NuForce Ref 9 V2 Quick start guide

Nuforce V2 board upgrade (4/19/07)
This instruction is pertaining to the F15HER3D version of Nuforce V2 amplifier PCB
(Printed Circuit Board).
The upgrade is essentially a drop-in replacement of the existing 9.02 PCB (Printed
Circuit Board). On the V2 board all of the necessary power supplies (a separate power
supply for the input driver) are on the single PCB, therefore, the external 24V DC/DC
converter as part of the original SE package need not be used. A new Zobel Filter is
included for soldering to the speaker terminals.
The power supply (SMPS) should be upgraded as well to change Over-Current protection
threshold to 500W in order to reliability power-up the V2 boards.
Upgrade procedures for Ref 9 and Ref 9SE:
1. Unsolder the speaker cables and the output capacitor filter on the speaker terminals.
To prevent overheating the Eichmann binding posts, please connect a speaker cable to
the binding posts to serve as heat sink.
2. Unsolder and remove the input wires on the RCA and XLR.
3. Unplug the Red/Black DC power cable from the board. For the 9SE, remove all
other power wires as well (black, blue, and brown wires).
4. Remove the 6 screws on the PCB, and 3 heat sink screws on the bottom (use #3
Philips screwdriver bit) and remove 9.02 PCB completely. Use a paper tower to
clean up the heat sink compound on the heat sink and the bottom of the chassis. The
removed, functioning board should be kept as spare parts for Ref9/RefSE
replacement or repair.
5. On Ref9SE, an additional 100 Ohm resistor is required to be soldered between the
negative of the RCA (outer connection, i.e. shell) to the signal ground on the XLR.

You may use any value from 50 to 200 ohm, it is not critical and does not affect
sound. Nuforce provides the 100-ohm resistors with the upgrade kit.
6. Install the new board, you will notice that the V2 board is slimmer and the heat sink is
on the opposite side close to the edge (9.02 board heatsink is closer to the power
supply). The green ground wire should be connected to one of the screws.

7. The 3 heat sink holes can be plugged with the included nylon covers. V2 heatsink is
not attached to the base of the chassis.
8. Install the new Zobel Filter under the speaker terminal and bend the leads so they are
against the speaker solder tab. Do not solder yet. (The Zobel filter is integral to the
operation of V2 and you must install it).
9. Solder the 3 input wires between V2 board and the connectors, according to the color.
White is Positive (+) signal, Red is Negative (-) signal, and black is Analog Ground.
XLR pinout: Pin1 – GND, Pin2-Positive, Pin3-Negative. **For reference only: 100-
ohm resistor between RCA Negative signal to XLR Ground. XLR Pin-3 (Negative) is

shorted to the chassis pin on the RCA.
10. Solder the speaker cable together with the Zobel filter in one soldering action.
Remember to keep the speaker cable connected while doing the soldering to prevent
heat damage to the Eichmann binding posts.
11. Locate a black wire near V2’s DC power input socket. The black wire should be
connected to the 5V terminal on the power supply. Use the provided short wire (2cm
short) to connect between the 5V ground to the 52V ground. Notice the short wire on
the DC supply terminal block. The 5Vdc is shared with the LED.
12. Plug in the Red/Black DC power cable into the V2 socket. For 9SE chassis, cut off
the 3 wires on the relay on the capacitor bank (relay is the white square component
between the capacitor and the black Nuforce DC/DC converter – no longer used.

13. Check all the connection.
14. If all the connections checked out fine, before putting the cover back, check that the
amplifier is functioning by playing music. If the 2 red LEDs on the V2 PCB do not
light up, check and make sure the 5V wire and the Ground wire of the 5V is
connected.
15. When closing the cover, please be careful as the heatsink makes a very firm contact
with the top cover for heat dissipation, and may need a firm pressure to close the
cover.
Increase the Over Current Protection Threshold on the power supply
(3/21/2007)
As part of the V2 upgrade, identify IC3 and DZ2 on the SMPS power supply, add a 50V,
10uF (or higher rating) capacitor. The +ve pin of the capacitor should be connected to
Pin-4 of IC3, and the –ve pin of the capacitor connected to DZ2 pin closer to IC3 (see
photo below).