Friends,
I have a bassman 10 and I am considering mods to make it closer to it's Bassman brethren. I was considering changing the PI to a 12 ax7 and using a cathodyne phase inverter instead of the current ltp. Any thoughts?
Improving a bassman 10
Moderators: pompeiisneaks, Colossal
Re: Improving a bassman 10
Which brethren ? There are a lot of variations on the Bassman.sdorer wrote:Friends,
I have a bassman 10 and I am considering mods to make it closer to it's Bassman brethren.
The 4x10 open back Tweed style ? Or do you want to keep the cabinet as-is ?
Is this for guitar or bass ?
The Bassman 10 is a great mod platform with lots of space to add tube sockets.
See the "Bazzman" thread for one approach.
You have to be careful about overdriving a cathodyne.I was considering changing the PI to a 12 ax7 and using a cathodyne phase inverter instead of the current ltp. Any thoughts?
The same thing that lends a cathodyne to be used with 6V6s can be a limitation with 6L6s that want a higher drive signal.
Make sure you have a good sized grid stopper and plenty of B+ on the plate.
rd
Re: Improving a bassman 10
Oh yes, now I'm getting excited! 
I've learned much of what I know about tube amps by working on my Ten for years. It's sort of my lab. I'm Doctor Ten!
Seriously, like rd says, it's easier to help if you can specify what you want to achieve.
First of all, the original speakers really do suck (and I don't usually use that word). So does the cab construction, for guitar purposes.
A cathodyne would not be like any other bassmans, and I don't really see why you would do that. But why not.
You can put a 12AX7 in the PI as it is without any mods.
When it comes to making it exactly like another bassman, your options are limited since you'd need one more preamp tube.
But the studio channel, with a few mods, is basically like the 'normal' channel of any silverface Fender.
I've learned much of what I know about tube amps by working on my Ten for years. It's sort of my lab. I'm Doctor Ten!
Seriously, like rd says, it's easier to help if you can specify what you want to achieve.
First of all, the original speakers really do suck (and I don't usually use that word). So does the cab construction, for guitar purposes.
A cathodyne would not be like any other bassmans, and I don't really see why you would do that. But why not.
You can put a 12AX7 in the PI as it is without any mods.
When it comes to making it exactly like another bassman, your options are limited since you'd need one more preamp tube.
But the studio channel, with a few mods, is basically like the 'normal' channel of any silverface Fender.
Re: Improving a bassman 10
The 5e6 has a cathodyne phase inverter at least it appears so to me. What would you suggest we do with the speaker config. This is my son's amp. I find this amp sounds thin with a guitar and no mids at all. I was hoping replacing the 12at7 would give a little beef. Should we try a paraphrase inverter?
Re: Improving a bassman 10
You don't have to change the PI circuit to run it on 12AX7. Just replace the tube, it works fine. It will make the amp a bit more "lively", at least when turned up.sdorer wrote:The 5e6 has a cathodyne phase inverter at least it appears so to me. What would you suggest we do with the speaker config. This is my son's amp. I find this amp sounds thin with a guitar and no mids at all. I was hoping replacing the 12at7 would give a little beef. Should we try a paraphrase inverter?
The 5e6 has a cathodyne, but it's a completely different circuit.
To boost the mids, you could increase the value of the mid pot in the 'studio' channel. It's now 10K. Make it 25K, or even 50K.
The 'normal' channel is a more involved affair, with something reminiscent of a Baxandall tonestack. The studio channel is better suited for small mods.
But I still think the key in your case is the speakers and the cab.
Unfortunately there is not much to do unless you want to ruin the original cab. Which you might not, in an old Fender.
The not-so-good speakers are inside a closed plywood box, which in turn is inside the closed-back outer cab. Might work for bass, but not so good for guitar.
For my Ten, I simply built a new cab, in a more portable 2x10" format.
By the way, do you know what year the amp was made? The late Tens have ultralinear output stages.
This is the schematic for the older version.
[img:800:603]http://www.ampwares.com/schematics/Bassman_10_alt.jpg[/img]
