Adapting HMV 5A soundbox for small tonearm

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kirtley2012
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Adapting HMV 5A soundbox for small tonearm

Post by kirtley2012 »

A while ago when I was wanting a simple gramophone just so I had a way to play my 78s I bought a tatty HMV 145 gramophone from facebook marketplace, I got it cheap and I mainly wanted the HMV 5A soundbox that was on it, I've since upgraded from the 145 so took the soundbox and listed the machine for sale cheaply then set about adapting the 5A, it would obviously only fit on the large bore HMV tonearm, and the rubbers in the back were rock hard, I had a spare rubber meltrope collar and found that it fit's fairly comfortably inside the 5A, so even just a loose fit it will go on the expert tonearm snug, and airtight, I only gave it a quick go but it seems to sound very good through the big horn, it also seems to be a much lighter soundbox than the Expert and Meltrope soundboxes
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Re: Adapting HMV 5A soundbox for small tonearm

Post by epigramophone »

You were lucky or clever to have removed the old fitting without damaging the fragile pot metal back plate.
I have seen many HMV soundboxes ruined by attempts to change their back fittings.

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Re: Adapting HMV 5A soundbox for small tonearm

Post by gramophoneshane »

The HMV Model 11 electric pick-up actually came with an adaptor/sleeve in its throat which can be used to fit a 5a soundbox to a small necked tonearm.

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Re: Adapting HMV 5A soundbox for small tonearm

Post by chunnybh »

it also seems to be a much lighter soundbox than the Expert and Meltrope soundboxes
That may well be it's drawback. Try adding weight to the 5a. I stuck a thick strip of blu-tac to the back of the 5a and found it's bass response improve on an Expert. With that in mind, I tried it back on a re-entrant but couldn't hear any difference.

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Re: Adapting HMV 5A soundbox for small tonearm

Post by Frankia »

Alex, I must have missed this thread the first time. Nothing new about that though. I have done what you have done with a HMV 5a or b box in the past and also with a Victor Orthophonic. Neither sounded as good as the EMG or Expert 4 spring that I had at the time. You may well have come across a particularly good example, or maybe one whose characteristics suit the EMG/Expert sound reproduction system? Certainly interesting. It would be great if the HMV 5a/b worked well, because their lightness would suit them for steel needles and they're a lot more available than EMG and Expert 2 springs.

I also want to say that both HMV boxes a and b and the Victor Orthophonic are lovely sounding boxes when used on their own gramophones. I've usually found that the Victor can add a richness in the treble to the HMV sound train that its own soundboxes don't. But good examples
of both are very pleasing to listen to.

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Re: Adapting HMV 5A soundbox for small tonearm

Post by shoshani »

I bought a 5A on eBay specifically to have its back adapted for my smaller bore HMV New Gramophone models; Wyatt Markus (micamonster) installed his proprietary isolator compound and used the brass ring and bayonet pin of the type/size found in the No 4 and No 2. As it turns out, the difference in diameter between the 5A and the 4 (for which the older HMV tonearms were designed) resulted in unexpected tracking error on my two HMV 109s. However, the tracking error is minimal - only toward the center, beyond where normal record grooving is - on my HMV 101 portable. On which, by the way, the 5A soundbox sounds phenomenal. Really opens up the treble on a machine that already has outstanding bass considering its size.

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Re: Adapting HMV 5A soundbox for small tonearm

Post by shoshani »

gramophoneshane wrote:The HMV Model 11 electric pick-up actually came with an adaptor/sleeve in its throat which can be used to fit a 5a soundbox to a small necked tonearm.
I wonder if there's anyone with a small machine shop who could make these today. I'll bet there'd be a small market for them.

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Re: Adapting HMV 5A soundbox for small tonearm

Post by Inigo »

I use the red rubber connectors someone sells for the Meltrope soundboxes... The outer size fits perfectly on the back of either the no4 or the no5a/b. About the inner diameter, there's one wider which fits on the thick hmv reentrant tonearms, and there's also another for the narrow bore swan neck tonearms of the new gramophones, without the inner brass ring, of course The advantage is that as you omit the internal brass ring, the fitting of the rubber on the tonearm is perfect, and you can adjust the vertical angle of the needle, so you can get almost perfect tracking in all these machines including the 101. I have installed them in several of my machines...
Inigo

