Low Plate Classic with loop and reverb?

[Bob-I]

I've been drawing this up for awhile but I'm concerned about the sheer number of PS nodes I'd need for all of this. This one will use Music Man iron so the PS is a voltage doubler with screens taken from the 1/2 voltage point. I planned 2 PS rails, 3 nodes on each. One PS rail will power the preamp and PI, the other the loop and reverb. Calculations say that I'll have sufficient current so I'm not concerned about that, just the sheer size of the rails.

Does this look like it'll work?

[Cliff Schecht]

As far as power supply filtering goes it does look like you have a lot. The way I go about designing my decoupling setup is by only adding decoupling every other inverting stage. Two cascaded inverting stages tend to cancel out hum naturally, so they can share the same node and not introduce too much noise. You can carry over this concept all over the amp though, like if two inverting stages are followed (or preceded) by a cathode follower then all three stages can be run on the same node without adverse affects (things might change tonally, but this is for many reasons).

Also, I have a hard time staring at layouts trying to figure out what's going on, especially with the Dumble style builds (I'm not well versed in the different topologies and what not). Perhaps posting a fuller schematic would make it easier for us to see any redundancy in the power supply.

[talbany]

Bob
On the Schematic looks like you have the reverb supply and preamp dropping string backwards or am I missing something..
If it is it looks ok accept you are going to need to drop the voltage a bit more than a 22k to the PI and reverb plates.. @700v on the plates a 40k 10w should put the PI plates at roughly 300v in the stock MM
Does this help!!

Tony

[Bob-I]

Bob
On the Schematic looks like you have the reverb supply and preamp dropping string backwards or am I missing something..

The reverb/loop supply is parallel to the PI/preamp rails. What I'm trying to accomplish is to supply the reverb first, then the 2 nodes for the loop on one rail, the PI and preamps on the other.

I tried one node on a loop in another amp and it simply didn't sound right so I had to rework the PS completely.

If it is it looks ok accept you are going to need to drop the voltage a bit more than a 22k to the PI and reverb plates.. @700v on the plates a 40k 10w should put the PI plates at roughly 300v
Does this help!!

Tony

Copy and paste error, you're right 22K will be far too much voltage on the PI. 40K may be a tad much since the B+ is more like 660, not 700. I can work with this value and adjust easily enough. Same goes for the preamp rail.

[talbany]

he reverb/loop supply is parallel to the PI/preamp rails. What I'm trying to accomplish is to supply the reverb first, then the 2 nodes for the loop on one rail, the PI and preamps on the other.

I see it now!!..

Copy and paste error, you're right 22K will be far too much voltage on the PI. 40K may be a tad much since the B+ is more like 660, not 700. I can work with this value and adjust easily enough. Same goes for the preamp rail.

Yeah start with maybe a 32K since your reverb supply rail will pull it down as well.. Good Luck!!

Tony

[talbany]

Bob Also.. don't forget to add a diode off the plates (on the socket) in case it wants to arc..660v
Screen resistors are 150 ohms for 6L's
Tony

[txbluesboy]

The presence circuit doesn't look right to me.

[Bob-I]

Yeah start with maybe a 32K since your reverb supply rail will pull it down as well.. Good Luck!!

Tony

I have some 33K 10W, I'll start with that.