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Author Topic: Sudden loss of volume in my power amp  (Read 1714 times)

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Armaegis

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Re: Sudden loss of volume in my power amp
« Reply #10 on: February 27, 2015, 05:48:11 AM »

I agree with the rest, one tends first of all  rather thinks of some simple cause for this. You have not forgotten to turn the power amp on?

This one time I was scratching my head trying to figure out what was wrong with my amp because all I was getting was a faint distortion when I turned my dac all the way up. Checked the wiring, the interconnects, power switches, power bar, etc, it all looked good. I tested the dac separately and that was fine... it took me half an hour before I realized that the power cords were plugged into the bar but the IEC ends weren't connected to the amps.  ::)
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kothganesh

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Re: Sudden loss of volume in my power amp
« Reply #11 on: February 27, 2015, 09:55:05 AM »

I agree with the rest, one tends first of all  rather thinks of some simple cause for this. You have not forgotten to turn the power amp on? Well that may be too simple. But turn it off, have a good sleep (or go to work or smth) and have fresh look at it the next day.


That is hilarious. Trust me on this one. All power cords in and working. I just found out from my cousin who was fiddling around with the adapter box when I had left the room. He decided the connections were loose and reconnected them except he reversed the connections, i.e. L to R and R to L (freakin retard). He heard music from only one side and panicked. That's where my travails begin. So now I truly don't know.
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uncola

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Re: Sudden loss of volume in my power amp
« Reply #12 on: February 27, 2015, 11:18:14 AM »

I think you bias the amp to adjust for dc offset depending on your incoming wall voltage or uh.. how out of spec the components get as they age?  I could be totally off but I do remember that klaus' amps all allow for bias adjustment.  I think it only causes distortion or speaker driver damage though.. not low output

there's a test spot inside the amp you touch with your multimeter and a little potentiometer you adjust with a screw to set it.. I guess you want it to read 0mV?  not sure :P

here's a cool video showing vacuum tube bias adjustment


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Ringingears

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Re: Sudden loss of volume in my power amp
« Reply #13 on: February 27, 2015, 12:18:33 PM »

This one time I was scratching my head trying to figure out what was wrong with my amp because all I was getting was a faint distortion when I turned my dac all the way up. Checked the wiring, the interconnects, power switches, power bar, etc, it all looked good. I tested the dac separately and that was fine... it took me half an hour before I realized that the power cords were plugged into the bar but the IEC ends weren't connected to the amps.  ::)

I did almost the same thing, but found that one of my cats had helped me by turning off the power bar. I even went outside to check my circuit breakers!!  :)p8  :spank:
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RexAeterna

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Re: Sudden loss of volume in my power amp
« Reply #14 on: February 27, 2015, 12:44:34 PM »

I cannot fathom how an amp would suddenly lose 1/2 its output and still be otherwise normal. My first thought was that it was a balanced amp and the adapter box shorted the negative channel and took it out - balanced amp only driving a positive leg = 1/2 power.  But the amp is single ended , the balanced inputs are shorted at the input to single ended , so connectors are merely there for convenience but no benefit driving this amp from a balanced source.

It might be a good test to remove the amp out of the normal rig and test it independently but I agree with most of the considerations that this is some sort of digital volume limiting issue. 

..dB

Same. I been thinking for like a good half a day from time to time trying to figure that out. First time I ever experienced an issue like this was that I was not paying attention and used rca to trs adapters to my crown amp and was trying to figure out what I did. Checked dc and bias abd everything was super but later on I realized I was using trs intead of ts adapters. After simple switch everything came back to life. That was one of my big idiot moments besides me forgetting to hook up a pair of cables from preout to power amp.

Koshganesh, I really don't know what else say. Only other way an amp would lost output is something wrong inside but it just going like that for no reason and not being pushed hard is unusual. Can check fuses if amp uses fuses as a protection method. Fuses being blown from some unknown surge can cause an amp to act up if it didn't take out the ouputs already.
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chetlanin

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Re: Sudden loss of volume in my power amp
« Reply #15 on: February 27, 2015, 02:12:37 PM »

That is hilarious. Trust me on this one. All power cords in and working. I just found out from my cousin who was fiddling around with the adapter box when I had left the room. He decided the connections were loose and reconnected them except he reversed the connections, i.e. L to R and R to L (freakin retard). He heard music from only one side and panicked. That's where my travails begin. So now I truly don't know.

So it has been seriously wrongly connected? Than changes everything. The amp seems to have:

4 internal fuses 250V/6.3A, 5x20mm, fast blow
Additional electrical protection fuse

Check the fuses first of all. (and turn off amp to re-set electrical fuses, who knows how they are working)

If some output devices are blown, try to get replacement from from the manufacturer (of either amp or transistors), the world is full of fakes.

Wish you best of luck.
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kothganesh

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Re: Sudden loss of volume in my power amp
« Reply #16 on: February 27, 2015, 04:46:40 PM »

So it has been seriously wrongly connected? Than changes everything. The amp seems to have:

4 internal fuses 250V/6.3A, 5x20mm, fast blow
Additional electrical protection fuse

Check the fuses first of all. (and turn off amp to re-set electrical fuses, who knows how they are working)

If some output devices are blown, try to get replacement from from the manufacturer (of either amp or transistors), the world is full of fakes.

Wish you best of luck.

Thanks. It makes intuitive sense. A friend of mine who repairs amps is going to take a look at it over the weekend hopefully.
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dBel84

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Re: Sudden loss of volume in my power amp
« Reply #17 on: February 27, 2015, 09:35:59 PM »

I just found out from my cousin who was fiddling around with the adapter box when I had left the room. He decided the connections were loose and reconnected them except he reversed the connections, i.e. L to R and R to L (freakin retard). He heard music from only one side and panicked.

This means the amps outputs were shorted to ground and who knows what craziness ensued. Most likely nothing horrendous as it still plays and you are not hearing masses of distortion. My guess would be the one of the bias resistors overheated and has changed its value as a result. This will impact the output devices. Possible that the driver circuitry was affected too but this would take a careful going over. You are doing the best thing and that is to take it to someone who understands audio circuits and is capable of doing some troubleshooting.

best of luck ..dB


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Thad E Ginathom

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Re: Sudden loss of volume in my power amp
« Reply #18 on: February 28, 2015, 07:34:21 AM »

Maybe time to visit Mr Sayeed?

Hoping for better news of your amp next week.
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kothganesh

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Re: Sudden loss of volume in my power amp
« Reply #19 on: February 28, 2015, 08:48:59 AM »

He's the one that helps me....:).
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