My Luxman Integrated has AC Inlet Envy

@imhifiman

THe unit was too heavy for me to play and trace it back and forth between the bottom PCB and the top, but no. It looked like the main transformer plugged directly to the fuse. You can see it in the picture I took. There’s a service transformer for the standby circuit, then the inlet plug, then fuses and then a wider plug which I believe goes straight to the main transformer.

Also, going from the drop in line voltage when I turn this beastie on, no, there’s no soft-start.

The PCB markings below the fuse say 15A and that’s exactly what was in there.

Luxman may have produced 10s of thousands of these units, so they probably know their materials very well, but given how difficult a field replacement of those wires, and fuse sizing I would have 100% used thicker than 20 gauge.

The transformer may be 20 gauge but the fuse is 15A.

Interesting, 15A fuse for a 110Wx2 amplifier! No soft start circuit?

Yes, but inferior sound quality.

Wow, I'm so glad my old Audio Research SP8 preamp has a captive power cord. Those connectors are just another point of failure. Even my ancient Mac MC40 monoblocks have a captive power cord, looks to be lampcord as well. All original and still in good condition. Can't come up with a reason to replace it unless it becomes brittle and starts to crack.

Way to many other things to think about, no need to invent imaginary issues.

BillWojo

If the power transformer primary winding wire is thinner than 20 gauge, I don’t see there will be any improvement using thicker wire.

Well there’s a practical reason for this. The transformer may be 20 gauge but the fuse is 15A. Also, it may be just how much effort I’ve put into this but I swear it sounds better. 😂

I won’t say Luxman is wrong since it is a double insulated Class II equipment.

Is it? I can’t tell by looking at the construction. I was expecting more plastic shielding somewhere compared to a non-double insulated amp. Looks the same to my untrained eyes. There’s nothing between the tin fuse caps and the bottom cover, for instance.

However, if your power cord is polarized, swap the wire let it fused on Live side. No harm to make it even safer.

Already fixed it internally.

Sadly the cord used from the power board to the inlet, about 8" long is 20 gauge. Kind of disappointing honestly, but probably exactly to spec. The choice of a Molex Spox connector I believe limits the maximum gauge to 18 anyway, so assuming I did have a Molex crimper ($700 or so for the manual versions) I still couldn’t improve much here.

If the power transformer primary winding wire is thinner than 20 gauge, I don’t see there will be any improvement using thicker wire.

The big deal however is that the assembly leaves the wrong side of the AC inlet fused.

I won’t say Luxman is wrong since it is a double insulated Class II equipment.

However, if your power cord is polarized, swap the wire let it fused on Live side. No harm to make it even safer.

@imhifiman

Things got curioser and curioser as I worked.

Sadly the cord used from the power board to the inlet, about 8" long is 20 gauge. Kind of disappointing honestly, but probably exactly to spec. The choice of a Molex Spox connector I believe limits the maximum gauge to 18 anyway, so assuming I did have a Molex crimper ($700 or so for the manual versions) I still couldn't improve much here.

The big deal however is that the assembly leaves the wrong side of the AC inlet fused. I wrote about it in detail here:

https://inatinear.blogspot.com/2023/04/luxman-507ux-ac-inlet-mistake.html

Tomorrow I replace it.

Good luck and please keep us updated with your progress!

I've dismembered my Luxman and have had the original C18 outlet on my workbench for a couple of days.

The pins measure exactly to spec.  I can't find anything at all wrong with the pins or the casing at all. In fact the pin to PCB construction is impressive.  They look like a single piece of cast metal that retains it's thickness through the PCB connectors. 

I'm now 100% sure that the weakness I was feeling in the grip of cables is due to the missing ground pin.  Also, without the ground pin the Wattgate 320i sucked.

Tomorrow I replace it.

These are not convertible transformers.

Thank you for your confirmation!

@imhififan 

To answer your question the Luxman transformer has 3 wires on the secondary and exactly 2 on the primary. These are not convertible transformers.

Best,

Erik

I'm awaiting one more part from Mouser before I change out the inlet. I don't want to open it up and find out I have the wrong parts. :)

@imhififan 

This is a purely personal aesthetic. It's my equipment and I get to be the decider. :)

Ground goes on top. 😀

Unlike AC Receptacles, IEC 60320 inlets can install in any orientation, some Marantz and Denon even put it sideways.😀

The aftermarket plug is fine in every other inlet. Ground goes on top. 😀

I am absolutely replacing the inlet.

Whether I use a generic, Connex or wattgate it feels wrong. When its out Ill be able to measure more adequately.

I have a chance I can do everything through the outlet hole.

If possible, try turn the original C18 inlet 180° before you replace it, perhaps that can help the aftermarket plug stay in better since the two pins are on upper side.

