CD Line out - PC sound

[nilblade]

I am hoping somebody can point me in the right direction:

I trying to create an AUX input,

I have found where the audio from the CD player enters the main board of my hifi - I have disconnected the cd from the hifi, for it to be PreAmped and Power Amped, but when I connect it to my computer, the sound is very quiet even though the computer is at max volume. Is this because the CD player main is shutdown because the hifi knows theres no 'CD' so to speak - is there any way around this. my hifi is a sony pmc 202

thanks

nilblade

 

[indianajo]

It took about a month of fooling around to find out how to boost the gain inside my computer. Are using Audacity to record? there are some secret buttons on there (no mouse over text) that select the input, and more buttons that change the gain. I was using alsamixergui and qjackctl programs that I downloaded with the audacity, which were superceded when the audacity was running.
The line in jack on the PC audio I/F is the blue one, another secret revealed only in some $25 book somewhere. Audio jack color is surely not covered in "upgrading and repairing PC's" 12 edition.
Other operating systems, you are on your own. My op system was ubuntu studio version of Linux.
Theoretically a CD player earphone output should be able to overdrive the computer line input, since earphones take up to 7 VAC. The line output is more like 2 vac max. BTW on my 1986 CD player the jacks are labeled, but the 2005 CD player the earphone jack is the green one. Another **** secret code.
Oh BTW, it took a couple of tries of fooling around with an AC voltmeter to get cables that worked, too. I had DC continuity, but the AC wasn't flowing for some stupid reason until I resoldered the connector the third time. 1/8" stereo phone plug male to same, you might have bought something, but 1/8 stereo phone plug male to two 1/4 mono phone plug male, I had to make the **** cable. Especially I needed a 20 foot one since I keep the PC well away from the hifi for RF interference reasons.

 

[sgrossklass]

@OP: Mind explaining what it is that you want to achieve with this setup?
I mean, why go to the trouble of connecting a CD player to the analog in if you might just as well stuff the CD into the optical drive and rip it?

 

[nilblade]

Thanks for the replies

I feel I should add a little background to this:

The CD player itself has developed a tracking problem it only plays to about track 4 and loses position, subject of another thread, but seen as i dont have O-scope theres very little I can do.

Anyway I had this crazy idea that I could disconnect the cd player from isnt internal header and wire up a 3.5mm jack to that header, thus creating an AUX input into the CD audio header - hope this makes sense

But either the pre-amp or the power amp arent switching on, i dont think because the sound is really really quiet even at full volume (I wired up a 3.5mm plug to the internal header)

Sorry for the confusion -thanks for your time

hope someone can help
nilblade

 

[sgrossklass]

Ah, so you want things the other way round. Now that makes more sense.

According to the problem description, I'd say you either have a bad flex cable going to the pickup, a bad spindle motor or some other mechanical problem that blocks pickup movement. Is there any crud visible on the surfaces that the pickup slides on (both sides)? Can the pickup actually be moved further?

Mmkay, let's look at the service docs...

KSS-213B pickup there, that's a fairly common type of drive. You should be able to pick up a whole KSM213 drive without spending an arm and a leg.

Decent single-chip radio section there. RF overload handling may not be particularly great though. Knowing Sony, ceramic filters CF1 and CF2 may be rather wide 280 kHz jobs, so there may be some tweaking potential depending on where you live (here in Germany with its crowded FM band, 180 kHz types would be considered appropriate for general listening).
</obligatory radio nerd comment>

Hmm, basically using the CD input ought to work - the cable carries L, R and AGND outputs, plus supply voltages for the CD section, but nothing else. There's considerable input attenuation since the preamp section appears to work at very low levels and presumably the CD player outputs 2 Vrms or so.

There is a cable going over to the control board though, and I'm afraid that this one expects some cooperation on part of the CD board. And there's muting circuitry in front of the power amplifier and at the headphone output. Usually the outputs are not unmuted until playback has actually begun. This could become tricky.

