Has anyone changed the output load impedance on a Classic 60? I just purchased this and it is set to the factory default 4 ohm. My speakers are 8 ohm so I want to match the outputs to the load.
I contacted CJ and the tech was reluctant to give out any information about the conversion. He insisted that the factory default was Ok and that I should not notice any difference, but I think I do.
It is common knowledge that you must match the impedance as close as possible between the amplifier and speaker to allow optimum transfer of power to the speaker while preserving minimum distortion operation of the amplifier. CJ is the first vendor I have run across that said it did not matter. My thinking is that they don’t want anyone poking around inside the amp and making the change on their own for fear that the user will mess up the amp.
The wiring for the transformer is the same as the Premier 11 & 12 so I know how to reconfigure the wiring. The question is what about the feedback network resistors? I am thinking that I will need to change the feedback resistor values as is required for the Premier 11&12 to maintain the correct amount of negative feedback. Does anyone know what the correct value for the feedback resistors is when configuring for 8 ohm load on a Classic 60?
I would appreciate anyone sharing their knowledge on this subject.
Thanks,
Best regards, Tim
Classic 60 Feedback Resistor Value for Impedance Matching
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Big Dog RJ
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Re: Classic 60 Feedback Resistor Value for Impedance Matching
Hey mate, just came across this post.
Having been in the world of audio my entire life and hopefully many more years to go (started noticing a few grey hairs here and there...) in my experience of 30 years, I wouldn't mess with or try to adjust the original design.
Cj has been in the high-end audio business of over 40 years making true high-end products with a passion for superb sound with real value. If they claim that the factory setting at 4ohms is fine, trust me they know what they're talking about.
I have owned far too many power amps from cj including with various types of speakers, and have never had any issues driving them with cj amps in terms of impedence mis-match whatsoever.
If you feel that there is an issue with impedence or some sort of "not right" feeling with the amp driving your current speakers, then that is probably an issue somewhere else along the chain. Could be several areas in the system. That you would need to investigate carefully.
Changing the impedence or any other factory setting, unless it was carried out by cj, I wouldn't even think of it.
Not a good idea mate.
If you're not happy, I would try to seek help from my trusted dealer first or a tech expert in amplifier design and go from there. In my experience, a 4ohm setting actually drives a speaker better than a 8 ohm setting. The classic60 is an awesome amplifier and can drive most speakers with ease. An 8ohm speaker will be a breeze for the classic60. Also remember, that these impedence ratings from speaker manufacturers are nominal ratings, impedences vary drastically when signals are applied.
These impedence ratings are only an average of what the load would tend to swing. Hope this helps.
Cheers, RJ
Having been in the world of audio my entire life and hopefully many more years to go (started noticing a few grey hairs here and there...) in my experience of 30 years, I wouldn't mess with or try to adjust the original design.
Cj has been in the high-end audio business of over 40 years making true high-end products with a passion for superb sound with real value. If they claim that the factory setting at 4ohms is fine, trust me they know what they're talking about.
I have owned far too many power amps from cj including with various types of speakers, and have never had any issues driving them with cj amps in terms of impedence mis-match whatsoever.
If you feel that there is an issue with impedence or some sort of "not right" feeling with the amp driving your current speakers, then that is probably an issue somewhere else along the chain. Could be several areas in the system. That you would need to investigate carefully.
Changing the impedence or any other factory setting, unless it was carried out by cj, I wouldn't even think of it.
Not a good idea mate.
If you're not happy, I would try to seek help from my trusted dealer first or a tech expert in amplifier design and go from there. In my experience, a 4ohm setting actually drives a speaker better than a 8 ohm setting. The classic60 is an awesome amplifier and can drive most speakers with ease. An 8ohm speaker will be a breeze for the classic60. Also remember, that these impedence ratings from speaker manufacturers are nominal ratings, impedences vary drastically when signals are applied.
These impedence ratings are only an average of what the load would tend to swing. Hope this helps.
Cheers, RJ