Hopefully you don’t need to replace the inlet after all 😌

IME, install the IEC inlet 2 pins on upper side is better even if it is a C14 inlet.

@imhififan I will IF I open the Lux.

I have a chance I can do everything through the outlet hole.

I'm afraid that in my years of reading on Accuphase vs. Luxman, the lack of a multitap primary on the transformer was always a given.  If I find out otherwise I"ll let you know.

Great! @erik_squires 👍

Please let us know your progress. BTW, since you going to open the chassis of your Luxman, Would you do us a big favor to check the power transformer primary winding if there multi tap or not, so we can be sure the possibility of voltage conversion.

TIA

Gang,

I ended up writing this up in a blog.  I'll add more when I've pulled the Luxman connector out.

https://inatinear.blogspot.com/2023/04/wattgate-320i-measurements.html

@erik_squires Wrote:

As a matter of fact, what I ordered wasa not a C14 but a C16 inlet. The only difference I can tell is that the C16 inlet has a plastic ridge under the ground pin.

I agree, I think your Luxman originally has a C-17 C-18 two prong plug.

Mike

@ditusa

As a matter of fact, what I ordered wasa not a C14 but a C16 inlet. The only difference I can tell is that the C16 inlet has a plastic ridge under the ground pin.

If you notice a lot of DIY male plugs have a little ridge cut out under the ground pin. That’s to mate with the C16.

I’m not sure if there’s any practical benefit to the ridge in a C16 inlet except to ensure a straight fit. Based on this chart, the only difference I can see is the maximum pin temperature, which I hope never actually gets near 70C:

https://www.webberelectronics.com/info/iec-chart

@erik_squires;

Remember IEC 14 inlet see below:

Mike

https://www.schurter.com/en/datasheet/6100-3

PPS -
 

Yeah, I'll use a 3 pin plug, and add a little heat shrink on the inside so it looks purty.

PS -

I’ve done some totally not scientific testing of the contact overlap. Using a multimeter and shorting out the plug I’ve determined that from the point that the plug reaches minimum resistance to the fully seated position is 5 mm. That is, you have to pull the plug out 5 mm before the resistance would rise above zero. That’s a lot better than what I’m experiencing on the Luxman which seems to disconnect at 1-2 mm.

Thanks @Corelli !

I agree the Wattgate feels wonky.  After extensive testing with the Mouser inlet I agree the replacement of the inlet is the way to go.

When I first built the AC cable I used a Parts connection plug.  It was always a little loose so I thought (incorrectly) a Wattgate plug would fix the problem. It did not.  Both plugs do significantly better on the new inlet that's sitting on my workbench behind me.

Eric, re-read my post.  You're not the only one to notice this.  Your bigger problem is the poorly designed Wattgate.  If you are afraid to change the IEC on the amp(which may NOT fix the problem) , just try a better plug such as the one I listed.

fo.q ta 32 tape, it's 0.3mm thick has anti static properties too, a bit like furutech ncf. Dampens vibrations too, also comes in ta102 which is 1mm thick.

highly reccomended can be bought on eBay from Japanese sellers very reasonably.  

@ditusa We all have our own opinions and experiences.

I'm not sure what a screw type connector is.  I think I'm going to go with a very discrete replacement.  Either the $2 Mouser or a $20 Furutech which looks identical from the outside. :)

@cleeds Wrote:

Mods such as that on gear such as Luxman tends to hurt resale value, even when it's pitched as an "improvement."

I agree!

Mike

carlsbad

... you might try an upgrade to a screw type connector. Since you make your own power cables this would not be a problem for you and when you sell the amp, this would be a nice upgrade that should be positive ... I have a mill with a DRO so it is easy for me to drill precise holes ...

Mods such as that on gear such as Luxman tends to hurt resale value, even when it's pitched as an "improvement."

Eric,

I read this yesterday and decided to wait and see what you had to say about replacing the male fitting on the amp. I don't have any experience with Luxman so I can't answer your actual question.

With Furutech not being the pancea that most people think it is, you might try an upgrade to a screw type connector. Since you make your own power cables this would not be a problem for you and when you sell the amp, this would be a nice upgrade that should be positive.

The problem with this is that a quick search didn’t find anything I like at a reasonable price.

But I’ll keep an eye open and if you like this idea and find something you like I’m sure you will post it. I’m having a custom amp built and the power cables between chasses are screw type so I’ll ask my amp builder what he used.

I have a mill with a DRO so it is easy for me to drill precise holes so if you need an adapter plate made, sketch it up and I’ll be glad to make it for you.

Jerry

I think I came here to see if anyone else had a similar problem, because these parts are so standardized and Luxman is not known for being cheap that I’m honestly more than a little surprised at the issues I’m having.

PS - Thanks for the image, @imhififan  I have been trying to find that from parts drawings without any luck.

@imhififan

Have you measure it?

