Not too long ago I purchased two Denon AU-320 S.U.T.'s. Curiosity always gets the better of me so I decided to take a peak inside as I know these are early 1970 devices. Sure enough, the foam had rotted into dirt on both. Not surprisingly, both were wired slightly differently. One was all stock wiring, the other was redone in a poor way with a big blob of white silicon preventing shorting around the 3 way switch. It looked ugly but the device worked fine.
The signals passing through both devices worked fine with my DL-103 and 103R, but I wanted to clean up the inside, redo the soldering and also the foam. While researching the AU-320 I found an old thread online where a user modified it to eliminate the switches, and turn the top set of RCA's into the 3ohm input and the bottom set into the 40ohm inputs by direct wiring. His photos however, didn't give me any clue about wiring.
I was liking that idea of shorter wire runs and a more direct signal path, however, after literally long hours of search I could not find any information regarding wire color of the transformers. Therefore, I decided the old fashion method of reverse engineering and documenting to find out how this wonderful transformer functioned.
A big part of the puzzle was the 3 way switch and how it routed the signals for each position. Once that was solved, I was able to determine how the wire colors needed to be configured to work exactly how it should but without any switches in the path.
When you modify the AU-320 as I present, you lose all functioning of the switches. The top RCA IN is L/R for 3 ohm function (1:36). The bottom RCA IN is L/R for 40 ohm function (1:10). It becomes an all manual device. One could replace the stock RCA cable, but I find it is a very adequately shielded cable. I did clean up the nearly 50 year old metal connectors on the whole device with Deoxit.
So far, I've only done one device and it works perfectly! It functions the exact same way except without the switching. I could swear it sounds much better, but I'll leave my subjective commenting at that. (except that I do prefer 1:10 with 103R). I do like that I have new soldering and very clean innards.
I did this for nothing but the challenge, and ending up with a better device according to my needs. If you can live without the other functionality, you will have an awesome 1:10 or 1:36 S.U.T.. Prices are still very attractive on eBay. I just bought a Cinemag 3440AH S.U.T. and the newly modded Denon holds it's own. A truly marvelous S.U.T.. Enjoy the attached diagram with the correct color coding! Just wanted to share something and that's it .....
EDIT: CAUTION / DISCLAIMER .... because I literally don't know ....... I assume only one turntable can be plugged in at a time into the AU-320 after this mod. Please use only one set of L/R, RCA inputs when using the device as modified here to prevent potential damage to all related equipment.
The signals passing through both devices worked fine with my DL-103 and 103R, but I wanted to clean up the inside, redo the soldering and also the foam. While researching the AU-320 I found an old thread online where a user modified it to eliminate the switches, and turn the top set of RCA's into the 3ohm input and the bottom set into the 40ohm inputs by direct wiring. His photos however, didn't give me any clue about wiring.
I was liking that idea of shorter wire runs and a more direct signal path, however, after literally long hours of search I could not find any information regarding wire color of the transformers. Therefore, I decided the old fashion method of reverse engineering and documenting to find out how this wonderful transformer functioned.
A big part of the puzzle was the 3 way switch and how it routed the signals for each position. Once that was solved, I was able to determine how the wire colors needed to be configured to work exactly how it should but without any switches in the path.
When you modify the AU-320 as I present, you lose all functioning of the switches. The top RCA IN is L/R for 3 ohm function (1:36). The bottom RCA IN is L/R for 40 ohm function (1:10). It becomes an all manual device. One could replace the stock RCA cable, but I find it is a very adequately shielded cable. I did clean up the nearly 50 year old metal connectors on the whole device with Deoxit.
So far, I've only done one device and it works perfectly! It functions the exact same way except without the switching. I could swear it sounds much better, but I'll leave my subjective commenting at that. (except that I do prefer 1:10 with 103R). I do like that I have new soldering and very clean innards.
I did this for nothing but the challenge, and ending up with a better device according to my needs. If you can live without the other functionality, you will have an awesome 1:10 or 1:36 S.U.T.. Prices are still very attractive on eBay. I just bought a Cinemag 3440AH S.U.T. and the newly modded Denon holds it's own. A truly marvelous S.U.T.. Enjoy the attached diagram with the correct color coding! Just wanted to share something and that's it .....
EDIT: CAUTION / DISCLAIMER .... because I literally don't know ....... I assume only one turntable can be plugged in at a time into the AU-320 after this mod. Please use only one set of L/R, RCA inputs when using the device as modified here to prevent potential damage to all related equipment.
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