Below are the part no and values for the circuit:fcel said:
R1 - 120K
R2 - 18K
R3 - 5.6K
R4 - 39K
R5 - 47K
R6,R7 - 1K
R8 - 2.2K trimmer
C1,C4 - 100uF 16V
C2 - 47uF 16V
C3 - 22uF 16V
D1 - IN4148
Q1,Q2,Q3 - BC548 NPN
K1, K2 - 6V relays
The input sensitivity of the circuit is variable and can be adjusted for different amp/speaker combinatons by means of the trimmer R8. The signal is applied to the input of the circuit through the resistors R6 & R7 which correspond to the right and left channels respectively according to the schematic diagram. When a peak signal appears in one of the inputs (or at both of them) the two capacitors C2 & C3 which are connected in series charge and the voltage across them increases. When this voltage becomes sufficiently high, the transistor Q2 is biased through R8 and is turned on. This brings the collector of Q1 at a very low potential and the transistor is switched off. When this happens Q3 is turned off and the relays are deactivited disconnecting the speakers from the output of the amp. If the output signal falls below the critical level, the voltage across C2 & C3 is reduced accordingly and Q2 is turned off, allowing Q1 & Q3 to turn on, activating the relays and connecting the speakers back to the output of the amp. The capacitors are there to filter out very short duration peaks which are not dangerous and to keep the circuit off slightly longer than the duration of the dangerous peak (while the capacitors are discharging through R8 And R3) to ensure that the danger has passed. During power on, the circuit should be wired in such a way as to receive power at the same time as the amp. When the circuit is off, the relays are deactivated and the speakers are disconnected. As soon as the circuit is powered up, the capacitor C1 starts charging through R1. As long as the capacitor is partly charged, the voltage across R5 is maintained low and the transistor Q2 is kept off. As soon as the value of this voltage reaches the biasing voltage of Q1, the transistor is turned on and biases the output transistor Q3 which in turn activates the relays. The diode D1 protects the circuit from any back emf that could appear across the relay windings when the circuit is switched off. The capacitor C4 is there to smooth the supply voltage in order to avoid spurious triggering of the circuit which could be annoying
Peter Daniel said:fcel,
This is not speaker protection circuit nor soft start circuit, but inrush protection. It is providing the same as thermistor on primary, although sligtly better.
You are right, it is not speaker protection. But a soft start, that surely is! Otherwise I have inrush protection and soft-start
mixed up in my mind. To me, they seem to be same thing. No?
MOSFETs failure mode?
I've been playing with the Hitachi's since 1980. I've done all kinds of stupid things to them (some on purpose to see what would happen) and they simply wouldn't die.... Except one time - I accidentally applied 40V gate to source voltage. They failed open.
I've been playing with the Hitachi's since 1980. I've done all kinds of stupid things to them (some on purpose to see what would happen) and they simply wouldn't die.... Except one time - I accidentally applied 40V gate to source voltage. They failed open.
phase_accurate said:
Don't count on Mosfet failing soft. Typically with a
damaged Gate they conduct like crazy.
Count on fuses. One of the reasons I like monoblocks is
that you can fuse them on the primary for just one channel,
not two.
Also worthy of note: I have actually seen Mosfets survive
80 V Gate to Source voltages. But not often, or very long.
damaged Gate they conduct like crazy.
Count on fuses. One of the reasons I like monoblocks is
that you can fuse them on the primary for just one channel,
not two.
Also worthy of note: I have actually seen Mosfets survive
80 V Gate to Source voltages. But not often, or very long.
When the universe was created (in theory) with the big bang all the mass and therefore all the energy in the universe was all at a single point - as the universe rapidly expanded from the explosion this energy was dispersed - causing the temperature to decrease.
As our universe is a closed universe (which has been proven with some rather complex maths) it's rate of expansion is negative and therefore at some point "the big crunch" will occur - bringing back all the matter and therefore energy to one place.
Very Hot!
Heat death to the extreme
As our universe is a closed universe (which has been proven with some rather complex maths) it's rate of expansion is negative and therefore at some point "the big crunch" will occur - bringing back all the matter and therefore energy to one place.
Very Hot!
Heat death to the extreme
...here's a thought - if you want to create an amp from scratch the first thing you have to do is create a universe.
I don't think DocP was being literal - most people here probably know that sound needs a medium to travel through - and yes I too hate it when they put such huge explosions in space films, although it does make some nice rumbles
I don't think DocP was being literal - most people here probably know that sound needs a medium to travel through - and yes I too hate it when they put such huge explosions in space films, although it does make some nice rumbles
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