On Friday 15 December 2006 17:05, Mikkel L. Ellertson wrote: >George Arseneault wrote: >> At the risk of sounding dumb: >> >> How old is the phono-player? >> >> The reason I'm asking is because some of the older >> players have a different style of pre-amplifier and >> require a special input. (long time since I dealt with >> this... I think it was called a "ceramic input") >> Without the right input on your amplifier it would >> sound very faint or possibly not be audible at all. > >I thought the ceramic input actually gave a higher level input the >the magnetic ones. In any case, the phono pre-amp also has to >compensate for the response curve of the magnetic cartridge. This is >why amps (used to?) have a phono input besides the aux unput - the >levels and response curve is different between a phone-player and a >tape deck. > >Mikkel Yes, the magnetic cartridges are very hard put to generate more than a few millivolts of output, and they are not amplitude sensitive, but velocity sensitive. Low frequencies from the vinyl result in very slow effective velocities and low output. This translates to a need for a gain characteristic in the preamps that fairly well matches a 6 db increase in needed gain per octave below about 5khz. Above that, the recording and pickup coil inductances compensate enough to get by, generally speaking. Ceramic or 'crystal' cartridges are generally amplitude sensitive, but they also have a capacitance effect in series with the generator symbol, so they need very high load impedances to preserve the bass response, 2.7 to 10 megs being the typical input load for those. You can get an idea of that problem by actually measureing the capacitance of the device. One well versed in this now elderly art could write at least 10 pages in a manual describing how to get the best results for the money spent on either of these devices. And then there was the Weathers capacitative pickup, but since it wasn't stereo, good as it was (and it was damned good in 1959), it went away. So todays epitome of fine cartridges pretty well describes the Shure V15 series, even radio shack sold them at one time. Audibly cleaner than anything else, and hundreds of times easier on the recordings than any other cartridge then, or probably even now. It will need a good arm and a stable turntable as its optimum tracking pressure is 1.5 grams, which includes about .8 grams used for a carbon fiber brush that cleans the dust out of the grooves in front of the needle. I put a pair of them in at a radio station back in '80, and it took our most ham handed DJ 6 months to wreck the first needle. In that 6 months we saved the cost of the needle several times over just in the 45's we didn't have to replace because of cue burns on the leadin track or general deterioration of the sound the older Stanton 500 catridges did as they plowed their way around the record with needle pressures in the 6 to 8 gram range. Needle life was 2-3 weeks with those. >-- > > Do not meddle in the affairs of dragons, >for thou art crunchy and taste good with Ketchup! -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Yahoo.com and AOL/TW attorneys please note, additions to the above message by Gene Heskett are: Copyright 2006 by Maurice Eugene Heskett, all rights reserved.
