2. amps-preamps
  3. 119371-3515

Unique problem - one channel silent under different variables

Bought a mint (looking) Cary slp 98 on eBay, connected to two reconditioned Hatachi HMA 7500 mosfet amps, work perfectly for years since reconditioning - biamping NHT 4 towers, bought new. 
When the preamp is turned on, a series of pops through the speakers, then Only the right channel plays. Switched tubes, didn't solve issue. Changed inputs from preamp to left and right amp and immediately both channels worked. Switched off, waited 5 minutes and still both channels working. Came back a few hours later, switched on again (having reversed the inputs to normal) and again same sequence: left channel silent and after switching inputs, both work and remain working until I switch off and come back when the units are cold.
I can understand that that there may be a resistor/capacitor that need to be hot before working, but why would switching input cables from left out to right input of amp and vice versa immediately fix it!
so every time I want to hear music I have to go thro this rigmarole! Why does switching cables fix the problem????
any solution will be greatly appreciated! I'm sure it will end up back at Cary but I wondered  if anyone (Almarg???) has an answer?  Does the popping on switching on, both channels pop, provide a clue?

springbok10

Showing 5 responses by springbok10

springbok10 OP
711 posts
 
Al,
Thanks for your thoughts. I have found that if I leave the preamp on constant standby, the issue is resolved. It seems that the unit/tubes/caps/resistors work if kept "warm". Forgive my indignation at the thought of doing anything with power on! To me that's like driving s car with the hand brake on or playing with the innards of a 1500 w amp with the unit on and plugged in :)

springbok10 OP
711 posts
 
I learned 20 years ago to  turn amp on last, off first. What makes you think I do all these cord exchanges with power on? Did I say that? No, I think you assumed it. With due respect, and I know you are being helpful, if I haven't learned that basic, I shouldn't be  wasting your time posting. Thanks for your input,
Denis
springbok10 OP
711 posts
 
Yogiboy, I think you're right, because my last preamp was silent on left side and is currently being checked. Never thought it could be the amp - could transients and "pops" emanate from and cause a ss mosfet amp to shut down? How?

I will do the experiment.
springbok10 OP
711 posts
 
I just switched it on cold and switched the left and right cables (there are 2 pairs as I am biamping) and sure enough, the left amp turned off after 5 minutes. So it's the amp! So it cant be the preamp, since the right channel is supplying the left amp and its always been the left side that's muted.

Thank you all!
springbok10 OP
711 posts
 
Confirmation that it was the amp - replaced with another amp and no muting or popping.......
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