I'm not sure, a video showing what exactly 🙂
What we really need is some means of accurately seeing the lack of low frequency to get a real idea what we are looking at. This takes far longer to read than to do 🙂
I'm attaching another MP3 file which concentrates on low frequencies much more. It goes from 10Hz to just 400Hz this time over 4 minutes. This means the frequency changes very slowly.
Lets try a totally different approach to measure this. A lot depends on your meter and how good it is 😉 but we can give it a try. What we are going to do is measure the AC voltage of the signal. We have two options to do this and which one works best 100% depends on your meter sensitivity. Easy method first.
1/ Set the meter to AC voltage and select the highest sensitivity range (to measure low AC voltages)
2/ Play the file on the good player and from around 2 minutes into the track note the voltage reading. You are measuring across one of the RCA outputs.
This is where it is meter dependent. If the meter can not resolve low AC voltage and just show a 0 or 1 volt then this method will not work. What you should see is a constant reading from just a few seconds into the track all the way to the end.
If the meter is not up to that then you can connect the meter across one of the speaker terminals and play the file through your amp. I suspect this will be the way you have to do it unless your meter is really well specified.
Start at low volume and play the track from a couple of minutes in so the frequency is high enough to hear. Set the volume to give say 4.00 volts on your meter. That will sound really really loud but is only 2 watts rms into 8 ohms. If its unbearably loud then you can disconnect the speakers and just measure the voltage on the open wires. Do not short them with the amp on.
With the good player the reading should be very constant from a few seconds in to the end of the track. That is our baseline.
Now play the Cambridge and readjust the volume as above to give 4 volts from around 2 minutes in.
Now compare and see if the voltage reading is low from the start of the track.
Assuming it is you can then make a quick table comparing both players. For the good player read the voltage every 10 seconds and write it down.
So you should see something like this typically:
10 sec 3.7 volt
20sec 3.9 volt
30 sec 4.0 volt
40 sec 4.0 volt
50 sec 4.0 volt
and so on all the way to 240 seconds.
Now do the same for the Cambridge. Always remember to set the initial 4 volts around 2 minutes and later into the track.
If the bass is down you might see:
10sec 0.7 volt
20 sec 0.9 volt
30 sec 1.1 volt
40 sec 2.6 volt
50 sec 3.5 volt
And so on.
What we really need is some means of accurately seeing the lack of low frequency to get a real idea what we are looking at. This takes far longer to read than to do 🙂
I'm attaching another MP3 file which concentrates on low frequencies much more. It goes from 10Hz to just 400Hz this time over 4 minutes. This means the frequency changes very slowly.
Lets try a totally different approach to measure this. A lot depends on your meter and how good it is 😉 but we can give it a try. What we are going to do is measure the AC voltage of the signal. We have two options to do this and which one works best 100% depends on your meter sensitivity. Easy method first.
1/ Set the meter to AC voltage and select the highest sensitivity range (to measure low AC voltages)
2/ Play the file on the good player and from around 2 minutes into the track note the voltage reading. You are measuring across one of the RCA outputs.
This is where it is meter dependent. If the meter can not resolve low AC voltage and just show a 0 or 1 volt then this method will not work. What you should see is a constant reading from just a few seconds into the track all the way to the end.
If the meter is not up to that then you can connect the meter across one of the speaker terminals and play the file through your amp. I suspect this will be the way you have to do it unless your meter is really well specified.
Start at low volume and play the track from a couple of minutes in so the frequency is high enough to hear. Set the volume to give say 4.00 volts on your meter. That will sound really really loud but is only 2 watts rms into 8 ohms. If its unbearably loud then you can disconnect the speakers and just measure the voltage on the open wires. Do not short them with the amp on.
With the good player the reading should be very constant from a few seconds in to the end of the track. That is our baseline.
Now play the Cambridge and readjust the volume as above to give 4 volts from around 2 minutes in.
