QUAD EIGHT

CA-127 TO CA-227 CONVERSION

&

HOMEMADE CA-227'S

UPDATES
30 Jan 2004 - Added PDF circuit board trace image.
31 Jan 2004 - Changed large images to Acrobat PDF files.
12 Feb 2004 - Added DIY CA227 page

This is my card. I don't guarantee that the same changes will work for you, but I hope they would. Please check all of my work before setting off and soldering. GOOD LUCK!

A friend of mine had acquired some Quad Eight line cards, like the one you see above, and had been told (and had heard) that they can sound really nice. Equipped with some schematics and pinout diagrams, he gave them to me and said "Rack 'em".

I worked off of the following shematics (click on the schematic to download a larger .pdf file) :

• Apparently there are different versions of Quad Eight's CA-127. The one on this page seems to be the first one.
• When I modified the CA-127 cards, I kept the output transformers, which aren't exactly the same as those on the CA227. The CA-127 schematic I have shows that circuit using an output transformer with a ratio of 1:1/1 (secondaries can be wired in series or parallel). My friend had been recommended to wire the output secondaries in parallel, by the person he bought them from. Thinking about it now, this would seem to act as a step down transformer (opposite of the CA-227), so if anyone has anything to add here, please contact me.
• The "blue" in the schematic denotes the D.I. circuit mod that Bo Hansen, of Sweden, was so kind to help out with. You can check his stuff out at http://www.hansenaudio.se/. He also dontated the +48 scheme and XLR notation. Tack, Bo!
• The "red" in the schematic denotes a section in which I am unclear. The original schematic that I have shows the part in red, but a friend of mine, who has been letting me know how his mod is working says he has some original CA-227 cards without that connection. If you choose to wire it as the schematic, it's as easy as a jumper.
• The "Gain Adjust" between pin 9 &10 was noted on a CA-127 application note I have, as resistors of different values, giving varying gains. You can find that paper here: CA127_APP_NOTES.pdf
• I used a UTC "Ouncer" O-10 transformer (wired backwards) for the input. That gave me the option to choose between 3 impedances. It seems logical that you could use any transformer with the right ratio.

CA227 PARTS OVERLAY AND PCB
Note: the PCB for the CA127 and CA227 have the same traces

• I used pins 11-14 & 8 for connecting the input transformer secondaries.
• Part numbers on the overlay refer to the part numbers on the CA-227 schematic.
• The red jumper near Q5 refers to the red in the schematic.
• C1, C7, & C8 are originally axial capacitors, and the original pcb will not show the traces as such, but further apart. I had redrawn the pcb traces to allow me to use radial caps instead.
• In my application of the D.I. mod, I wired R4 directly across the secondaries of the input transformer and wired the 1M resistor for the modded circuit in place of R4, so pin 15 became the wire coming from the D.I. section.
• "+IN" & "-IN" refer to the secondaries of the input transformer.
• Here is the PCB drawing. It is real life size, based on the CA-127 card I have, with the original spacing for the axial capacitors. Resolution is 600dpi. I have made my own CA-227 derivative from the layout and it is working quite nicely.