As I got the amp the left was maybe 3db lower than right.
I swapped 1 c4000 left to right and I maybe lost 1-2 db.
I swapped the corresponding 5000 and lost 1-2 db.
That transistor pair swap lost me 4+ db, and I took lower hfe ones out of the left and pout in higher hfe ones in.
So swapping in more hfe = lower volume ??
I'm stumped, but I also think there is somehting off in the transistors - not to mention the other parts of the amp.
Cool.
Srinath.
I swapped 1 c4000 left to right and I maybe lost 1-2 db.
I swapped the corresponding 5000 and lost 1-2 db.
That transistor pair swap lost me 4+ db, and I took lower hfe ones out of the left and pout in higher hfe ones in.
So swapping in more hfe = lower volume ??
I'm stumped, but I also think there is somehting off in the transistors - not to mention the other parts of the amp.
Cool.
Srinath.
JMFahey: This amp has nothing but a power switch. And there is 2 led's one for power and 1 for protect. No other controls.
wg_ski: It has been working for almost an hour @ 1/2 volume, set to 10 o clock, yes it may have distortion, but not overly so, the speaker distortion still is more than the amp and its not audible, so I dunno. It could have 10 x the designed distortion and I'd never know.
And I swapped the transistors back the ones I pulled from the left and put in the right - came back to the same spots they left last week ... and the difference is back to ~3 db.
Its about 10 O clock on the preamp balance where they are equal. I didn't run this pre map before on this amp at all. The pre I ran had a sliding balance and volume (yea sae MKXXX something or other) weird.
Thanks.
Srinath.
wg_ski: It has been working for almost an hour @ 1/2 volume, set to 10 o clock, yes it may have distortion, but not overly so, the speaker distortion still is more than the amp and its not audible, so I dunno. It could have 10 x the designed distortion and I'd never know.
And I swapped the transistors back the ones I pulled from the left and put in the right - came back to the same spots they left last week ... and the difference is back to ~3 db.
Its about 10 O clock on the preamp balance where they are equal. I didn't run this pre map before on this amp at all. The pre I ran had a sliding balance and volume (yea sae MKXXX something or other) weird.
Thanks.
Srinath.
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You speak about ~3 db difference, then increasing by ~1 or ~2 dB extra, but you seem to refer to an estimated audible difference.
Let's measure a little to make certain.
Please download a 1KHz standard tone fom Download Audio Tone Files , such as:
http://www.mediacollege.com/audio/tone/files/1kHz_44100Hz_16bit_30sec.mp3
Play it from an MP3 player, a computer or a smartphone.
If possible, set it to loop, so you have a continuous tone.
Most earphone outs can easily give you 100mV audio.
Make a cable with a stereo earphone plug in one end, whatever your amp uses on the other (usually a couple RCA) and play it through the amp.
Measure with any regular multimeter the audio voltage at the speaker out.
Just to make sure, repeat but inverting the RCA connectors, to check that it does not depend on any difference in the driving signals (unlikely but not impossible).
Please post both audio voltages, at channels A and B.
This way we actually measure and avoid any possible difference in the preamp.
Let's measure a little to make certain.
Please download a 1KHz standard tone fom Download Audio Tone Files , such as:
http://www.mediacollege.com/audio/tone/files/1kHz_44100Hz_16bit_30sec.mp3
Play it from an MP3 player, a computer or a smartphone.
If possible, set it to loop, so you have a continuous tone.
Most earphone outs can easily give you 100mV audio.
Make a cable with a stereo earphone plug in one end, whatever your amp uses on the other (usually a couple RCA) and play it through the amp.
Measure with any regular multimeter the audio voltage at the speaker out.
Just to make sure, repeat but inverting the RCA connectors, to check that it does not depend on any difference in the driving signals (unlikely but not impossible).
Please post both audio voltages, at channels A and B.
This way we actually measure and avoid any possible difference in the preamp.
I've run the thing off 2 different pre's. I have also flipped the RCA's so left goes to right etc.
The speaker that is connected to the left output of the amp is lower volume under all circumstances. You know when I had amotorcycle that was losing 1 cyl and I was trying to be certain if the crank pick up was at fault, I pulled its ignition advancer out and indexed it 180 degrees out and put it back in, and it promptly lost the other cyl.
