Acoustic to electronic conversion?

[jboger]

One of the advantages of an electronic pick-up and amplification was that the user could easily adjust the volume with a turn of a dial. Because these early non-electric machines could be quite expensive, especially some of the floor models, were any kits sold that allowed the owner to "upgrade" an acoustic machine by supplying an electronic pick-up and amplifier?

John

[jboger]

Poking around some more in an attempt to answer my question, someone dropped a remark that the acoustic phonographs could be wired to a radio for amplification.

[Inigo]

Since the very beginning of radio popularisation, I think, or very early around 1925, it was always possible to buy an electronic pickup and tonearm to install on the motorboard and play records through a radio set. Probably an inspection through the Wireless Works or Gramophone magazines numbers from 1925 on, will reveal when the first strand alone pickups were offered for sale. Maybe, I bet, there were such things offered prior to 1925, in those early radio years when improvements and all sorts of accessories and inventions for radio applications were booming like flowers in the spring...

[herrickpickups]

I wrote this article a couple of years ago, I think it's mostly correct.
https://www.herrickpickups.com/origins- ... ic-pickup/

[epigramophone]

In the 1930's, especially in mainland Europe, portables were made for both acoustic and electric playing. Some, such as the Paillard pictured, also had both spring and electric powered motors.

[jboger]

The Forum webpage is responding painfully slow this morning.

Thanks, everyone, for your responses.

Herrickpickups: I read your article. Very nice; just what I was looking for. I watched the three videos, two of late 1920s pickups and a third of a home-made pickup assembled by you. I take it the two leads go to an amplifier, then the amplified signal goes to a speaker with an electromagnet and a paper cone.

I hadn't thought much about sound reproduction by the earlier diaphragm reproducers, although I know many people here on the Forum have. Your statement that these purely mechanical reproducers were poor for bass reproduction got me thinking about wavelengths: the longer the wavelength (towards the bass end of the spectrum), the poorer the sound reproduction given the small diameter of the diaphragm compared to the wavelength it needs to reproduce. It's a question of scales. One might have the same problem with a speaker with a paper cone that vibrates: a larger cone would be better for the bass, yes? And that's why today's speakers have woofers and tweeters.

So if I'm on the right track with all of this (and I'm not sure that I am), then this might explain why some of the early acoustic reproducers had larger diaphragms than others--for a better bass, although it seems to me that the larger diaphragm really wouldn't be that much of an improvement. Well, in any case by having the the amplification take place away from the needle, one could build a speaker as big as you want. You can't do that with a mechanical reproducer that rests on top of the record and must be moved by hand. Not practical. About the only thing you could work on would be the horn. Isn't that what EMG did?

I think I have an early pickup laying about somewhere. I'll see if I can find it.

John

[herrickpickups]

1 thing that EMG did was experiment with the Percy Wilson Exponential principle, but I'm out of my depth with mechanical amplifiers, my Girlfriend is making headway with this stuff & has reproduced papier-mache horns for both Gramophones & Cylinder Phonographs. another thing that makes a difference is the hole in the rear face of a soundbox, around 10mm & less is much louder & clearer than larger openings, due to the air pressure ? you can compare this with an HMV No.2 & No.4 although they are of different diameters also, just to confuse any experimentation. The Gramophone magazine published an article in 1927 "Soundboxes for Electric recordings" that discusses in minutiae of detail, design factors that make the perfect soundbox. Iv'e built a few recreations of the EMG & EXPERT soundboxes myself & this paper was really helpful they sound better when the details are used.
To use a 1920's add-on pickup you can attach the 2 leads to a mono jack & input into an amplifier , the resistance is around 1000-2000 Ohms D.C & according to various wireless world articles, the output is less than 5 Volts for this early electric period. If yours has been sitting around for a while it may need the rubber damping replaced or will lack the proper suspension & sound thin & scratchy. You can use soundbox diaphragm gasket for the needle bar pivot at the base & perhaps some natural rubber sheet for the top part...if there is one. Kilner jar sealing rings are a good source for natural rubber sheet, while they are still available. Hope this is helpful