DIY Tube/Mosfet Hybrid amp

[6v6]

Follow up from my [url="http://basschat.co.uk/topic/218992-diy-mosfet-hybrid-amp-donor-amp-suggestions/"]post[/url] asking for ideas for a donor amp for a DIY hybrid tube (preamp) and mosfet (poweramp) project.

Thanks to bertbass, I now have two BK 450watt mosfet power amp modules - these are similar in design to the power amp sections of the amps mentioned in the initial post (Mesa Walkabout, some Trace and Ashdown etc), so I'm hoping they will get me where I want to go (fat/punchy/warm, vintage-voiced tube preamp, with a mosfet power stage to save on weight/cost of a tube output stage)

The pics below show the starting point - the BK module, and a donor amp for the preamp, which is a previous DIY guitar amp (an [url="http://ax84.com/classicprojects.html"]AX84 P1[/url]) - the transformer in that will run around 5-6 typical preamp tubes.

So far I've stripped out the chassis, and modified it so the tubes will mount horizontally instead of vertically. This should allow me to mount it all in a head box which is not too huge (should end up similar dimensions to a classic tube head). The idea initially is to build up the preamp using whatever I have on hand, experiment with preamp designs until it sounds good, then rebuild into something a bit neater

I should probably also add the obligatory disclaimer given the nature of this project - amplifiers, and tube amps in particular, have lethal high voltages inside - [b]don't attempt anything like this unless you're very sure you won't hurt yourself or anyone else[/b] - touching the wrong part of a tube amp (or wiring it up wrong) can easily kill you.

[Beer of the Bass]

Looks like an interesting build. What are your plans for the preamp - keeping it simple or including some bells and whistles?

[JapanAxe]

Subscribed!

[6v6]

[quote name='Beer of the Bass' timestamp='1382560080' post='2253777']
Looks like an interesting build. What are your plans for the preamp - keeping it simple or including some bells and whistles?
[/quote]

I'm going to start simple, then add some bells & whistles

My plan is to start with a simple Fender-style preamp, two 12ax7's probably, gain stage, passive tone stack, gain recovery, cathode follower driver stage -> power amp

I generally play with a bit of compression, so when I've got the basic sounds dialled in, I'd like to add a tube compressor, and a tube driven transformer-coupled DI out.

Initially I was planning to model it all in gEDA, but I started and it's just too time-consuming. So instead I'll do what I've done on all my previous amp builds, cobble it together by nicking bits of existing amp designs, then tweaking until it sounds good

[JapanAxe]

[quote name='6v6' timestamp='1382692483' post='2255414']
I'm going to start simple, then add some bells & whistles

My plan is to start with a simple Fender-style preamp, two 12ax7's probably, gain stage, passive tone stack, gain recovery, cathode follower driver stage -> power amp

I generally play with a bit of compression, so when I've got the basic sounds dialled in, I'd like to add a tube compressor, and a tube driven transformer-coupled DI out.

Initially I was planning to model it all in gEDA, but I started and it's just too time-consuming. So instead I'll do what I've done on all my previous amp builds, cobble it together by nicking bits of existing amp designs, then tweaking until it sounds good
[/quote]
Sounds like a plan!

[Beer of the Bass]

[quote name='6v6' timestamp='1382692483' post='2255414']
I'm going to start simple, then add some bells & whistles

My plan is to start with a simple Fender-style preamp, two 12ax7's probably, gain stage, passive tone stack, gain recovery, cathode follower driver stage -> power amp

I generally play with a bit of compression, so when I've got the basic sounds dialled in, I'd like to add a tube compressor, and a tube driven transformer-coupled DI out.

Initially I was planning to model it all in gEDA, but I started and it's just too time-consuming. So instead I'll do what I've done on all my previous amp builds, cobble it together by nicking bits of existing amp designs, then tweaking until it sounds good
[/quote]
Cool. I'd be interested to know which design you base your compressor on. I'm slowly working on a valve preamp/class D module amp myself, but decided that all the schematics I'd seen for compressors were a little more complex than I wanted to incorporate.

[sprocket123]

Look forward to this project .