I have a CD6 bought in or around 2000. It has been stored for years as it had a sound issue in that there is very little low frequency output. This player has both single ended and balnaced outputs, both exhibit the same problem. This player has as it's Dac a first version Dacmagic Dac inside. I think I need to check the opamps on the Dac board and also the voltage regulators to check they are functioning properly. Are there other areas that I should be checking e.g Caps or other components?
I repaired my original Dac Magic Mk 2 some time ago, I don't remember the symptoms but a general recap worked wonders, I didn't have to change any silicon. Probably not what's inside your CD player but my later DacMagic which upsamples, sounds even better, but its more modern, mostly surface mount, I've not fancied working on that yet. This might be useful: http://audiopurist.pl/en/mods-en/cambridge-audio-dacmagic-100-modification-eng/
Lack of LF can only really be caused by either a degraded cap directly in the signal path but therein lies a conundrum... if both left and right channels are affected then that is unlikely.
Only three things come to mind.
1/ You have a phase inversion on one channel somewhere in the entire path from source to speaker causing apparent lack of bass.
2/ The DAC has been modified and an unsuitable/incorrect choice of parts has been used.
3/ The DAC is AC coupled at the output and you are loading it to heavily with what ever you have it connected to. That would take some doing but stranger things have happened.
It can not be an opamp causing this.
Ideally you should play a frequency sweep test tone and monitor the output on a scope and see what the response looks like.
Only three things come to mind.
1/ You have a phase inversion on one channel somewhere in the entire path from source to speaker causing apparent lack of bass.
2/ The DAC has been modified and an unsuitable/incorrect choice of parts has been used.
3/ The DAC is AC coupled at the output and you are loading it to heavily with what ever you have it connected to. That would take some doing but stranger things have happened.
It can not be an opamp causing this.
Ideally you should play a frequency sweep test tone and monitor the output on a scope and see what the response looks like.
Thanks Mooly. The CD player appears not to have been modified and is untouched by me. I got it from an open box sale at Richer Sounds. In what way could it be overloaded? I do not have any problems with other players.
Both channels are affected wiht either single ended or balanced. I was given a Velleman hand held oscilloscope many years ago but have never bothered to try to use it which is really not good enough I know. I know that I should at least have a go at using it and if you have any "idiots guide" info that might assist I would be very grateful. I have looked for same online but I could be reading Swahili (other languages are available) as it seems somewaht incomprehensible.
Both channels are affected wiht either single ended or balanced. I was given a Velleman hand held oscilloscope many years ago but have never bothered to try to use it which is really not good enough I know. I know that I should at least have a go at using it and if you have any "idiots guide" info that might assist I would be very grateful. I have looked for same online but I could be reading Swahili (other languages are available) as it seems somewaht incomprehensible.
If an output coupling cap were to low in value for the impedance it works into. For example a 10uF cap working into 1k loading would be -3db down at around 160Hz
The scope simply measures voltage but instead of giving a number on a display it traces the voltage out over time.
You need a simple test tone to begin with such as 1kHz tone to get the idea of what it does. Attached is a Mono MP3 File that plays for 30 seconds and goes from 10Hz to 10kHz. If you play the file on something suitable and look at the output on the scope you should begin to make sense of what happens and what the scope shows. You can use the scope to look at the output from the amp playing the tone and see what really happens.
The scope should show something like this and the amplitude (from top to bottom) should be constant.
If you post details of the scope (model etc) we can talk you through getting it to work.
Thanks for that. I will burn the test tone to a CD and play it after I have found the correct scope setting to record the results.
https://cdn.velleman.eu/downloads/0/user/manual_hps40_10-uk.pdf
https://cdn.velleman.eu/downloads/0/user/manual_hps40_10-uk.pdf
Thanks for the link 🙂
The important settings are these:
The input sensitivity determines how far the trace moves up and down for a given input voltage. At this stage you just want something in the right ballpark such as 2 volts per/division. The Timebase set how long the 'spot' tracing the waveform out takes to move across the screen.
A 1kHz sine takes 1ms (1 millisecond) for 1 cycle and so a setting of say 1ms/division would trace out 10 cycles if the screen has 10 divisions on the horizontal axis.
The frequency sweep will look a bit like this but my file has the frequency increasing smoothly rather than in jumps like this one. Notice how the amplitude (top to bottom) remains the same. That is what you want to see.
I would recommend that to begin with you set the scope input to AC coupling and use the X1 setting on the probe.
The important settings are these:
The input sensitivity determines how far the trace moves up and down for a given input voltage. At this stage you just want something in the right ballpark such as 2 volts per/division. The Timebase set how long the 'spot' tracing the waveform out takes to move across the screen.
A 1kHz sine takes 1ms (1 millisecond) for 1 cycle and so a setting of say 1ms/division would trace out 10 cycles if the screen has 10 divisions on the horizontal axis.
The frequency sweep will look a bit like this but my file has the frequency increasing smoothly rather than in jumps like this one. Notice how the amplitude (top to bottom) remains the same. That is what you want to see.
I would recommend that to begin with you set the scope input to AC coupling and use the X1 setting on the probe.
I have made a video of the scope and what it is showing when connected to one single ended out. I have tried many ways to attach it to a post but I have had no luck. It is an MP4 file.
YouTube?
How big is file? It will attach if you put it into a Zipped folder providing its not to large.
How big is file? It will attach if you put it into a Zipped folder providing its not to large.
I zipped the file and thought I was getting somwhere as it slowly downloaded, but then got the message again...."Oops We seem to have run into some problems" I am going to have some time in the sun now 😉
Oh right, I will have to clean my brain cell and see how to reduce it if it is too large. Thanks again.
Does this help. If you use W11 this may be installed by default (Clipchamp)
It works, click the link in the window.
It works, click the link in the window.
The footage is not as clear as before having used my YT "channel" something I set up years ago and until your last post I had completely forgotten about! I will do the sweep again tomorrow.
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I don't think I am doing very well? I can't seem to get the footage any clearer. Is there anything about the trace that tells you anything?
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I saw you trying on Sunday but the link didn't work so haven't looked since 🙂
I'm looking at the last video and that looks OK actually. The sine wave closing up as it goes along is the increase in frequency. That is what is supposed to happen.
To put detail on it... the amplitude (from top to bottom of the sine) should be constant at all frequencies. The low frequencies need a very low sweep speed (the speed the spot on the screen moves from left to right). Can you manually set that to something like 50ms (milliseconds) per division?
I can do you a few spot frequencies as a test. That might help.
I'm looking at the last video and that looks OK actually. The sine wave closing up as it goes along is the increase in frequency. That is what is supposed to happen.
To put detail on it... the amplitude (from top to bottom of the sine) should be constant at all frequencies. The low frequencies need a very low sweep speed (the speed the spot on the screen moves from left to right). Can you manually set that to something like 50ms (milliseconds) per division?
I can do you a few spot frequencies as a test. That might help.
This shows the change at 30 seconds in as it goes from 20Hz to 40Hz.
The spot frequencies are 20Hz, 40Hz, 100Hz and 400Hz. Your scope should show equal amplitude for all four and it will show whatever frequency is playing. You will not see the changeover point stationary on the screen like this on your scope.
The spot frequencies are 20Hz, 40Hz, 100Hz and 400Hz. Your scope should show equal amplitude for all four and it will show whatever frequency is playing. You will not see the changeover point stationary on the screen like this on your scope.