The Multi Amp aka Dynalo Mk2

[sbelyo]

10 hours ago, mypasswordis said:

Many thanks, Kerry! @sbelyo want to change the Dynalo board to this version or add these to the group buy?

Sure, I can add this to the group buy.  Let me check how much it'll be

[sbelyo]

Board is added to the group buy.

 

Group buy thread is here: 

 

Spreadsheet is here:   https://docs.google.com/spreadsheets/d/1Z1L3MQuuY4ZTUyPQb1qBmVJp8MtC7qEzBUui3z5dFrQ/edit?usp=sharing

[sbelyo]

Should we get a stencil?

[RudeWolf]

I'm good with smt soldering and wouldn't want to ruin my oven! And that paste is super expensive.

[sbelyo]

if enough people commit we can up the copper to 3oz.  Any issues with that?

If we can get to 20 boards it only goes up about $1.25 a board

Edited September 23, 2016 by sbelyo

[RudeWolf]

Narp, extra 1.25$ wouldn't be an issue. Any news on how's the best way to case the thing?

[gepardcv]

Looks excellent. I'm in for 3 mini Dynalo boards.

[Kerry]

2 hours ago, sbelyo said:

Should we get a stencil?

Each person would need one.  See how much it would cost for multiple.

[Pars]

That thing is sweet Kerry! Really nice job. What layout software were you using?

Also, what pot is this set up for? Alpha? Would a TKD601 work?

Ooops, just figured out what pot you are using, so no go on that

[palchiu]

Should be alpha's pot. there.  GB boards with pots?

Is that possible to modify another version to fit mulitple kind of pots? like  4CP601/2500 RK27 as Pot PCB GB's version? Maybe board will longer but more options to fit volume pots.

[swt61]

really nice!

[Pars]

55 minutes ago, palchiu said:

Should be alpha's pot. there.  GB boards with pots?

Is that possible to modify another version to fit mulitple kind of pots? like  4CP601/2500 RK27 as Pot PCB GB's version? Maybe board will longer but more options to fit volume pots.

Anything is possible, but probably not happening. I still haven't figured out what the 4th pin per row is for and the datasheet doesn't seem to define it. I'll have to examine the gerbers for Kerry's board more...

[chiguy]

Would an adapter PCB for different pots work?

[cspirou]

14 hours ago, Pars said:

Anything is possible, but probably not happening. I still haven't figured out what the 4th pin per row is for and the datasheet doesn't seem to define it. I'll have to examine the gerbers for Kerry's board more...

The data sheet I found says one of the rows is a tap, similar to a transformer tap. In the PCB that row of pins isn't wired to anything.

Edited September 24, 2016 by cspirou

[luvdunhill]

It's a "loudness" tap.

[swt61]

^ Go get some sleep strep boy!

[cspirou]

10 hours ago, chiguy said:

Would an adapter PCB for different pots work?

There should be a way to make a interfacing PCB with a potentiometer on top and pins sticking out the bottom that are compatible with the Alpha pin configuration.

[Pars]

I defined a library part for the Alpha 3RP pot and played around with it on the current 3 pot board to see what the pin layout was like. As you can see from the pic below, it might be possible, but there would be some drill overlaps, and the pot would have to be offset 2mm due to the 4 pins per row instead of 3.

[Pars]

From looking at Kerry's layout, it looks like he is connecting pins 1 (gnd), 3 (output?) and 4 (input) on the pot. I assume that I am looking at the right pot (Alpha 21mm 3RP-2142G, from Alpha in Oxnard, CA)? There is also a Taiwan Alpha and a Korean Alpha, but the pots I find from there aren't 4-ch, look nothing like this one, etc.

The data I found on the CA Alpha company website just shows pins 1-3 on their schematic diagram, so I assumed the 4th pin (right side row) were loudness or unconnected. I also made the assumption that the pin numbering starts from the left lower corner:

13 14 15 16

9  10 11 12

5  6  7  8

1  2  3  4

If anyone has the correct datasheet or a link... this is what I was looking at.

http://alphapotentiometers.net/html/21mm_pot_4.html

[mypasswordis]

I don't have a 10k alpha pot either but if it's like the 50k the third pin in each gang is not connected to anything. Second pin is wiper and 1st and 4th are the ends. 

 

I think I'm gonna end up just scrounging up some k170/j74 if the 50k alpha pots fit, easier than buying 1000 alpha pots

[Pars]

^ That doesn't match what Kerry did on his boards from L-R top (or front):

1    -    2     -    3     -    4

Gnd  open  output  input

                   (wiper)

Edited September 24, 2016 by Pars

[sbelyo]

we've made it to 20 boards so far in the group buy.  Any objections to going with 3oz copper?  The price will go up about $1.25 a board

[gepardcv]

No objections from me. 

[mypasswordis]

2 hours ago, Pars said:

^ That doesn't match what Kerry did on his boards from L-R top (or front):

1    -    2     -    3     -    4

Gnd  open  output  input

                   (wiper)

 

That's because normally you look at the pins from the bottom. You can't see the pins from the top. We're in agreement.

Edit: actually even flipping it 180 degrees works, it's all a matter of perspective

Edited September 25, 2016 by mypasswordis

[Pars]

OK...

Normally, #1 pin is the lower left (which from the bottom would be the upper left, I guess). The "schematic" Alpha has on their website labels the pins 1-3, so I assumed that pin 4 in each row was the open or loudness or whatever pin. I can't find any mention of this on their website, and they don't seem to have complete datasheets. Seems like a typical CA company, with their website and all

Where can you actually buy these things, as they have a 1000 pc. min order?