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

[jazzyvee]

Ok I got the goods today and may be you can tell me if the PF-6 card is complete.
The In-2 looks in much better nick than the auction pictures led me to believe, though the metal nuts holding the switches and sockets on look oxidised so that may be an indication as to the insides of the sockets too. (not taken the back off yet)
There is an input jack on the front so it will be interesting as to what outputs that will have access to.
In the tin box here are three dual gang pots and three single pots, two don't have an alembic stamp on but all look the same.
There are 5 IC chips on cream holders, but nothing in the black one, resistors and capacitor and things that look like transistors with more than 3 legs.
The pickups are one complete set including the hum cancellor and a single pickup and hum cancellor.
As the auction had no indication as to the size of the bridges, I ended up with three and only one is the same width as my 4 string alembics so I guess the others will be sold on as soon as I can find a fair price but as long as I don't lose out on it I'm not aiming to make a killing.  Just a fair price. I will take some measurements next week and pop them on here.


I do have an external 240 - 110v transformer somewhere so I will have a go at trying it out in the week and in the meantime if anyone has any documentation on how I can wire it up and what the sockets on the back "From Preamp to Low z Output" does. I presume its related to the DI, so how do Use that and still get my signal to my power amp.
Have a great weekend.

 

[JimmyJ]

Jazzyvee,

I still can't get over this haul, what a catch!  The preamp card looks intact and is from the time before they were built with IC sockets.  You also have spares of theses flat-pack opamp chips plus spares of the FET front end (transistor-like with a black top).  Again, the black socket on the top of the board is for the instrument's wiring harness, not a chip.  And it also has the older mini-coax connectors for the pickups.

Other than the extra 1/4" input, the IN-2 is normally wired like this: both A+B instrument output channels are "normaled" to the DI's transformer inputs.  Depending on how you set the selector switch, you would get stereo, mono, or even "A both" or "B both" out of the two XLR outputs.  If you plug into the rear jack marked "from preamp to lo-z output" you interrupt that "normal" connection and the DI boxes become like any normal external DI.  (And you have two of them!)

Please pop the lid off that IN-2 and post some pics for further info.  Also give us an idea of your usual setup, like where you normally insert a DI box in your big rig, and we'll see if we can figure out the best signal routing.

Really cool!
Jimmy J

[sonicus]

Jazzyvee.
Indeed that is a sublime bundled acquisition ! I send you my congratulations !
I own two such Alembic 1N-2 units .The first one that I acquired was a gift from a friend  . It was in disrepair and in rough condition  , It cleaned up well !.  As well , I needed to replace the power supply section that consisted of an epoxy potted regulated unit .I sent the specs to Acopian.com,  who sent me a replacement that wound fit in the rack enclosure  made to order ( not cheap ).  I did the work my self with Ron's kind advice . The second IN-2 was pristine in all regards .

[gtrguy]

The PF6 card looks complete, with the extra chips and transistors as spares? If you ever want to sell that card let me know. I need one like it for a project!

[jazzyvee]

I plan to try it out in my short scale series I this coming week with the new pickups. Being on this side of the pond with series  basses its is sensible for me to hang on to it in case i ever need a spare. No idea on the cost of a pf6 card from alembic plus shipping to the uk would be, but it’s most likely seriously expensive. That is assuming they would even sell one to me as opposed to requiring me to send the bass back to the factory.

[goran]

Damn I just saw that, Jazzy that's a great find, can't believe that was on basschat

[jazzyvee]

Hey Goran, that is where i discovered the auction. I chose (selflishly) not to mention it here to avoid a battle for the bits i really wanted which were the pickups and pots for my Series shorty and In-2. Thankfully i got both. 

[jazzyvee]

Oh here we go. I have just taken the top off and inside is spotlessly clean, except for the chassis screws which are oxidised and the jack contacts just needed exercising to clean the jack contact area. Not sure how to clean the 5 pins and the DI socket pins on the front though. You are right Jimmy it does look like a basic box with a lot of space.  The jack input socket on the front near the 5 pin seems to be a mono socket  that connects directly to both the A & B sockets and the "from preamp" sockets. Which if I'm correct makes it a much easier way to share the unit with my non series basses.

