Fender Idea Needs Fresh Eyes...

[dorrisant]

Here is something that I've been working on....

Bandmaster channel with added Middle control.

Tweed Bassman with added Slope control.

Global Blackface reverb.

Global Vibroverb.

I think I have this right. I am still questioning the mixer/reverb tap and inject points. Also wondering if I have the Presence control correct. I guess it doesn't really have to be there, but I think it would be a nice complement to the Bassman ch in particular. Also, should the BF channel get a 10k mid pot instead of the 25k I have in there?

Although not shown, it will have a PPIMV and relay control of channel, reverb and tremolo.

This is what a friend and I came up with a few weeks back, back of the envelope to schematic. It is kind of what we think is some of the best of Fender organized in one chassis. Please look over the schematic and tell me if anything looks wrong. If there is any interest, I will share a board layout that will fit the normal board footprint, although the mount locations are different. Note - This amp will have two extra preamp tube sockets and an extra filament TX. Don't know where I'll put them, but it will have them.

[Stevem]

Where’s the reverb pan?
All I see is the pan drive transformer!

Also in regards to having a good sounding reverb which hinges more on driving the transformer with a good level of current I would use the common 12at7 or even a 12au7 to replace the ax7.

Depending on your needs and or wants of the black face channel you might want to address the fact that the common Fender tone stack can not produce a mid boost, only a cut, that is unless you run the treble and bass way down and the mid cranked, which when done that way gives you a bit of a mid boost, but leaves you with little overall signal level left.

Also in my opinion you made the same mistake that Fender did in that your powering 3 gain stages off of one filter node.
I think it’s best to never have more then 2 gain stages powered off of any one filter node so that good decoupling is guaranteed!

[bepone]

Please look over the schematic and tell me if anything looks wrong.

you are missing some supply electrolytic on the schematic? elcos are cheap no need to save on them

[pdf64]

Given RV4 the shunt feedback resistance of 5k, at 820ohms, the series feedback resistor R40 value seems rather low. The power amp would have low gain, and possibly operational issues, eg poor stability. Something in the range 10k to 100k would be more typical.

[dorrisant]

Thanks guys, I will add more filtering, not a problem. Also, I completely spaced on the tank. Holy cow. I think the Middle pot will stay, just trying to decide on 10k or 25k. Not really trying to boost the mids on that channel. I mislabeled the reverb drive and PI tubes. Those will be 12AT7s. The NFB resistor is one of those that gets a placeholder, so to speak. I put the typical Super NFB value in the schem. In reality, I use a decade box to find what really works the best. So the 820R is just making sure that I remember it in the layout.

Thanks for looking, I will edit accordingly and repost.

[dorrisant]

Ok... here we go. Revised. Although, I'm not sure if the 1k dropping resistors separating the new nodes are adequate. No tank, but I left room for it.

[Stevem]

Your power supply at node 4 is still missing a filter cap.

[dorrisant]

Good eyes Steve. Thanks again.

[Firestorm]

It's worth noting that in later tweed amps that had it, the middle was a 25k linear. But in the blackface amps with a middle pot it was 10k log. It's why the Twin sounds more "scooped" than the Pro. If you set the mids on "5," resistance to ground at the bottom of the stack will be 1k or 1k5.

[TUBEDUDE]

The grid of V1b might need a resistor inline with the diode to prevent signal rectification.
The tweed channel could have a pentode with contact bias.