While playing music for five minutes in a high volume (3 out of 10 in this amp face plate is pretty loud), i place my hand on the big alluminum cooling unit, which the transistors are screwed to and the unit is
very hot to the touch (while the amp cover is open).
I can't really measure the temprature but it's very hot to the touch.
Is that normal? does it need to be only a bit warm?
very hot to the touch (while the amp cover is open).
I can't really measure the temprature but it's very hot to the touch.
Is that normal? does it need to be only a bit warm?
Your information needs to be more precise for an answer to your question. What amplifier? How much power? What temperature? Does it get hot with volume at zero?
With a typical class B amplifier at, say, 50% efficiency, it would dissipate one Watt for every Watt of power output. A little more than that, actually.
With a typical class B amplifier at, say, 50% efficiency, it would dissipate one Watt for every Watt of power output. A little more than that, actually.
Well, if it works for 5 minutes, it's probably normal. It could be somebody has fiddled with the internals though, turned up the bias current. That could result in it getting hot but still working. The only way to be sure is to show it to somebody expert enough to know.
w
It's a Pioneer SA-7300 amplifier 37 watts per channel.
What does class B mean?
I didn't try it with the volume at zero.
Hi,
the speakers may be part of the problem.
4 to 8ohms speakers are usually a 2way with a crossover connecting the amp to the two drivers.
The bass/mid driver is usually a 4ohm unit and the treble is usually an 8ohm unit.
Most of the average power going to the 4 to 8ohm speaker actually goes to the 4ohm bass/mid unit.
The amp thinks it is driving a 4ohm load.
Is the amp specified for reactive 4ohm speakers?
I suspect there is another problem inside the amplifier. Get it checked/sorted before you damage it or your speakers.
the speakers may be part of the problem.
4 to 8ohms speakers are usually a 2way with a crossover connecting the amp to the two drivers.
The bass/mid driver is usually a 4ohm unit and the treble is usually an 8ohm unit.
Most of the average power going to the 4 to 8ohm speaker actually goes to the 4ohm bass/mid unit.
The amp thinks it is driving a 4ohm load.
Is the amp specified for reactive 4ohm speakers?
I suspect there is another problem inside the amplifier. Get it checked/sorted before you damage it or your speakers.
You don't sound technically minded but just try measuring the DC voltage at the speaker terminals with NO music and ZERO volume. If its not ZERO (or VERY close to ZERO), the amplifier has a problem.
Also, if you've got access to a multimeter, also try disconnecting the speakers and measure their DC resistance. It should lie somewhere in the 2 - 60 Ohm range. This may not be valid with speakers with crap crossovers in them.
Another quick check to see if the speakers are the problem is to run the amplifier with no speakers. DO NOT do this with a valve amplifier.
Also, if you've got access to a multimeter, also try disconnecting the speakers and measure their DC resistance. It should lie somewhere in the 2 - 60 Ohm range. This may not be valid with speakers with crap crossovers in them.
Another quick check to see if the speakers are the problem is to run the amplifier with no speakers. DO NOT do this with a valve amplifier.
Just because the volume control is at "3 out of 10" doesn't mean that the amp isn't putting out full power. The position of the volume control isn't an indication of the relative output power.
I am not, i don't need to own a multimeter if i don't know how to explain
what it reads.
im not dealing with electronics much, i came to this forum at first for
asking about a replacement cap brand for my amp, i didn't know i needed
a multimeter to ask a few questions.
You don't need a multimeter to ask a few questions.
The meter would make it easier to provide you with some answers.
As a pure guess, I'd say that the amplifier is putting out as much power as it can.
Turn the amp on with the volume all the way down. Let it run that way for 10 minutes or so and see if the heat sink is getting hot. If the heat sink is hot, the transistors are probably drawing too much idling current. The bias is set too high.
If the heat sinks remain cool, that would indicate that you've been pushing the amp pretty hard ... perhaps to full power or beyond.
Hope this helps.
The meter would make it easier to provide you with some answers.
As a pure guess, I'd say that the amplifier is putting out as much power as it can.
Turn the amp on with the volume all the way down. Let it run that way for 10 minutes or so and see if the heat sink is getting hot. If the heat sink is hot, the transistors are probably drawing too much idling current. The bias is set too high.
If the heat sinks remain cool, that would indicate that you've been pushing the amp pretty hard ... perhaps to full power or beyond.
Hope this helps.
A new Member that appears to have almost no access to resources for DIYaudio projects raises alarm bells for me.
A multimeter is probably the most basic instrument a DIYer needs to start his hobby. Without it you will always be asking yourself questions and have no resource that is capable of giving you the answers.
If you have a problem and ask the Forum a question, you usually need to give us information to work with.
Voltages are a very indicative bit of that data.
Ask all the questions you like, both of yourself and of the Forum. But, without an interchange of information, do not expect useful answers.
edit
I have decided to go further:
If you are not prepared to invest time in learning which resources you need and learn how to use them and buy/borrow them, then I consider you are definitely in the wrong Forum.
Last edited:
OK. Lets lose the teeth into this guy.
The SA 7300 was specified as 35W into 8 Ohms which in general terms will give you about 17W into 15 Ohms.
