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From: firstname.lastname@example.org (N. Thornton)
Subject: Re: 40W bridge audio amp + signal-level crossover
Date: 12 Sep 2002 05:05:12 -0700
NNTP-Posting-Date: 12 Sep 2002 12:05:12 GMT
In article <email@example.com>, firstname.lastname@example.org
>email@example.com (Bob Wilson) wrote:
>>> The voltage needed are essentially
>>> related to your load impedance and your desired power level only.
>>> rail voltage needs to be theoretically 50 Volts (plus a little
>>> for the transistors to work) for a non-bridged topology. So, say
>>> Volts, or +/- 30V for a split rail.
>>I do believe I said bridge mode :) Can I safely say halve this? 0 to
>>non-bridged is the same as -30 to 30 bridged, no?
>No, of course not.
A single ended 60v amp will deliver the same max V to the load as a
bridged amp running on 30v.
But the supply Vs quoted are vague. -30 to +30 would be a 60v supply,
if thats what you mean.
>"Bridging" is NOT splitting the power supplies (i.e. changing a 0-60
>suply to a pair of rails that are -30 and +30. To the amplifier,
>the same thing).
>Bridging is the process of driving 2 identical amps
>anti-phase, and connecting a speaker BETWEEN their outputs.
>A pair of
>bridged amps is theoretically capable of outputting 4x as much power
>amp operating from the same supply voltage (the speaker sees double
>drive voltage, and power output is V^2/R). In practice, it is a lot
This is a very popular myth. if a single amp can deliver W watts, then
2 of them in bridge mode can deliver 2xW watts. Not 4x. A load of
twice the impedance will be needed too. An amp does not suddenly
acquire twice the max power diss just because it is being used in
>>> A blocking cap is simply a poor man's high pass crossover for a
>>> If you are bi-amping the tweeter, the crossover is already taken
>>> of, and a blocking cap will be useless (there will be nothing to
>>Not even a small DC offset due to bad amp design? Or to guard
>You aren't concerned about this when connecting a woofer, so why are
>concerned about the effects of an amp failure on the tweeter? Both
>simply 8 Ohm pieces of wire. If you have a "bad" amp design or a
>any directly connected speaker can be toast.
IRL many amps do concern themselves with dc offset and possible
Lots of amps have output caps to the woofers...
1 to keep inevtiable dc offset off the speaker
2 to keep possible dc offset off it
3 to protect the speaker in case of amp failure.
An output cap is (generally) good design practice.
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