Yet another Dumble conversion...

[Normster]

I got tired of tweaking the Pignose and started ripping Loren's SF Bassman apart. ;)

Here's the story so far...
Bassman conversion, pictorial essay (http://thenormster.com/LorensSFBM/)

Mostly inspired by Gary at Glaswerks.com but with a few minor tweaks. Hopefully I'll get a chance to finish it up next week and see if any smoke leaks out. :eek:

[macula56]

nice looking stuff Normster. if you don't mind me asking, what schematic are you working off of? jmac

[Normster]

Originally posted by macula56
nice looking stuff Normster. if you don't mind me asking, what schematic are you working off of? jmac
It's basically the '77 Hybrid-A schematic with a tube reverb circuit added in place of the effects loop. Channel switching will be done via a Weber low power board. Tone stack switches will include a 500pF to 250pF treble cap switch, boost switch, and possibly a combination bright/deep switch.

[memphisrain]

Damn you Normster!!!

I just decided that I would get a Zendrive and wait until I could have Fuchs do a mod on my SF Bassman, but here you are doing that to the exact same model of Bassman I have...


G.A.S. attack......

Where did you come up with that snazzy layout sheet that you've got under the board? And where can I get a copy of it?


Thanks,
mR

[glasman]

Originally posted by Normster


Mostly inspired by Gary at Glaswerks.com but with a few minor tweaks. Hopefully I'll get a chance to finish it up next week and see if any smoke leaks out. :eek:


Glad to see someone looks at the site. Hmmmm, that reverb looks mighty familar. :)


Good luck with the amp..


BTW, what kind of tweaks? Always curious to see what others are trying.

Gary

[Normster]

memphisrain - The diagram is in Visio format. Shoot me an email (nfeaster <at> comcast.net) and I'll mail it to you. It's not completely accurate so you'll have to use the Hybrid-A schematic on blueguitar.org to verify the switch connections.

Gary - Your site has been a major inspiration for me. I especially like the way you mounted the relays to the board...makes for short elegant connections to critical tone circuits. This time around I'm just using a Weber channel switch board, but as you can see, I left plenty of room on the board for relays. :)

The tweaks are mostly in the tone stack area. I'm going to be trying a few different combinations of Dumble's switching schemes to see which ones I like best.

BTW, where did you mount the 220k grid resistor (return from tank)? I see it on your schematic but can't locate it on your board.

Thanks,
Norm

[glasman]

Originally posted by Normster


The tweaks are mostly in the tone stack area. I'm going to be trying a few different combinations of Dumble's switching schemes to see which ones I like best.


I did the same thing on my personnal amp. The treble and mid caps have three different settings available.





BTW, where did you mount the 220k grid resistor (return from tank)? I see it on your schematic but can't locate it on your board.

Thanks,
Norm

Hey Norm, you discovered the missing component on the board. When I designed that version I forgot to add it to the board so I ended up putting it right at the RCA jack for the reverb return. I have since corrected this devine screw- up in later boards.

I just drilled up 8 new boards of two different designs that I will be using in a set of amps I am currrently building. The first three amps of this set are a 20 and 50 watt that are similar to the previous amps I have built and the third is a 50 watt amp with a few (LOT) more bells and whistles.

Gary

[TheAmpNerd]

Now that looks like a lot of phun.

Me thinks I could be inspired.

[Normster]

Originally posted by TheAmpNerd
Now that looks like a lot of phun.

Me thinks I could be inspired. Check your mail. ;)

[scottl]

Originally posted by glasman
the third is a 50 watt amp with a few (LOT) more bells and whistles.

Gary

Sounds great!!! Sign me up!!! LOL

;)

[Normster]

Finally done!!!

One minor wiring problem on first fire-up. (Had to reverse the OT wires.) After I fixed that, the amp just sang! I dropped it off at Loren's today and he's grinning from ear to ear. Hmmm...I wonder what I should build next? ;)

[glasman]

Originally posted by Normster
Finally done!!!

One minor wiring problem on first fire-up. (Had to reverse the OT wires.) After I fixed that, the amp just sang! I dropped it off at Loren's today and he's grinning from ear to ear. Hmmm...I wonder what I should build next? ;)


So how did the reverb work out?


Gary

[Normster]

Originally posted by glasman
So how did the reverb work out?


Gary Reverb came out pretty sweet. I used a 1Meg pot (since I didn't have any 2Megs lying around) so it's very subtle, but Loren uses very little reverb anyway. It does act a little strange past 2 o'clock...like a boost circuit, but as I said, Loren doesn't use much reverb.

After he plays it for a week or so, I'm going to get it back, install the foot switch relays, and put in the correct pot value.

Thanks again for sharing your layout (and wisdom)!!!

Norm

[Richard Guy]

Very nice :)

[darkbluemurder]

Gary - Your site has been a major inspiration for me. I especially like the way you mounted the relays to the board...makes for short elegant connections to critical tone circuits. This time around I'm just using a Weber channel switch board, but as you can see, I left plenty of room on the board for relays. :)



Thanks,
Norm

Normster,

how did you wire the Weber relay board to the switch - I am confused since it says it should connect the tip to the ring and neither of them should be grounded. Do I need an isolated stereo jack to do this?

Any help would be greatly appreciated.

Thanks a lot and keep on rockin'
Darkbluemurder