Re Ampico A and B Compatibility
By Craig Brougher
I would like to answer Bob Taylor's letter now about my article "Ampico Misconceptions" (Digest 96.11.10). Bob is a fine roll coder, and this cannot take away from his expertise or knowledge. However, we can all learn and profit from someone else's viewpoints and information.
The title of Bob's rebuttal letter in Digest 96.11.12, "The Ampico B AND Ampico A Are Not Compatible", is absolutely correct. As a matter of fact, it is the very reason I wrote the article to begin with. No direct equivalence between models is necessary, as long as both are equally compatible with the standardized roll coding format Ampico settled on in the early 20's. In this we fully agree.
Bob wrote:
> Even though Craig Brougher has claimed that the Ampico B plays the
> early "A" rolls (pre 1926) in a truly compatible fashion, it is my
> opinion that this not the case. I find that the Ampico "B" only
> achieves its maximum volume by using both full intensity setting
> (level 7) simultaneously with full crescendo travel. Conversely, the
> Ampico "A" may achieve its maximum level of play with EITHER (not
> both) of those two volume control components at maximum. The problem
> is that many Ampico "A" rolls lack simultaneous coding of the
> crescendo and intensity steps when maximum playing volume is desired.
> The result is that the "B" plays these passages at only 50% of its
> maximum power, while its predecessor is at maximum effort volume.
> This is a very common event in a broad spectrum of rolls from the
> inception of the Ampico until the first "B" rolls (popular series)
> were introduced in Nov. 1927. ("Blue River" 209161-E, first
> released fully coded Ampico "B").
While this is _theoretically correct_ and I have no problem with the possibility of doing it as Bob suggests, in practice the "1922 standard format" coded roll never raised the pump pressure above the normal setting using discrete intensity codes alone. Crescendos were ALWAYS used. Here is why:
The intensity codes are intended to accent certain notes and chords instantly, by momentarily increasing the stack pressure just before the rolls plays the note or chord! In neither the models A or B is the stack pressure able to go higher than nominal pump pressure, unless the pump pressure is increased. So with crescendos or without, the highest pressure a model A achieves is limited by the pump pressure.
Unless the higher pressure needed is _anticipated_ by the roll, and unless the pump pressure is increased _beforehand_ with (usually) "fast" crescendo, even the highest intensity desired will seldom rise above nominal pump pressure. If a higher intensity were left on for a period of time, it is possible, in the model A, to tighten the spill valve and raise the pump pressure. However, this happens through _positive feedback_ to the pump, through the amplifier directly by stack pressure, and therefore happens relatively slowly. As a matter of fact, you can watch the Ampico amplifier pneumatic slowly tightening the spill spring. It is prompt but not sudden, and must follow the intensity. It cannot accompany the intensity for accents.
Intensity codes, as I said, are discrete pressures intended for instant accents, while crescendos are "continuously ramping pressures." Crescendos in the A piano raise the overall "platform" pressure, or pump pressure which the intensities build upon. Neither model A or model B, in practice, can use the intensity codes in the way they were intended and still raise pump pressures on the fly. It is physically impossible.
Crescendos are also needed so that there is a discernible difference in volume when the piano is switched between Brilliant and Normal mode. This is because the mode switch only alters the action of the amplifier, so coding with intensities alone -- without crescendos-- would sound about the same in both Normal (Medium) position and Brilliant position, since the pump in the model A cannot respond instantly to the intensity codes.
By the way, Larry Givens wrote a letter questioning my comment that only one copy of the model 1A Ampico (actually the precursor of the Stoddard Ampico) had ever been built. I rechecked my statement and found that to be in error. I meant the "model 1", not the "model 1A". The "model 1" is mentioned on pg. 68 of the Ampico Reproducing Piano, by Richard Howe. It is the model I (Roman Numeral 1) that was the precursor of the model B. I should have written: "In the first place, you don't have to worry about the so-called "Ampico model 1" which is actually the pre-model B. Only one of them was ever built!" I also could have said, "Besides that, the Ampico never had a zero intensity!" Many thanks to Larry Givens for bringing this to my attention.
I think that you can see, despite the knowledge to code rolls and rebuild pianos, that a full understanding of the Ampico has not necessarily been required up until now and so becomes largely a cut-and-try method which, sooner or later, will still yield satisfactory results. It's just a lot slower that way. Still, it would be much easier if we would take this accrued knowledge and refine it to recreate the "Ampico standard roll coding format". That cannot be done however until these misconceptions are largely cleared up.
There's nothing quite like shining a bright light on the real problem, and it is this MMD forum that has made it all possible! It is the free-for-all discussion which has allowed the facts to surface here. (And it's about time!)
Craig Brougher
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(Message sent Fri 29 Nov 1996, 15:38:45 GMT, from time zone GMT.) |
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