Transistor equivalent

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Ah, only need 1 fuse in main power 220V? Because one supply rail which the fuse didn't blow will destroy my amp? Or make a relay circuit that can turn off both supply rail when only one blow?
Use slow-blow fuse to make sure it will not blow when I turn on the amp?
 
One slow blow fuse in mains supply. Slow blow especially important if toroid transformer used because of the high inrush current at turn on.

No fuses are best from a hifi point of view, but if you do have fuses you must make sure that if one fuse blows the other will too. That will protect your speakers and limit damage to the components in the amps.

A relay in the PSU would be the Rolls Royce approach and can be used to provide not only protection but also to eliminate turn on and turn off thumps in the speakers.
 
Nikolai Petrenko said:
Yes, relay circuit with capacitor delay for few seconds will eliminate thumps sound in the amp when turn on or off.
Click to expand...

Here is a +- 35V PSU which I did before I read your post above:


​
ERRATA
(1) Change TIP41/TIP42 to TIP35/TIP36
(2) Place a 1R 2W resistor in the collectors of the TIP35/TIP36
 
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The amp need at least 9A power supply for safe reason. So TIP41-42 will not work well, use TIP35-36 instead.
Do you have dual rail supply circuit which has relays protection with feature: overload (or shorted) in one rail can turn off all 2 rail? Regulated is not necessary, too clumsy.
I am trying to make the circuit.
 
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Nikolai Petrenko said:
The amp need at least 9A for safe reason. So TIP41-42 will not work well, use TIP35-36 instead
Click to expand...

Do you mean TIP35- TIP 36 for the protection circuit. If so they would be better in theory, but TIP 41/ TIP 42 would be fine. The protection transistors don't normally don't do anything, but if the two supplies get out of balance the power transistors will conduct a huge current and blow the fuses pretty fast. After that they will do nothing again so their average power dissipation will be extremity low. They don't even need to be on heat sinks. Not sure what you mean by 9A for safe reason. If you are talking about the transformer current capacity the more the better, but under normal use, the two 3A quick blow fuses should be fine. The RMS power of an audio amp is very low. But you may like to fit 5A fast blow fuses if that makes you happier. Note that the fuses and fuse holders must be solid high quality types.

UPDATE Yes TIP35/TIP 36 will be needed. I had forgotten about discharging the lage reservoir capacitors.
 
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Nikolai Petrenko said:
This circuit use shunt circuits?
Click to expand...
The PSU is not stabilised. Normally the four transistors do nothing. They only conduct if the + and - supplies become different under fault conditions. Then they conduct a large current and quickly blow the fuses, so that both supplies output zero volts and your speakers are protected. If this happens you will need to replace both fuses to get the PSU working again.
 
Ok, I understand now.
Audio amp only reach high power if input is squarewaves.
Bussmann fuse well?
 
It can overload or shorted protecting, right? Because overload or shorted cause voltage drop, so voltages will not balance.
 
Nikolai Petrenko said:
Ok, I understand now.
Audio amp only reach high power if input is square waves.
Click to expand...

Sine wave is worst, but principle is correct. As an experiment take one of your existing amps and put an ammeter is series with one of the supply lines. Play your favorite music as loud as you can stand and watch the ammeter- you are in for a surprise.


Nikolai Petrenko said:
Bussmann fuse well?
Click to expand...
Bussmann is a good make. Do you have a specific fuse and fuse holder in mind. If so post part number and I will check if it is OK.
 
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Nikolai Petrenko said:
It can overload or shorted protecting, right? Because overload or shorted cause voltage drop, so voltages will not balance.
Click to expand...
If either supply line is overloaded the line voltage will drop, but the other line will stay the same. The protection circuit will detect this and blow the fuse for the good supply line. Then the transistor on the bad supply line will blow the fuse for that too. The net result will be that there will be no output voltage from either power supply lines.

If both supply lines are loaded equally, say by loud reggae music (continuous bass line), the protection circuit will be happy and do nothing.
 
Will have a think about relay. But in any case use car (auto) relay around 40 Amps, double pole single throw (but double pole, double throw is standard and will be fine): solid and dirt cheap too. Rolls Royce implementation would be special high conductivity contact relay, but much more expensive and probably not necessary.
 
I like relay than fuse in device like amps. I will use a snubber circuit to prevent contacts of relay create sparks. I also will use capacitor delay to remove nasty thump will turn on or off (it made children scare).
I will try to find DPST or DPDT relay at stores.
 

Nikolai a snubber circuit is absolutely not not required. The inductance of the speakers is not significant and besides which little power will be switched.

Each speaker, left and right, will connect to the amps via the relay. In the relay non energized state the speakers will be disconnected from the amps.

When the PSU mains switch is turned on the PSU and amps will stabilise, probably within 5 seconds. If all is well then the relay will connect the speakers to the amps.

While the system is operating any sniff of problems with either amp or PSU and the relay will instantly disconnect the speakers.

When the mains PSU switch is turned off the relay will instantly disconnect the speakers from the amps.
 
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Ok, I am waiting for the circuit now. I have draw but not sure it work. Mostly like your post, but current pass through transistors go to bridge rectifier, thyristor and relay
 
In general terms, there are three areas to be protected:
(1) Speakers
(2) Amps
(3) PSU

Speaker protection is the most important, and most difficult to do without compromising audio quality. I suggest only provide protection for the speakers at this stage of the development.

There will be a signal called: Not Disable Speakers (NDS). When NDS is low the speakers will be disconnected. There will be a number of detector circuits influencing NDS. If any of the detector circuits finds a problem they will make NDS low which will instantly disconnect the speakers. You can add/ remove detector circuits as you please.
 
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