I am pretty certain its 3 db down as it stands, and I have another pair of transistors to flip side to side - and see if that makes a difference.
Then I have to get into more complicated experiments - including borrowing/buying an oscilloscope.
Cool.
Srinath.
The speaker that is connected to the left output of the amp is lower volume under all circumstances. You know when I had amotorcycle that was losing 1 cyl and I was trying to be certain if the crank pick up was at fault, I pulled its ignition advancer out and indexed it 180 degrees out and put it back in, and it promptly lost the other cyl.
I am pretty certain its 3 db down as it stands, and I have another pair of transistors to flip side to side - and see if that makes a difference.
Then I have to get into more complicated experiments - including borrowing/buying an oscilloscope.
Cool.
Srinath.
Please MEASURE .
I gave you a very simple way to do it.
All you need is a $10 MP3 player and a $10 multimeter.
Thanks.
I gave you a very simple way to do it.
All you need is a $10 MP3 player and a $10 multimeter.
Thanks.
I know, but I dont have an Mp3 player, I dont even have a CD burner. I'd have to get a test tone CD from someone and play it.
Yes I am that technology retarded.
My wife had a player - but its dead now.
I have a smart-ish phone - but not the micro sized cable it needs - and I guess I have to graft RCA's to the other side of that cable.
I'll get on it, but for now, its easier for me to swap the front most on the right transistor with the same on the left and play it - hear the difference, and repeat with the rear most. That's all that's left. But maybe I'll do a cable run today, I am going to a few places to buy stuff today after work.
Thanks.
Srinath.
Yes I am that technology retarded.
My wife had a player - but its dead now.
I have a smart-ish phone - but not the micro sized cable it needs - and I guess I have to graft RCA's to the other side of that cable.
I'll get on it, but for now, its easier for me to swap the front most on the right transistor with the same on the left and play it - hear the difference, and repeat with the rear most. That's all that's left. But maybe I'll do a cable run today, I am going to a few places to buy stuff today after work.
Thanks.
Srinath.
OK I am done with the experimental swapping left to right.
The front one was swapped (5000) and it seemed to make the 3 db difference sound like 2 db to my ear.
I swapped the rear one and it went right back to 3 db. I'll swap the rear one back and check.
I have a couple questions now.
With all the swaps and even before that - there is a smear of the heat sink compound in the pin holes for the legs of the transistor.
How do we get that out, and does it matter ?
Thanks.
Srinath.
The front one was swapped (5000) and it seemed to make the 3 db difference sound like 2 db to my ear.
I swapped the rear one and it went right back to 3 db. I'll swap the rear one back and check.
I have a couple questions now.
With all the swaps and even before that - there is a smear of the heat sink compound in the pin holes for the legs of the transistor.
How do we get that out, and does it matter ?
Thanks.
Srinath.
You are wasting time (yours and ours) , don't search for more excuses not to measure.
I'm quite sure the computer or notebook you are writing these questions on has a soundboard and earphone out.
You can get a couple dead headphones, pull the transducers and solder a couple RCA .
Media Player will happily play any MP3 ... or if you wish download the WAV version of the tones, from the site I linked.
No need to burn any CD .
I'm quite sure the computer or notebook you are writing these questions on has a soundboard and earphone out.
You can get a couple dead headphones, pull the transducers and solder a couple RCA .
Media Player will happily play any MP3 ... or if you wish download the WAV version of the tones, from the site I linked.
No need to burn any CD .
Srin.
measure the amp and post the results.
You have been asked repeatedly to measure. You are losing any support that could be available.
measure the amp and post the results.
You have been asked repeatedly to measure. You are losing any support that could be available.
I'll do that next step, thanks so much guys.
I had to finish the transistor swap you understand. I started it, so I had to finish it.
Atleast now I know what made it go to 6 db down, so if the voltages dont look that far off left to right, then I can measure it with the things swapped up just to see if it is wider.
Cool.
Srinath.
I had to finish the transistor swap you understand. I started it, so I had to finish it.
