Came across a Triad Thunder plate subwoofer amp. Contacted the company to try to get specs but they said they don't have them anymore for that model (built in 1994) but did know it was sold with two different subs, one was 125 watts @ 8 ohms, the other 250 watts @ 8 ohms but they couldn't identify which I had. Not even from the circuit board identification.

Silliness aside from not being able to identify your own product regardless when it was made, I see it has two pairs of @sc3281/2sa1302 in it (2 of each type). Specs sheets online show these could produce 150W. Given there are two pairs, and this has a mono output, is it likely this is the 250watt version?

 

Hi,
What actually you need to know for that given spec of pnp and npn transistors.
Does your circuit not working like no sounds output.
What idea should you want to know more about your amplifiers.

 

Sounds logical to use two pairs in parallel to boost the output wattage.

 

A 250W into 8 Ohm amp will require power supplies of about 68V, a 125W one 48V. If you can measure the rails, or if rhey are marked on the board, you should be able to dustiguish them.

Bob

 

It works fine. I'm just trying to determine if this is the 125w version or the 250 watt version since the manufacturer can't tell me that. So, Dodgydave, are you of the opinion this is more likely the 250w version?

 

A 250W into 8 Ohm amp will require power supplies of about 68V, a 125W one 48V. If you can measure the rails, or if rhey are marked on the board, you should be able to dustiguish them.

Bob

At the moment I have a filter cap out waiting on replacement but will do that when it comes in.Thanks!

 

Did you know that the loudness difference between 125W and 250W is only 3dB which is a small difference that might not be noticeable? Ten times the power sounds twice as loud since the sensitivity of our hearing is logarithmic.

 

Did you know that the loudness difference between 125W and 250W is only 3dB which is a small difference that might not be noticeable? Ten times the power sounds twice as loud since the sensitivity of our hearing is logarithmic.

Yep fully aware. Believe me, I've tried to educate many people on that fact. This is more about being able to advertise it accurately. I don't want to over spec it (or under).

 

At the moment I have a filter cap out waiting on replacement but will do that when it comes in.Thanks!

A 250W into 8 Ohm amp will require power supplies of about 68V, a 125W one 48V. If you can measure the rails, or if rhey are marked on the board, you should be able to dustiguish them.

Bob

Which reminds me - The filters caps are rated 63v, so if 68v is the expected nominal voltage for a 250 watt amp, then this couldn't be a 250watt amp and would have to be less.
So assuming for a second it really is a 125watt - why would there be two pairs of those transistors present?

 

Many amplifiers that are advertised to produce 125W actually produce 25W maximum.
The 25W is before clipping. If the amplifier is clipping like mad with 10% distortion then the power might be 50W. The peak power of 50W is 71W. If it can produce 71W peaks continuously then it might produce 125W for only a moment before the power supply voltage sags.

I think a second pair of Oriental transistors costs less than a good big heatsink.

 

Many amplifiers that are advertised to produce 125W actually produce 25W maximum.
The 25W is before clipping. If the amplifier is clipping like mad with 10% distortion then the power might be 50W. The peak power of 50W is 71W. If it can produce 71W peaks continuously then it might produce 125W for only a moment before the power supply voltage sags.

I think a second pair of Oriental transistors costs less than a good big heatsink.

It already has a MASSIVE heatsink on it.

 

"It already has a MASSIVE heatsink on it."
The datasheet for the transistors say that they can dissipate 150W each IF the case is held at 25 degrees C (with liquid nitrogen or something very cold). With your massive heatsink and in an air conditioned room then maybe each transistor chip will be at its maximum allowed temperature at 100W? But cooler at 50W then it will last longer.