Power cable dilemma

Other than a resistance measurement…

But if you put the good looking cable back in, and it does the same thing again… then we know it was not the amp running in some semi protection state… (If that is even possible?)

You should have used a variac to gradually power up the amp for at least several hours before connecting it to speakers. This would give the power supply caps time to reform. With the first power cord the caps were still not at full charge. By the time you switched to power cord two the caps were near or at full charge. Nothing to do with the quality of the power cords. 

Electronic components that have been sitting unplugged for an extended period should be run up on a variac before use to prime the power supply caps.

So cable deniers don't believe you need a heavy gauge power cord.  I am a "cable denier" of sorts in that I think that 99% if not more of the gain available in a cable can be achieved with an inexpensive but heavy gauge cable.   

You have described the exact symptoms of too light a power cable.  

I'll tell a quick story. In my tube amp journey I wanted to try a Decware amp.  There is a 2 year wait list for decware so I started looking on the preowned market.  Being an early riser, I found one listed late saturday night and bought it at 0400 Sunday morning.  It was an unpretentious and relatively inexpensive SET.  It was only 6 wpc (SE34I.5 for those curious).  When the ap arrived there was a note with it "I have included an upgraded power cord I bought for this amp".  It was obviously very light.  I looked it up, it was only 16 awg and cost $300.  This guy had "upgraded" his power cord and ruined the sound from his amp. I was very fortunate to benefit from his misfortune. this amp excells and I eventually upgraded to a top end Decware amp.

As a physicist, I see many examples of google educated scientiists missing the mark and shooting themselves in the foot.  Most tube amps are a 200 watt load or less.  Look at the book and you'll see that 16 awg is plenty for a 200 watt load.  (I think that amp was closer to 100 watts),  But dynamics and base require the ability to supply very high currents for very short times.  Overall it averages out to 100 to 200 watts, but for short times much higher current is required.

Jerry

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?

It is not exactly “high end”. It’s a $40 Pangea cord. 

Unless it is a Pangea AC-9, it's too small for the ML amp. 

BTW: Your room & system look fantastic!

Thanks! Really? Too small? I didn’t even know that was a thing with power cords. 😂

The pangea power cords are either 14awg or 7awg I don't know why they call it an ac 9

I’m using cheap Pangea I do not like but I do not know on what direction to proceed with power cord to power Harbeth 30.1 with 300 S/S. ????

The Pangea AC-14… assuming that was what you have is made for components like CD players. So, it is made for low current applications. It is also very far at the low end of the budget category, so, I would be surprised if it would sound better than a stock cord on any high end gear.

The amp you purchased has a very good reputation among folks that like the Mark Levinson sound. It would probably be worth while putting a good quality power cord on it. Power cords for amps are very specifically constructed for high current can make a startling difference in amp performance… I mean really surprising,. I suspect you just experienced that… but kind of in reverse.

I recommend you try several high end power cords… like DHLabs Powerplus or higher, Cardas Clear, or ever better one of the AudioQuest Storm Series power cords. These can be revelatory. Try about three, make sure you can return them, it is likely the result will be very surprising. I doubt you will want to, but if not worth the money, just return them.

I tried several high end  power cords on my amp over a year until I found the AudioQuest Hurricane (~$2K)… the difference was just striking. When I can afford it, I will definitely be looking to upgrade to a Dragon. 

It would make no sense at all for the Levinson to ship with an inferior power cord. 

Just use what the engineers supplied.

I have no idea what the Levinson originally shipped with. I bought it used and it is probably close to 30 years old.  
 

As far as spending $2k on a power cord, that probably won’t happen. I’m getting really great sound out of the cord I’m using now (plain heavy duty black cord). 

Nice room! Sorry to miss the party. Spend for a great power cord and you shall be rewarded. Many you can audition. 
As for a break in with a variac, does the manufacturer recommended this?

" I’m getting really great sound out of the cord I’m using now (plain heavy duty black cord)."

There should be some printing or embossing on the side of the black heavy duty cord. For example: Type SJT 3x12 AWG. This means 3 runs of 12 ga. wire. 3x10 AWG = 10 ga., etc.

Thanks! Really? Too small? I didn’t even know that was a thing with power cords.

It's not. 

I’ll bet you had a kink in the cord, like when you’re trying to wash the car and there’s a kink in the hose, you know like that

Be careful if you hang the cables in the sun for too long they’ll sound too bright

I’m careful to make sure my amp is lower than the wall socket so the electrons can flow downhill via gravity. 
 

