What kind of transformers are used ?

Thread Starter

ilker06

Joined Jun 26, 2018
34
Dear masters,

I have found a horn amplifier circuit but I am not sure if it is really powerful as it's attested. Even I am not sure if it works or not. I kindly would like to get your opinions about it's output power and the transformer types can be used on it. Your advises about the brand or model number for these transformers will be appreciated. Another issue is the connection method of the power transistors. They are used as parallel. Is it really so powerful horn amplifier that needs to use 2N3055 as parallel ? I will use a 16 ohm horn driver as the speaker.

Although the output transistors are stated as 2N3055 the pin points seem like TIP3055. Can it be used TIP3055 instead of 2N3055 on this circuit ?

Thanks in advance for your comments and advises.

ilker PCB Layout.jpgCircuit diagram.jpg
 

Thread Starter

ilker06

Joined Jun 26, 2018
34
There is an error in the circuit diagram - the PCB layout does not have the error. The connection marked with a red cross in the attachment should not be there.
Yes Albert I have noticed but since it is corrected on PCB I don' t care about it. Thank you.
 

ronsimpson

Joined Oct 7, 2019
824
I can not imagine that such a small transformer can drive a 100 Watt speaker:
We all know that with "audio" 100 watts does not equal 100 watts or even 50W maybe 25W.
I also questioned why the input and output transformers are the same size. This is for a siren so there does not need to be any Base notes. Transformer size is related to low frequency response. It might work at 2khz but certainly not at 100hz.

I also noticed it is not temperature stable. Cross over distortion! Circuits.com Consider the source.
 

Audioguru again

Joined Oct 21, 2019
1,757
Most cheap amplifiers are rated in momentary Whats with very high distortion at one frequency. Real Watts are continuous with low distortion over the entire audio frequency range.

The circuit is at least 64 years old. Vacuum tube amplifiers used output transformers and in 1956 a little Philips amplifier used an output transformer with germanium transistors.
The output transformer steps up the output voltage swing so the amplifier can be powered from only 12V in a car, and since it is for a siren then distortion and low frequencies do not matter.

For 100 real Watts into 16 ohms then the output transformer must be 18V-24V center-tapped to 113V.
 

Thread Starter

ilker06

Joined Jun 26, 2018
34
Most cheap amplifiers are rated in momentary Whats with very high distortion at one frequency. Real Watts are continuous with low distortion over the entire audio frequency range.

The circuit is at least 64 years old. Vacuum tube amplifiers used output transformers and in 1956 a little Philips amplifier used an output transformer with germanium transistors.
The output transformer steps up the output voltage swing so the amplifier can be powered from only 12V in a car, and since it is for a siren then distortion and low frequencies do not matter.

For 100 real Watts into 16 ohms then the output transformer must be 18V-24V center-tapped to 113V.
And what about the TIP3055 instead of 2N3055 issue ?
 

Audioguru again

Joined Oct 21, 2019
1,757
The very old project has no details.
Obviously, the output transistors will produce a lot of heat, at least a total of 200W. Then the 2N3055 metal case transistors are bolted to a huge finned metal heatsink and connected to the circuit board with wires. TIP3055 transistors will overheat, especially since there is no space for the huge heatsink.
If you ever find a suitable output transformer then it will also need to be connected to the circuit board with wires.
Why not make a modern amplifier project or kit that has all the details?
 

Thread Starter

ilker06

Joined Jun 26, 2018
34
The very old project has no details.
Obviously, the output transistors will produce a lot of heat, at least a total of 200W. Then the 2N3055 metal case transistors are bolted to a huge finned metal heatsink and connected to the circuit board with wires. TIP3055 transistors will overheat, especially since there is no space for the huge heatsink.
If you ever find a suitable output transformer then it will also need to be connected to the circuit board with wires.
Why not make a modern amplifier project or kit that has all the details?
Up to now I could not have found a powerful horn amplifier which can work with 13,5 volts DC. I made the below one. Not bad and the most powerful horn amplifier I have ever made but still far away from a police car sound level. Is it impossible to find such amplifier ? beepramp_highpower.png
 
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