OBERHEIM SYNTH

Dear Group,




I just did a full calibration on my OB-Xa yesterday and ran into a couple of things I would like feedback on.

The biggest issue is that the individual voice cards (I have 8 in mine) - all put out similar but different volume levels. It seems for instance that the bottom tray is a bit weaker on the output than the upper tray.

I use the synth in MONO much of the time via the MONO output and wonder if there is any way to equalize the volume settings via the individual voice cards. One thing I did not address in the tune-up was the VCA offset pot because I don't have a small jumper cable with tiny alligator clips on it to do the tweak at the moment.

Any info would be helpful - thanks!



jbrey21@yahoo.com

James,



Thanks for your feedback - but a few questions:

I am running my OB-Xa in MONO from the MONO out on the synth - this is where I have the level disparity problem - I can certainly come out stereo and adjust at the board but do not want to. Any ideas for level parity in this scenario? Is there any kind of adjustment possible on the individual voice boards?

Not sure what you meant about using headphones, etc, please clarify.

Also, what is your web site URL - I'd like to check it out.

Thanks.


jbrey21@yahoo.com

I had the same problem with my OB-Xa (one tray was louder than the other). It took two techs to figure it out, but the final solution seemed to require using different resistors on the individual tray outputs until the levels roughly matched. It wasn't a real "fix" in that they never figured out what caused it, but it worked. The fact that yours is doing something similar seems to be symptomatic of a specific issue.

The other, much simpler method would be to pan the upper/lower tray to the left/right outputs, respectively, and then match the levels on your mixer. I think this is what the other poster might have been suggesting. Simple, but effective.

Group,


Thanks for all who responded - I appreciate the information. I wish there was more of a definitive solution, but I will make due now based on the info I have.

I'm going to complete the calibration this week and see if that helps at all by tuning the filters and the VCA offset.

The next problem in getting this OB-Xa 100% - the pitch bender problem. I have looked at a lot of past posts regarding the issue of the PITCH BENDER not returning to perfect zero and have seen about 5 different answers and approaches to the problem.

Is there a consensus opinion at this point as to what is the best way to fix this problem permanently? Is it install a new pot of the exact same values, or the dead band mod, or what? Just looking for a tech out there that found the easiest solution to fix this problem for the long haul.

My unit has been mine since new in 1981 and I have never addressed the problem even though needed - just want to get it done now that everything else is up to snuff.

Is this the right part:

Honeywell Clarostat 10kOhm 2W Rotary Potentiometer JA1N200P103UA NIB

TIA.



jbrey21@yahoo.com