SF2 Filter B does not work in mono mode

[djmay]

I have had the SF2 unused for 17 years (long story). I set it in mono mode, plugged into front jack, Filter A sounds wonderful and nothing out of Filter B. I set stereo mode and checked both filters independently, plugging into rear jacks. Both filters work. Any ideas?

Second question; can the two filters be used in series, in stereo mode. Take output of Filter A into input of Filter B?

Thank you for any assistance.

[jazzyvee]

Hi there djmay welcome to the club.
Here is a link to the SF-2 pdf manual so you can check the connection options.
http://alembic.com/support/SF2_Manual.pdf

[djmay]

Thank you. I already have the manual. The problem is that Filter B is not functioning in mono mode and I cannot figure out why.

[rv_bass]

Maybe it has to do with having to clean all pots and jacks.  If it was sitting unused for years you may have some corrosion/oxidation built up.  Turn all control knobs fully both directions fifty times at least.  Then take a 1/4” cable and plug it in and out of each jack fifty times each to try to clean them out.  If the signal travels through connected pots and jacks whether plugged into them or not it can get interrupted by corrosion/oxidation, from what I understand.  Worth a try.

It may also have to do with the way you have it wired.  Are you going in and out of a preamp effects send and return?  If so, check the manual wiring diagrams again to make sure you have it right.

[edwardofhuncote]

I have had the SF2 unused for 17 years (long story). I set it in mono mode, plugged into front jack, Filter A sounds wonderful and nothing out of Filter B. I set stereo mode and checked both filters independently, plugging into rear jacks. Both filters work. Any ideas?

Second question; can the two filters be used in series, in stereo mode. Take output of Filter A into input of Filter B?

Thank you for any assistance.

Regarding the second question; I seem to remember that there is a way to jumper and do this on the back of the unit. Should be in the manual you have. My SF-2 is in the effects loop of my F-1X, so your scenario may be different.

[StephenR]

Here is a screen grab from the manual that shows the connection option utilizing a jumper cable between the output of channel A and channel B. I have never tried this and been curious as to what sonic advantage this would have over running in mono by plugging into channel A and out of B for the return.

[cntrabssn]

+1 for cleaning the jacks, especially the "B IN" jack. It comes into play with respect to stereo/mono switching.

Regards,
-nate.

[djmay]

Maybe it has to do with having to clean all pots and jacks.  If it was sitting unused for years you may have some corrosion/oxidation built up.  Turn all control knobs fully both directions fifty times at least.  Then take a 1/4” cable and plug it in and out of each jack fifty times each to try to clean them out.  If the signal travels through connected pots and jacks whether plugged into them or not it can get interrupted by corrosion/oxidation, from what I understand.  Worth a try.

It may also have to do with the way you have it wired.  Are you going in and out of a preamp effects send and return?  If so, check the manual wiring diagrams again to make sure you have it right.

Thank you. I will try that in a few days. I brought the SF2 back to Switzerland and have to buy a power supply for here.

[djmay]

Here is a screen grab from the manual that shows the connection option utilizing a jumper cable between the output of channel A and channel B. I have never tried this and been curious as to what sonic advantage this would have over running in mono by plugging into channel A and out of B for the return.

Thank you

[djmay]

+1 for cleaning the jacks, especially the "B IN" jack. It comes into play with respect to stereo/mono switching.

Regards,
-nate.

Thank you

[StephenR]

Thank you. I will try that in a few days. I brought the SF2 back to Switzerland and have to buy a power supply for here.

Make sure you get the right power supply. If the polarity is wrong it will fry the choke in the SF-2 and it will need to be repaired. If you haven't seen it here is a link to the FAQ about the power supply.
https://club.alembic.com/index.php?topic=264.0

Where do you live in Switzerland? I went to college there at the now defunct Albert Schweitzer College which was in Churwalden (20 minutes or so up the pass outside Chur). I loved Switzerland but sadly have never had a chance to go back. I am pretty amazed that recent pictures I have seen of Churwalden show very little change in the area over the last 50 years.

[gtrguy]

I believe that unit has internal switching on the jacks that will look like a set of points on an older car. You might need to open it up and clean the points by using very fine sandpaper (I use 1000 grit 'wet' style sandpaper but with no water) across the points. You spread them apart slightly and insert the sandpaper and close them and then gently rub the sandpaper around, then you pull it out.

[djmay]

Thank you. I will try that in a few days. I brought the SF2 back to Switzerland and have to buy a power supply for here.

Make sure you get the right power supply. If the polarity is wrong it will fry the choke in the SF-2 and it will need to be repaired. If you haven't seen it here is a link to the FAQ about the power supply.
https://club.alembic.com/index.php?topic=264.0

Where do you live in Switzerland? I went to college there at the now defunct Albert Schweitzer College which was in Churwalden (20 minutes or so up the pass outside Chur). I loved Switzerland but sadly have never had a chance to go back. I am pretty amazed that recent pictures I have seen of Churwalden show very little change in the area over the last 50 years.

I live in Horgen, Kanton Zurich.

[djmay]

I believe that unit has internal switching on the jacks that will look like a set of points on an older car. You might need to open it up and clean the points by using very fine sandpaper (I use 1000 grit 'wet' style sandpaper but with no water) across the points. You spread them apart slightly and insert the sandpaper and close them and then gently rub the sandpaper around, then you pull it out.

Thank you. I was also considering spraying contact cleaner on jacks and switches.

[edwardofhuncote]

Contact cleaner is okay (such as DeOxit 5) but rather than spray directly, put a small amount on a pipe cleaner, or even on a 1/4" plug. Just don't do what one Wire Dunce did (points sheepishly at self) and hose one out with that handy little straw they give you.