prophet64 and installing 2'nd sid chip

[klx300r]

anyone installed a 2'nd sid chip in their 128 ?? I have just started using prophet 64 with my 128 and posted on the prophet64 site with no luck...was hoping someone here has done the sid2sid mod on their 128's:D

[Mangelore]

I was thinking the same thing just the other day. I was tempted to install a second SID in  a metal case 128D as there's plenty of room.

[Andrew Wiskow]

I did a quick search of old posts on the comp.sys.cbm newsgroup, and I found the following instructions posted back in April 1999 for doing this exact thing:

----------

Here's how it works - there is a lot of soldering to do!

Interface
---------
First, stack the two SID chips together, leaving as much space as possible
between them.


On the second SID chip, bend out pins 1-4, pin 8, pins 23 and 24, and pin
27.  Do not connect these pins to any point on the first SID chip.


Solder all other pins of the second SID to corresponding pins on the first
SID.


On pins 1-4, attach two filter capacitors ("caps").  One to pins 1 and 2,
the other to 3 and 4.


If your 128-DCR has been modified to accept a 6581 SID, these will be 470 pF
caps.  If not, you should use an 8580 instead (of course), and use a pair of
22000 pF caps.


Leave pins 23 and 24 alone, thier function is of no use in a Stereo-SID
setup anyway.


Addressing
----------
Connect pin 8 to one of the following on chip U3 (a 74LS138):


Pin 12:  $D700
Pin  9:  $DE00
Pin  7:  $DF00


I recommend using $D700, as the other two addresses are often used by other
devices such as your REU and Swiftlink cartridges.


Audio Output
------------
On pin 27, the last pin left to connect on the second SID, you will find
the audio output.


You'll need to hang a small preamp circuit off of this pin, routing the
output of that pre-amp to the back of the computer as the final output. It
consists of a 2SC1815 transistor, four resistors and four capcitors.


It is the small block of circuits found next to the 6581, connected to pins
14 and 27 of the SID, in the C64 and C128 schematic diagrams, which can be
found in the back of your Commodore 64 and 128 Programmer's Reference
Guides.


If you don't have the schematics available, you should be able to find them
on ftp.funet.fi.  You will need to use a machine with high-end graphics
capabilities to download and print the schematics.


--

[klx300r]

thanks for the info wiskow but I dont wnat to piggy bank the sids but rather use the sid2sid board as shown on prophet64.com

[Andrew Wiskow]

ahhh... understood...  well, sorry, I can't help you with that.  :/

-Andrew