Replace pwr cord w/IEC socket on vintage gear?


I have thought about this many times, as I own a fair amount of gear from the '80s. Yesterday I picked up a KILLER Heathkit pwr amp, but it has a really wimpy pwr cord. The shop where I bought it will install an IEC socket for 1 hr. labor plus the part. Given that this opens the amp up to the world of better power cords, this seems like an attractive, low-cost upgrade.

Has anybody here done it, and how'd it turn out?
johnnyb53
You don't need to put an IEC inlet on the amp. You can just remove the existing cord and replace it with a new power cord. It will make experimenting with different power cords more difficult, but it will require no drilling or cutting out holes in the chasis.
In prior discusssions of IEC replacement, the consensus was the IEC would not devalue the equipment.
As far as being able to do cord swapping: Priceless.
I agree with Elizabeth.
You might even increase the value if done right.
I got the amp for $219, it's a keeper regardless, so I'm not concerned about loss of market value. The question would be different for an all-original 1961 McIntosh MC275.

With something like a Mac, I could see replacing the power cord by hardwiring as Onhwy61 suggested. That operation would be reversible. In my situation I don't know if I'll settle on PS Audio, Zu, Shuyata, Monarchy Audio, or Pangea. When I picked a cable for my Onkyo integrated amp, I went through every audiophile power cord in the house until I settled on the PS Audio Prelude. Later when I recabled everything with Zu, I replaced the PS Audio with the matching Zu, and voila! Instant synergy.

So for my purposes the IEC socket is a must.

Here's something else to think about: There are a lot of classic power amps from the '80s, with captive power cords--Electron Kinetics Eagle, Sumo, Precision Fidelity, VSP Labs, PS Audio, Amber, and so on. As good as these amps can still sound, I'm dying to find out how much they may improve with an aftermarket cord. After all, if it improves the sound of a Parasound, or Levinson, why not a Heathkit or Sumo?
Go for the IEC jack. I had one installed on my cj PV 12L. Cost was minimal and being able to experiment with power cords yielded fine results. Cost effective and fun!
I have a Sumo 9 that has gone through a full rebuild and has an IEC power connector cord in place of the original captive cord. With just a budget Volex 17604 power cord I'm getting really good results with it in my 2nd system. I'm tempted to spend more money on different power cords but I'm controlling myself. If it isn't broke I'm not fixing it. Kudos to Mike Bettinger at GasAudio.net. That guy really knows Sumo gear.
I installed an IEC jack and replaced some wiring on a Harman Kardon amp I got off ebay. It was a nice little project and the results were well worth the hour it took. Go for it.
In my opinion installing an IEC on vintage equipment is a mistake and it does devalue the equipment. I personally would not buy a vintage amplifier with an IEC modification. Besides, the amplifier was voiced with the existing power cord.

In fact, at one time I owned two sets of Quicksilver Silver 90's. One set had the original power cord and the other an IEC with an aftermarket cord. Guess which one sounded better. The one with the stock power cord.

With vintage equipment it is more important to make sure the polarity is correct when you plug it into the wall outlet.

06-27-11: Rrog
In my opinion installing an IEC on vintage equipment is a mistake and it does devalue the equipment. I personally would not buy a vintage amplifier with an IEC modification. Besides, the amplifier was voiced with the existing power cord.
You may have a point there. I don't know how much consideration Heathkit put into the power cord, but it *is* a bit odd, even for that era. It's a high current design amp with a massive power supply--40 lbs for a rated 125 wpc. The power cord is a 2-conductor (no ground) small diameter cord. It reminds me of the stock used for extension cords for Christmas tree lights.

When I first plugged this amp in, it sounded pretty thin, but I figured that the capacitors had to charge up. So I stopped the music and let it warm up and charge up. That helped immensely.

The thing is, I've now left the amp on about 30 hours, playing music for at least 8 of those, and the sound is so superb I don't think I want to mess with it after all. When I posted this thread 12 hrs ago, there was still a slight edge that I figured a fatter cord might fix. But now--geez you guys will think I'm crazy--its tonal balance, low noise, speed, dynamics, and low level detail remind me the most of an early '90s class AB Rowland Research amp. And for a 30-year-old amp I picked up for $219, that's good company to be in.

I'm playing an album I've had for 15 years, that I've heard many times on many systems, and through Sennheiser HD580s, and this amp is revealing low level cues and details I didn't know existed. But it presents them in a totally natural perspective, not in a hyper-detailed way. It just makes everything sound more real than I ever heard this recording before.
I don't think the amp was voiced for the stock power cord. The amp probably wasn't voiced at all. It was spec'd out, and well spec'd out at that. Heathkit offered some excellent products. It's fine to replace the power cord, particularly if it's frayed or totally wimpy, but swapping power cords to find the right one kinda' goes against the vintage vibe, if you know what I mean. Just stick an Acme or Volex on it -- it's more along the lines of what the designers at Heathkit would do.
Onhwy61, So, you don't think Heathkit listened to their products? They just built them to specs and got lucky? I don't believe it's a fluke that some vintage equipment sounds better than others especially when "stereo" was actually more accepted than it is now or ever will be.

