Blackvibe 6V6 layout - grounding thoughts

Hey all - I'm in the planning process for a build of Rob's 6V6 Blackvibe design. Given all the recent talk about single star grounding, I thought I'd do a bit of a faff around in DIYLC for the first time to try to incorporate some of those single bus/input jack ground thoughts. Thanks for the layout and schematic, @robrob .....bloody fabulous for DIYLC rookies like me!

I plan to add the Presence and a Frondelli Master Volume. I'll use dual core coax on the MV (one going board > pot and a second one for pot > grids) and ground those shields at the pot end. I also have a switched 1meg pot so thought that might work as a push/pull bright switch on the vol/gain control.

Have a look at what I have done with this layout and please comment regarding the grounding. Note I have thrown in a nominal AB763 bias circuit but haven't settled on values yet given the 50v bias secondary. Thanks for your thoughts.

 

Wow - thanks for all the great responses fellas!

I'll implement these changes and drop an updated layout into the thread. I'll put up a separate build thread once I have finalised the nuances of the layout.

The other are of contention is where to ground the x2 single core coax shields that run from the master volume pot to the power tubes. By my reckoning, I have these options: The case of the dual gang pot (easy) or the bus bar itself. Thoughts on that? I want to use coax there due to the long run back to the power tube sockets. I could even use a third, dual core coax from the grid caps to the MV pot. By the looks of things, that will be pretty close to the pot so 2 individual, standard hookup wire may be fine.

With respect to specific questions/responses:

Awesome - will do this.

Thanks for these! With my other builds, I've always used a flying bus bar so will be doing the same here. I will build my own board too. I was thinking about the Presence ground when I was adding it in...you have confirmed my thoughts. The other suggestion on the OT secondary/ground is excellent. I want to apply these grounding principles as practically as possible.

Thanks mate - I guess this is something I can easily test. I'll connect it to the first cap as per Rob's suggestion in the first instance. If no good, I can provide a dedicated ground tab on the chassis and see what difference that makes.

My PT is running the 330-0330 spec as per Rob's design (Deluxe Reverb). The only change I made to his design was to flip the second cap in series so the negative was closer to the bus and the grounding itself. I've got the caps in stock, so no issue there. TBH, I was considering using a JJ cap can with the 40-20-20-20 sections (ala Princeton Reverb) to reduce the board real estate. From a $ perspective, that's more expensive as compared to individual caps.......then there's the grounding principle I'm trying to evaluate.

Thanks! I'll definitely hang them off the tube socket with a 3 lug terminal strip and some dual core coax. Do you think it would be better to ground that coax at the tube socket or the input jack end?

 

Righto - I've added in the changes as suggested.

A couple of other things to ponder:

1. Where best to ground the Frondelli MV coax shields. I figure the back of the pot is fine?
2. Should the star ground at the input be a dedicated bolt or is the jack fine with a star washer?

Thoughts?

I'll most likely relocate the switches over near the rectifier as I've got a large Hammond black steel chassis and plan to use an IEC socket for the mains. The fuse can go into the tray (blackface champ style). That should allow me to route the Standby switch wiring and B+ feed of the GZ34 together to the left of the power tubes. The eyelet sharing the choke and standby switch wires can also move left between the A filter caps. I'd like to keep the noisy stuff over between the GZ34 and the power tubes if that helps things. Perhaps that's a bit OCD ??

 

Excellent! I'll implement these changes.

@Nickfl - I was looking at the fused IEC sockets and thought about incorporating one. The only thing that kept me from deviating was the fact I had standard IEC sockets and fuse holders on hand. To be honest, I think it is a great idea to use the all in one option.....one less hole to drill!

 

Righto - updated layout. I've added in the fused IEC socket, shifted the B+1 eyelet left and removed the standby switch. I've also substituted shielded wire between the volume pot and V1b.

Thoughts? Now to start looking at bias circuit values - in particular, the 470R and 37K total provided by the pot and resistor to ground. I have that 100uF/100V cap on hand so will use that for sure.

 

@andrewRneumann ^ this is super. I've actually got Merlin's book but have struggled to understand this star concept properly despite the nice pictures! The penny has dropped with your explanation.....thanks heaps!

With respect to the master volume ground point; I assume that applies to those types that send unwanted signal to ground?

 

Here's an up to date version incorporating the star grounds.

I've drilled and populated the board with eyelets to this layout. I've used x2 turrets where the bus bar connects to the board (ie left most A Filter cap and at the D filter cap. All other points are eyelets. That will get the bus up in the air a bit without the need for extra bends in the bar which should be more sturdy and neater from a lead dress point of view. I may look to put a third turret in about half way along the bar (near the red Presence wire) for extra support only.