Rotel RB-1090 Protection Circuit

[SAaudiophile]

Is there anyone out there that's modified the over-current protection circuit of a Rotel RB-1090 power amp? I suspect that this protection circuit is far too sensitive as it kicks in when the amp is still running ice cold and neither the speakers nor amp sounds under strain. I am using a pair of Infinity Reference Standard 9 Kappa loudspeakers. Any ideas/suggestions?

[JohnMichael]

Is there anyone out there that's modified the over-current protection circuit of a Rotel RB-1090 power amp? I suspect that this protection circuit is far too sensitive as it kicks in when the amp is still running ice cold and neither the speakers nor amp sounds under strain. I am using a pair of Infinity Reference Standard 9 Kappa loudspeakers. Any ideas/suggestions?

One thing that comes to mind is the Rotel's traditionally do not like high capacitance speaker cables and they have been known to trigger protection circuits. What wires are you using?

[mazdamanic]

Is there anyone out there that's modified the over-current protection circuit of a Rotel RB-1090 power amp? I suspect that this protection circuit is far too sensitive as it kicks in when the amp is still running ice cold and neither the speakers nor amp sounds under strain. I am using a pair of Infinity Reference Standard 9 Kappa loudspeakers. Any ideas/suggestions?

Your speakers are known to have nasty impedance dips (1 ohm?) causing this. Great speakers though but need SERIOUS amplification.

[SAaudiophile]

One thing that comes to mind is the Rotel's traditionally do not like high capacitance speaker cables and they have been known to trigger protection circuits. What wires are you using?

Thanks, I wasn't aware of that. The speakers are biwired by Monster's "Powerline 2" Speaker Cable. Sounds very neutral and seems like a fairly thick (high current) cable. What do you think?

[SAaudiophile]

Your speakers are known to have nasty impedance dips (1 ohm?) causing this. Great speakers though but need SERIOUS amplification.

Yes thanks, I am aware of the impedance dips and was hoping that the Rotel would do the trick. From the information provided on Rotel's site: http://europe.rotel.com/products/specs/rb1090.htm, it really seems like a truly high current amp. For instance, they state that it has "two large 1.25 kVA custom made, multiple-secondary toroidal ransformers" and that the amp weighs in at 83.6 pounds! All of what's stated on their site implies a really powerfull amp! I honestly expected more from a amp with these sort of credentials, which is why I think that the protection circuit is over sensitive.

[GMichael]

Is there anyone out there that's modified the over-current protection circuit of a Rotel RB-1090 power amp? I suspect that this protection circuit is far too sensitive as it kicks in when the amp is still running ice cold and neither the speakers nor amp sounds under strain. I am using a pair of Infinity Reference Standard 9 Kappa loudspeakers. Any ideas/suggestions?

Have you checked and re-checked all wires and conections for possible shorts?

[JohnMichael]

Is there anyone out there that's modified the over-current protection circuit of a Rotel RB-1090 power amp? I suspect that this protection circuit is far too sensitive as it kicks in when the amp is still running ice cold and neither the speakers nor amp sounds under strain. I am using a pair of Infinity Reference Standard 9 Kappa loudspeakers. Any ideas/suggestions?

I read your other post about crossover problems and maybe when you get that problem taken care of your problem with the amp might disapear. Good luck.

[mazdamanic]

A quick look at the owners manual on the Rotel website states the overcurrent protection circuit engages when loads dip below 2 ohms and is not related to the thermal overload circuit. Seems like you would have to find a way to bypass this circuit.

[SAaudiophile]

Have you checked and re-checked all wires and conections for possible shorts?

Yes, thanks. Even changed banana plugs to WBT high current connectors. I would think that if there was a short the protection would have kicked in immediately when the amp is switched on, which is not the case. The problem only occurs on fairly high volume (far from excessive) on highly dynamic pieces of music / movies. For instance, church organ (Bach Tocatta) is no problem with it's contant deep notes, but expolsions/gun shots etc usually results in a sudden silence....

[SAaudiophile]

A quick look at the owners manual on the Rotel website states the overcurrent protection circuit engages when loads dip below 2 ohms and is not related to the thermal overload circuit. Seems like you would have to find a way to bypass this circuit.

Thanks for having a look. Yes, it is most likely what i would need to do, but am very aware of the risks and therefore would ideally like to chat to someone that's done it to hear of any complications etc.

[SAaudiophile]

I read your other post about crossover problems and maybe when you get that problem taken care of your problem with the amp might disapear. Good luck.

Thanks, I initially thought so too, but what's lead me to believe differently is the fact that when the protection circuit kicks in, both channels kick in at exactly the same instant. This is strange as the Rotel's owner's manual states that the protection circuit operates totally independent for each channel. (There is also a led on the front panel for each channel, which lit up when the protection circuit is activated). Therefore, I suspect that if the crossover trouble was causing the problem, then only that channel's protection circuit would have kicked in, but both channels kick in.