Brass HMV 5A? Soundbox

[Watanabehi]

Hello HMV Lovers,

I have a brass HMV 5A? soundbox. Do you have any information about it? I bet it is very rare, but I have no idea about what HMV model it was used for. It doesn't have any script of whether it is No.5A or B on the back. Thanks.

Hideki

[Steve]

It's a 5A diaphragm.

Is it definitely brass? The backplate looks painted in the photo.

[Watanabehi]

Yes, it is all brass, since I tested by scratching the surface and put them apart and cleaned them.

Hideki

[Inigo]

Wyatt a rare jewel... It must sound beautifully!

[Watanabehi]

Yes, it sounds great, but it is heavier than regular pot-metal HMV 5A or 5B soundboxes.

Hideki

[shoshani]

They are probably as scarce as hen's teeth; I have a brass 5A back that I purchased a few years ago, and Wyatt Markus (micamonster) inserted his famous isolator, and built a 5A from parts we had. I will add as a caveat that it took some experimentation to insert the brass pin-ring correctly, because when the pin was lined up with where the top retaining pin screw is on the extension flange at the back, the needle chuck was incorrectly positioned.

(Wyatt favors the Victor method of having the bayonet pin machined into the brass ring and surrounded by the isolator material, believing it to be better at removing stray vibrations than the HMV method of having the brass ring drilled, and inserting the bayonet pin through the soundbox back and the rubber isolator and brass ring.)

As with yours, mine does not indicate any sort of model number; from that, I surmised that it (and thus yours) may be a pre-production prototype for engineering the dies for casting the pot metal backs.

[Watanabehi]

They are probably as scarce as hen's teeth; I have a brass 5A back that I purchased a few years ago, and Wyatt Markus (micamonster) inserted his famous isolator, and built a 5A from parts we had. I will add as a caveat that it took some experimentation to insert the brass pin-ring correctly, because when the pin was lined up with where the top retaining pin screw is on the extension flange at the back, the needle chuck was incorrectly positioned.

(Wyatt favors the Victor method of having the bayonet pin machined into the brass ring and surrounded by the isolator material, believing it to be better at removing stray vibrations than the HMV method of having the brass ring drilled, and inserting the bayonet pin through the soundbox back and the rubber isolator and brass ring.)

As with yours, mine does not indicate any sort of model number; from that, I surmised that it (and thus yours) may be a pre-production prototype for engineering the dies for casting the pot metal backs.

Interesting!! I would like to see it. Would you please post some photos of it. Thanks.

[Inigo]

That issue with the pin could be similar to what happens with the HMV no4, and that is that the back lettering is intended to be read straight when the soundbox crook is in the upwards resting position. an error i committed the first time I reassembled one was to install the back with the lettering to be read with the soundbox needle downwards. All perfect, except that the arrangement is not symmetric, so the neck pin resulted misplaced! then I discovered that the good position for the back was with the lettering upside down.
I see that this is not the case in this brass 5A, but could be in the commercial models...

[shoshani]

That issue with the pin could be similar to what happens with the HMV no4, and that is that the back lettering is intended to be read straight when the soundbox crook is in the upwards resting position. an error i committed the first time I reassembled one was to install the back with the lettering to be read with the soundbox needle downwards. All perfect, except that the arrangement is not symmetric, so the neck pin resulted misplaced! then I discovered that the good position for the back was with the lettering upside down.
I see that this is not the case in this brass 5A, but could be in the commercial models...

Oh, mine is intended also to be read straight that way; I just went to my phone texts with Wyatt and found an image from the first build, and the problem was that the needle rested almost vertically in the groove. It took a bit of measuring and calculation, but I sent it back with a mark on the back where it seemed the best place to align the pin. He did, and when it came back it worked perfectly.

[shoshani]

Interesting!! I would like to see it. Would you please post some photos of it. Thanks.

I'm actually out of town for a while and don't have it with me; I'll rustle around my phone and see if I have any decent pics of it. But it pretty much looks the same as yours, to be honest, right down to the somewhat squared-off typeface embossed into the back.

Again, this was not a complete soundbox, just the back. I fastened a phase plug where it goes, and sent it and a spare 5A to Wyatt to basically switch the backplates. The screws that hold the backplate on, or rather the holes for the screws, are at a slightly different angle than where they are on a standard HMV 5A/5B; they do line up, but the angle for the retaining pin is a few degrees off in comparison. If yours is a complete soundbox from whatever production run this was, it may all be aligned correctly for placement on the tonearm. Mine is a frankensoundbox, assembled from parts that, while authentic, are from different production models...