freestompboxes.org

Hello! It's my first time posting here. I was inspired by ROG's Professor Tweed and decided to take the '63 bassman and reproduce it using JFETs instead of tubes. I took cues from the Prof Tweed and this schematic for a modified Bassman amp and came up with this. I was wondering if anyone could have a look at this stripboard layout I came up with and tell me if I was on the right track or if I missed something.



Bassman schematic here: http://web.archive.org/web/200203170604 ... assman.gif
Professor Tweed schematic here: http://www.runoffgroove.com/professor.html

It'd be easier if you drew up a schematic for your design to reference.

I followed this: http://web.archive.org/web/200203170604 ... assman.gif
It was also at the end of my original post. The only difference is that instead of having a power transformer, it's just 9V running through a 100k pot to bias the transistors.

Niether of those circuits resemble a Fender Bassman of any vintage I've ever seen...

The 5F6-A is the classic most copied Bassman circuit and the basis for the Early Marshall amps and a bunch of tweed bassman copies...

If you're looking for a distortion box it would be a good circuit to look at...

TT

jaylow wrote:I followed this: http://web.archive.org/web/200203170604 ... assman.gif
It was also at the end of my original post. The only difference is that instead of having a power transformer, it's just 9V running through a 100k pot to bias the transistors.

What I mean is draw an actual schematic of what you're trying to put to board, not give us two different schematics and say that your plan is to combine them. There's a lot of variability there.

tictac wrote:Niether of those circuits resemble a Fender Bassman of any vintage I've ever seen...

You've NEVER seen a Blonde, Blackface, or Silverface Bassman? Pity you, they're great amps...

You've NEVER seen a Blonde, Blackface, or Silverface Bassman? Pity you, they're great amps...

Actually I've seen and worked on plenty of all the above.... Never seen a Blonde, Black, or Silverface Bassman with a 25k mid control and a 3rd stage that had negative feedback and a presence control. But hey I'm willing to say I don't know everything... If you have a schematic of a Bassman like that I'd love to see it or at least know the model number you're refering to.

I've got a complete set of vintage Fender schematic books and a set of factory schematics and the closest circuit this so called "Baby Bassman" resembles is the Normal channel of a 6G6-B.

In the 6G6-B There's no 25k mid control, the treble control is different (350k tapped pot w/ .005 uF to ground), and there's no 3rd gain stage. So I still don't see why you think this is a Fender Bassman circuit. It looks more like a Blackface Showman but with different values and no bright switch....

If I've missed something please feel free to educate me...

TT

It is a 6G6-B, it's just been modified for that extra stage and mid pot. I think the guy who designed it used to post here. I think he's one of the people who also started suggesting the use of fets for tubes in circuits like these. Once I got to the final fet, I wasn't sure what to do, which is where the professor tweed came in. That's where I borrowed ROG's "artistic license" and adopted the twin low pass filters that they used on their circuit.

Anyway, I redrew my schematic from scratch. I did it by hand because I couldn't figure out how to draw out the schematic diagram for pots in DIYLC. I also couldn't fit together as a single schematic so I broke it into two halves. The stars show where to connect the two. Please let me know how my stripboard compares with the diagram. Thanks!

So how does it compare to the schematic?