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

I don’t think it was due to the caps needing to power up. I had run the amp the previous day for about an hour, but at lower volume as background music while we cleaned and decorated the room for a party my wife was having. The caps should have been charged sufficiently. Also, if they were not charged, for them to suddenly become charged at the exact moment I substituted the power cord, would be an unbelievable coincidence. 

In thinking about my experience with this cord, I may have discovered another instance of something odd occurring. I purchased a Line Magnetic LM150 integrated tube amp. It was borderline powerful enough to drive my speakers based on the specs. When I put it in the system, it performed very well. I kept a close eye on the meters to be sure the amp was not getting too stressed. The peaks never went higher than 50%-75% on the meters. I ran the amp for about three weeks and added some new ribbon speaker cables. Much to my dismay, at similar or lower volume levels I noticed the meters were pegging out. I attributed it to the unusual impedance of the speaker cables. I pulled the amp temporarily and ran a beefier solid state amp for a bit. Fast forward a month later and I tried the LM 150 again. This time the meters behaved as they did at first. I was both relieved and puzzled. I have had the amp in and out of the system numerous times over the past couple months and sometimes the meters are fine and other times they max out. I honestly do not remember what power cords I was using each time, but I’m going to guess there is a correlation between the meters maxing out and the “bad” power cord. This will be an easy thing to check. 

I would recommend you use a quality 10 gauge power cord, like a Kimber PK10 and use the balanced connections to your preamp.

Are you using the single ended inputs or balanced inputs? If single ended inputs are you using the shorting straps between pins 1 and 3?

I’m using balanced on the Ml 23.5. The Line Magnetic uses only single ended. 

Out of curiosity what is the name of the high-end power cord you purchased several years ago that you spoke of in your original question?