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Re: Adapting HMV 5A soundbox for small tonearm

Post by shoshani »

Inigo wrote:I use the red rubber connectors someone sells for the Meltrope soundboxes... The outer size fits perfectly on the back of either the no4 or the no5a/b. About the inner diameter, there's one wider which fits on the thick hmv reentrant tonearms, and there's also another for the narrow bore swan neck tonearms of the new gramophones, without the inner brass ring, of course The advantage is that as you omit the internal brass ring, the fitting of the rubber on the tonearm is perfect, and you can adjust the vertical angle of the needle, so you can get almost perfect tracking in all these machines including the 101. I have installed them in several of my machines...
I believe that's chunnybh. Now I'm curious as to whether without the brass ring, if there's such a thing as being able to just interchange the replacement rubber bits on the back of a soundbox so it would fit either a 101 or 102 tonearm as desired.

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Re: Adapting HMV 5A soundbox for small tonearm

Post by Inigo »

Shoshani, I'm not sure about the meaning of your question... So I'll explain myself better to make clear what I did.
1. The original black rubber connectors of the no4 and no5 HMV sbx were externally equal. The two backplates have the same bore diameter at the neck housing where the rubber connector is fitted. Only the inner diameter of the rubber connector is different, plus the brass ring they carry inside, fixed to the rubber at the factory. So the two connectors are in fact interchangeable: you can put a no4 in a reentrant machine (thicker tonearm) only by changing the rubber connector at the back for one from a no5 sbx.

2. The small pinned screw at the sbx back neck oritrudes trough the rubber and brass ring, providing a fixed point that fixes the position of the sbx on the tonearm when it is inserted and twisted to the lock position. The other small screw at the opposite side is shorter, and has a conical point. This fots into a little recess on the rubber connector, just to fix it in position. As years have passed, usually the rubber connectors are dried, frozen and have got stuck on the neck, so removal of them is difficult without destroying it. Nevertheless, other connectors have dried and frozen, but are still easily removable.

3. The red rubber connectors sold for Meltropes are plain rubber, they don't have the brass collar inside. But they fir snugly on the tonearm. That brass ring is not needed. and the rubber alone makes a perfect airtight fit on the tonearm.

4. These red rubber connectors fit in the neck at the back of the sbxes, simply sliding them into the neck. You put one of the right inner diameter (according to the wide or narrow tonearm) inside the neck of the sbx. As this rubber connector hass no holes for those two tiny screws, you don't replace the screws. Store them apart. Then, with aid of a bit of water or vaseline added to the inside of the rubber, you insert the sbx on the tonearm, by a little hand pressure and twisting the sbx, then rotate it to the desired position, adjustable infinitely, as there are no fixing pins. You can adjust the vertical needle angle of the sbx on the record, and so, you can adjust the correct tracking on the record. As you install at a steeper needle angle, the point of the needle falls nearer the tonearm bearing, so it is like making the tonearm shorter. If you put a more horizontal angle, it is like making the tonearm larger. I've found that any needle angle between 55-65 degrees work well, and this gives you enough room for adjustment of the tracking, because different angles make the needle fall at different distances. Of course, with short tonearms as the 102 it is impossible to get good tracking, particularly at the start of 12" records. But the 101 has a longer tonearm, and it's more or less possible to achieve fairly good tracking. Of course, the longer the tonearm, the better the tracking. I'm using a HMV194 machine which has a large tonearm, and this achieves almost perfect tracking all along a 12" record.

5. So if you have the two red rubber conectors, it is very easy to innterchange them. You can take them off the sbx neck just with your finger. And so you can interchange sbxes only by fitting the right connector at the back for the tonearm bore. So you can use a no4 sbx on a big reentrant machine or a 102, or the opposite. I've used it for installing a 5a on an HMV127 (narrow tonearm tabletop) and it sounded great! Much more treble than the original no4 sbx. But the sound was so strong that the machine buzzed here and there in loud musical passages (must be loose horn adjustment, or the needles in the needlepots, or the hinges in the doors, or the wooden slats...). The sound is good, but I felt that the no5a sbx was a bit too strong for that small horn. On the big 194 it sounds still better, for more energy goes to the bass, and thus the sound is more equilibrated, and the large air volume of the horn requires more energy, so the sound is a bit softer in general and more pleasant.

Hope this helps...
Inigo

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