Here is a photo.
I also found a 240v to 110v, 100W transformer that I bought when i got a samson VHF wireless transmitter whilst on tour in the states in 92.  So I can at least try it out and see if it is working and crackle free until I can find a 240v transformer.

[sonicus]

Jazzyvee ,
Both of my units have the same layout . On the right are the  Lovely UTC " Ouncer" audio transformers  . On the left the encapsulated epoxy potted regulated power supply . I had to replace that on my first IN-2 after watching and monitoring the  unsteady voltage activity for several hours while I bench tested it . It eventually completely ceased to register any voltage output .

[jazzyvee]

Ok I just plugged it into my rack and here is what I found. From the front
A  to input 1 of F-2B, B to input 2 of F-2B
output from F-2b outputs A & B to the respective the rear jacks in IN-2 marked "from preamp to lo-z output" then
output A and output B from IN-2  to individual left and right channels of my Power amp.
Bingo all worked first time no noise interference. Just sound. :-)

What I need now is to get my SF-2 into the signal chain somehow. If I take the rear outs from the F2b to the A and B inputs on the back of the SF-2 then the outputs of the SF-2 to the power amp via the "from preamp to lo-z output" or even just direct to power amp I still get a huge CRACK sound when i play notes. The only way I can get rid of that noise is to put the SF-2 in front of the F-2B but then I have to take the A &b B outs from the front of the IN-2 via long cables routed around the outside of the rack to rear and into the SF-2 A & B, then the outs of the SF-2 all the way round to the front of the rack to the F-2B inputs then out of the back of the F-2B to the power amp either  via In-2 or direct to power amp input.  Which is quite untidy.

I'm a bit stuck with an alternative wiring strategy at the moment.

[JimmyJ]

Hey Jazzyvee,

Great to hear it fired up and seems to be doing what it was built to do.  A note on that 1/4" input mod: following the wires in the photo, I believe that is a stereo jack.  Meaning with an older model Alembic bass or guitar with battery operated stereo 1/4" output, a stereo 1/4" cable would allow you to plug straight in - without powering up the IN-2 - and the signal routing would be intact.  Make sense?

And just to mess with you more, it could also serve as an OUTPUT of an instrument plugged into the 5-pin connector.  HA!

I still believe that the "crack" you are describing is because you are overdriving something in the chain.  Remember, your instrument can have almost a line-level output (enough to directly drive a power amp), then the F-2B is another preamp with a ton of gain, and then the SF2 is yet another.  Try that setup you've described but turn the instrument's master volume down to about 1/2 and see what kind of volume / tone / noise you get using the other pres for gain.  Remember that turning down our master volumes does not change the tone.  It could be something as easy as that.

As for routing... IN-2 outputs are front and back, SF2 has inputs and outputs on the rear panel, but the F-2B is front in and rear out only.  If you don't have an open slot in your rack which you could pass short cables through, this is where MODIFYING the IN-2 gets interesting. You will not likely need double sets of outputs on the front and the rear of the IN-2.  So one set of those 1/4" jacks could easily be wired as a passthrough from back to front if you needed that.  Furthermore, depending on what kind of signal you want to make available to the DI outputs, things can be wired accordingly with linked 1/4" DI inputs, mono summing resistors, etc.  It's kind of endless!

I'll leave it there and let you think about all that.  Sorry I get all nerdy when talking about this stuff.  HA!


