• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Tube preamp scheme.

#4
Take a look at the front end of an Ampeg B15. It's about as simple and straightforward as a pre-amp can be. If you are wanting to use this to drive a SS stereo power amp, you'll need to add a cathode follower to the output, preferably with some kind of output transformer. That should be a simple task for an engineer with a knowledge of tube electronics.
 
#13
bgavin said:
Has anybody seen an "open source" schematic for the ultimate DIY design?
Click to expand...

Are you volunteering? ;)

A nice idea might be to show a preamp build, progressively, starting with the most basic features. A couple of gain stages with a passive tone stack in the middle is about as basic as it gets. Then you can add things like midrange, DI, etc.
 
#14
fdeck said:
Are you volunteering? ;)

A nice idea might be to show a preamp build, progressively, starting with the most basic features. A couple of gain stages with a passive tone stack in the middle is about as basic as it gets. Then you can add things like midrange, DI, etc.
Click to expand...

+1
I agree that starting with a very basic pre would be the way to go. At least starting out, you could probably get nice results with a couple gain stages, a SIMPLE eq, and cathode follower.

It would not be the most versatile device ever crafted, but you would have the ability to tweak it more to your liking, and develop a better picture of where you want to take it from there.

And you never know, a simple clean pre with minimal eq just might be your dream tone :D
 
#15
A single channel Alembic F2B is about as easy a tube preamp build as you will find. And they sound great. I did one a while back and I love it. It was however my 27th amplifier or preamplifier build. Mine isn't exactly stock either--D.I. out as well as the normal output, cathode follower, a few extra switches. So do some reading, look at a LOT of pictures of finished builds to get an idea of how these things are put together.
 
#16
fdeck said:
Are you volunteering? ;)
Click to expand...
I wish, but I'm not at all literate in circuit design. Speakers are my thing.

I've seen a few point-to-point photos here on TB of units that are superbly constructed for ease of service.
These don't have the compromises required for mass production, i.e. surface-mount, printed circuit boards, pots soldered to boards, etc, etc.

This is not the correct forum, but I suspect somewhere there is in-depth discussion about circuit design for the ultimate bass preamp.
My SVP-Pro schematic thread got a bit of discussion going, but it did not continue.
Some of the smart design guys were chiming in as to why a particular circuit was good or bad, and what was required to improve it.

I wouldn't object to paying top dollar for a well-designed custom preamp, with full schematic, that is fully serviceable (point to point) long after the maker exits the business.

My daughter's 1985 JCM-800 is an amp like this.
 
#17
bgavin said:
I wouldn't object to paying top dollar for a well-designed custom preamp, with full schematic, that is fully serviceable (point to point) long after the maker exits the business.

My daughter's 1985 JCM-800 is an amp like this.
Click to expand...


What's your idea of top dollar Bruce? And how custom would it need to be?

Personally, I don't consider turret or terminal board construction to be functionally any better or worse than good printed circuit boards -- especially if they're wired by a beginner's hands. The '85 JCM800s used a printed circuit board, BTW. '85 is right around when Marshall started doing board-mounted pots and jacks too, so your daughter's amp is quite desirable if it's the old style build.
 
#19
I mistook the OP's comment to read that he considered the Alembic F2B or Ampeg SVT Pro to be an example of the "must not be expensive" type. :hmm: I think you'd struggle to find a tube preamp simpler or less expensive than an F2B. Maybe with no tone controls?
 

Latest posts

Top Bottom
Back