I'll start a thread here about this project.
I will post a part 1 at an appropriate time once I have enough content.

This will be my last "Woden" Bass amplifier, the name I used back in 1970-1990.
My very first guitar amplifier had 6V6's in push pull with store bought transformers.
The transformer cost was so high, (I was buying at retail) the amp was made at a loss.
That was the main reason I started to wind my own.
Winding techniques were not a problem as I was winding all sorts of things at work, motors, alternators, reactors and so on.
There may have been a little "foreign order" work done at first but once I found out where to buy or cadge small quantities of wire and insulation I kept it all at home. Besides I had moved on at work to different areas out of winding.
Once I had my home workshop built I could moonlight all I liked and made all sorts of music amps, studio desk equipment and magazine kits.
Woden Amplifiers was a great little earner with my mate George hacking out the cabinet's and getting sales, I just made the electronic bits.

Anyway enough of that, this thread is Fender Bassman time, stand by for part 1.

Fred.

Woden Bassman Fender Copy - Part 1
Woden Bassman Fender Copy - Part 2
Woden Bassman Fender Copy - Part 3
Woden Bassman Fender Copy - Part 4

I have completed part 1 where I have the basic build firmed up with a chassis made, ready to wire.
The transformers are wound and the circuit finalised.
I will build the chassis and test that for "performance" in part 2.

Then a part 3 will cover finishing the cabinet off, looks like I will cover the box with black leather, I discovered a roll of this up on a shelf.
The boxes I made back in the 70's were 1/2" or 3/4" chip board and the leather covered all the rough work nicely.
Those boxes weighed a ton but back then we were fit and strong and hardly noticed.
No body ever pinched my stage stuff, too heavy to just grab and walk away!
Bass boxes of that weight just sat were you put them and the bit that vibrated was the speaker cones not the front panel like some other cheap rubbish.

I'll work on the chassis slowly and get back with part 2.

Part 1 sent to Brad to pin to this thread.

Document uploaded to Post 1.

I have got to finish part 2!

In this I whip the amplifier into working shape and look at fitting the chassis into the cabinet.

That will be a part 3.

I will send part two to Brad to pin to this thread.

Cheers, Fred.

Part 2 uploaded.

Your practice of using a 1 Ohm resistor in series with cathodes is an excellent tip Fred.

This technique can be applied to almost any circuit, and is sure to save many incorrectly set meters from going bang.

Yes BBTV, it was especially handy when wrangling a bank of output valves and detecting the lazy or weak one.
Particularly when using 6 or 8 6CA7 in push pull. (200 to 300 watt)

I would put the valves into a duct to guide the hot air and have test points accessible so I could put a multi-meter on the test points while energised. That way a poor tube could be localised without needing asbestos gloves and trying to swap valves while hot.

Frustrating but there is not one photo or circuit details of any of my big valve amps, no build details at all.
Somehow the paper work and pictures have disappeared, there is a big gap in my build history there.

Fred.

Got the amp to a working point with a Celestion Bass driver and did an evaluation with a Guitarist.
Amp is now finished bar the front panel and cabinet bling.
Have sent a part 3 to Brad to pin to this thread.

Fred.

G'day Fred,

My apologies for the time it took to get this one uploaded. All done now.

I have finished this project and produced a part 4 for Brad to clip to the thread.

The finished amp looks great together with the guitar and plays nicely as well.

There will be another project, I made the statement that a B/W TV power transformer will be a natural for a valve guitar amp.
I skirted about the output transformer a bit so I'll put my money where my mouth is.
I'll make a unit using an Astor doubler tranny and all other parts from what you can buy from Altronics and Jaycar.
It will use 8 pin pentodes having the 6V6/EL34 pin outs.

You will have to make the chassis and cabinets yourself of course!

All suggestions welcome.

Fred.

Oh, I sent an article length summary of the project to SC for consideration for the vintage section.

Fred, some years back I was playing with some valve amp LTSpice simulations (PP 6BQ5s) and I found the simulation very accurately predicted the real thing.

I found you could get 2x the power before clipping by using transformer coupling instead of a valve phase splitter. The clipping was cleaner too.

Looking at the horrible distortion you get when you overdrive a capacitively coupled pair in AB2, I had the idea of using cathode followers in front of the OP stage grids instead of the transformer.. Doing this allows you to drive the bottles into grid current on peaks (same as you do with transformer coupled Class B) and the 6BQ5s really sit up and take notice, saturating nice and hard.

10 watts before the followers were added, 20 watts after.

I've noticed that there are some high-power valve guitar amps that do this.

Double the power is a good deal in return for adding a 12AU7 or a 6SN7! Although you do need a negative rail - about -100V or thereabouts, to pull the cathodes down. OP valve bias is applied to the grids of the followers and 1 ohm resistors in the OP cathodes allows the bias to be tweaked.

I'll see if I can find my sim circuit.

Part 4 uploaded.