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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: Batteries vs. Mains Power Supplies posted by andyr on June 29, 2004 at 19:48:13:
Andyr,
from your description, it would seem that instead of the shield (outer connector in your RCA) being only connected at one end, it is connected at both ends for your phono stage, and you have a ground loop. This was not manifesting itself when you were mains powered because the ground potential was the same at both ends ie both ends were both connected to earth well...Switching to battery, there is the significant probability that there will be a difference in the 'earth' potential (or Zero volt refernce) between the two componants, causing a current flow through the shield.
The pro way of eliminating this is a 100R bypassed with a cap from the ground of your RCAs to the signal ground of your pre to reduce this, or having no 'ground' connections at the input RCAs of your pre also works.
My take on battery supplies is simple.
Batteries require as much design work as a linear mains PSU, to gain maximum benefit. The capacitance required to bypass is small (4uF is usually plenty for HF punch, but adjustment to taste is in order), and series inductors in all three PSU legs (+, - and ground) are also in order before the bypass caps to stop electrochemical noise. These do not need to be large in value (the knee frequency needs to be around 10KHz), but must be high current and low R and preferably air cored. This will produce a battery PSU with noise specs as good if not better than a full blown regulated supply, with a low impedance, and will sound unlike anything you've heard before.. :-)
Dont burn your fingers
Owen
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Follow Ups
- Re: Batteries vs. Mains Power Supplies - Owen 09:12:53 07/06/04 (5)
- ground? - pburke 10:56:27 07/30/04 (0)
- What is the "knee frequency"?? - andyr 15:46:48 07/09/04 (2)
- Re: What is the "knee frequency"?? - Owen 00:59:14 07/10/04 (1)
- Much obliged, Owen ... I'll go and look at the JR power filters (nt) - andyr 01:36:24 07/10/04 (0)
- Thanks, Owen ... - andyr 13:53:02 07/06/04 (0)
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