Now compare and see if the voltage reading is low from the start of the track.
Assuming it is you can then make a quick table comparing both players. For the good player read the voltage every 10 seconds and write it down.
So you should see something like this typically:
10 sec 3.7 volt
20sec 3.9 volt
30 sec 4.0 volt
40 sec 4.0 volt
50 sec 4.0 volt
and so on all the way to 240 seconds.
Now do the same for the Cambridge. Always remember to set the initial 4 volts around 2 minutes and later into the track.
If the bass is down you might see:
10sec 0.7 volt
20 sec 0.9 volt
30 sec 1.1 volt
40 sec 2.6 volt
50 sec 3.5 volt
And so on.
I just thought that as the video would have sound that it might work. I will read the above and get on it later. Thanks.
Use what you have. A suitable CD playing through the machine that has a fairly consistent bass presence, out through the outputs, using what you have to test the outputs, separate Dac, pre and so on, use your hifi to hear and 'eliminate' potential faults as you go along.
This way you are confirming the fault in its operating condition as it would be under normal listening conditions. Working through post 68, would take a few hours. If you get to the end of that without the fault identified, you have confirmed (point by point) WHAT IT IS NOT, narrowing the search.
Mooly may be interested to help further. The fault you describe sounds as though it's likely to be simple, locating it, another matter!
For many faults its a myth you need all the test gear, a good multi meter and the procedure mentioned, post 68.
If this is beyond your practical abilities and you don't feel confident that you can acquire these, it may be a better idea to play around with something less challenging and gain valuable experience of the do's and donts of electronics, with a handful of minor repairs/ projects. Shelve the Cd player and come back to it in a few months?
This way you are confirming the fault in its operating condition as it would be under normal listening conditions. Working through post 68, would take a few hours. If you get to the end of that without the fault identified, you have confirmed (point by point) WHAT IT IS NOT, narrowing the search.
Mooly may be interested to help further. The fault you describe sounds as though it's likely to be simple, locating it, another matter!
For many faults its a myth you need all the test gear, a good multi meter and the procedure mentioned, post 68.
If this is beyond your practical abilities and you don't feel confident that you can acquire these, it may be a better idea to play around with something less challenging and gain valuable experience of the do's and donts of electronics, with a handful of minor repairs/ projects. Shelve the Cd player and come back to it in a few months?
Just to let you know that I have been in and out a lot more than I usually am as my wife is celebrating another signifcant birthday shortly, so I will be doing what has been suggested but just more slowly 😉
This afternoon I cleaned up the mess on the XLRs and corrected the incorrect R channel wiring on the the board. Is it agreed that the correct orientation of the sockets are Pin1 Grd, Pin 2 Pos and pin 3 Neg? I also Apologise for having originaly suggested that the machine had not been tampered with.....😳
If it's true that an image is worth more than a thousand words, I would try with the following one where perhaps to use related colors further reduces the risk of errors. IMO
If you carefully look at the pics above you notice that the blue wires are incorrectly welded on the central pin where the red ones should instead go.
I have not re-wired the XLRs I removed the wires as Mooly asked to Scope certain points. I have asked for confirmation of the correct pins for each wire.
I never said you did it.
The pics caption is obviously short for reasons of opportunities or instead of "your wiring" I would have had to write: "The wiring of your current connectors that has been wrongly welded not by you?". 🙄
OK. Just make sure the centre feed to each is from the same opamp output on each board.
Look at the circuit. The upper opamp of the pair should be the signal feed to the RCA. If one channel used the feed from the lower opamp it would be out of phase.
So it is the feed from pin 1 (through that 100R series resistor) that is the correct one to use for both channels and not the feed from pin 7.
Look at the circuit. The upper opamp of the pair should be the signal feed to the RCA. If one channel used the feed from the lower opamp it would be out of phase.
So it is the feed from pin 1 (through that 100R series resistor) that is the correct one to use for both channels and not the feed from pin 7.