Two Rock CRS V2 layout

[neskor]

Hi.
Recently I get a PM message for schematic of my old blue chassis Two Rock CRS V2.
So, I'm just checking is there any interest to trace the schematic, so somebody with more knowledge make a nice layout.
I can post very detailed pictures, so it won't be really hard to do it.
It will be like a small community project on this forum.
Please let me know your thoughts.
Thanks.

[Colossal]

I would be interested. Thanks for offering to do this.

[neskor]

Pictures of the amp are here:
https://drive.google.com/drive/folders/ ... sp=sharing

[neskor]

It has Full/Half power switch with 6 pins.
One row is switching between two power supplys and the other row is switching two bias pots. One bias pot for full power and one for the half power.
Standby switch is placed just before the choke.

[neskor]

It has Full/Half power switch with 6 pins.
One row is switching between two power supplys and the other row is switching two bias pots. One bias pot for full power and one for the half power.

[neskor]

I used the Two Rock schematic from here and edited. That was so much easier for me.
Also sorry for the mistakes in KiCad drawings, never used this software before.

[rccolgan]

I used the Two Rock schematic from here and edited. That was so much easier for me.
Also sorry for the mistakes in KiCad drawings, never used this software before.

Thanks so much for doing this!!

[neskor]

tried to draw in KiCad from scratch
not sure if there are some mistakes

[neskor]

hopefully somebody with some experience will chime in and draw nice laout
please let me know if you need more info

[rootz]

If you’re building on an eyelet board, wouldn’t it be easy to just hand draw a layout based on a real Two Rock?

I just finished a Two Rock Jet lookalike amp by the way. Two Rock used almost the same schematic for that amp. I think a very big downside of the design is the master volume in front of the reverb. With the master volume low the drive signal to the tank is in millivolts and return is even lower. I could literally hear it when I blew some air over the reverb springs.

[neskor]

What software do you recommend for drawing the layout?

[rootz]

Depends. I usually just design a pcb in Eagle or Fusion360. Occasionally in Microsoft Visio. When working with software like Eagle or Kicad, you always have a working schematic. That limits the possibilities of mistakes. I usually place wirepads where eyelets should be, because the components pads itself are useless if you want an eyeletboard. Then just print in 100% scale and tape the print to a blank board. Done dozens that way.

[M Fowler]

You talented guys are so lucky and smart.

I have to beg for help or wait until someone sells boards.

Mark

[nuke]

You talented guys are so lucky and smart.

I have to beg for help or wait until someone sells boards.

Mark

Practice makes perfect. Lots of screwed up boards in the pile eventually lead up to the one that works.

Trick is not to start with the most complex and difficult project.

For eyelet boards, there is a method and it works like the way the old guys in the 50's and 60's managed circuit design. Make a "netlist" on paper. CAD software will do this automatically as you draw the schematic, because that's how it works. But you can do it with pencil and paper too. That's how I learned to do it, so we could then load things into SPICE with text files for simulation.

If you take any section of schematic where two or more points are connected together, give it a name of some kind and write it down. In the next column write how many junctions are connected together, then list the components and pin numbers that live on that junction.

So take this little snippet here, with the two arrows, one red, one blue.

example-netlist.jpg

We make a little table like this:

Node-name | #junctions | component 1 | component 2 | component 3 | component ....

blue node : 3 : ground, preamp : C7 (-) pin 1 : R23 pin 1

red node : 3 : V1b pin 8 : C7 (+) pin 2 : R23 pin 2


If you were going to make a corresponding eyelet or turret board, you know you need two eyelets, each eyelet will have 3 things in it. The eyelet named, "blue" will have a wire to the preamp ground point, the minus pin of C7 and one pin of R23.

The eyelet named "red" will have 3 things in it, a wire to socket V1b pin 8, the + lead of C7 and one pin of R23.

The process is similar for a hand-layout of a PCB, except the eyelets are strips of copper connecting the donut pads where each component is soldered to the board.

The mechanical placement of stuff is both art and science. It gets real hairy for stuff like DDR5 memory and high speed circuits, but audio is usually not too hard. This is where examining successful and proven layouts for eyelet boards is a good thing. For instance to layout a preamp stage in a guitar amp, examine say, an old Fender design that has a stage similar to what you have in mind, draw it all out on a bit of graph paper in real size, with the real parts in your hand. Then cut out the paper, hold it up in the chassis to see if it makes sense.

Then you iterate.

The old engineers would take the schematics, make net-lists, do the board layouts, then write up the assembly instructions and QA/QC instructions for the assembly line workers, work out the order in which to stuff parts in the boards, how to count each up to make sure the right number of things are in each hole, and that the right things are in those holes.

It is tedious, but that's the process. They did it by hand, pencil and paper, drafting tables, the whole deal.