Specifications

AMP2-T assembly instructions. © 41Hz Audio / www.41hz.com Revision 1.0T boards
c. There are three low ESR 100uF (150 uF) 35V for the onboard V10 PWM supply.
These are the C300, C19 and C71.
d. There are two 47uF for the bootstrap circuitry, C17 and C18.
11. Solder the inductor L4 and the Q1 MOSFET for the V10 supply.
12. Wind the toroid inductors. You should use 29 turns of 1.2 or 1.3 mm enamel insulated
wire for the T108-2 toroids included in the kit. The inductance should be 11 uH. Wind as
tight as you can. Tight winding minimizes any stray signals. This thick wire is a
challenge to wind. Leave a bit of wire so you can pull the toroids snugly to the board.
i. For high frequency, high current windings like the main inductors, a good
alternative is to use several thinner wires, with the same cross section area,
in parallel. A bundle of thin wires is easy to wind and the insulation
between strands reduces the “skin effect” and thereby reduces losses. You
can buy “Litz” wire which is simply a pre-made multi-strand wire, where
each strand is separately insulated with enamel insulation.
13. Scrape the enamel off the wires where they will be soldered and solder the wires to the
PCB. It may be a good idea to glue the toroids to the PCB to prevent the copper wires to
break from fatigue in case the PCB is subjected to vibrations. Use a temperature resistant
glue as the toroid will be warm at high loads.
14. Optionally solder board connectors ***J1 for power and J5 and J6 for speakers.
Connectors should have a current rating exceeding the currents you expect to have and
also exceed the current limit setting you use. The default for the AMP2 kits is 10A. If you
do not use connectors, solder the power cabling and speaker output cabling in place.
15. Connect signal connectors. Again consult the APPENDIX 4 and decide what connections
you would like to make.
a. Bridging or no bridging? Permanent bridging or an external switch?
b. Mute switch? Strongly recommended! If you do not use a switch, you should
permanently ground pin 11 of J2
c. Hmute indicator? The Hmute (pin 9 of J2) can drive an external LED via a 2 k
resistor. The LED will be on if the amplifier is muted by pin 11 or due to over
voltage or over current limit has been exceeded.
16. Mount the four MOSFETs in positions M1, M2, M3 and M4. IMPORTANT. Take care
that the leads of the MOSFETS do not touch adjoining tracks before soldering them. The
legs of the provided MOSFETs have a fairly wide shoulder that may short circuit to
adjoining tracks. Therefore the MOSFETs should be lifted by about a millimeter before
they are soldered. Make sure they are in line, at the same height and flatly on the same
surface. They need to adhere well to the heat sink.
17. You are now ready to test the amplifier as described below. A heat sink is not required
for low power testing but will surely be required for higher power levels.
Trimming and testing
- Put the amplifier to Mute (J2 pin 11 to pin 8)