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.

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.

@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

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.

@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. :)

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.

@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.

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

@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

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.

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. :)

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.

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.

@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.

🤣

Sorry, to be clear: 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.

I’m considering a Furutech replacement but my luck with the brand has been terrible. OTOH, they only run $20.

Luxman use 3 prongs inlet, is your 507ux utilizes quick connect (no soldering required) C-14?

@imhififan  - Well I have no idea what those are but mine is definitely a 2 prong.  I haven't pulled the connector out yet.  I'm can deal with either situation, and it's definitely not gold plated. :)

@stereo5, I can make the plastic snug in the socket with tape. The issue is what feels like onlhy 1-2 mm of contact in the conductors, the contacts don’t touch until the plug is almost completely in. That’s when the Amp lights suddenly turn on..Using the same cable with a cheap, Mouser sourced inlet I can feel it make contact with the pins a lot sooner. Pulling the plug out maybe 1 mm is enough to turn the amp off.

It’s not just about keeping the plug from falling out, it’s also about ensuring a wide contact area and this inlet isn’t giving me the confidence.

Imagine if the pins on your coffee maker got cut in half.... Yeah, I can tape it to the wall, but still it doesn’t inspire confidence.

Thanks @ryder Does your amp have a ground pin on the inlet?