Author Topic: Alembic F-2B knobs (Read 305 times)

lowfreq · « **on:** November 03, 2005, 11:07:21 PM »

I bought serial number 4318 off ebay not too long ago, and the unit sounds great. The tubes needed to me changed but I guess that's a good thing in Tube Land.
Anyhow, the EQ knobs seem to be mislabeled/missoldered. The Bass knob on both channels affects mids, and the Mid knob affects bass. Also, the B channel is about equal in volume to the number 2 input of the A channel. Is it supposed to be voiced that way? Can anyone help with information or troubleshooting tips?
Thanks,
Justin

mica · « **Reply #1 on:** November 04, 2005, 11:07:05 AM »

The controls are interactive, and so changing the bass setting will change the mids and treble. There is always the influence to get a nice EQ smile just like the tradifiton Fender circuits the F-2B is based on. Start out at 2-10-2 (bass-middle-treble) as the closest thing to flat. These numbers describe the labels on the dial, not on a clockface.

The channels are identical. If the settings are the same on each channel, using input 2 on either should be the same volume.

As for the tubes, what sound are you noticing that indicates the tubes need changing? There's a couple of entries in the for the F-2B that you might find useful as well.

lowfreq · « **Reply #2 on:** November 04, 2005, 04:22:35 PM »

The tubes that came with it were sovtec. I replaced them with telefunken, groove tube, and tesla tubes. This was just a matter of taste.
On mine, both channels are not identical. We just tested them with matched Telefunken tubes, and channel B is noticeably quieter.
What I meant about the EQ is, when sweeping the bass knob, mostly mids are changed: when sweeping the mid knob, basses are the mostly changed. This happens on both channels.
As far as age, this has the teal/black casing with the aluminum knobs mentioned in the FAQ, and Santa Rosa, CA is the city on the back.

mica · « **Reply #3 on:** November 10, 2005, 06:53:19 PM »

Taking great care to only touch the capacitors, wiggle the 6 orange capacitors on the circuit board and see if it changes. Strangely, we just repaired an F-2B where Tony had the same observation - the bass control seems like the mid control. We found these caps were clipped short before soldering, and therefore did not make a good connection.

If you find they are loose and want to resolder them, unplug the F-2B and wait 5 minutes before working on it.

If you feel uncomfortable about testing this (I can understand - high voltage is dangerous), we'll be happy to test it for you no charge.

mica · « **Reply #4 on:** November 17, 2005, 04:23:55 PM »

Hi Justin,

Have you tried this to see if there is something funky with your preamp?

lowfreq · « **Reply #5 on:** November 19, 2005, 02:39:25 AM »

No I haven't had time to look at it yet. I can get it to work and the sound is suitable, but I would like to take a better look at it soon and ask for more details regarding what I'll need to resolder/fix