Re: Foot-pump Marque Ampico Crescendos
By Craig Brougher
Benjy Templeton was wondering if the Marque Ampico was missing its crescendos.
No, actually the Marque was designed as the foot pump version of an Ampico, and while it was able to produce, probably 20" vacuum, due to a small treadle bellows and long lever for power it could never produce continually what the grand rotary pump could come up to, so there was really no reason to put a crescendo on it, since it was the crescendo's secondary job to operate the pump amplifier. If you were to leave the Ampico grand "Modify" switch at "Medium" or "Normal" (both terms were used), the crescendo's function of raising the pump pressure above nominal 18-20" cannot be utilized, anyway.
So a Marque is fully able to reproduce as well as the full-blown Ampico upright on "Normal" setting. You will hear practically no difference. It is only when you switch the full Ampico to "Brilliant" that the differences are heard.
The "crescendo" in an Ampico is to provide primarily a constant spring tension, anyway. It maintains the first intensity as a reference which cannot be changed by the stack pressures. (Think of a balance beam scale with reference weights in one tray that are the standards). The rolls normally were cut to do all the expressing in "Normal" mode without crescendos, otherwise, there would be no difference between Normal and Brilliant in an Ampico. The mechanical analogy of first intensity maintenance _is a spring_, in fact. And in the full Ampicos, the crescendos act upon a bellows called the "Spring" pneumatic to do the same thing. This is the pneumatic which takes the place of an actual spring. So, unless the pump can be increased, no Ampico would need more than a Marque spring.
If you want to know more about this subject, MMD has quite a bit about the Ampico crescendos in its archives.
Craig Brougher
|
(Message sent Mon 13 Jan 1997, 14:47:05 GMT, from time zone GMT.) |
|
|
Mechanical
Music Digest™ Archives
