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In Reply to: 47 labs phonocube! posted by stark on December 2, 2005 at 17:36:39:
The unit you refer to is a current amp design which has a fixed input impedance of virtually 0 (ZERO) ohms. This means the utput voltage of the cartrdge used is reduced to a fraction of the normal output so the amplification has to be 75 r 90 dB just to get a useable output. Check out the various reviews and you will see even with the 90dB version the effective output to the linestage is barely adequate. I am not against this kind of amplifier but one must understand what's going on here.A typical MC cartridge loaded at 1 ohm (and we're talking here of virtually 0 ohms) has an output 1/10th that when loaded at the DC resistance, more or less and about 6% of the output compared to a load at ten times the DC resistance of the cartridge.
So the effective gain, amplification is not 90dB but only 70dB at 1/10th the cartridge output (compared to a DC resistance laod) and only 65dB compared to a load of 10x the DC resistance. And that is the 90dB version the 75dB version is much "worse".
So as you can see the gain in dB cannot be taken at face value by such a product.
Nevertheless the total 72dB gain he now has, assuming I did not misunderstand, would only be achieved with one or two very expensive products and I am skeptical about the quality of that high an amplification. The high feedback etc. could be very detrimental to the sound.
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Follow Ups
- Wrong! - garth 18:19:18 12/02/05 (8)
- hmm very interesting - stark 20:40:20 12/02/05 (2)
- Depends on the cartridge impedance. - garth 21:05:15 12/02/05 (1)
- Depends on the cartridge current. - Mark Kelly 21:54:42 12/02/05 (0)
- Transfer function - Mark Kelly 20:39:25 12/02/05 (4)
- Great, so what does that mean for normal persons? - garth 20:59:29 12/02/05 (3)
- Transfer function again. - Mark Kelly 21:46:16 12/02/05 (2)
- thank you! - stark 11:17:18 12/03/05 (1)
- A little more complex - Mark Kelly 14:54:33 12/03/05 (0)