B-15 Preamp

[ogrepraxy]

Hello everyone. I am currently trying to learn to read schematics, and the how the various parts of an amp work together.

I’m wanting to build myself an Ampeg B-15, but just the preamp, and add an active direct out.

Can anyone help with this mod?

 

[ruffrecords]

First thing you need to do is post a schematic so everyone can see what you are talking about.

Cheers

Ian

 

[rock soderstrom]

I’m wanting to build myself an Ampeg B-15, but just the preamp, and add an active direct out.

Can anyone help with this mod?

Hi ogrepraxy,

here you will find some info on this topic:

https://groupdiy.com/threads/direct-out-for-ampeg-b15-style-build-a-la-reddi.68043/#post-866948

The first question you should ask yourself is the purpose of the preamp. What should it be able to do? Should it work in front of a power amplifier or as a recording pre amp directly into a line input of your audio interface? Do you need to drive real low impedance inputs like 600R of some vintage gear like compressor/limiters?

The B15 already has an output for an external power amplifier. If you want to drive lower-impedance inputs, you need a corresponding output section, which can be realized in different ways.

A tube cathode follower with or without transformer (do you need galvanic isolation?) would be conceivable or a solid state variant like this source follower would also be possible. You choose...

Check out groupdiy, a similar topic has already been thought through here for a modified Alembic F-2b.

Attached b15 schematic:

 

[Newmarket]

Hello everyone. I am currently trying to learn to read schematics, and the how the various parts of an amp work together.

I’m wanting to build myself an Ampeg B-15, but just the preamp, and add an active direct out.

Can anyone help with this mod?

I'm going to have to say that if you are currently learning to read schematics, then you need to concentrate on that before taking on a build project. And yes - by all means post a schematic along with any questions about it.

 

[fazer]

Here’s some schematics

Early to late 60s

 

[abbey road d enfer]

Hello everyone. I am currently trying to learn to read schematics, and the how the various parts of an amp work together.

I’m wanting to build myself an Ampeg B-15, but just the preamp, and add an active direct out.

Can anyone help with this mod?

First question: are you able to isolate the preamp part in the global schematic?
When you have, you'll have to figure out how to power it; you don't need the big power supply the full amp has. This something you'll have to create. The output stage comes later.

 

[Tubetec]

The sound of the B-15 isnt only due to the preamp ,
in fact most of the character comes from the O/P stage and speaker ,
which distorts readily at low frequencies ,