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Power cable dilemma

I have to ask the community for an explanation to account for an issue I encountered this past week. 
 

I received a Mark Levinson ML-23.5 amp this past week. I plugged it in with a high end power cord I purchased years ago (because it looked better than the cheap cord that came with the unit. Lol). I switched from an ML-9 so I had certain expectation of the sound. After listening for about 30 minutes, I noticed that the amp did not sound very dynamic. I got up to go feel how hot it was and the heat sinks were barely warm. I turned up the volume and listened for another 15-20 minutes. I got up to check the temperature and the heat sinks were still barely warm. Also, I was playing the amp at volume level 28 on my Cambridge 851N. That is pretty high. The sound was still lifeless. I shut everything down and just sat there, dejected. Was the amp defective? Was it just a bad match? Were my expectations too high? I don’t know what made me try it, but I swapped out the power cord with a plain black cord and powered up the system. Unreal. I was now listening at volume level 22 to the same song, with staggering dynamic impact, at what seemed to be a similar volume. Furthermore, after about 20 minutes, I went up to feel the amp and the heat sinks were very toasty! So the question is: what could have possibly been wrong with the original cord that would result in lower volumes and no heat buildup? It is like it was throttling the current. To me, a cord either connects or it doesn’t. It works or it doesn’t. There should not be an in between. Does anyone have an explanation for this?

jrimer
holmz's avatar
holmz
2,328 posts
 

@jrimer if you have not repeated the process, and found that the cable does it more than once, we are still left not knowing. 

parnelligq
25 posts
 

I would try powering down and switching cables again. If there is a problem, the results should repeat. If the problem repeats, try the cable on other equipment. Then check the cable for resistance. At that point I would pull the ends and check for loose connections. Then check the cable with an ohm meter for breaks.

holmz's avatar
holmz
2,328 posts
 

I would try powering down and switching cables again. If there is a problem, the results should repeat. If the problem repeats, try the cable on other equipment. Then check the cable for resistance. At that point I would pull the ends and check for loose connections. Then check the cable with an ohm meter for breaks.

One could also envision a hot spot somewhere, if the cable is a current bottleneck.

dpop
293 posts
 

@jrimer

It would be interesting to see what the results would be if you switched the sequence of cables around next time in another study of your perception of amp temperature and performance, ie, starting out next time (with a cold amp) with the "plain black cord" for the exact same duration of time you used the Pangea cable last time (as the first power cable used). Understand what I’m saying? If the same results take place, maybe it’s just the amp venting some of it’s heat to the heat sinks after being powered up for a certain total length of time (using a combination of both AC cables), no matter what AC power cables were used, and in what sequence.

I don’t know the entire design of the amp, so I don’t know if all of the operating current flows through the front panel ML-23.5 ON/OFF power switch, or if the front panel switch operates an internal relay, and all of the AC power/current then flows through relay contacts. From over the years arcing, some AC switches that pass high amounts of in-rush current can develop dirty contacts. It’s possible that maybe working the front panel switch a few times cleaned the contacts on the switch. These are just a few of my initial thoughts, but I do find your discovery interesting.

It would also be interesting to measure the resistance of each cable, with a test meter (measuring one leg/conductor at a time), to see if there’s any kind of difference between the two.

pennfootball71's avatar
pennfootball71
274 posts
 

I like how he does not mention what “high end” power chord he purchased.

Most older power cables are not great anymore and cable technology has made quantum leaps over the past 5 years!!!

Try a  2 meter $2500 Kubala Sosna Elation! 
 

let it WARM UP 3 hours! It takes 3 hours to warm up any amplifier that you disconnect the power supply! Then listen.

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