Atleast now I know what made it go to 6 db down, so if the voltages dont look that far off left to right, then I can measure it with the things swapped up just to see if it is wider.
Cool.
Srinath.
OK I did this test, it was a lot easier than I thought, once I got hold of the right cable (LOL), but it also told me somehting less than I was hoping ... but it may be somehting you guys can decipher better than me.
So, I ran 100 hz, 250 hz, 440 hz, and 1khz and checked AC voltage @ the output.
In all cases I read .2v AC on the right output and 0 v on the left
My meter may not be precise enough to catch a lower voltage if it made less than .1v on the left.
I should try it with an oscilloscope which I have to buy shortly I think.
Thanks.
Srinath.
So, I ran 100 hz, 250 hz, 440 hz, and 1khz and checked AC voltage @ the output.
In all cases I read .2v AC on the right output and 0 v on the left
My meter may not be precise enough to catch a lower voltage if it made less than .1v on the left.
I should try it with an oscilloscope which I have to buy shortly I think.
Thanks.
Srinath.
Something is wrong. There is no way this only makes .2v at the output.
I ran the tone through the amp and pre amp. so yes its sending it out both channels - I can hear it and I will check to be sure, but I think the low freq is closer left to right, but by 440 hz, I can hear the difference, and 1k definitely so.
Cool.
Srinath.
I ran the tone through the amp and pre amp. so yes its sending it out both channels - I can hear it and I will check to be sure, but I think the low freq is closer left to right, but by 440 hz, I can hear the difference, and 1k definitely so.
Cool.
Srinath.
OK I tested it again (sadly I dont have a better multimeter). OK The best results I got were with 440 hz, oe 250 hz. 1K was not producing as much chnaging results.
Left channel reads 0 but it sometimes reads -0 and then 0 ... as in its moving around but not enough to register a reading.
Right channel reads .1 and .2 and keeps flipping between them.
Maybe I should measure it with speakers attached and playing the tone.
Thanks.
Srinath.
Left channel reads 0 but it sometimes reads -0 and then 0 ... as in its moving around but not enough to register a reading.
Right channel reads .1 and .2 and keeps flipping between them.
Maybe I should measure it with speakers attached and playing the tone.
Thanks.
Srinath.
you need a DMM with AC voltage scales of 600Vac, 200.0Vac, 20.00Vac, 2.000Vac and crucially 200.0mVac.
This should also have DC scales from 1000Vdc all the way down to 200.0mVdc
You don't need any other scales, so don't pay a lot for extra facilities.
A 200.0mVac DMM can be had for <$10 with a decent accuracy on it's 2.000Vdc of around +-0.5% +-2digits, or better. Other scales and particularly AC will be less accurate.
With this you can measure input signal of 10mVac to 1Vac and the respective output signal ranging from 100mVac to 30Vac with sufficient accuracy to determine the overall gain of the power amplifier. This particular measurement, input signal for a fixed output signal, is the amplifier sensitivity. It is usually given for a 1W output, or for maximum specified power output.
Amplifier gain is slightly different. It is the output signal divided by the input signal after passing through any filters and/or attenuators.
This should also have DC scales from 1000Vdc all the way down to 200.0mVdc
You don't need any other scales, so don't pay a lot for extra facilities.
A 200.0mVac DMM can be had for <$10 with a decent accuracy on it's 2.000Vdc of around +-0.5% +-2digits, or better. Other scales and particularly AC will be less accurate.
With this you can measure input signal of 10mVac to 1Vac and the respective output signal ranging from 100mVac to 30Vac with sufficient accuracy to determine the overall gain of the power amplifier. This particular measurement, input signal for a fixed output signal, is the amplifier sensitivity. It is usually given for a 1W output, or for maximum specified power output.
Amplifier gain is slightly different. It is the output signal divided by the input signal after passing through any filters and/or attenuators.
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1) what you post is impossible
Do you know how to use a multimeter?
2) I told you to go straight into the power amp, not through the preamp.
3) your MP3 player, soundboard in a PC, any audio source, will give you typically 200mV AC at the headphone out, definitely not less than 100mV AC.