It it helps there are IEC pigtails that can be purchased.

They use the same or slightly larger hole from the original cord for connection to the internal wiring and allow after market cord connections minimal alteration of the vintage component case. The cord connects externally at the end of a short pigtail.

I modded a pair of Dynaco mono amps with them. Not easy to find but they do exist.
"With vintage equipment it is more important to make sure the polarity is correct when you plug it into the wall outlet"

power cords on stock vintage gear can be plugged into an outlet either way theres no difference in the size of the prongs like on modern cords. it dose not matter which way they are plugged in. im talking about 60s and earlier not 80s which i dont consider vintage.

its up to the owner which way to go IMO those as mentioned 16/18 gage power cords do not do justice to those fine music making machines from the golden age of audio. if its the music and not collecting thats important i go with an iec every time.
Paying near $90 for IEC + spending another $100 for aftermarket powercord isn't worth effort. Having IEC will just be another contact connection instead of solid joint wire. DIY is OK if you're savyy. If powercord is bad, than you can replace it with one having same parameters from either partsexpress or digikey. There are ones for audio applications shielded that would do great job for less money.
Johhnyb53, I had to make this same decision with my ARC D70Mk2. I went with all stock and I'm glad i did. A friend who bought a D115 Mk2 changed out the stock cord with an IEC and a Shunyata and also changed the speaker cable strips to the newer Cardas connectors along with the RCA's. For some reason, we both were very disappointed with his results! The amp seemed to loose some of its ability to portray depth and a little of its punch in the bottom end. A big surprise as we both thought that these areas would likely be improved. My friend then tried to sell the amp and found out that the market was calling for a non-modified unit and so he ended up selling for a little less than hoped for..:0(
Stltrains, You are mistaken. There is a right way and a wrong way to plug in vintage equipment. Without any other equipment connected to the subject component plug it into the wall outlet and take a voltage reading from the chassis to ground. Then turn the plug over and take another reading. Whichever reading shows the lowest voltage is the correct polarity. When vintage equipment is plugged in the correct way they sound modern. When plugged in the wrong way they don't.

Has anyone ever been shocked by an old refrigerator when you were a kid? If you did it was because it was plugged in the wrong way and there was too much voltage riding on the chassis. Turn the plug over and no shock.

It's not a matter of personal preference. There is a right way and wrong way.
There are a lot of classic power amps from the '80s, with captive power cords--Electron Kinetics Eagle
I've never seen an Electron Kinetics Eagle with a captive power cord. I've had7 of them, and seen dozens more and they all have an IEC connector.

I've installed IEC connectors of many vintage amps and never had an issue reselling them. Further, it's a tedious job - 1 hr labor is not a bad deal.
Rrog on vintage fisher amps/preamps ive bought and replaced out of spec original caps and resistors the sams and fisher schematics for those units shows the a/c plug feeding the power transformer power windings and service receptacles with no polarity marked hot or neutral and the instructions do not mention a right or wrong way to plug these units in. these power amps and integrateds have a so called death cap installed for the shock hazard you mention on fridges due to there super high stepup voltages. these units are late 50s early 60s built when life was simple and much better.

Marakanetz thats very true on the cost of iecs and the added connection but in the end worth it for better sound imo.
If that Heathkit is a tube amp without a protective cage, you do not want a grounding power cord for the same reason toasters and lamps are not furnished with three-prong plugs -- live parts exposed from damage have no bond to earth. Also, the grounded power cord can put the signal and chassis to the same ground, possibly causing sonic problems such as humming from ground looping. This really should be done by a pro.
Stltrains, I am also referring to vintage Fisher, Scott, Dynaco, Sherwood, Harman Kardon, Audio Research and any other vintage equipment with a non-polarized plug. This is especially important with mono amplifiers and preamps since it does affect the sound depending on how they are plugged into the wall. This is also true with vintage turntables and tuners.
The procedure Rrog describes for orientation of two-prong plugs is good practice, although it may or may not make any difference with any given component in any given system. And in many cases the measurements being compared for the two orientations will be low and pretty much the same.

What the procedure does is to minimize low level leakage between the hot side of the ac line and chassis, which may particularly occur to some degree as a result of stray capacitance, and perhaps also degraded insulation, in the power transformer. Besides conceivably having effects on the sonics of the particular component, it could also result in extraneous low level ac hum and noise currents flowing through the return conductor of cables connecting that component to other components it may be driving, which would be indistinguishable by those components from signal voltages.

Regards,
-- Al
Rrog, you really think the engineers at Heathkit listened to the amp with different power cords and "voiced" it to their sonic preferences? You need to be careful when applying modern sensibilities to times gone by.

