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In Reply to: Why do I need a preamp posted by airtime on March 22, 2014 at 10:35:46:
IMO, passive preamp is an oxymoron. Passive control center is the terminology I prefer.When the signal source(s) is/are at 2 VRMS (that of a "standard" CDP), a line stage with gain is usually inappropriate.
A passive control center can be fine, under those circumstances. For a 10 Kohm passive control center to work well, the I/P impedance of the power amp should be at least 100 Kohms and the interconnect cables both short and low capacitance, as in unshielded. Please observe that the signal source(s) must be compatible with a 10 Kohm load. Commercial CDPs meet the need. A 50 Kohm passive should work into 500 Kohms. The 470 Kohms found at the I/P of some tube amps is OK, but don't go lower. These are examples of the 1:10 rule, which states that a driving impedance of X Ω should be loaded with 10X Ω.
Frequently, the conditions for satisfactory use of a passive control center are not present. Then, a buffered volume control is appropriate, as it provides the low impedance/high current drive needed for long, high capacitance cables and also provides a high I/P impedance.
Eli D.
Edits: 03/22/14
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Follow Ups
- RE: Why do I need a preamp - Eli Duttman 12:27:41 03/22/14 (4)
- What do you think of the Ciaudio pres? - airtime 13:10:36 03/22/14 (3)
- RE: What do you think of the Ciaudio pres? - Eli Duttman 13:56:50 03/22/14 (2)
- RE: What do you think of the Ciaudio pres? - rosendds@frontiernet.net 04:57:37 03/23/14 (1)
- Gonna look into converting my preamp - airtime 10:28:36 03/23/14 (0)
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