Well I burnt the test tones and assumed that I could put them on YT as before. I am having a real fight to get it to do the same. I will keep trying!
That doesn't look right at all.
If you play the tones they should sound very pure. The scope image seems almost like noise. You should see similar to what you saw with the sweep (pure sinewave) except now the frequency is constant. Try just playing them and make sure they sound OK. You can use the sweep tone as well as a reference.
(also if you play it loud enough you should be able to measure the AC voltage across the speaker. It is AC voltage remember. Most meters are fairly accurate in the 40 Hz to 1kHz range. Even 1 or 2 volts signal will sound very loud but will not damage the speakers)
Have you nothing you can play the tones on without having to keep burning them?
If you play the tones they should sound very pure. The scope image seems almost like noise. You should see similar to what you saw with the sweep (pure sinewave) except now the frequency is constant. Try just playing them and make sure they sound OK. You can use the sweep tone as well as a reference.
(also if you play it loud enough you should be able to measure the AC voltage across the speaker. It is AC voltage remember. Most meters are fairly accurate in the 40 Hz to 1kHz range. Even 1 or 2 volts signal will sound very loud but will not damage the speakers)
Have you nothing you can play the tones on without having to keep burning them?
I see what you are saying and forgive my ignorance. I assumed that to scope the CD player all I had to do was play the sweep/tones through the player and get the results. I should be using the CD player as normal by playing through the system in the normal way and then scoping, I have always said that it is hard to educate an idiot🙄.
You should be able to directly look at the audio from the CD player but because of the last result (looking just like noise) I wanted to be sure the tones played OK audibly and that they sound totally pure in tone like a sine wave should.
Just to clarify and getting my head around this, the CD player has no digital IN and therefore the only way to hear the test tones is to burn them to a CD. I will play them through to hear them today.
I have played the 10Hz t0 10 Khz sweep through another CD player and I get the lowest and the highest tones. As I have OB speakers I have 2 subwoofers as well. When the sweep is played through the CD6 the subs are not energising and there is no deep bass. I haev taken some pics of the scope using the sweep at 10s, 20s and 25s as I thought it easier to use pics.
Attachments
Last edited:
Interesting. So the CD6 appears not to really be lacking in bass. That is very strange actually. The pictures you show look correct and you say it seems to sound correct as well when played on another CD player. So the test CD is OK and your system seems OK.
Looking at photos of the CD6 I see it has standard RCA sockets and also balanced outputs. Are you using the RCA outputs? as those are the easiest to work with. You should see the same signals as you show in your pictures.
I've no service info or user manual for these... and it such a bizarre issue. Are there any switchable user filters or anything like that, maybe accessible from the remote?
You say you bought this around 2000. I suppose its just remotely possible there could be some cap problem and if so then that would be in the very final audio stages. If you have a service manual and can post the circuit that would help. Otherwise I think you need to look visually at the circuit and use the scope to see if the audio is being lost at a coupling cap.
Good pictures of the analogue stages might give a clue where you should look.
Looking at photos of the CD6 I see it has standard RCA sockets and also balanced outputs. Are you using the RCA outputs? as those are the easiest to work with. You should see the same signals as you show in your pictures.
I've no service info or user manual for these... and it such a bizarre issue. Are there any switchable user filters or anything like that, maybe accessible from the remote?
You say you bought this around 2000. I suppose its just remotely possible there could be some cap problem and if so then that would be in the very final audio stages. If you have a service manual and can post the circuit that would help. Otherwise I think you need to look visually at the circuit and use the scope to see if the audio is being lost at a coupling cap.
Good pictures of the analogue stages might give a clue where you should look.
There is not the same depth of bass with the CD6 and the overall performance is anaemic due to the lack of bass. I am using the balanced outs when listening, but I have tried the RCAs and the result is the same. The scope readings have been made with one channel of the RCA out. I will take some pics and also see if Cambridge Support can provide a service manual. I have attached the scope to one balanced channel and the readout was the same.
It certainly is odd and the fact it is on both channels makes it more odd actually, that is why I wondered if there were any hidden user settings for filters of any sort.
The generic CD spec is a flat response from right down to around 2Hz up to 20kHz. Your three pictures show that the amplitude on those is constant at the different frequencies and the CD6 should be identical.
In a standard analogue circuit (like the output stage of any player) only caps can cause issues like this.
