Hi-Fi Kit Building

AudioNote PQ Signature Kit1 - Final Checks

The final day had arrived when all the wiring was complete. This is a tempting time for taking shortcuts and bypassing final checks but they must be done.

The first check was to switch on with no valves installed. You can then check all the AC voltages and the DC voltage across the 300B heaters.

Once satisfied, switch off and insert the 300B valves. Switch on and check that they are 'lighting up'.

Next, switch off and insert the remaining valves. All the remaining voltages can then be checked. The table below lists all of the voltages that I checked. The expected column represents the voltages specified in the manual.

As you can see, there is always going to be some variation with measured voltages. Some are down to capacitive effects as you can see them varying before eventually settling, while some are down to component tolerances etc.

AC Voltages

Description Expected voltage Measured voltage
Between pins 7 & 8 of 6SN7 on driver board. 6.3 7.2
Between pins 4 & 8 of the 5697's 6.3 7.2 / 7.2
Between pin 4 of the 5U4G rectifier valve and C1 on driver board (and chassis) 420 420

DC Voltages

Description Expected voltage Measured voltage
Between pins 4 & 4 of the 300B's 5 4.97 / 5.0
High Voltage (H.T.) on pin 1 of 300B's 425 428 / 430
H.T out of PSU Board (W7 / W8 PSU Board) 435 431
300B Cathode Voltage (pin 3) 70 68.7 / 68.9
H.T. to 5687 Valve (W14 & W15 Driver Board) 395 393 / 393
H.T. to 6SN7 Valve (W18 & W19 Driver Board) 375 372 / 374
Pin 9 (from Below) of 5687's 200 196 / 196
Pin 6 of 5687's 8.4 9.1 / 8.7
Pin 2 and Pin 5 of 6SN7 175 179
Pin 3 and Pin 6 of 6SN7 4.8 4.8
W13 of PSU Board 85 84

All that is left now is to secure the baseplate, fit the volume control knob, and connect everything up for the real test.

Although everything is connected, begin with the source switched off and the volume control in its lowest position. Switch on and allow to warm up for a minute or so.

The first thing to do is to slowly advance the volume control and make sure no nasty sounds come out of the speakers. I am glad to say that not even any noticeable hum came from the speakers in maximum position. Remember, I didn't install the 0.015uF capacitors so no hum was a relief.

Turn the volume to its lowest position and switch on the source. Advance the volume slowly again. If sweet music comes from the speakers, you deserve a nice rest.

I am glad to report that mine worked first time and sounded superb from the outset.

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