps are covered or not so it seems premature to make statements about costs.

But none of us knows the circumstances so this should all be sorted out with Parasound.
coli
291 posts
 
It needs to be repaired, if you send it to Parasound the bill will be around $300-400 bucks.
bgpowell
70 posts
 
The impedance of the speakers is different, therefore load is different. Replace center JC-1 with one of the others and run your system. If the new center amp runs hot, then it is the speaker load making the difference. If it is not hot like the original center amp, then you would investigate the difference between the amps.
pryso
1,927 posts
 
I found my JC-1s sounded best in high bias so I've used that for critical listening and low bias for background music. Even when I owned Duntech Princess speakers with very complex (read - not an easy load) crossovers they would get quite warm but never what I'd call hot. I could leave my hand on a heatsink without discomfort.
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dbphd OP
1,628 posts
 
I've done that and he does. He's been very helpful with JC1, 2, and 3 as well as A23. It may not matter, if I set all three amps to low bias, but if I want to use high bias all around, I need to send the amps in for service. I don't think I want the amps to get that hot, so if they switch from class A to A/B at 10 watts, that's probably OK for 90 dB sensitivity and moderate listening levels.

db
pryso
1,927 posts
 
Have you thought about contacting Parasound with your concerns? I've found their customer service to be top notch and Richard responds quickly.
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