Did the player work OK when you got it? Was the player new? If not could it have been modified by someone incorrectly?
I'll look in later 🙂
The generic CD spec is a flat response from right down to around 2Hz up to 20kHz. Your three pictures show that the amplitude on those is constant at the different frequencies and the CD6 should be identical.
In a standard analogue circuit (like the output stage of any player) only caps can cause issues like this.
Did the player work OK when you got it? Was the player new? If not could it have been modified by someone incorrectly?
I'll look in later 🙂
Yes when I got the player it performed as I expected and it was not until I tried after some years it was clearly unwell. The Dac board is unmolested and all the caps appear good (no doming) or leakage. I have found a service manual (attached)
file:///C:/Users/User/Downloads/cambridge_audio_cd6_service_en_low_res%20(1).pdf
file:///C:/Users/User/Downloads/cambridge_audio_cd6_service_en_low_res%20(1).pdf
Last edited:
You will have to attach it as a pdf using the attach button. This will open a window where you can browse your PC for the file 🙂
I did do that and when I clicked on it it opened the file on my laptop, as you don't have my laptop I assumed that to attach it was no good for you. When I copied it and pasted it into google it opened.
OK 🙂 Web browsers will open pdf's but of course that file path is just one on your own PC.
Right then, this is really bizarre. The audio stages are DC coupled, no coupling caps. What you need to do is use the scope to try and look at this audio signal internally in the player. This is the left channel from the manual. The right channel is identical. The DAC is at the left and the analogue filtering and buffer are the two opamps at the right. The opamp at the top just generates a clean reference voltage. The pin numbers show the opamps at the right are in fact a single package with two opamps inside.
You can try playing the test tone and probing the opamp pins. Pins 1 and 7 are both outputs and should look the same on the scope. The amplitude of the tones should be identical at all frequencies.
If that shows a problem then look this time on pins 3 and 5. That should show the audio but there may be high frequency noise making the trace look a bit 'furry'. That's normal.
If that is no good then look with the scope at the points arrowed.
If you try all this then have the player running in isolation... nothing connected to the audio output sockets. As both channels have the same fault you can measure on either channel. Keep the scope ground lead connected to to the players ground at all time (such as the outer part of the RCA sockets). Be careful when probing the pins and try not short them accidentally but opamps are well protected and nothing bad is likely to happen if you do slip... but try not too 🙂
No need to attach videos at this point now we know what is happening, just do a quick measure with scope and see if its still faulty at these points.
Right then, this is really bizarre. The audio stages are DC coupled, no coupling caps. What you need to do is use the scope to try and look at this audio signal internally in the player. This is the left channel from the manual. The right channel is identical. The DAC is at the left and the analogue filtering and buffer are the two opamps at the right. The opamp at the top just generates a clean reference voltage. The pin numbers show the opamps at the right are in fact a single package with two opamps inside.
You can try playing the test tone and probing the opamp pins. Pins 1 and 7 are both outputs and should look the same on the scope. The amplitude of the tones should be identical at all frequencies.
If that shows a problem then look this time on pins 3 and 5. That should show the audio but there may be high frequency noise making the trace look a bit 'furry'. That's normal.
If that is no good then look with the scope at the points arrowed.
If you try all this then have the player running in isolation... nothing connected to the audio output sockets. As both channels have the same fault you can measure on either channel. Keep the scope ground lead connected to to the players ground at all time (such as the outer part of the RCA sockets). Be careful when probing the pins and try not short them accidentally but opamps are well protected and nothing bad is likely to happen if you do slip... but try not too 🙂
No need to attach videos at this point now we know what is happening, just do a quick measure with scope and see if its still faulty at these points.
In a spare moment I checked the pinout for the NE5534. Pin 1 is siad to be BAL and Pin 6 is said to be OUTPUT and pin 7 V+?
The 5534 is the single one that generates the reference voltage. There is no audio on that one.
The one with audio is the dual opamp. Look at the diagram above that I posted. That was from the manual. It shows the opamp as an AD712 which looks like this. This is the one to measure on:
There are two opamp's in the package. Pin and pin 7 are outputs.
The one with audio is the dual opamp. Look at the diagram above that I posted. That was from the manual. It shows the opamp as an AD712 which looks like this. This is the one to measure on:
There are two opamp's in the package. Pin and pin 7 are outputs.