06-27-11: Gs5556
If that Heathkit is a tube amp without a protective cage, you do not want a grounding power cord for the same reason toasters and lamps are not furnished with three-prong plugs -- live parts exposed from damage have no bond to earth. Also, the grounded power cord can put the signal and chassis to the same ground, possibly causing sonic problems such as humming from ground looping. This really should be done by a pro.
It's solid state. In fact, here's an ad with specs. I hadn't mentioned it, but the captive cord is 2-prong, and it's quieter than the 3-prong amp I replaced it with. This thing can really dig out the low level detail.
06-27-11: Onhwy61
Rrog, you really think the engineers at Heathkit listened to the amp with different power cords and "voiced" it to their sonic preferences? You need to be careful when applying modern sensibilities to times gone by.
I was originally skeptical of Rrog's assertion, but why would this amp sound so *GOOD*? Here's this heavy, high current amp with a very modest 2-conductor cord. The amp sounds like the design was heavily prototyped, listened to and voiced carefully. It's fast but not edgy, resolving but not hyper-detailed, linear and accurate but not sterile.

The same store where I bought it has an '80s Precision Fidelity M-8 hybrid amp, This Stereophile review of an Electron Kinetics Eagle 2 indicates that the Precision Fidelity is the lusher and more musical amplifier.
Stltrains,
Units built in 60's 70's are very often have more advanced engineering than today's 'pure and minimalistic' designs. Having the fact that parameter tolerances for electronic and passive devices were much less precise, designing a well sounding unit was a great challenge.
These units might benefit from new parts equivalents but very tiny-likely you'll get desirable ROI from IEC/PC...
A solution is the KEEP the stock cord as an extra, with an IEC plug on it too. Make certain that cord is marked as to where it comes from.
The the 'original' cord can certainly still be used.
Onhwy61, No I don't think the engineers at Heathkit tried different power cords, but I believe they voiced their product with the existing power cord. Got it?
Elizabeth, The problem is the addition of another connection and materials by installing an IEC. Audio Research resisted IEC sockets for many years because they said it was detrimental to the sound of their equipment. Finally they gave in because the market demanded it.
Well, plenty of (in fact nearly all) manufacturers now use an IEC.
Use a Furman male, and a good plug. No problems.
I think those comments were back when all IECs were nickel plated (read cheap) junk.
Almarg i believe Rrog is talking about having all components in phase with each other by using the chassis and a good ground for measurements for proper phase. not a bad thing to do with any gear even phased plugs of newer gear have been known to be wired wrong.
Stltrains, I don't follow what you are saying. What does having "all components in phase with each other" mean in the context of orienting a two-prong non-polarized ac plug?

Regards,
-- Al
When you check phase you reverse the plug and get voltage readings in each position the lower reading is in phase do this for all pieces of gear in a system its suppose to contribute to better sound.
06-27-11: Stltrains
When you check phase you reverse the plug and get voltage readings in each position the lower reading is in phase do this for all pieces of gear in a system its suppose to contribute to better sound.
Yes, which is what my initial post above addressed, and which is what I feel certain is what Ron (Rrog) was referring to. However, I would not refer to the procedure as resulting in anything being "in phase" or "out of phase," in part because those terms have no meaning without being referenced to something. What is occurring is that ac leakage to chassis is being minimized.

Regards,
-- Al
ok al sounds good to me.
Al, Thanks for your comments. I have been using this method for many years with a variety of components and I have always been able to notice an improvement. The improvement in sound quality varies from one component to the next and it seems to coincide with how much the voltage readings vary. Is this related to the transformers and their windings?
Is this related to the transformers and their windings?
Hi Ron,

Yes, most likely, as stray capacitance in the transformer, and possibly insulation resistance, figure to generally be key factors in the ac leakage I referred to.

It's interesting to hear your observations. I have also routinely done this for many years, but I haven't taken the time to assess the differences it may have made, my philosophy being that it can't hurt and might help.

One point that's worth noting is that the value of the voltage readings will vary considerably depending on the input impedance of the meter that is used (which is commonly unspecified). Since the resistance of the leakage path in the component will typically be very high (on the order of several megohms or more), a meter having a relatively low input impedance (such as many analog meters, particularly on their lower voltage scales) will load down the voltage and indicate a much lower reading than a quality digital meter that presumably and hopefully has a high input impedance. The higher the readings are that the meter makes possible, the more pronounced the difference between the two voltages will be.

Best regards,
-- Al
I must have gotten lucky when I plugged this Heathkit in and got the optimum orientation. It has a 2-prong plug and its noise floor is subterranean. I hear low level details on familiar recordings (all in correct musical perspective) that I hadn't heard before, not even on headphones.
I had a certified technician who I've known and trusted for a long time put IEC's into my Conrad Johnson Premier 12 mono blocs. Best move I've ever made. While they sounded perfectly great with their captive stock cables (and a noticeable step-up they were when compared to much of the other "captives" out there), playing with the aftermarket cords has dramatically improved the quality of my system and the ability to customize the sound is truly condiment(s) to the smorgasbord. Priceless. Well worth it. Don't hesitate, just do it.
BTW, if it's the ONLY modification done to an otherwise stock amp, I agree it will probably INCREASE its marketability and value....The one thing that discourages me from otherwise being attracted to vintage gear is knowing I have to get the IEC's done. Generally speaking, why be stuck with stock captive power cables when there is so much more potential within virtually all amps when you partner them up with a cable that enhances/synergizes "Just right" for your own system!!! Enjoy.