Well, here are some thoughts following a couple of days experimenting with the mechanical demands and acoustic results of a record played by a Garrard 10B spring-driven motor versus a Garrard 301 electric transcription motor. In both cases every other detail is identical---same EMG two spring soundbox, same Burmese colour thorn needle with corresponding newly sharpened projection, same overlap of 0.550 inches in an EMG Mk Xb base unit with EMG Mk IX 22 inch diameter horn. I hope I will be forgiven for not using an Oversize horn which I cannot physically manage to continually mount/dismount on my own these days !
I have learned the following along the way :
1. The great height of the 301 turntable above the deck-board produces many challenges.
2. It is impossible to close the lid of an EMG base unit when the record is being played.
3. The angle of the needle is considerably altered.
4. A record can, in fact, be played but the tolerances are extremely tight and the half-round screw head below the bulge on the tonearm swinging joint clears the disc by less than ⅛" (approx' 3mm) ! Little room for error or a slightly warped record. Not ideal !
5. A Mk IX base unit cannot be utilised as the tonearm bearing is central to the case and the correct tracking distance cannot therefore be achieved due to lack of case length.
6. A Mk X base unit has the happy advantage of having the tonearm bearing somewhat to the side at approximately one o’clock.
7. It is not possible to mount the 301 motor and turntable spindle centrally in the case as tracking is severely compromised.
8. Correct tracking demands a distance of eleven inches between tonearm bearing centre and motor spindle centre.
9. It
is possible to mount the 301 motor very much to the left of centre to achieve good tracking but unfortunately it is also necessary to cut into the rear deck-board to the extent of a lateral line lying behind the extremity of the tonearm bearing flange.
10. Point 9 does not present a problem for the current experiment as the 301 motor was mounted on top of the deck-board in the usual way and the back of the motor is able to oversail the rear deck-board. However, if the motor level were to be dropped, a front deck-board of awkward shape would result.
11. Handling clearances for the easy and safe use of the soundbox within the case are very tight and undesirable. Inadvertent damage may result to diaphragm or record---particularly in respect of a twelve inch disc.
12. Although the experiment demonstrates that it is
possible to achieve a working gramophone with a 301 motor in an EMG case, it also clearly shows that an improved design is called for if a sensible permanent solution is to be achieved.
13. There is just enough depth in an EMG base unit to allow use of a 301 motor if the front deck-board were to be lowered by perhaps up to one inch if solidly mounted. There may, additionally, just be enough room for spring mounting---as yet unquantified. In the event of spring loading being possible to achieve within the given space, the inside structure of the case would have to be redesigned to give good clearance horizontally all around the deck-board.
14. The great debate is, of course, whether all such work would be worthwhile ! Does the use of a 301 motor achieve a discernible difference when compared to the 10B equivalent ? The listener must decide.....................I have to say I cannot tell the difference. Spring-mounting
might improve on the 301 performance but, in my opinion, not by much in an
acoustic set-up :
https://www.youtube.com/watch?v=fMLhO7YDLLM Garrard 10B spring-driven.
https://www.youtube.com/watch?v=BGQDetpy-DQ Garrard 301 electric transcription motor.