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Reel to reel, cassette and other analogue tape formats.

RE: Tape Preamps...why?

In most machines the preamps were compromized in that they had to accommodate several functions and equalization schems. When you change the speed of the tape everything changes; output level, EQ, ETC. When you change function-everything changes. Also some machines used the same preamp for mic input in Record mode that the playback head used in playback mode. Electronics is a compromise. It's just a matter of how much one is willing to compromise. A commercial product also has input from the marketing department that takes president over the engineering department. Most pro machnines have seperate record and playback amplifiers. Also head geometry is very dependent of tape speed. A 30 ips playback head has to have a much longer pole piece because of wavelength in order to reproduce flat bass frequencies. Slower speeds require shorter pole pieces. So the preamp has to be mated to the speed and the heads (inductance). The highest signal to noise ratio results when the resonance of the head is within the audio passband which correspnds to a head of 400=600mh. For good record penetration the record head needs to have a low inductance to accommodate a high freq bias without burning up the tape and this corresponds to a head of around 4mh or less. So a lot of compromise! Solid state circuitry has benefitted from more modern transistors with less impurities and sophisticated topologies. In fact it's taken about 60 years to learn how to design good sounding solid state gear for high definition audio. There are discreet opamps like the Jensen 990 and a newer FET990 that can be adpated to tape. M.B.
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare


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  • RE: Tape Preamps...why? - mobiasloop 15:18:52 09/29/14 (1)

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