AMB Laboratories DIY Audio Forums

[Pieterh]

My back panel is ready. Here are the photo's:

12 Back Panel ready 1.jpg

13 Back panel ready 2.jpg

14 Back panel ready 3.jpg

[Pieterh]

Here are two detailed photo's of the XLR and RCA wiring. In the end I used flexible wires here. I had started with small pieces of the Belden cable for maximum shielding. But working with that cable in small pieces was quite fiddly.
On the second photo one can see the wide heatshrink with the R/C inside between the chassis and pin 1 XLR and RCA ground. RC parallel--> R=10 Ohms - 5 W (Mouser no 286-10-RC), C = 0.1uF - 250V (eg. Mouser no. 539-158X104K).

7 Back Panel audio in 1.jpg

8 Back panel audio in 2.jpg

[Rabbit]

Looking fantastic. Thanks for documenting your build.

[Pieterh]

To reduce the number of braided sleeves, I combined in one braided sleeve the 35V power lines to the S22 and the wires to the thermal breakers. I thought to have a connector in between the thermal breaker wires, but that connector was ideally located under the S22. However, there is not enough space between the S22 and the heatsink to accomodate this 2 position/1 row Mate-N-Lok connector. So, I forgot about that connector and soldered the thermal breaker directly to the wires. In case I have to disassemble the chassis at a later moment, I only have to unscrew the thermal breaker.

16 Combining wires in one braided sleeve.jpg

[Pieterh]

Hmm, I just realised I forgot to install the Zobel network at the output connectors. So I have to come back to you with a new photo including the Zobel in place......

This link enclosure-for-beta24-t3573-20.html#p33748 shows some measurements by cobretti with and without Zobel in place.

[Pieterh]

And here is the Zobel 'network': 10 ohms/5W and 47nF/100V in series, mounted between the loudspeaker binding posts. One can also see (middle photo) the additional bracket I made on the back panel to reinforce the connection with the 3 mm thick chassis bottom plate. I made a similar bracket on the front panel (lowest photo). I used stainless steel 15mm profiles (1.5mm thick) to make those brackets. I made two rectangular caveties for the two closeby standoffs that support the PSU bottom plate.

5 Zobel series.jpg

6 Zobel installed.jpg

4 reinforcement bracket.jpg

[Pieterh]

Here is a photo of the completed wiring of the PSU bottom plate.

1 Bottom wiring complete.jpg

And here is a more detailed photo of the barrier strip I used to organise most the necessary connections such as the separate star grounds for left and right, etc. I used a strip with 8 rows (two connections per row) from mousers. The connection scheme is as following (see photo: strip from top to bottom):

Row 1: right channel starground for 2x30V and the Sigma 22 ground, jumper to row 2;
Row 2: right channel starground for 2x35V, main capacitors ground, jumper to row 1;
Row 3: right channel thermal breaker wire, thermal breaker wire to E24;
Row 4: relays (two) negative wires, negative to E24
Row 5: relays (two) positive wires, positive to E24
Row 6: left channel thermal breaker wire, thermal breaker wire to E24;
Row 7: left channel starground for 2x30V and the Sigma 22 ground, jumper to row 8;
Row 8: left channel starground for 2x35V, main capacitors ground, jumper to row 7;

2 Barrier strip wiring order.jpg

And here is a photo of two hour endurance testing of my B24's. In this ventilated position the temperature of the heatsinks reached about 42 degrees centigrade. Offsett is between +/- 10mV and often close to a few mV.

3 two hour amp testing.jpg

Next task on the list: cross the finish line and warn my neighbours! --> Drilling a number of holes into the chassis bottom plate and assemble everything into a real B24 (V)AMP.........

[amb]

Looking good!

[Pieterh]

Progress report....here we have the bottom plate with all the holes predrilled with 2 mm (for accuracy), final drilling with 4 mm for bolts to the chassis/reinforcement brackets, 5 mm for the 4 anti-vibration feets and for the M5 bolts to the PSU standoffs.

4 Holes drilled and ready for mounting.jpg

Next I mounted the heatsinks without the Sigma22's as we need space to bolt those sinks to the bottom. The original bottom plate has only 2 holes to mount one side to the heatsink bracket. However, the heatsink bracket has four holes. As we are talking about a nearly 20kg Amp I found it better to drill two more holes in the bottom plate.

5 Mount heat sinks - S22 not installed yet.jpg

On the photo one can see that one of the two holes in the bracket is a bit higher than the other. At that 'higher hole' below the Sigma22 board, I found that I needed to use a low profile M4 nut at the bracket. A larger nut would prevent a proper mounting of the S22 board.

6 Use of low profile stainles steel nuts.jpg

[Pieterh]

Next item was the front panel with the reinforcement bracket.

7 Mount front panel with reinforcement bracket.jpg

.....installed the Sigma22's again, checked for correct polarity between the S22 output to B24 board inputs.....and installed the Bulgin button.

8 Install S22 and bulgin button.jpg

9 Stereo has two channels.jpg