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B&K AVR 305 Amplifier Channel Change
		This is a step by step guide to changing the channels driven by the amplifiers on a B&K AVR 305/307. If you add a separate amplifier to drive other channels, you can reconfigure the 305/307 to drive Zone 2 or the rears so the amplification is not wasted. This operation should be performed by your dealer to keep your warranty intact. Remember to be aware of static electricity as well. I take no responsibility for any damage done by you. The pictures are of a AVR 305. Step 1. Remove the cover. All references are from the front of the receiver. The amp module on the rear left side of the unit are wired for the front mains. They have 6 output devices per channel. If you have a 307 there would be an amp module on the front left. The amp module on the front right side is wired as center. It has 6output devices also. The rear left amp module is wired as the side surrounds. It has 4 output devices per channel.

		Step 2. Remove the screw on the bottom of the heat sink.

		Step 3. Remove the retainer bar on top of the heat sink.

		Step 4. The Molex connectors for zone 2 and the rear surrounds are stuffed underneath the video connector board. (Zone 2 was clearly marked but the front channel wire was not. You can follow the wires back to the board where they are labeled if there is any confusion.) Carefully remove the wires from under the board. Disconnect the Molex connector from the amp module and replace it with whichever output (zone2 or rears, etc ) you wish to drive. You can do this for any channel. The preamp does not know or care. Only the labels on the speaker connections will change. You can also see the spare power connector to connect another amp module to make a AVR307. Reverse steps to reassemble.

B&K AVR 305 Pictures

		Here is a comparison shot of the inside of the AVR305 on the left and the REF3220 amp on the right. The amp modules are very similar. The capacitors on the REF3220 are the size of soup cans but actually have a lower rating of capacitance if I'm reading it right.

		A top view of the inside. You can see the space reserved on the left heatsink for an addition amp module to make the 305 a 307. Interesting to note the power supplies would remain unchanged. The 305 thus has extra power on tap than the 307 if all channels happened to be driven simultaneously.

		Looking tword the front of the 305. You can see the preamp/processor components at the rear of the chassis. The power supply is up front. A 682VA Plitron torroidal transformer sits under the power supply board w/ (4) Nippon 33,000 microfarad capacitors.

		This is the center channel amp module. It has 6 output devices.

		This is the entire right side containing the center amp module in front and the side amp module which has 4 output devices per channel

		This is the front amp module. 6 output devices per channel.

	B&K Ref 3220

		The heat sinks in the REF3220 are actually smaller than the 305. The torroidal transformer and capacitors look bigger.

		These are the same output devices used on the 305. Except there are 8 per channel.

		A close up of the transformer and capacitors. I was unable to find a VA rating on the transformer or cross-reference it with the manufacturer, AMVECO. The caps are twice the size of the ones in the 305. There are 4 and they're the size of soup cans. They are made by BC and are stamped 15000UF. If this means 15,000microfarads, the 3220 has 60,0000microfarads of capacitance versus 132,000 in the 305. Sounds fishy.

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