Alembic Tube Preamp F-2B question?

[Tomass_17]

I was wondering if this is something a intermediate project builder could tackle, i have never built something from a schematic so if anyone has a parts layout of this, that would be great. Also i live in Australia so our power rating is 240AC, would i have to use a 240V mains transformer? Everything is availible at the local Jaycar so thats no problem, neither is cost

[bancika]

sure, my first electronics project was ax84 firefly
just be careful

[KB]

I don't think that there would be many problems.  Just be careful, the voltages in this thing are a lot higher this thing runs on 300V.  If you are unsure about high voltages then find someone who is and ask for help.

More information is available at Charlie Bath's site:

http://moosapotamus.net/IDEAS/F2B/alembic.htm

He has drawn up some schematics and layouts and had some information about the power supply. 
As I understand it the F2B is very similar to a Fender Blackface Bandmaster preamp that has been modified for Bass guitar frequencies.  So get the Bandmaster schematic to help.

I know David Gilmour uses one and have read that it has been modified for guitar, how I am not sure.

Kevin

[moosapotamus]

Don't let me discourage you, but... If you do not know how to translate a schematic into a finished build, I suggest you tackle something that is designed to operate at 9V instead of 300V or more.

The first high voltage tube circuit that I ever built was a kit that came with PCBs and great instructions. The F2B I'm currently in the process of building from scratch is now the second HV project I've tackled. I would not have had the confidence to build something like this (high voltages) from scratch unless I had first done that kit. So, I would be remiss if I didn't also write...

WARNING: The voltages in this circuit can kill you. If you are not familiar with building amplifiers or other high voltage circuits, go educate yourself before diving in. At an absolute minimum, do a www search and read up on safety concerns when working with high voltages.

If you still want to build an F2B, I'd suggest working out your power supply first. It's the most dangerous part of the build and you need to account for your particular mains voltage. I would not recommend building the PSU that is shown in the schematic. It contains a voltage doubler and the transformer and input/output voltages are not specified. Much safer to just put your own PSU together.

The transformers I used have dual primaries and secondaries. So, they can be wired in either series or parallel to either accept or generate different voltages. If you haven't already, go get Duncan Amps' PSU Designer. You might be able to use a PSU circuit like mine with some wiring changes.

You should probably be able to work it all out yourself. Don't just do what some guy on the internet said. Rather, read up and convince yourself that what you are doing is safe and will work as you expect.

It's a great sounding circuit (I'm planning to use it for bass), and it'll be very cool once it's properly built. But, until then, it's potentially very dangerous. Be cool. Be careful... then have fun.

~ Charlie

[JonFrum]

Here's a nice rack mount build:

http://www.frontiernet.net/~jff/af2b/Dual_Channel_Blackface-style_Preamp_for_Bass_Guitar.html


If you're going to do it, I'd suggest that you ask for advice over at ax84.com. There are guys over there that have done similar builds, and the builder of the linked amp above hangs out there sometimes.

For general amp building info, go here:

http://aikenamps.com/TechInfo_2.htm

First, read the safety tips in the Beginner section, then read as much of the rest as you can. Randall Aiken is The Man in tube amp building.

[Tomass_17]

thanks for the great advice, that preamp that JonFrum posted looks more promising. I plan on going around to the local electronic repair shops and showing the schematic of both preamps and just ask for advice on the high voltage situation. I will also ask one of my school teachers about how i would go about building this. Its not something worth dieing over.

[wui223]

I am planning to build Alembic F2B also. Recently built a McTube2. I plan to match the Alembic with a SS power amp to use with bass guitar.

[JonFrum]

If you are a careful worker, there's no reason to worry about the voltage. Thousands of DIY guitar amps have been built by guys with little or no electricity/electronics education. When you fire up the build, you do need to know how to remain safe, but the rules are few and simple. Read the Aiken article I mentioned above and you'll know more than most guys that buy kits.

[fikri]

The F-2B is similar to other types of fender preamps. I have built it for guitar use http://fikri_ilyas.blogs.friendster.com/photos/fender_in_a_box/img_4390.html And use a doubler as the power supply.

Find yourself a 'safe place' to build this project. Happy building !

[Ben N]

This is an interesting thread, and a great project.  But I have always wondred about the utility of having two identical channels--I mean, how many people ever used both channels on an actual Fender?  Might it make more sense to use the second 12ax7 either as (a) a switchable overdrive section, a la Dumble, or (b) as a fully padded fx loop, like the Dumbleator or Vox?

Just a thought.  Good luck with your project.

Ben

[JonFrum]

This is an interesting thread, and a great project.  But I have always wondred about the utility of having two identical channels--I mean, how many people ever used both channels on an actual Fender?  Might it make more sense to use the second 12ax7 either as (a) a switchable overdrive section, a la Dumble, or (b) as a fully padded fx loop, like the Dumbleator or Vox?

Just a thought.  Good luck with your project.

Ben

To keep it simple, I'd just voice one channel for guitar and one for bass. Otherwise, your suggestions are definitely good ones.  As a first project, a Firefly, P1 or Champ are probably better - more bang for the musical buck.