"By Heck" on the Radiola 47

[beaumonde]

Here is novelty "tap dance" medley played by Nat Shilkret and the Victor Novelty Orchestra (Victor 22228-B). All that's missing is the tap dancing, so you can supply your own...

By Heck

As recorded (with Audio Technica mics) from my Radiola 47...

[FloridaClay]

WOW That is one heck of a tone arm!!!

Clay

[beaumonde]

It's called the inertia tonearm, and was actually an early '30s upgrade on this 1929 machine (originally had a horseshoe magnet type pick up). Despite its formidable appearance, it is designed with an internal counterweight, so that it actually produces very little if any record wear (esp. compared to the horseshoe magnet pick up or compared to an Orthophonic sound box).

[gregbogantz]

Yes, that tonearm is known as the "inertia" arm. It has that name for a reason - it has significantly more MASS than earlier designs. Extra mass means increased inertia. You will note that the "wings" at the front of the arm have extra masses built into them. This would increase the tracking force, but that extra force is cancelled by the inclusion of even more mass at the back of the arm in the form of a counterweight. The purpose of the extra mass is to reduce the mechanical tonearm/pickup resonant frequency when used with the typical horseshoe magnet pickup of the day. This is the same pickup as used on most of the earlier electric pickup arms. Because of the low stylus assembly compliance of the magnetic pickup, reducing the tonearm resonance was necessary to improve bass frequency response of the tonearm and pickup system. For all of its massive appearance, the counterweight results in a tracking force of this design at about 150 grams, about the same as the earlier electric pickup designs and about the same as the Victor acoustic orthophonic reproducer. Record wear is not insignificant - it is about the same as that produced by those earlier designs.

[barnettrp21122]

Nice recording, Adam!
You can use cactus needles in these early electric pickups. I use them in my Edison C2 with pretty good results, and I doubt that they wear the records much.
Just for laughs sometime you might try recording directly off the pickup, assuming there are accessable wire leads. I've done this on the C2, using a pair of connectors with alligator clips going to a regular RCA plug, then into an appropriate line input on your recorder. Don't use the phono input-the signal would be too strong!
The result I've found is a sound heavy in the mid-range and bass. Here's an example:

"Boy, Oh Boy, Oh Boy, I've Got It Bad" Fox Trot
(The High Hatters with vocal by Frank Luther) VE 22703-B

http://www.box.net/shared/4s9pqinr8m

I used a soft-tone steel needle for this, not cactus.
Bob

[beaumonde]

Thanks for the detailed explanation, Greg.

I was just basing my judgment of wear on the seemingly lesser amount of "black dust" that I get when playing records. I actually don't use the Radiola terribly much (a few records every week or so, not more than my Credenza, 8-35, or acoustic machines overall), so I'm not too worried about wear in general. I made this recording a couple of years ago I think.

Bob, no, I haven't done what you did with your C-2 (I wouldn't know how on my own, I'm afraid), but I think I've captured the warmth of the Radiola's speaker quite effectively. I haven't used fibre or cactus; I tend to use half-tone needles (both new or NOS, various brands) with good results (best with NOS RCA Victor Half-Tone or Columbia Talkie needles). I don't like Tungs-tones with an electric pick up (or much at all, really).

[FloridaClay]

Adam, regardless, it is a nice recording and the Radiola is a handsome machine.

Clay

[Edisone]

By Heck a little earlier, By Eugene Jaudas' Society Orch: http://digilib.syr.edu/cdm4/item_viewer ... OX=1&REC=1

[Guest]

[quote="gregbogantz"]Yes, that tonearm is known as the "inertia" arm. It has that name for a reason - it has significantly more MASS than earlier designs. Extra mass means increased inertia. You will note that the "wings" at the front of the arm have extra masses built into them. This would increase the tracking force, but that extra force is cancelled by the inclusion of even more mass at the back of the arm in the form of a counterweight. The purpose of the extra mass is to reduce the mechanical tonearm/pickup resonant frequency when used with the typical horseshoe magnet pickup of the day. This is the same pickup as used on most of the earlier electric pickup arms. Because of the low stylus assembly compliance of the magnetic pickup, reducing the tonearm resonance was necessary to improve bass frequency response of the tonearm and pickup system. For all of its massive appearance, the counterweight results in a tracking force of this design at about 150 grams, about the same as the earlier electric pickup designs and about the same as the Victor acoustic orthophonic reproducer. Record wear is not insignificant - it is about the same as that produced by those earlier designs.[/quote]

