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 Post subject: Re: Ideal tonearm length ?
PostPosted: Tue Feb 18, 2020 12:16 am 
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Victor II
Joined: Wed Dec 04, 2019 9:31 pm
Posts: 220
I wasn't expecting a precise answer.
There is usually a sweet spot in any trade off which is as much a matter of opinion as anything else.
I was looking for a range which delivers an appreciable advantage with moderate trade offs while avoiding a fall off in reciprocity.


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 Post subject: Re: Ideal tonearm length ?
PostPosted: Tue Feb 18, 2020 8:49 am 
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Victor IV
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Joined: Mon Dec 18, 2017 2:51 am
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Location: Madrid, Spain
My engineer advice, if you want to build from scratch a new gramophone, use an HMV tonearm. Preferably the huge model used in the big reentrants 193/4 and 202/3. This tonearm is made to use an hmv no5/5a/5b soundbox, and had a low tracking error and a good mass. It can also use a Meltrope soundbox, although the success depends on the horn size. The tonearms used in lower models (163, 157, etc) were shorter.
I've also managed to get a good sound and tracking with the thin hmv tonearm as used in the 101 and these models. This is shorter than the other, but it's thinner, very elegant, good and very easy to find. If I ever built a new gramophone, a 101 tonearm and a no4 mica soundbox would be my choice. This tonearm can also use a Meltrope, or a no 5/a/b soundbox (changing the rubber connection) with amazing results.
Inigo


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 Post subject: Re: Ideal tonearm length ?
PostPosted: Tue Feb 18, 2020 9:45 am 
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Victor II
Joined: Wed Dec 04, 2019 9:31 pm
Posts: 220
Inigo wrote:
My engineer advice, if you want to build from scratch a new gramophone, use an HMV tonearm. Preferably the huge model used in the big reentrants 193/4 and 202/3.


Thanks Inigo, thats very good advice. I actually have been looking for one of those the last few days. The last time I saw one was about 6 months ago. So that tonearm may be hard to find. If anyone has one for sale please do let me know. Until I do find one I'm planning on a 102 tonearm cut through on the straight section and with a 4 inch length of carbon fiber tube spliced into it to lengthen it. What do you think?


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 Post subject: Re: Ideal tonearm length ?
PostPosted: Tue Feb 18, 2020 9:49 am 
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Victor II
Joined: Wed Dec 04, 2019 9:31 pm
Posts: 220
Inigo wrote:
I've also managed to get a good sound and tracking with the thin hmv tonearm as used in the 101 and these models. This is shorter than the other, but it's thinner, very elegant, good and very easy to find.


I already have two of these but I don't want to cut them to lengthen them because as you point out they are very good.


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 Post subject: Re: Ideal tonearm length ?
PostPosted: Tue Feb 18, 2020 10:35 am 
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Victor IV
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Location: Madrid, Spain
The 102 tonearm problem (too short) could be solved by inserting a straight section at the appropriate location, but be careful with the soundbox angle. The design of the 102 (speaking from memory) is engineered for that short length, having almost zero tracking error at the inner grooves of a record (2" or so?) and also at the other minimum occurring at small radius, displacing all the bad error to the outer grooves. This is done giving a great deviation angle to the soundbox, which could be too much for a longer tonearm.
I would try with an unmodified narrow bore 101-style tonearm. I want to include one question here; in the 101 Saga of new gramophones of 1925, with this tonearm and the no4 soundbox, did all machines use the same length of tonearm? Of course the table models 103, 109, 126/7 used the same as the 101, but I'm wondering if the bigger consoles and uprights (161, 181, 162, 192, 201, 211, 261, 461, 511, etc) used the same or maybe longer tonearms...??? If there is a longer version available, it must be great!
Inigo


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 Post subject: Re: Ideal tonearm length ?
PostPosted: Tue Feb 18, 2020 10:55 am 
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Victor II
Joined: Wed Dec 04, 2019 9:31 pm
Posts: 220
Inigo wrote:
The 102 tonearm problem (too short) could be solved by inserting a straight section at the appropriate location, but be careful with the soundbox angle. The design of the 102 (speaking from memory) is engineered for that short length, having almost zero tracking error at the inner grooves of a record (2" or so?) and also at the other minimum occurring at small radius, displacing all the bad error to the outer grooves. This is done giving a great deviation angle to the soundbox, which could be too much for a longer tonearm.


The curved section of the 101 and 102 tonearms are interchangable and are different in angle. So I plan to cut the 102 straight section to lengthen it and subsitute the curved section of the 102 with that of the 101 to correct the angle.


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 Post subject: Re: Ideal tonearm length ?
PostPosted: Tue Feb 18, 2020 10:58 am 
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Victor II
Joined: Wed Dec 04, 2019 9:31 pm
Posts: 220
Inigo wrote:
I want to include one question here; in the 101 Saga of new gramophones of 1925, with this tonearm and the no4 soundbox, did all machines use the same length of tonearm? Of course the table models 103, 109, 126/7 used the same as the 101, but I'm wondering if the bigger consoles and uprights (161, 181, 162, 192, 201, 211, 261, 461, 511, etc) used the same or maybe longer tonearms...??? If there is a longer version available, it must be great!


I can confirm that the 101 and 161 use the same tonearm.


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 Post subject: Re: Ideal tonearm length ?
PostPosted: Tue Feb 18, 2020 11:16 am 
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Victor V
Joined: Mon May 13, 2013 2:04 pm
Posts: 2335
Daithi wrote:
Inigo wrote:
I want to include one question here; in the 101 Saga of new gramophones of 1925, with this tonearm and the no4 soundbox, did all machines use the same length of tonearm? Of course the table models 103, 109, 126/7 used the same as the 101, but I'm wondering if the bigger consoles and uprights (161, 181, 162, 192, 201, 211, 261, 461, 511, etc) used the same or maybe longer tonearms...??? If there is a longer version available, it must be great!


I can confirm that the 101 and 161 use the same tonearm.



No they don't , the 101 tone cannot be used on any machine except a 101 , use it on another machine and the soundbox will be at a very strange angle , they are not the same !


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 Post subject: Re: Ideal tonearm length ?
PostPosted: Tue Feb 18, 2020 12:32 pm 
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Victor V
Joined: Mon May 13, 2013 2:04 pm
Posts: 2335
Daithi wrote:
Presumably a longer tonearm has less tracking error.
So why are so many tonearms so short?
And what is the ideal practical length for a tonearm to minimise tracking error?


They are the length they are to track from the centre of the horn hole to the centre of the turntable , any longer or shorter and they would skip off the record at the end


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 Post subject: Re: Ideal tonearm length ?
PostPosted: Tue Feb 18, 2020 12:33 pm 
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Victor II
Joined: Wed Dec 04, 2019 9:31 pm
Posts: 220
soundgen wrote:
No they don't , the 101 tone cannot be used on any machine except a 101 , use it on another machine and the soundbox will be at a very strange angle , they are not the same !


I stand corrected,thanks.


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