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I De Tweeded My 5F6A Bassman 
I got snowed in Dec. 24, and have only been able to get out 6 times until this week. (Not so much snow here but I am 63 with a 300 foot uphill driveway and a bad ticker LOL)
So I went a little nuts looking for something to do, so I tore into the 5F6A Tweed Bassman clone I scratch built in 1998/99, I got the transformer set from Doug Hoffman so they are the real deal replacements as far as I know.
I think it turned into a pretty cool and versital sounding combo amp but all the "Tweed" is gone. I am not quite sure what to call this amp now so I just refer to it as my "DeTweed" combo amp.
I started at the first stage and gave myself 3 different switchable voices (load lines) to choose from. It doesn't throw you directly into a JM45 but it does add a bit of variety.
Then I added the Weber Active Tone Stack in place of the usual drain to ground tone circuits from Fender, Vox, Marshall etc. Wow what an impact it has on my over all tone. The midrange is the most "dynamic" of the three controls. It took a bit of "tweaking" but I like it's performance and the added gain.
I changed the Presence circuit from the Tweed style to the 6G6 style and that made a little improvement in it's performance.
I left the PI alone, but I added a Post PI Master Volume control to the power amp making the original volume control the master GAIN control. This improvement alone is well worth a few dollars in parts and little time it took to do this mod.
Then I went back and orphaned V1-B to use later for an upcomming modification. Either as a reverb recovery OR as a Boost stage to V1-A
I had to stiffen up the power filtering a bit, so I am now at 40-C-40-20-8
I added a Hum Balance pot which eliminated the little bit of heater noise I did have, but it seems to make my PT run hot so I removed it and went back (for now) to the floating 100 ohm resistors.
As long as I was playing around in the power supply I decided to add a Solid State - Tube rectifier switch just for grins and giggles. A simple no brainer install and was dirt cheap to do. I get about a 40VDC gain at the first filter.
While I was doing all this over a several week period I changed all of the signal and coupling caps. In the Active Tone stack I used the AES foil in oil MOD capacitors. The .022 coupling caps are the MOD FIO and the first two coupling caps are those Russian PIO caps that are on the current market.
I forgot to mention in the beginning of this post that when I originally built my 5F6A I built it with a 4x6V6 power amp instead of 2x5881/6L6. I also added 1.5K swamper resistors and 1 ohm bias test resistors to the power amp.
I am refurbishing the 12 year old Walnut cabinet and Cane grill while I am at it too.
I know every one here already knows what a 5F6A Tweed bassman schematic looks like but...
http://www.el34world.com/charts/Sche...SSMAN_5F6A.pdf
So here is what my severely "De Tweeded" Bassman? looks like on paper.
These drawings reflect "as built'.
I am going to use the orphaned triode for a BOOST stage later.
I got snowed in Dec. 24, and have only been able to get out 6 times until this week. (Not so much snow here but I am 63 with a 300 foot uphill driveway and a bad ticker LOL)
So I went a little nuts looking for something to do, so I tore into the 5F6A Tweed Bassman clone I scratch built in 1998/99, I got the transformer set from Doug Hoffman so they are the real deal replacements as far as I know.
I think it turned into a pretty cool and versital sounding combo amp but all the "Tweed" is gone. I am not quite sure what to call this amp now so I just refer to it as my "DeTweed" combo amp.
I started at the first stage and gave myself 3 different switchable voices (load lines) to choose from. It doesn't throw you directly into a JM45 but it does add a bit of variety.
Then I added the Weber Active Tone Stack in place of the usual drain to ground tone circuits from Fender, Vox, Marshall etc. Wow what an impact it has on my over all tone. The midrange is the most "dynamic" of the three controls. It took a bit of "tweaking" but I like it's performance and the added gain.
I changed the Presence circuit from the Tweed style to the 6G6 style and that made a little improvement in it's performance.
I left the PI alone, but I added a Post PI Master Volume control to the power amp making the original volume control the master GAIN control. This improvement alone is well worth a few dollars in parts and little time it took to do this mod.
Then I went back and orphaned V1-B to use later for an upcomming modification. Either as a reverb recovery OR as a Boost stage to V1-A
I had to stiffen up the power filtering a bit, so I am now at 40-C-40-20-8
I added a Hum Balance pot which eliminated the little bit of heater noise I did have, but it seems to make my PT run hot so I removed it and went back (for now) to the floating 100 ohm resistors.
As long as I was playing around in the power supply I decided to add a Solid State - Tube rectifier switch just for grins and giggles. A simple no brainer install and was dirt cheap to do. I get about a 40VDC gain at the first filter.
While I was doing all this over a several week period I changed all of the signal and coupling caps. In the Active Tone stack I used the AES foil in oil MOD capacitors. The .022 coupling caps are the MOD FIO and the first two coupling caps are those Russian PIO caps that are on the current market.
I forgot to mention in the beginning of this post that when I originally built my 5F6A I built it with a 4x6V6 power amp instead of 2x5881/6L6. I also added 1.5K swamper resistors and 1 ohm bias test resistors to the power amp.
I am refurbishing the 12 year old Walnut cabinet and Cane grill while I am at it too.
I know every one here already knows what a 5F6A Tweed bassman schematic looks like but...
http://www.el34world.com/charts/Sche...SSMAN_5F6A.pdf
So here is what my severely "De Tweeded" Bassman? looks like on paper.
These drawings reflect "as built'.
I am going to use the orphaned triode for a BOOST stage later.
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