Power supply board - Will this work?

[Normster]

I'm laying out my PS and trying to use some stuff I've got laying around. (2 x 100uF/350V Atoms and 10 x 47uF/350V Xicon radials)

The amp will be a '97 ODS-style with single tube reverb. B6 to CL, B5 to OD, B4 to reverb, B3 to PI. Assuming a 100 watt Marshall tranny (370VAC) will this layout work? Anyone have a better layout or maybe suggestions on different resistor values?

Thanks,
Norm

[ayan]

I'm laying out my PS and trying to use some stuff I've got laying around. (2 x 100uF/350V Atoms and 10 x 47uF/350V Xicon radials)

The amp will be a '97 ODS-style with single tube reverb. B6 to CL, B5 to OD, B4 to reverb, B3 to PI. Assuming a 100 watt Marshall tranny (370VAC) will this layout work? Anyone have a better layout or maybe suggestions on different resistor values?

Thanks,
Norm

Your grounds could be decoupled, but other than that, your board should work as well as any. Not a better layout necessarily, but attached is a sketch of my PS board.

Gil

[jazzyjoepass]

Normster,

Is the extra B+ for your reverb?



Gil,

Could you explain why the need for separate grounds?



Thanks.

Mike.

[ayan]

Normster,
Gil,

Could you explain why the need for separate grounds?

Thanks.

Mike.

Hmmm... there is quite a fair amount of material written on grounding schemes. The short version of the story is: not all grounds are created equal, and not everyone necessarily agrees on what the best grounding scheme is for a given situation. Let me point you to this link for some reading:

http://www.aikenamps.com/StarGround.html

Bottom line is that the grounding scheme I showed goes with the amp(s) I got the inspiration from to build mine -- which I believe are the same ones the rest of the folks on this board are studying.

Gil

[Bob-I]

I'm not a fan of star grounding per se. The concept of careful elemination of any potential for a reference difference between grounds is good, but star grounding can cause issues in itself with the stray signals around the chassis.

I've never had an issue with a common ground in the filter area myself. I'm a bit more afraid of NOT coupling the grounds possibly creating ground loops.

I'm still not sure why the grounds should be de-coupled.

[jelle]

Hi Normster,
That's a nice looking layout! Thanks for sharing.
Maybe you want to try this:
If there's a choke: screen filtering 47 II 47 uF,
if there's a resistor instead of a choke: 100 II 100uF (6L6). (220 II 220uF for EL-34's)
2x270K instead of 2x220k.
Deviders B6 10K B5 12k B4 1K B3 2.2K B2 resistor instead of choke.

I personally think that an amp can be partially tuned with the power supply. The value of the devider resistor regulates the bass response of that part of the amp. Big value, lower emphasis and small value, higher freq emphasis.

Well, this is what works for me.
Good luck!

Jelle

[Tdale]

Is there a choke betweenthe two big caps and the next stage? I see there are resistors between all the other stages, but not between the two first..

Nice layout by the way. All the pics and schematics that are posted here really inspire and help me. It would have been great to have a "Dumble convention" where all Dumble builders meet to look at each others work.....

Tomm

[Normster]

Thanks for all the help! I found a few mistakes after looking at Gil's board and swapped a few resistor values around based on advice from Jelle and others. Here's the final version.

(Mike, yes the extra stage is for the reverb tube.)

[BobW]

FWIW, The best reason to provide separate grounds to each stage is to keep the circulating currents within their own respective stage, since noise is most often created when return currents are provided a BETTER return path through a different stage. This is more evident when each adjacent stage inverts the signal. Normster's common ground layout should work fine, it's just that providing separate ground returns insures it will work.

btw, Normster, you layout looks great, IMO, I'd try your layout first, then change the grounding scheme only if required. hth

[Jim Donelson]

Hi Normster,

The value of the devider resistor regulates the bass response of that part of the amp. Big value, lower emphasis and small value, higher freq emphasis.


Jelle

I don't understand - I thought those resistors were to equalize the voltage across the caps. How do they affect the frequency response ?

BTW This power supply design is pretty standard in large RF amplifiers. According to the ham literature, that's what those resistors are for, but I am open to any alternate explainations of how they affect tone.

[Icetech]

Norm you have a pic of the completed board loaded yet?

[Tdale]

Hi.

Are you sure the standby switch is in the right place? Won't there still be current flowing from B1 even if the standby is open? In the overdraft specimen schematic, the standby switch is placed before the first big filter caps at B1...

Tommy

[Normster]

Good catch! B1 is actually connected to the other side of the standby switch. This allows the first two filter caps to charge while in standby (I think).

[Tdale]

ok

Tommy