Since typical gain in 99% of power amps is around 20X , you must at least have 0.2V * 20= 4V RMS at the speaker terminals.
No way you can have 0V , .1V or .2V nor will it have a + or - polarity sign which means you are in a DC scale.
Audio is AC . 😀
4) make it easy, use just 440Hz or 1kHz and stick to it .
Later we can test at other frequencies .
5) AndrewT is suggesting you a better multimeter, try to get one if someday you decide to mess with your amplifier innards.
Oh!! You already doing that? 😱
Then RUN to the shop to get one 😉
That said, even the cheapest 2-AC-scales-only multimeters, those with just 200 and 600/750VAC scales can measure 4 VAC 😱
Maybe not with great precision, a few % error, but anyway we are comparing channels here so it does not matter much.
OK, go, test and post results.
It seems like you are measuring DC at the speaker outputs, not AC
Do you know how to use a multimeter?
2) I told you to go straight into the power amp, not through the preamp.
3) your MP3 player, soundboard in a PC, any audio source, will give you typically 200mV AC at the headphone out, definitely not less than 100mV AC.
Since typical gain in 99% of power amps is around 20X , you must at least have 0.2V * 20= 4V RMS at the speaker terminals.
No way you can have 0V , .1V or .2V nor will it have a + or - polarity sign which means you are in a DC scale.
Audio is AC . 😀
4) make it easy, use just 440Hz or 1kHz and stick to it .
Later we can test at other frequencies .
5) AndrewT is suggesting you a better multimeter, try to get one if someday you decide to mess with your amplifier innards.
Oh!! You already doing that? 😱
Then RUN to the shop to get one 😉
That said, even the cheapest 2-AC-scales-only multimeters, those with just 200 and 600/750VAC scales can measure 4 VAC 😱
Maybe not with great precision, a few % error, but anyway we are comparing channels here so it does not matter much.
OK, go, test and post results.
I was measuring AC. But I have a cheap meter.
I didn't go through the preamp to measure it - I only used the preamp to make sure I was getting sound out both channels of the phone. I didn't know how loud it would be so I ran it via pre amp but I had to have the preamp @ full volume so I basically ran it straight after that.
I suspect the amp isn't turning on when it senses the output is open. Its a weird amp that way, but I was reading .2 v AC on the right channel, and 0v ac in the left channel.
Thanks guys.
Srinath.
I didn't go through the preamp to measure it - I only used the preamp to make sure I was getting sound out both channels of the phone. I didn't know how loud it would be so I ran it via pre amp but I had to have the preamp @ full volume so I basically ran it straight after that.
I suspect the amp isn't turning on when it senses the output is open. Its a weird amp that way, but I was reading .2 v AC on the right channel, and 0v ac in the left channel.
Thanks guys.
Srinath.
It is not got protect mode in the traditional sense of amps.
It has a triac and it fires the thing fully into its cycle when it senses the loads and there is no excessive draws.
I'll get pics of my test and post it.
Thanks.
Srinath.
It has a triac and it fires the thing fully into its cycle when it senses the loads and there is no excessive draws.
I'll get pics of my test and post it.
Thanks.
Srinath.
I understand the protect modes and it has enough of them that it will shut down the power supply if you stare at too long and your tongue isn't hangin' right. Are all of your DC voltages correct? No DC offset on the output? Basically right now you have very, very little output and since this amp doesn't have speaker relays that may be all you get if it's in one of it's protect modes. Are both channels silent or almost silent?
Craig
Craig
It works nearly fine when connected to speakers, but left channel is about 3 db lower than the right.
I try to measure the AC voltage when playing 440hz tone and I get .2v in the louder channel and 0 v in the weaker one.
I get good 440 hz in speakers with left being lower than right with the same test tone played.
DC offsets are nearly 0 (un measurable with the lousy DMM I have).
Thanks.
Srinath.
I try to measure the AC voltage when playing 440hz tone and I get .2v in the louder channel and 0 v in the weaker one.
I get good 440 hz in speakers with left being lower than right with the same test tone played.
DC offsets are nearly 0 (un measurable with the lousy DMM I have).
Thanks.
Srinath.
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