I will after I pull it out! :)

Seems like replace the inlet in your Luxman is the solution. No?

Yes, that's why I'm about to replace it.

My Anticables plugs have good connectors but the stiffness of these cables can sometimes make them sag enough to affect contact. Lately, I have been making loops from tape that first wrap around the cable just behind the plug and then are brought to adhere to the top of the chassis enclosure and tensioned enough to resist gravity. Same approach with HDMI cables which often have poor contact as well.

Of course, these are not issues with pin "grip" so much as they are issues with the weight of the cables.

I bought a cheap replacement inlet but it’s not yet in the Luxman. I just bought it to test fit my cables and it seems to do a lot better than what’s in the Luxman both electrically and mechanically.

Seems like replace the inlet in your Luxman is the solution. No?

It seems many who reply are missing the part about SHORT CONTACT DISTANCE.

The inlet on your L-507UX is a C18 (2 prongs), the pin height should be 12mm. A C14 inlet is 3 prongs, the two pins height are 12mm and the ground pin is 15mm.

Have you measure it?

Thanks @Ryder I guess it’s possible my particular unit, the original UX, not UX II version of the 507, got a bad inlet.

It has no ground pin, so locking plugs are useless, and even if they are, the short contact distance between the plug and inlet has to change.

I am going to change this inlet. I have one from Mouser (3 pin) I can use right now or I can order a Fancy Furutech from Parts Connexion.

I just think it’s weird I’m the only one who had this problem.

It seems many who reply are missing the part about SHORT CONTACT DISTANCE. Let me try to draw this out:

=== Luxman IEC inlet

....========= Plug

====== Cheap Mouser IEC Inlet

In the diagram above you see the Mouser sourced inlet has much more overlap with the plug contacts. Gluing the plug or bending the contacts inwards doesn’t increase the contact distance.

This is not your normal loose plug problem. :) Again, imagine you go to plug in your coffee maker and notice the pins are half as long as they should be.  I might be able to keep it attached to the wall by tape or bending the pins but neither really solves the contact area problem.

My 505UXII has had no issues with cables from Pangea, Shunyata, Cullen, or PS Audio.

A simple way is to find a Furutech dealer and try there how tight is the fit between their inlets and iec plugs. That means probably you would have to change the iec inlet on your Luxman.

It's rather easy to resolve.  I wouldn't modify the Lux except to ever so slightly bend the pins inward 2-3mm.  Then take the end of the cord that plugs into the Lux and shave the end back to bring the mating contracts closer to the end.  A belt sander makes short work of this but can be done by other methods.  I did this on a MoodWright years ago and completely resolved the connection issue.

My Marantz Ruby has no ground on the IEC C-14 like yours.  I have quit using Wattgates as their IEC plugs have a bad design as you have found out. Try these instead--much better pin geometry:

https://www.amazon.com/gp/product/B08332R442/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

I plan on replacing the two pin IEC C-14 with a three pin.  Easy to swap out.  Just leave the ground unconnected.

@erik_squires there is no ground pin on the IEC inlet of my L-590AXII. Just two pins. Perhaps try a power cord which can stay firm inside the inlet of your L-507UX? There's no issue with my Acrolink cord staying put inside the inlet. 

I did have such problems but not with Luxman.  One intermittent drove me crazy.  The receptacle had a pin break loose and would be push inward as the plug was inserted.  But the pin would be pull back outward when the plug was removed.  Visually it looked okay.

Since you make your own power cables and have already Replaced the inlet receptacle, this should not be a problem for you to perform.  But you have to have a lot of commitment to the cord you are using. 

If it does not Feel Right, I bypass the inlet receptacle altogether and hard wire the power cord straight to the power supply circuit board or wherever those wires from the inlet receptacle go to.

Replace the inlet is the only solution. Use a 3 prongs and leave the ground pin unconnected.

I could use superglue if I wanted, doesn’t make the metal to metal contact any better.

@erik_squires

The IEC LOCK+ is utilize a metal plate at an angle to clamp the ground pin. However, you may not need it if the replacement inlet is good enough.

Anyone else have issues with Luxman inlets??

BTW, the Luxman 507 photo that I posted earlier could be an aftermarket IEC socket.

I hope my responses make sense.😉

@erik_squires Wrote:

@imhififan  No, but again, it's not just about how easily it pulls out, but how good a contact it makes.  :)

I agree, all non locking IEC will not make a good electrical contact because they arc. IME, the money audiophile amps cost they should have locking IEC for the AC mains. 😎

Mike 

@imhififan  No, but again, it's not just about how easily it pulls out, but how good a contact it makes.  :)

I could use superglue if I wanted, doesn't make the metal to metal contact any better.

That's great guys, just great.  What I really need to do is either switch to Boulder, or hack the cabinet of my amp to put in a connector with a completely different form factor.

🤣