I talked about this amp in before but now it is done and I wanted to give it its own complete thread.
I bought it in working condition but when I pulled the cover, the well built last american made Marantz model had gotten its insides all messed up. The original power amp board was gone and had been replaced by some other dodgy looking board with all kind of different transistor on both channels, some very poor solder joints and a few leaky capacitors. Everything was connected to the output transistors (4 different models and brands) and the power supply (that had also been modified partially destroying the tracks) with a whole lot of very poor quality wires. The case was damaged and rust started to form on the connectors and the transformer. The feet were also missing.
I started by pulling everything that wasn't original and getting the power supply back to original. At that point the amp worked perfectly as a preamp.
I managed to find a power amp board with the original power transistors in working condition. the seller added some other parts and screws some of which came in very handy.
Next thing was a full recap. I pulled all the boards out and gave the case, and transformer a good cleaning and respray.
I bought it in working condition but when I pulled the cover, the well built last american made Marantz model had gotten its insides all messed up. The original power amp board was gone and had been replaced by some other dodgy looking board with all kind of different transistor on both channels, some very poor solder joints and a few leaky capacitors. Everything was connected to the output transistors (4 different models and brands) and the power supply (that had also been modified partially destroying the tracks) with a whole lot of very poor quality wires. The case was damaged and rust started to form on the connectors and the transformer. The feet were also missing.
I started by pulling everything that wasn't original and getting the power supply back to original. At that point the amp worked perfectly as a preamp.
I managed to find a power amp board with the original power transistors in working condition. the seller added some other parts and screws some of which came in very handy.
Next thing was a full recap. I pulled all the boards out and gave the case, and transformer a good cleaning and respray.
For the filtering caps I went for some screw terminal (as original) cornell Dubilier 12000µF.
All the boards recapped (I based the choice of capacitors on different existing threads about this model)
Last but not least, reassembling and rewiring the whole amp, cleaning the faceplate, potentiometers and relay contacts, setting bias and offset and mounting the new feet.
I heard a lot of great things about this amp so I was eager to test it which I did on a pair of B&W DM4. What immediately struck me was the detail in the high and mid range, the different instruments had plenty of room to express themselves and nothing seemed to get lost. I heard new stuff on songs I have been listening to for ages. I was a little disappointed by the low end though, it definitely went very low in frequency but the bass was a little vague, not as tight as with most other amps I tested on these speakers.
I read that these DM4 are known to lack in bass (which I don't find to be true, especially not with my Sansui AU-222) so I decided to try it on a pair of Ditton 66 Legend and everything got back in its right place, I maybe lost a little in detail but the bass had all the precision and depth I was hoping for.
Most definitely a keeper 😀
All the boards recapped (I based the choice of capacitors on different existing threads about this model)
Last but not least, reassembling and rewiring the whole amp, cleaning the faceplate, potentiometers and relay contacts, setting bias and offset and mounting the new feet.
I heard a lot of great things about this amp so I was eager to test it which I did on a pair of B&W DM4. What immediately struck me was the detail in the high and mid range, the different instruments had plenty of room to express themselves and nothing seemed to get lost. I heard new stuff on songs I have been listening to for ages. I was a little disappointed by the low end though, it definitely went very low in frequency but the bass was a little vague, not as tight as with most other amps I tested on these speakers.
I read that these DM4 are known to lack in bass (which I don't find to be true, especially not with my Sansui AU-222) so I decided to try it on a pair of Ditton 66 Legend and everything got back in its right place, I maybe lost a little in detail but the bass had all the precision and depth I was hoping for.
Most definitely a keeper 😀
Good job tracking down the correct parts and doing that amp some justice. On to the next!!!!!
Craig
Craig
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