Headphone output ?

[MasterBoard]

I have one problem with my MB 6582 .

All is working fine , but I have one problem and I am not really sure why .

My individuals outputs works all great , but when I connect my headphones i can only hear the sid engine 1 . I can choose the other sid engines , 2 , 3 or 4 but when I press play I can hear only the sid engine 1 .

No matter what sid engine I choose I always hear the sid engine number 1 . This problem is in the headphones output.

If I select Sid engine number 1 and press play the screen looks like this 1PPP and I hear the sid engine 1

If I select the 2 sid engine and press play the screen show this P2PP but in the headphone I hear only the sid engine 1

If I select all the sid engines the screen looks like this 1234 but when I press play I can hear only the sid engine 1

I think that I should hear all the SID Engines right ?

Anybody knows what is the problem ?

Thank you

[nILS]

What did you connect the headphone socket to? It's not part of the original design, so you probably put some thought into what to connect it to, right?

[julienvoirin]

headphone socket is a add on. Wilba thought to this in order to make a ALL 4 SID in one stereo pair. Somewhere he explains how to cable it (with 10k resistor to attenuate crossrejection signal). If you can find it, i am interested too.

You hear SID1 (and only this one) in the headphone cause headphone is connected to stereo jack of SID1 (and only this one, that's why there is the 1k parallels resistor trick to create under the PCB)

If I well understand, the 1k resistors form a passive mixer and there is a trick with the cutting jacks

http://www.panoramiccomputing.com/TomAnselmo/Computing/12.0Speakers/PassiveMixer.gif

Edited November 16, 2011 by julienvoirin

[Wilba]

See bottom of the wiki page: http://www.midibox.org/dokuwiki/wilba_mb_6582

What's the purpose of the J70 header?

This is a passive mixed output of the four stereo channels, which you can connect to the small phono jack above the power switch. Totally optional.

This was a late design idea I threw into the prototype, the resistors below each audio socket are used to connect the audio signals together when there is no plug in the switched audio socket, i.e. it will only mix those sockets without plugs. You need to connect it together with insulated wire under the board though…. I didn't want to mess up the ground plane with tracks. To the right of the resistors R70-R77 (below the stereo sockets) are pads, these pads should be connected in two sets of wires, one set connects the pads that are next to R70, R72, R74, R76, the other set connects the pads that are next to R71, R73, R75, R77. (NOTE: R2 boards do not require the wires, there are tracks on the top layer.)

I used 10K resistors there because that's what I've seen before in passive mixer designs, but the output is very attenuated, and I am guessing that you could drop these to 1K or less, as the outputs of the audio buffers after each SID can probably handle that. Someone with more audio electronics (and SID!) knowledge can probably answer that question.

I just added that you don't need the wires with R2 boards. Do you have an R1 or R2 board? i.e. did you get the board from me or from SmashTV?

Note that you will NOT get the mixed audio if you are NOT using switched stereo sockets, because the audio only gets mixed for channels which do not have a plug in the socket.

So maybe you have plugs in those sockets, or you didn't use switched stereo sockets.

Or alternatively, you didn't add the resistors R72-R77 (near the audio sockets)... R70,R71 must be there or you wouldn't get SID 1 output.

Or alternatively, you have an R1 board and didn't add the wires... if so, look at the PDF of the R2 board and add wires to match the top layer tracks that connect one end of each of R70-R77

[MasterBoard]

Thank you for all the answers , yes wilba you are right .

I have the R1 board and I didn't add the wires

Thank you very much for your help

A greeting