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65' bassman mods

WaltC

Member
Messages
2,129
What are you looking for? The amp is pretty valuable box stock, so why mod it? Many mods will *significantly* affect the value of the amp and don't, on balance, really add much to the sound. Many mods have been done over the years to try and make the Bassman sound like a VHT or a Mesa or a Marshall, and the amp usually ends up sounding worse and not all that much like the intended amp.

It's been my experience that if you want an amp the sounds like a Mesa, then buy a Mesa. Anything less will screw up the donor amp and leave you unsatisfied anyway.
 
Messages
1,059
Mod the bias to aa864 specs. Good american 6l6gc's. RCA 7025's and a fresh servicing of caps. Add a mid pot where the ground switch is located. Stand back and be prepared to be amazed.
 

Swarty

Member
Messages
1,130
Make it a "real" guitar amp... turn it into a 5F6A w/ solid state rectifier. You have just inputs and knobs.
 

hasserl

Member
Messages
4,711
Make it a "real" guitar amp... turn it into a 5F6A w/ solid state rectifier. You have just inputs and knobs.
The stock Bass channel is pretty useless as a guitar amp, it makes a great platform for mods IMO. A modified 5F6A circuit works great, you've got an extra triode sitting there unused that you can use for the cathode follower to drive the tone stack. This sounds fantastic and is a nice option to have on hand vs the stock Bassman normal channel, gives you tweed and bf in one amp. I like to jump the channels and use both together and blend the volumes to suit the tune and/or my mood. Such a mod does not entail any permanent changes to the amp, just a few wiring and component changes on the board, and IME does not negatively impact the value of these amps, if anything it enhances it.
 

JDJ

Member
Messages
3,705
The stock Bass channel is pretty useless as a guitar amp, it makes a great platform for mods IMO. A modified 5F6A circuit works great, you've got an extra triode sitting there unused that you can use for the cathode follower to drive the tone stack. This sounds fantastic and is a nice option to have on hand vs the stock Bassman normal channel, gives you tweed and bf in one amp. I like to jump the channels and use both together and blend the volumes to suit the tune and/or my mood. Such a mod does not entail any permanent changes to the amp, just a few wiring and component changes on the board, and IME does not negatively impact the value of these amps, if anything it enhances it.
Any links to schematics for this mod?
 

zombiwoof

Silver Supporting Member
Messages
5,819
There's a pretty cool mod that used to be done by a couple of amp guys (Allen Amps, for one, when they used to do mods), that makes one channel into a Marshally channel and the other optomized for the Fender sound. If I still had my Bassman, I would have looked into that mod. Not sure who does it these days.

Al
 

jamme61

Gold Supporting Member
Messages
1,351
i took my bass channel and made it ito a marshall 2204. You have the extra side of the 12ax7 sitting there not being used. I was able to wire it just like the marshall 2204, and leave the normal side alone. I did also add adjustable NFB pot (mounted in guitar input 2 of normal channel) and added a cap to add presence, to the amp. On the bass channel of the amp, I have the one input for guitar, the next guitar input is now the gain pot, the bright switch, is now where the volume pot is, and then I have treble, mid, bass, pot. it works freakin great! and this has become my ultimate amp. i did also double up the filtering which added more bass and punch. i swear this amp sounds great. I did use shielded wire for all my grid wires, for the marshall side. to me this is what i always wanted, a marshall on one side and Fender on the other.
 

hasserl

Member
Messages
4,711
There's a pretty cool mod that used to be done by a couple of amp guys (Allen Amps, for one, when they used to do mods), that makes one channel into a Marshally channel and the other optomized for the Fender sound. If I still had my Bassman, I would have looked into that mod. Not sure who does it these days.

Al
This is basically the same thing I posted above, a Marshall is a copy of a Fender 5F6A.
 




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