Vetta II HD and Vetta II Combo

[warode]

Would like to know if the mainboards are the same in the HD and Combo and if it is possible to add a headphone jack to an HD like the Combo has by just accessing the mainboard connection for one. Any help would be appreciated!

 

[DickFoster]

According to the service info I have, yes the main borads are the same. Other than the lack of a headphone jack, the other difference between heads and combos is in the output power amp and the power supply powering the output amp.

There is a flag bit to the processor letting it know which amp it is so I don't know what effect there is in the software regarding a headphone jack however there is a flag from the headphone jack to DSP1 that mutes the power amp when headphones are plugged in with the combos. Supposedly the software ignores this bit for head units.  

 

Outside of that,  from the looks of it it's mostly a hardware thing involving a few parts, a couple of ICs U23, U24 one for each channel and their parts a few resistors and caps and the jack itself which is a stereo jack. 

The ICs are each a TL084 which is a fairly common quad op amp intended for audio applications. It is avaliable from several makers, TI, SGS and SG among them. Almost any distributor should have them but you don't have to use that chip as most similar chips would work just as well but the pinout should match if you're gonna use the same spot on the main board, the chips may or may not be stuffed already. Line6 could have put them in all the main boards regardless of which amp they are going into as it's not so costly a chip to bother with the differences. Take a look and see if U23 and U24 are on your board. If so you've lucked out. The headphone amp is fed by U14 which drives the Direct Outs.