Collins 6Q-1 Turret Board Layout Suggestions

[Matt C]

I'm getting ready to build a couple channels of 6Q-1 preamps and I'm planning on using turret board construction.  This is my first time doing turret board work so I could use some help and suggestions with the layout.  I've attached a layout design that seems to be fine, and if anyone has any critiques or ideas they would be much appreciated.  I didn't draw in lines for tube heaters, B+, or ground yet.  the dotted line is ground bus lacing on the bottom of the board.

I'm planning on building 2 channels (with PSU) into a standard 2RU case.  here are a couple questions and concerns I have with the current layout:

- not sure whether it would be better to stick the PSU to one side like most builds, or put the PSU in the middle and have the channels be mirror images of each other (so both channels' input wiring runs along the outer edge of the case, as far away from the PSU as possible)

- This design lets the tube heater wiring cross signal wires at a couple points. There should be enough room in the case to still keep them away from each other (and they will cross at 90 degree angles).  and I'll be doing the usual wire pair twisting and shielding where appropriate, but I'm wondering whether I should try harder to completely avoid that.

- similarly, I'm not sure if it might cause problems to have the B+ line running close to signal wires.  I figure it should be fine since it's just DC, but thought I'd ask.

 

[emrr]

The 212-A manual shows the turret layout. You have to connect the dots for the underside wiring. 

 

[buildafriend]

I wonder how this compares to the BA-2A..

I see some NFB

I see different tubes

I'm assuming different transformers.

It's also transformer to grid

 

[emrr]

There is no reason to build the NFB version.  I've written extensively about this already. 

 

[Matt C]

The 212-A manual shows the turret layout. You have to connect the dots for the underside wiring.

and here I thought I was being so productive coming up with a layout...

I figured I'd build in the option to have that NFB resistor, even if it's unnecessary.  same with a couple of those bypass capacitors. 

well, regardless of the original layout being available, anyone willing to give some feedback on the one I posted?

 

[emrr]

I'm on a phone, so cant see your layout too well. But, nothing wrong with an alternate layout.  Just worth knowing there's an official layout.  NFB is like 1.5 dB; waste of a resistor for modern use.  My pad mod is real NFB if you want to play with the difference.

 

[DaveP]

I think the earthing is always one of the most important parts of a layout.
I basically copy the flow and layout from the schematic but keep the heavy current returns away from the audio by the biggest distance possible within a given box.

The signal shields can be grounded on the chassis along with the pin 1's on your sockets but the chassis should only be grounded once near the power inlet.  Use star grounding to this point or a heavy busbar to it instead.

Try to keep your heater twist wires at right angles to your signal or use clean DC for the tubes.

Screen your power TX if possible or leave room to be able to rotate it if there is hum.  It might be a good idea to use a screening can for the input tube.

Keep the input TX well away from AC fields (think of it as a guitar pick-up) 

Lastly, study all the pics and threads on the forum on the 6Q-1, research pays dividends and saves tears down the line :'(

Hope that's helpful
best
DaveP

 

[Matt C]

keep the heavy current returns away from the audio by the biggest distance possible within a given box

I guess this is mainly what I'm wondering about.  I do have some vague sense of what stuff needs to be kept separate, but when you say "heavy current returns" I'm not sure what that refers to. 

and those suggestions are very helpful, thanks!

 

[DaveP]

Matt,
The heavy current returns are all in your power supply, like the cap negatives and centre taps of transformers and negative leg of a bridge rectifier.
DaveP

 

[Matt C]

cool.  i think with a separate PSU board and a fair amount of extra room in the case, it shouldn't be too tough to avoid noise and interference (hopefully)

 

[buildafriend]

if its not too much trouble please report back with how you like it and what it's characteristics are. I'm curious about it.

 

[Matt C]

if its not too much trouble please report back with how you like it and what it's characteristics are. I'm curious about it.

will do for sure.  Right now I've got a working prototype built up, although I still don't have the "right" transformers for the job (right now I'm using a Shure M67 mic input transformer, and a Cinemag 1:1 steel core output transformer.  also did some tests with a Cinemag CMMI-7C on the input).  It's sounding pretty nice so far but maybe not distorted enough. 

I'll try to document the project well and post it here when it's all put together.

 

[Dr Gris]

Interesting!

My plan was to build this P2P before I changed my mind and bought originals and racked them.
I'm looking forward to hear about your progress.

Good luck!

// M