Although not a huge amount of power this will, with efficient speakers, produce a modicom of volume.
Class A, Class A/B and Class B amplifiers are the norm. in the Hi-Fi world with Class D and onwards creeping into the specialist market.
How can I explain this to a non-technobrat. ????
Think of a common garden tap, of the water variety.
In Class A, the tap will always be ON, always dripping water. It must drip sufficient water to provide the amount of water required at full output (volume). This could be quite a significant flow of water, most of which will be wasted.
In amplifier terms, a Class A amplifier is always ON and drawing power, most of which is wasted, in this case as HEAT.
In real terms, this is unacceptable as the costs of getting rid of the heat far outweigh the commercial benefits of Class A.
Class B is the more common solution. Here we use two taps, one to provide the +ve side of the signal and the other to provide the -ve side. CONFUSED. If there is NO input oe output signal the taps are both, to all intents and purposes OFF so no water is wasted. In the amplifier world, no electricty or HEAT is wasted so it runs much cooler.
Class A/B is a mixture of the two and is the generally accepted "best of both worlds".
When commercial amplifiers are built they are constructed using the most economical components available which are generally less than perfect. This results in afinal design that needs some factory adjustment to work as designed.
The manufacturer will adjust the amplifier to work within certain design criteria, one of which will be heat dissipation.
Within limits there are sonic advantages to altering the "bias" of the amplifier from Class B towards Class A but care must be taken to ensure that all the components stay within their Safe Operating Area (SOA).
Many forums will give advice on how to play with this biassing. It is possible that someone has tried to adjust your amplifier or it may simply be a case that one or more components is failing and the amplifier requires attention.
As EVERYONE is saying. TAKE IT TO A COMPETENT ENGINEER. At this moment in time it appears that there is no REALLY EXPENSIVE damage, but operating the amplifier in this condition could cause it to fail catastrophically and could even take out your speakers at the same time.
The SA 7300 was specified as 35W into 8 Ohms which in general terms will give you about 17W into 15 Ohms.
Although not a huge amount of power this will, with efficient speakers, produce a modicom of volume.
Class A, Class A/B and Class B amplifiers are the norm. in the Hi-Fi world with Class D and onwards creeping into the specialist market.
How can I explain this to a non-technobrat. ????
Think of a common garden tap, of the water variety.
In Class A, the tap will always be ON, always dripping water. It must drip sufficient water to provide the amount of water required at full output (volume). This could be quite a significant flow of water, most of which will be wasted.
In amplifier terms, a Class A amplifier is always ON and drawing power, most of which is wasted, in this case as HEAT.
In real terms, this is unacceptable as the costs of getting rid of the heat far outweigh the commercial benefits of Class A.
Class B is the more common solution. Here we use two taps, one to provide the +ve side of the signal and the other to provide the -ve side. CONFUSED. If there is NO input oe output signal the taps are both, to all intents and purposes OFF so no water is wasted. In the amplifier world, no electricty or HEAT is wasted so it runs much cooler.
Class A/B is a mixture of the two and is the generally accepted "best of both worlds".
When commercial amplifiers are built they are constructed using the most economical components available which are generally less than perfect. This results in afinal design that needs some factory adjustment to work as designed.
The manufacturer will adjust the amplifier to work within certain design criteria, one of which will be heat dissipation.
Within limits there are sonic advantages to altering the "bias" of the amplifier from Class B towards Class A but care must be taken to ensure that all the components stay within their Safe Operating Area (SOA).
Many forums will give advice on how to play with this biassing. It is possible that someone has tried to adjust your amplifier or it may simply be a case that one or more components is failing and the amplifier requires attention.
As EVERYONE is saying. TAKE IT TO A COMPETENT ENGINEER. At this moment in time it appears that there is no REALLY EXPENSIVE damage, but operating the amplifier in this condition could cause it to fail catastrophically and could even take out your speakers at the same time.
The things you say are true, but i don't think your attitude is right.
You could have just recommend me getting or borrowing a multimeter
and thats it.
Hmmm... let's try to keep it friendly... the original question was "is it too hot" so let's see what we can determine.
rg12 Did you try as in post #6... does the amp cool back down naturally when you turn the volume back down ?
Check these,
1. With no speakers connected the amp should run cool.
2. With speakers connected the amp should still remain cool as long as no music playing.
3. When the amp plays music and is hot when the music is stopped then the amp should cool off... may take longer than you think.
4. It's unlikely if it were faulty, that both channels would be duff, so try it using just one channel and see as well.
And how hot is it... if you can hold a finger on the metal or the transistors for 5 seconds or so then it's OK. If it sizzles then it's too hot.
rg12 Did you try as in post #6... does the amp cool back down naturally when you turn the volume back down ?
Check these,
1. With no speakers connected the amp should run cool.
2. With speakers connected the amp should still remain cool as long as no music playing.
3. When the amp plays music and is hot when the music is stopped then the amp should cool off... may take longer than you think.
4. It's unlikely if it were faulty, that both channels would be duff, so try it using just one channel and see as well.
And how hot is it... if you can hold a finger on the metal or the transistors for 5 seconds or so then it's OK. If it sizzles then it's too hot.
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