Possible MOD for 3rd Gen Low-Plate ODS

[Paul-in-KC]

All - here is a novice question from a first-time D-type builder.

I am working on building a 3rd Gen Low-Plate ODS based on the "3rd Gen Period Correct" post which has a nice layout and schematic. And I wanted to build a 50W variant - so, I picked that documentation for my base.

Now, I purchased a chassis from Amplified Nation (Taylor Cox) - which is beautiful, but it's drilled and screened for what I will refer to as 4th gen + (though I don't know if that's really proper nomenclature). What I mean is, it has the Master and Presence controls (pots) in the Power Amp section of the front panel.

Whereas the 3rd Gen has a "Level" (Master Volume) and "Accent switch".

It looks like it would be fairly simple to add the "Ratio" (OD Volume) pot at the front of the OD circuit and swap the "Presence" pot/circuit for the "accent" switch in front of the PI.

Is there any reason I shouldn't do this?

Many thanks to all - as always,
-P.

[mojotom]

If you plan to build a 70's amp there is a layout on the forum (inspired by a 70's from Bludotone) with a separate master for the OD and a 12AT7 PI slightly modded with a later generation presence control (4k7/390R feedback network, 2k pot/1uF presence network).

The 70's didn't have a "master"or "level" on the OD (along with a specific OD entrance network) so his idea of switching masters (rather than an OD level and global master like later generations) seems like a good idea for those amps, especially if you have a regular chassis.

You could wire a presence pot and cap to the 3rd gen PI with 47R/100R and 820R feedback network like Fender but it won't be as useful (less range) than using later gen values.

70's bludodrive :
https://tubeamparchive.com/viewtopic.php?f=4&t=12533

I couldn't find the layout (inspired by the Bludo). Will check later.

[Paul-in-KC]

If you plan to build a 70's amp there is a layout on the forum (inspired by a 70's from Bludotone) with a separate master for the OD and a 12AT7 PI slightly modded with a later generation presence control (4k7/390R feedback network, 2k pot/1uF presence network).

The 70's didn't have a "master"or "level" on the OD (along with a specific OD entrance network) so his idea of switching masters (rather than an OD level and global master like later generations) seems like a good idea for those amps, especially if you have a regular chassis.

You could wire a presence pot and cap to the 3rd gen PI with 47R/100R and 820R feedback network like Fender but it won't be as useful (less range) than using later gen values.

70's bludodrive :
https://tubeamparchive.com/viewtopic.php?f=4&t=12533

I couldn't find the layout (inspired by the Bludo). Will check later.

mojotom,

Thanks so much for your comments and the reference material!

[erwin_ve]

Link to the 70-ies hybrid layout: https://tubeamparchive.com/viewtopic.ph ... 30#p352544

[Paul-in-KC]

Link to the 70-ies hybrid layout: https://tubeamparchive.com/viewtopic.ph ... 30#p352544

erwin_ve,

Thank you sir!