Won some alembic bits in an off chance finding of a guitar equipment auction

[JimmyJ]

Jazzyvee,

Either version 001 of 002 looks correct so I can't figure out what might be causing any kind of feedback.  I'd say, for testing, just skip the last loop through the IN-2 rear panel (DI Box mode) just to eliminate that as the issue. 

That front panel extra jack mod appears to be a stereo mirror of the rear panel output jacks.  Meaning, if nothing is plugged into the rear panel "from preamp to lo-z..." jacks, then it would work like a headphone output of your dry bass signal.  If something is plugged into the "from preamp..." jacks, then it would be a stereo output of that signal, just like the rear panel "through" jacks.

Jimmy J

[jazzyvee]

OK makes sense. I will try that later this evening.
late last night I did find a couple of crackly leads as I was moving the wiring about so will test those and make sure all the others are ok.

 thanks Jimmy.

[jazzyvee]

Ok been a busy day, lots of different permutations and after testing cables etc. I took Jimmy J's advice and skipped the loop through the IN-2 Rear panel (DI Box Mod) and that got rid of the feedback issue. ( thanks)
I got my mesa walkabout on the team and used it for taking the power amp feed into the return socket on the mesa amp.
I also used my mesa powerhouse cab instead of the BF cabs and that never went crack ever even on the same settings that caused the cracking sound on the barefaced cabs. ( strange).
I called barefaced to find out if what I was hearing is either because the speakers are damaged and what should I be listening for to tell if the speakers have been damaged (blown). He said you'd smell burning of the voice call. So speakers are fine.

Whatever permutation of wiring of the rig I tried the sound was ok unless the gain was too high on the F2-b which just caused the tube saturation which as a different thing altogether and not an area i venture in.
Just to make sure the rack power amp was ok I plugged my bass via the small DS-5 block into the mesa front end and took the send out from the mesa into the power amp and never got any of the crack sound. (quite hissy though).

So after all that I wired it back as in picture 1 except fir the loop back through the IN-2 and this time all is fine even at high volumes from my bass. I think there may be something up with the IN-2 so I think I will take it to my local servicing guy and get him to give it an overhaul maybe new jacks, resoldering though.... i could probably do that myself if I knew the jacks to buy. I will see how busy he is first. If he can do it quickly then I will take it to him to check out otherwise I may give it a go.

[JimmyJ]

That's all good news.  Blown speakers... aside from the "smell of burning voice coils" (really?), in my experience, the easiest way to see if all is good is to physically move the speaker cone back and forth with your fingers (don't press the center dust cap - too fragile).  If it moves freely all is good.  If there's any resistance or rubbing it needs to see a doctor.

I still can't quite figure out why the DI box function would be causing you problems, but there is one thing I see in the picture you posted which has me wondering...  At the modified 1/4" front panel jack it looks like the shield of the added gray wire is connected to the same pin as the blue wire.  That would not be right as it would short out your B channel or whatever is plugged into the "from preamp..." right rear jack. In fact, there's no need to shield that wire anyway as the chassis is acting as a shield.  You could easily snip that wire where it connects to each jack and remove it.  Not knowing what it's original purpose was, maybe you should just disable it.

I have another mod you may want to consider ... Say you want to run your rig in full stereo but want to send a mono signal to the PA.  There are 6 rear panel jacks available so what I would do is keep only 2 directly linked to the front panel (and thus as "dry" outputs of your bass), then disconnect the remaining two jacks from the front panel, link them together as a "through", and use two 20k resistors to make a summing network to send both "from preamp..." signals to one of the transformers, and out the front panel XLR.  It sounds more complicated than it really is but this is what I mean when I say the IN-2 being ripe for mods.   

Jimmy J

[jazzyvee]

I recently had some interest in one of the bridges which i will be taking to the post office to weigh for postage cost. Other than that not much interest in the second bridge.
So, any creative uses for the other bridge if i can't find a new owner. Current thinking is a door or drawer handle. :-)
Jimmy, i haven't tried using that extra jack as I have no idea if it's an input or output modification so next time I open it up I will indeed remove them. In the meantime I hope to get it to my local electronics service and repair centre and get new 5 pin and DI sockets. They do work fine but the pins are tarnished and not sure how to clean them.

[JimmyJ]

Hey Jazzyvee,

Again, these parts are fascinating to us in here but the audience for them is, shall we say, limited.  We hope you can find a drawer to put them in and just hang on until somebody from our small community has a need. 

Here are my thoughts on that mystery 1/4" jack: 
#1, if only the bass were plugged in it would serve as a stereo output and probably even drive headphones. 
But, #2, because of it's mounted right next to the 5-pin bass input I suspect it was added as a redundant input to be used in case the power supply failed.  All you'd need is a stereo guitar cable from the bass's 1/4" jack to that input and you'd be back into the rig with the bass running on battery power.  That's my current theory (a-hem, which is mine), that it's a backup input.

Jimmy J

[jazzyvee]

Interesting, i will try plugging in my non alembic bass first just in the unlikely, but theoretically possible, event that your your current theory has holes. ;-)
Thanks Jimmy.

[JimmyJ]

Um, not gonna work the same with a non-Series bass.  Think 1/4" STEREO cable (nobody has one of these) with one end plugged into the bass's 1/4" jack and the other end plugged into that mystery jack (disconnecting the 5-pin cable from the bass).  That would give you battery-powered signal from both pickups (stereo) feeding into the IN-2's audio signal path in the same way you've set it up to work with the 5-pin cable.  The reason I'm guessing that about it is because it's a stereo jack...

Keep experimenting though.  There are countless ways to set up and modify these fine pieces of gear.

Jimmy J

[jazzyvee]

Ok, i understand now.

[jazzyvee]

I'm almost certain that these parts were from Entwistle's tech.

Bang on, as usual. I was at a guitar show on Saturday and the auction house i got these bits from had a stand and i mentioned the stash i got and they confirmed it was all John Entwhistles stuff. The alembic stuff was brought in by someone from the WHO, and it was in the confidentially agreement that no mention of it's origin was to be mentioned until after the auction had finished.
So i have a real piece of rock history and using it. His In-2 in my bass rack and pickups in my shorty.

[JimmyJ]

That is super cool!  You also have several "spares" of the FET and the discontinued original flat-pack op amps in that stash.  I'm surprised Mica hasn't made you an offer on those.    I think it's just great that this gear has found an owner who can USE it rather than ending up in a Hard Rock Cafe somewhere.

[lbpesq]

Very cool!    Somewhere up there John is smiling.

Bill, tgo

[Wyzard]

I had the IN-2 that I got at the GH auction gone over and sorted by Neil Perry, and it's looking and performing vastly better than it did when I bought it.

I'll be selling it very soon I guess, as I've no real use for it now - I've sold off the last of my proper bass gear, and am sticking to guitar for the foreseeable.