Frequently asked questions v1.0

Q1: Why two versions (DualSID 6581-version/DualSID 8580-version)?

A1: Three reasons:

Q2: What is the difference of 6581 and 8580 audio out circuits?

A2: Here are the schematics:

6581-version:

8580-version:

Q3: What means: DualSID 6581-version and DualSID 8580-version?

A3: The version means what type of SID has to be used as SID2.

DualSID 6581-version: use 6581 for SID2
DualSID 8580-version: use 8580 for SID2

Q4: Can I put 8580-SID to SID2-socket of a DualSID 6581-version?

A4: No. Use 8580-version. Look at question 1 for the reason.

Q5: Can I put 6581-SID to SID2-socket of a DualSID 8580-version?

A5: No. Use 6581-version. Look at question 1 for the reason.

Q6: What's the point in J2 jumper settings then?

A6: The point is to choose the C64-mainboard + DualSID combination:

6581-mainboard (SID1) + 6581-dualsid (SID2) |O=O O|
6581-mainboard (SID1) + 8580-dualsid (SID2) |O O=O|
8580-mainboard (SID1) + 6581-dualsid (SID2) |O O O+<-external voltage
8580-mainboard (SID1) + 8580-dualsid (SID2) |O=O O|

Q7: Why is the external voltage needed to the rightmost pin of J2 when using 6581-dualsid on 8580-mainboard?

A7: Because 9VDC from SID socket of the 8580-mainboard can not be used to regulate 12VDC which is needed in order the 6581 to run. We need at least 14VDC to get 7812 regulator to output regulated 12VDC.

Q8: What about the model of SID1?

A8: The C64 mainboard type determines the SID1. The SID1 has to be same model as the SID originally mounted on the C64 mainboard.

Q9: If C64 mainboard type determines the SID1, how can I use a 6581 as SID1 in 8580-mainboard?

A9: You can't.

Q10: Why can't I use other the model of SID for SID1? For example 8580 in PCB-ASSY 250407 as SID1?

A10: Because the circuit on the DualSID PCB is only for SID2. The audio out circuit and the filter capacitors for SID1 are on the C64 mainboard.

Q11: Well, why do you advertise that any combination can be used in any mainboard revision?

A11: I have never advertised such thing. You can add any SID to any mainboard. You can't change the SID1 type with DualSID.

Q12: Can I use DualSID 6581-version with C64C or DualSID 8580-version with C64.

A12: Yes. Any DualSID version can be used with any mainboard revision. Just set the J2 to match your configuration.

Q13: How can I choose the address location for SID1?

A13: You can't. It's always at $D400.

You may however do a mod to be able to change priority of the SIDs:
DualSID, SID priority hack (do at your own risk)

Q14: How can I choose the address location for SID2?

A14: via jumper J1:

-----   -----   -----   -----   -----
|O-O|   |O O|   |O O|   |O O|   |O O|
|   |   ||  |   |   |   |   |   |   |
|O O|   |O O|   |O O|   |O O|   |O O|
|   |   |   |   |  ||   |   |   |   |
|O O|   |O O|   |O O|   |O O|   |O O|
|   |   |   |   |   |   ||  |   |  ||
|O O|   |O O|   |O O|   |O O|   |O O|
-----   -----   -----   -----   -----
$D400   $D420   $D500   $DE00   $DF00

Q15: How do I know which resistor/capacitor goes where?

A15: Here are the lists for parts

Q16: Why there aren't any pin headers/RCA-connectors/wires/etc. included?

A16: To keep the price down. Pin-headers are common and easy to desolder out of old PC-cards. Besides, you don't necessarily need to install pin headers. You can solder the wires directly to the PCB.

Here are the lists for parts included

Q17: Well, if I did that I couldn't change the address setting for SID2 now could I?

A17: Yes you could if you would solder a switch to J1.

Q18: How do you wire a switch for the address selection?

A18: Here is the pinout for J1:

      -----
   CS |O O| $D400
      |   |
$D420 |O O| $D500
      |   |
$DE00 |O O| CS
      |   |
   CS |O O| $DF00
      -----
The CS's are equal so to choose an address, connect an address to CS to select.