I have been collecting parts and information for my 69 Superbass build for about 5 months. I finally got my last parts-shipment 2 weeks ago and nearly got all the info I need as a newbie builder, so the build (and corresponding thread) will start soon.
I decided to implement SDM grounding on my build:
http://home.comcast.net/~jbjdav26/1959/ ... ubbers.JPG" onclick="window.open(this.href);return false;
Since I´m totally unexperienced in electronics, I´ll use the 100W Metro build instructions as my main building resource.
I compared the 100W instructions: http://metroamp.com/wiki/index.php/100_ ... structions" onclick="window.open(this.href);return false;
to the SDM-layout above step by step and tried to find all the differences. Most differences were easy to understand, but some things I didn´t understand. I´ll quote the corresponding sections from the instructions here and explain what is different in the SDM layout and what I don´t understand:
difference #1: page 11
"B. Neatly bundle the wires from the PT at the far end of the chassis and tie with two wire ties as shown. There are two plain blue wires for the amp’s bias circuit - one of them needs to route to the same ground lug [note: ground lug on F6] that the heater center tap was soldered to . (It makes no difference which of the blue wires you use.)"
--> If you take a look at the SDM-layout you´ll find that there is no bias wire (ground) attached to the ground lug on F6. First I thought that some PT connections were simply omitted but if you look at the board, you´ll see that the other bias wire (bias 100V, white) is attached to the 27k resistor in the bias section as it should be.
Question: Where does the bias ground go in the SDM-layout?
difference #2: page 22
"C. Route the red w/yellow stripe wire [note: PT CT] as shown to the F4 capacitor. Strip enough insulation from the end (about 3/4”) to join the two positive terminals of the F4 cap together as shown. Solder these connections, but leave some open space on the terminal that the wire goes to first for now; we have more wires to add to this terminal soon."
--> In the SDM-layout the PT CT is not connected to the F4 cap.
Question: Where does the PT CT go in the SDM-Layout?
difference #3: board values: page 56
Some values on the Superlead board from the SDM-layout differ from the 100W kit instructions board layout:
![Image](https://dl.dropboxusercontent.com/u/18415326/JMP100%20build/1959%20altgrnd%20snubbers-board-different%20values-scaled.jpg)
Questions: I´ll probably build a SB amp - but generally speaking: Can I use the values given in the 100W kit instructions or do I need to change some values for the SDM layout?
Hope somebody can give me advice on this and I´m really looking forward to any answers I get. Thanks in advance.
YF