Actually, Mr. Bogantz, the the stated purpose of the inertia arm was to increase needle point compliance at the low end of the audio spectrum. Earlier pick up arms tended to be rather rigid, forcing the heavily modulated grooves of the disc to fight against only the damper compliance in the pickup. In 1927 "Mac" Cottrell, an engineer at the GE who often tested competing commercial equipment was evaluating a pair of Pacent Phonovox pickups. One of these was fitted with a factory supplied carrier arm, and the other was made for attatchment to a talking machine tone arm in place of the usual reproducer. This unit used a clamp arrangement around a rubber collar fitted to the end of the arm. Cottrell noted that the bass response of the clamp-on pick-up was much better than that of the standard unit, and that needle chatter (evidence of the needle fighting the groove) was greatly reduced. He determined that the compliant joint between pick-up and tone arm was responsible for this improvement. Of course, this rather indeterminate resonant system was full of unwanted "wolf tones" as he put it. He began work on improved carrier arms, the first of which was adopted by Brunswick in late 1928. This unit used a pair of very slightly flexible support rods which increased low-frequency compliance whilst keeping the natural resonance of the system up in a range where it was believed to do little harm. The RCA Inertia arm was a further development of this principle. The stamped metal arm was designed to be very flexible at its waist, so as to tremendously increase needle point compliance. The purpose of the weights in the "wings" was to inertially damp the natural resonance of the vibratory system, or rather to lower the resonance of the system to below 100 cps. The increased compliance allowed the unit to be more heavily counterweighted. The needle point pressure of this assembly as installed on my E-35 Electrola is fully an ounce less than that on my 12-15, and a half ounce less than that on the Micro-Synchronous sets.

Cottrell was involved in the installation of electric recording equipment at the Gennett and Edison studios, and was involved in the remodeling of the Brunswick installation.

[gregbogantz]

Guest, you're saying the same thing that I said, but perhaps I was not sufficiently careful in making sure I was referring to resonant FREQUENCY as opposed to resonance amplitude: The extra mass in the tonearm lowers the tonearm/pickup system resonant frequency which improves bass frequency response by extending it downward to that new resonant frequency. Below the tonearm resonance frequency, the entire tonearm is free to vibrate which diminishes the vibration amplitude imparted to the signal generator system in the pickup, thus reducing output from the pickup at those low frequencies. Another way to reduce system resonant frequency is to increase the compliance of the stylus bar suspension bits, but the early designers apparently chose to keep the stylus assembly compliance relatively low as it had been in the acoustic models.

These early magnetic pickups are "moving iron" designs, which is the same technology as those later designs called "variable reluctance" (VR). Or "induced magnet" which was the phrase used by ADC in the 1960s. That is as opposed to the "moving magnet" type (Shure, Stanton, many more) or "moving coil" type (Ortofon, Denon, others). Why it took so long to increase the stylus compliance in these pickups is a good question. GE finally managed to get the tracking force down on its VR design in 1946 to about 30 grams. In so doing, they had to reduce the moving mass of the stylus assembly to keep the stylus resonant frequency sufficiently high as to be above the desired audio band. This is a completely different design philosophy than had been employed in earlier designs. But it was possible to move the mechanical stylus resonance above the audio band because amplification was now "cheap" and the resulting reduction in pickup efficiency was not the issue it had been in earlier days. Note that the requirements of these two system resonances are not the same - modern pickup designs place the mechanical stylus resonant frequency ABOVE the audio band to better control frequency response in the audio band. It's typically 15kHz or higher in modern pickups. Modern tonearm/pickup resonance frequency is still placed BELOW the desired audio band for the same reason it was with the inertia arm - to transfer all the desired frequencies to the pickup generator without having the tonearm itself vibrate. Modern tonearm system resonance is typically in the 5 to 10 Hz range.

Although there may have been variations in the weights of the various components in these inertia arm systems during their several years of manufacture, the several in my possession I have measured and they produce the same tracking force as the earlier straight arm in my RE-75 which is also about the same as that of the Victor acoustic orthophonic reproducer at around 150 grams.