DIY Alembic F-2B? Help Super-electro-Engineers!

AppliedStucco · #1 09-28-2007, 08:54 AM

Well, I decided to drop the DIY compressor project, since I figured out that if I want a well-sounding and adjustable comp, I will need to buy one. (prob. the Boss LMB-3)

So, I thought why not build a simple tube preamp, like the Alembic F-2B? I found a couple of schematics, but both of them lack an exact transformer specification: one of the three voltages is missing and I have no idea what to ask for. Could anyone of you many and totally ubercool

electric engineers in here help me out?

Thanks a bunch in advance...

http://www.freeinfosociety.com/elect...alembicf2b.gif
http://www.geofex.com/FX_images/alembpre.gif

Beachcoma · #2 09-28-2007, 09:03 AM

First of all, B+ needs to be around 300+ V. If you don't know how to get this, don't even think about building it as it could kill you.

Rob

AppliedStucco · #3 09-28-2007, 09:11 AM

Oww... Ok.

Project F-2B has been shut down due to dangerous conditions.

bongomania · #4 09-28-2007, 10:43 AM

Yeah, that's why I made that comment in the diy compressor thread about "you don't even want to try building a tube comp until you're more experienced"... it wasn't a knock against you, just an advisory about the inherent danger.

SneakyT · #5 09-28-2007, 11:30 AM

I love how everyone acts as though anyone building their first tube stuff is a moron and is going to plug the thing in and connect the leads from the power supply to their finger and kill themselves. Jesus!
Don't cancel the project just be cautious. Do lots of research. Seriously. Lots of it. If you don't feel comfortable at first and want to do a few pedals until your more comfortable that's cool, but don't let these guys scare you into completely abandoning the project. Just don't go into it blind. I mean, I cant think of an easier circuit than the f2b to start on as far as tube stuff goes.

I really like the power supply here
http://moosapotamus.net/IDEAS/F2B/alembic.htm
When I get around to building one this is probably the way I would go. Now prove everyone wrong and don't go kill yourself. Oh yeah, I am not liable if you are a moron and do go kill yourself either.

BTW: I will not get into a flame war over this. If some one disagrees and wants to argue their point; I won't even check back. Don't waste your time.

bongomania · #6 09-28-2007, 11:53 AM

Since you're not going to check back, you won't mind if I say there might have been a less reactionary, more constructive way to put all that. Also, I bet you've never come close to death from a serious electrical shock. I have! And I was following the foreseeable precautions that I knew about. I would not have taken that hit if I had known what I know today.

Jonyak · #7 10-04-2007, 01:25 PM

Its also not about plugging the mains into your finger. its all about the filter caps. they can retain ALOT of charge for a long time. and if you don't be really careful you can kill yourself just by touching the lead or any trace that is connected to the leads.

otherwise go nuts.

moosapotamus · #8 10-04-2007, 03:05 PM

Before I ever built anything from scratch that required mains power, I started off with a kit for a tube mic preamp. Just having all the right parts along with proper instructions gave me a lot of confidence, especially when it came to putting the power supply together. Then when I moved on to building the F2-B from scratch, I already had a little bit of experience under my belt, so it went together pretty well.

If you want to get into building high voltage tube circuits, I suggest starting off with a kit of some sort. If you hunt around on the net, you can probably even find a kit for just a power supply. After you've built the power supply, the audio part of the tube circuit can be a piece of cake.

Oh, and if you want to build my power supply, the mouser part number for the transformers I used is on the schematic.

~ Charlie

AppliedStucco · #9 10-05-2007, 03:15 AM

Thanks again all of you...

You have been of great help... I don't consider myself a moron

, but I do know I am inexperienced and many times just clumsy. I am still going to think about it a great deal, and perhaps I first should start with a kit, as moosapotamus pointed out.

For now, I will keep myself busy with the ultra-simple Ampeg Scrambler.

Sir Edward V · #10 10-05-2007, 09:11 AM

Good plan.

Tristan · #11 10-05-2007, 09:13 AM

If you get a bit more advanced you might consider build a JFET based F-2B clone... it would run on lower voltages and would probably sound pretty nice for solid state.

musicelectronix · #12 10-08-2007, 12:18 AM

AC voltage can kill you, even if the device is not plugged.

Go to runoffgroove.com and througly read the article about fetzer valve. Then go to http://www.storm-software.co.yu/diy/...ject=dr_boogey and check out the tube to JFET conversion.

Use the Gate resistor as 6.8 to 10K and the drain as 1.8 to 4.7. For bass guitars, use 47uf to 100uf for the drain cap. I would suggest 2n5457 or J201 as the jfet. If you can find 2n4856 is also a great choice, though no one produces it anymore.

I suggest using no caps for the first gain stage (before the tone stack) and for the second one put a series resistor along with the cap around 330-470 Ohms. Also use an input cap rated around 3.3uf-4.7uf and replace the output cap with the same value.

Here is your tube sound (well.. as close as it gets) without tubes!

Hawaii Islander · #13 10-09-2007, 11:52 PM

It really wouldn't hurt to take a home-based self study basic electronics course. At a minimum, I would get some basic electronics books and do some reading.

It may seem like a simple suggestion, but I highly recommend you set up a well organized workspace with appropriate tools and safety equipment. It will be especially important when working with high voltage / high current electronics. Do some research on how to setup and maintain a safe electronics workbench.

Good Luck!