How to increase power (MCS 3245 to 3275)

[Old HiFi Guy]

Great looking and sounding(going by what what was done to it) receiver. I have a few pieces of MCS gear mainly tuners that sound great. I am curious about the two Soundcraftsmen "shoebox" amps that the receiver is sitting on. The reason I as is I have one . The second most powerful amp I own at 205 WPC, only bested by my Sound Code Sytems SC2350A at either 240 or 260 WPC .

 

[Racingh11]

Great looking and sounding(going by what what was done to it) receiver. I have a few pieces of MCS gear mainly tuners that sound great. I am curious about the two Soundcraftsmen "shoebox" amps that the receiver is sitting on. The reason I as is I have one . The second most powerful amp I own at 205 WPC, only bested by my Sound Code Sytems SC2350A at either 240 or 260 WPC .

Those are a pair of PCR800. They are fully serviced with many new parts including all new electrolytics. They both have my input boards installed and running bridged to a pair of MTX TP2400 (dual 12" PA towers). They hit 900W bridged into the 4 ohm load. The amps are sold and will be paired up with 4 MTX TP1200(single 12" PA towers) running stereo 300W into each tower. Here is some info on the input boards. https://audiokarma.org/forums/index.php?threads/soundcraftsmen-input-board.987071/
The power caps used in this 3245 project are the same caps I put in those amps. I already had them in stock and the size was just right. The owner( @William Paul ) also has a pair of Soundcraftsmen PM860 that he bought restored from me. At least one of them has my input board installed. The PM860 is the pro version of the PCR800, it has more output transistors.

I can also install one of the input boards in the 3245 receiver to send a pre-out bridged to a subwoofer amp. With or without the low-pass filter.

 

[Old HiFi Guy]

Thanks for the reply. I have always have liked Soundcraftsmen gear since the 70's. Bought a MA5002 almost 20 years ago but it came completely trashed due to a very poor packing job. A shame because It was in very nice condition going by the pictures in the ad. To the sellers credit he took it back and refunded my money. I bought the PCM840 about 6 years ago, not the wow factor the MA5002 has but works and sounds good. Sorry to hijack your MCS thread.

 

[elvi]

I also replaced the emitter resistors with high quality wire wound.

Do that wire wound affect the signal in their calculated L value?

 

[Racingh11]

Do that wire wound affect the signal in their calculated L value?

It shouldn't since the originals are wire-wound too.

 

[elvi]

It shouldn't since the originals are wire-wound too.

Thanks for clarifying!!

 

[Racingh11]

I am working on another 3245 to 3275 build. This time with a 3245-00. The only one I did of those, was the one with the big toroid transformer. I had already gone through and recapped this receiver in the last few years. It is now getting the power upgrade, and all new transistors in the audio path. Some of greater voltage for the new levels.

 

[Racingh11]

Testing went well. Distortion coming in below .02% on both channels and 88W clipping into 8 ohm loads. Interestingly, the rail voltage is +/-49V at idle, when it is 46.6V on the 3275 with the same transformer. I also added a transformer for the +/-24V supply. There wasn't a good way to adapt the original 3275 windings to the 3245-00. I opted to put the current limit temp sensors on the heat sink on this one, instead of in the transformer. After further testing on the earlier ones, it was determined that transformer overheating is not going to be an issue. They really aren't needed on the heatsink either, but may save the amp if the fans fail. I had it blasting some MCS 8330 speakers and sounds great.

 

[Racingh11]

Here it is. The original knobs were in rough condition, so the owner found some aftermarket knobs that fit the sizing well.