I can tell this thread is devolving quickly….

This could be entirely dependent on the unit, but I spent just under $200.00 on a power cord and it made an easily audible difference for the better.  I would imagine spending more would be better…

The cord I’m using is 3x16 AWG. I have another that is 3x14 AWG that I will try tomorrow. 

16 ga. is too light for your amp, 14 ga. is marginal, however you might notice a difference. How long does the power cord need to be?

Right now it is only about 3’ going to a power strip. I want to upgrade the wall receptacle and run the power amp direct to its own 15 amp circuit, but for that I will need a 9’ cord. 

Ok, the power strip might be your weak link. Excellent going directly to a dedicated circuit. For a 9ft. run defiantly go with a 10 ga. cable. Many of the major high-end major manufacturers will offer their versions, however many are quite expensive. Check out some of the offerings on eBay, I noticed several small firms that make custom cables at very reasonable prices.

Thanks for the feedback. I’ll check it out. Since I ditched the Pangea cord, I haven’t had any issues. Even with a power strip and a cheap 16 gauge cord, the issues I mentioned in the original post have vanished. Everything sounds and performs wonderfully. 

You are welcome, I am sure when you hookup to your dedicated circuit you will be pleased with the results.

You should measure the resistance of the trick power cord to make sure it can pass sufficient current.

9 foot of standard 12 gauge won't cost much so make the change now and ditch the power strip.  Power strips suck.  Don't worry about the wall receptable.  It will be fine to pass the power your M-L requires.

Anyhow @jrimer you've learned the truth about trick power cords.  Go out and buy a nice meal with the money you're saving, or lots of meals.  Or a car if it was a really expensive one.

With respect. Ditching the power strip and plugging into a robust power conditioner or directly into an audio grade wall plug a great way to go

If that power cord was a bottleneck, then I would assume it would be heating up?

Even an 18ga wire should flow enough current to trip a breaker… or enough to melt it if the load wants that amount of current…

Without a redo of the cable, we are sort of left wondering.

This is what I don’t understand. It wasn’t a subjective difference in sound clarity I experienced. It was a volume difference and a temperature difference on the amp. These are both easily quantifiable. It honestly doesn’t make any sense. 

@jrimer  The only thing that makes sense to me is a bad connection within the “bad” cable. Loose connections can still pass some voltage but can act like a resistor in the circuit. The bad connection might be at a wire connection in one of the plugs, or even fingers of the IEC connector not having enough spring to make contact. If you have a multimeter you could troubleshoot it to check continuity. Or dissect it. Good luck with your mystery!

Use that pangea power cord to tie your next garbage bag. 

+1 rockrider. Likely the Pangea cord was defective. 

Going to a dedicated circuit is way to go. 

I appreciate all the feedback and trouble shooting. The good news is that the problem is solved and it isn’t a major power issue. Perhaps I’ve learned a bit in the process too. 👍🏻

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

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.

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.

@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.

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.

What does mentioning which cord it is have to do with anything? If you read the thread you will see it mentioned about a half dozen times. Are you telling me that power cords from today are vastly (quantum leaps) superior to power cords from 5 years ago? Because if you are, I would love to see evidence of that!

@pennfootball71 

If you look over the posts, the "high end" cable was revealed.

It’s a $40 Pangea cord. 

$40 is not a high end cable. Pangea uses a tiny amount of thin cheap cardas copper. It’s an in house brand from a mail catalog! It’s not even a real cable company. 

Again, where is the data that shows power cord technology has taken a quantum leap in the last 5 years? I’m anxious to read up on these advancements because, surprisingly enough, I was not aware of it. 

@jrimer 

Again, where is the data that shows power cord technology has taken a quantum leap in the last 5 years?

How can I put this delicately (and I mean no offense)? Are you new to the audio scene? There's an immense amount of information out there on this particular subject. All you have to do is search for it. There are power cords out there that go for thousands and thousands of $$, and audiophiles swear by their performance.   

Right. But where is the evidence that technology, and thus, performance, has advanced in the last 5 years? I’m not talking about price. I’ve been at this for 40 years, so I’m no novice. I’m also a rational thinking person that needs to see some concrete evidence to substantiate such absurd claims. No need to be delicate. Just show me the empirical evidence. Simple.