 

[nilblade]

Thank you for the detailed answer 🙂

I couldnt find a KSM213bam drive Mech as quoted in the service document

But I found a KSM 213 CCM on ebay would this do the job? I think I have a bad sled motor to be honest, could it be the servo logic on the CD board itself to which the CD drive mech is connected?

So are both the pre amp and the power amp off, until the CD is playing? There is no way of mimicking a CD 'playing'?

Could you show where the input for the radio is on the main board? maybe I could use some kind switching jack across the radio input?

Thanks again

nilblade

 

[sgrossklass]

I couldnt find a KSM213bam drive Mech as quoted in the service document

But I found a KSM 213 CCM on ebay would this do the job?

AFAIK these should be interchangeable. The "B" was apparently intended for portable stereos, while the C was for stationary devices. Whatever.

So are both the pre amp and the power amp off, until the CD is playing? There is no way of mimicking a CD 'playing'?

That's the question. You would have to find out what's happening on the SENSE and CD.DOOR lines. The latter seems to be connected to +5V when the CD tray switch closes (not sure which tray position that corresponds to).

Could you show where the input for the radio is on the main board? maybe I could use some kind switching jack across the radio input?

The radio part has a "Sense/Stereo" line, too, though I suppose it should work if you tune in a station that comes in well, or switch to AM.

The signal from the radio section arrives at R148/248; the radio section's output has 18k of output impedance, and you'd have to use about as much or a bit more (like 22k-24k) for your PC input.

 

[nilblade]

Hi

Thanks agsin

That's the question. You would have to find out what's happening on the SENSE and CD.DOOR lines. The latter seems to be connected to +5V when the CD tray switch closes (not sure which tray position that corresponds to).

Well have to researching the issue I found the datasheet - MSM65353A for the control processor in my hifi system and found that each of the IO pins on the processor can be set to OPEN or pull up. not sure what meant by pull up because my understabd was where there was nothing connected to an IO pin and it was set using an internal pull up resistor it would set itself to the logic level probably 5v in this case

It seens the CD Sense output from the microcontroller is reponse to the C_XLAT and SQCK which the CD door and a CD position timing output - i think,

my thinking is that if the microcontroller recieved a signal from CD-SENSE it would turn on the amps?

Would it therefore be possible to immitate a signal as if it were coming from CD-Xlat and SQCK using a pic/atmel, in order to initate CD-SENSE as per the service doc pg. 16. I have some programming knowledge having majored in Computer Science.



thanks
nilblade

 

[counter culture]

I think at this stage you might want to think about what you're doing and the effort involved.

If you're just enjoying fixing stuff, that's good. If you're time rich and cash poor, it may be the way to go. It might be time, however, to think about modernising your system, maybe move away from CDs to network storage.

 

[nilblade]

Hi

Good Point 🙂 I am definitely am in the 'fixer' category I was just looking upon it as a learning opportunity.

In no way did I mean to waste anyones time etc - apologies 🙂

 

[counter culture]

No suggestion that you're wasting anybody's time. If you just want to fix it, that's cool🙂.

 

[nilblade]

Hi there,

I fixed the CD player it was a dying laser

For information the CD player Mech KSM 213 CCM and KSM 213 BAN arent compatible, the motor boards are wired differently, although the lasers appear compatible and can be swap out relatively easily which is what I did.

The signal from the radio section arrives at R148/248; the radio section's output has 18k of output impedance, and you'd have to use about as much or a bit more (like 22k-24k) for your PC input.

How would this be achieved?

Could I wire a DPDT switch to R148/248 and wire a stereo 3,5mm jack the other side? How would I connect ground?

nilblade

 

[AndrewT]

...............KSS-213B pickup there, that's a fairly common type of drive. You should be able to pick up a whole KSM213 drive without spending an arm and a leg...........

googled and went to the first sales link: Farnell. Under £12
They offered that and similar products. Had about 30 different laser pickups in stock varying in price from £3 to £26.
thanks for the ref.