Jimmy J

[jazzyvee]

Thanks Jimmy, your experience is always welcome and i will try the gain suggestions. My previous use of the rig for the past few years is to max out the power amps and use a really low preamp setting which worked fine but one of the things that made me consider reducing the power amp setting was to hopefully  reduce the risk of blowing my speakers if something went wrong down between the bass and amp input resulting in a large signal hitting my cabs at full volume.
Anyway, i have just got the back off my Series shorty and the cables ends have the computer type connectors so my new, spare pf6 card wont connect to the pickups in my bass. So i presume my existing card is newer. But i would like to try it out if possible but how do i get the hum cancellor out?  Maybe i will give mica a call later as well and see what she advises. I have a local electronics expert who repairs musical instrument amps, audio gear and high end hifi systems. he may be able to make some sort simple adaptor cables so i can try any combination of the pickups and cards in my bass to check they all work and decide which to keep in the bass.

[sonicus]

 

[JimmyJ]

Jazzyvee,

Stop me if I'm driving you crazy with all these replies, ideas, and suggestions.  I've been fiddling with Alembic gear for so long now that I am getting close to understanding it.  HA!

Not to hijack this thread, and you can start another if you want, but the gain structure thing can be tricky.  And the more gear in the chain the trickier.  I get what you mean about wanting to save your speakers but I don't know if trimming the power amp inputs is the best choice, sonically.  My MAIN suggestion is that you always make sure your instrument is on standby before connecting or disconnecting the 5-pin cable.  If it's accidentally in the "on" position the preamp board sends a large audio THUMP down the line as it power's up.

But beyond that, there is not that much to fear and it's just a matter of balancing the ins and outs so that each consecutive piece is operating at its optimal input and output level.  Whatever is best for the signal to noise ratio, headroom, etc...

So describe (here or in another thread) the combinations that you really like.  For instance, for recording; do you like the sound of the instruments straight DI?  Or would you prefer to run through the SuperFilter?  Or would you also want to pass through the F-2B before the recording desk? 

Then what about live?  First question; do you run your rig in stereo all the way to two sets of speakers?  And would you want to send both signals to the PA board (with specific instructions for the FOH mixer)?  Do you pass through the SF first then the 2B or vice versa?  Have you tried it the other way around?

Give us a little more info on those questions and let's see if we can't come up with some ideas.

Now my next post will address your questions about that older model preamp card you've scored...

Jimmy J

[JimmyJ]

Right, so...  The first issue with trying to swap these older pieces into your shorty are:

#1 your hum canceller is glued in place and not easy to swap out without literally using a hammer.  Sometimes they have to drill into it and use a giant screw to pull it out (or maybe I dreamt that, but I'm pretty sure about the hammer).  I kinda doubt you want to go that far to make an A to B comparison. 

#2, take a close look at the size of that "spare" hum coil and compare it to the one in your bass now.  There's a good chance it is NOT exactly the same.  And there's no way to know if it's the same depth.

#3, the connectors.  I lived through the transition period and actually have two (oddly, not three) adaptors that I got from Alembic way back when.  See the pic attached.  The tiny coax connectors on the pickup side are highly unusual (in audio) and I'd be surprised if your local repair guy had ever seen one - unless he also dabbles in microwave work.  Furthermore, these adaptors are to get from older model pickups to a newer model preamp card, not the other way around.  So assuming you don't want to bust out your hum coil, I don't know if there was ever an adaptor made to connect new pickups to an old card.  That could be rigged but you'd need to make a solder connection directly to the board.

So ... if you had these two adaptors that I'm looking at (and Mica may still have some) you could swap in the older pickups (assuming THEY fit) and connect them to your current preamp card to see what happens.  However ... does your bass have Ron's magical noise-reduction mod?  If so, those fine-tuned components will no longer do their job properly if you swap pickups or hum canceller...

I don't mean to throw water on your plans but I must also add that I believe any difference in TONE between old/new pickups, and old/new preamp boards, will be extremely subtle and very difficult to notice.  Alembic has never "cut corners" on components.  It's never about cost.  They only make changes if a component is no longer manufactured, or no longer made to the specs that they require.  There is no magic "pre-CBS", "best vintage" situation with Alembic, if you see what I mean.


Jimmy J