Best way to enlarge the HP socket hole to fit a 4-pin XLR

[Loquah]

Can anyone recommend the best way to enlarge the hole in the stock S.E.X. chassis plate to fit a 4-pin XLR socket? My tooling options are:

• Dremel
• Variable speed power drill, but with no press so drilling by hand only
• Hand filing (please don't suggest this one  )

My concern is that I have a beautifully anodised chassis plate so I can't just sand back any areas that are visible. The XLR sockets have about a 2-3mm flange that will cover any rough edges so long as I keep my margin of error within that range.

[Jim R.]

With those tools I'd probably scratchh a line that you don't want to go past, use the dremel until you're fairly close and then finish with a rat tail file.

Believe me though -- it is much easier and cleaner with a good step bit and a drill press. No way to get use of one for a few minutes -- that's all it takes. and that's how I did mine.

HTH,

Jim

[mcandmar]

I used a hole saw 2-3mm smaller than the hole required, then did the rest with a half moon hand file.  As a guide for the hole saw i drilled a small hole into a piece of steel and bolted it to the chassis plate, then clamped it all in a vice and drilled it out.   Just make sure to cover both sides of the plate with tape to protect it from scratches.

[Paul Birkeland]

I'd build an adapter cable that plugs into the binding posts.

[Loquah]

I'd build an adapter cable that plugs into the binding posts.

I'm beginning to like the sound of that, PB. The only irk for me is the fact that I would then have a redundant HP socket. I know that's a really minor issue, but it still irks me slightly. 

[Paul Birkeland]

Oh come now, you have a balanced and unbalanced headphone jack...

[Loquah]

Not if I hard-wire the S.E.X. will I? I thought hard wiring (i.e. not using impedance switches) would mean doing away with the front HP socket because it shorted the earths. Is that incorrect?

[physicsmajor]

Not if I hard-wire the S.E.X. will I? I thought hard wiring (i.e. not using impedance switches) would mean doing away with the front HP socket because it shorted the earths. Is that incorrect?

The impedance switch upgrade using the stock switched unbalanced jack routes "ground" to the headphone jack separately from -L and -R; those go to the speaker posts. The +R and +L are shared from the headphone jack, but the grounds are not.

I'm not sure how to do this without the impedance switch upgrade, nor do I have more than one headphone jack installed. I think there is a note in the manual warning that if you have the Balanced switch on while using the unbalanced headphone jack, things won't sound quite right. So if you attempt this this without the impedance switch kit, you might need to wire in a couple of switches to toggle back and forth (unless I'm completely off base).

[Paul Birkeland]

You are quite correct, the impedance switch kit would be needed here.  Alternatively, one could implement the switching setup I designed into the Mainline, but I can almost still feel the headache from sitting down and drawing that out.  (The schematic reflect this experience)

[mcandmar]

That's a point PJ clarified for me in the other thread,

"TRS jack, set to balanced, and at 16 or 32 ohms: Then you are actually listening to only one of the secondary windings, making it effectively a 4 or 8 ohm winding. If you had 4 or 8 ohm headphones, you would lose a couple octaves of treble due to the increase of leakage inductance from incorrect usage. With headphones above 16 or 32 ohms, this effect is pretty much gone."

So its not really usable basically until you switch out of balanced configuration.

[Loquah]

OK, so the question comes back to redundant 6.3mm jack or adding impedance switches...

I'll think on it and see how I go

[Jim R.]

Put a bottlehead badge over the empty phone socket and build a similar extension for a 1/4" phone jack. Then you can build an extension for whatever cans you want.

--  Jim

[Grainger49]

I have two tools that can be used to enlarge a hole and keep the center where it is, a stepped bit and a ream. 

The stepped bit has some jumps.  But if you are careful you don't go very far.  A ream will take out just what you want and takes more work.