18 September, 2023

Denon DL-102 Adjustable Loading Resistor

Click pic to enlarge. The Red/White are the Tonearm Cables from my Technics SL-1200. The Orange Pair are loaded with small Trim Pots dialed to 1K by multimeter.

Letter from NYC (23-16): Denon DL-102, Part V
Talk DIY: Adjustable MM Loading Resistor

Written in Shenzhen

I have been using the Denon DL-102 for a long time - it's my mono reference. I have it on an SME type removable headshell. Whenever I scored a few mono LPs or simply wanted to hear some, I swapped it in. I always add some weight (a couple of blu-tac'ed coins) on the headshell and at the tail of the tonearm. I have written quite a bit on this cartridge (Parts I-IV scattered here), but usually in the context of comparisons with other cartridges.

The DL-102 made a significant impact in my record hunting. When I first set it up, I played my many mono Living Stereos (LM) and quickly concluded that the Heifetz and other soloists sounded  fabulous, perhaps even better than in in their stereo pressings. I also appreciate its way of playing a stereo record well. Say, while on a mono binge I suddenly wanted to play a stereo record, no problem! Unlike many true mono cartridges, it won't harm the stereo record. In fact, in Japanese Radio Stations, the DL-102 was used to play all records, mono or stereo!

The DL-102 is an MC cartridge, but a High Output one. Thus, most people, including me, just use the MM stage (standard 47K ohm). The vast majority of MM stages, even on phonoamps that accommodate MC, do not allow for loading adjustment in MM mode. Hence, 47K ohms is de rigeur. However, the DL-102 is said to be optimally loaded at 1K ohm (or is it >1K ohm?) and there are discussions on the internet. I have always wondered what a lower loading than 47K would sound like...

To alter the (47K ohm loading) of the MM phono stage, one has to insert a parallel resistor with the input. I discussed this with Andy and he lent me his ingenuous contraption (see top pic). Get a 2 (female) to 1 (male) RCA adaptor. Insert the phono cables into one set of female inputs, and in the other set insert a pair of RCA males loaded with desired resistors. This can be accomplished in 2 ways. The perfectionist can just solder (or screw on, with some connectors) the resistor of his choice between the + and - points of the male RCA connector. Or one can install a small Variable Resistor (VR) Trim Pot (like the ones commonly used as amp bias pots). The advantage of the latter is one can dial in a range of R values with the help of a multimeter. This is so convenient for experimentation - just make sure the pot has the range you want (the pot above looks to be 1-10K, just about perfect. Maybe 500-5K would be just as useful. Higher values near 47K are likely not necessary.

How to choose the Resistor Value? The law is of course 1/R = 1/R1 + 1/R2. So say we want 1K loading on the 47K ohm MM stage, it becomes 1/1000 = 1/47,000 + 1/R2 and R2 would be the resistor value you need. But no need to do that, as we all use the Parallel Resistor Calculators on the web! For the MM stage it is easy, you can even not calculate: since the 47K value is very high in comparison, the R2 value is basically just what you seek (within what we usually use - there are extremists out there) - say, 1000 ohm for desired 1000 ohm and 500 ohm for desired 500 ohm, 330 ohm for desired 330 ohm. Use a multimeter and dial in your desired loading. Error margin is smaller than the tolerance of the usual cheap digital meter.

How does it Sound (Loaded at 1K)? In a word, astonishing and transformative! One reservation I have always had with my Denon DL-102 running into 47K is it's a little too smooth. At 1K, there is significantly more top end air and a livelier demeanor. Very nice! Not kidding, sometimes one feels one hardly needs stereo!

Note: This is for MM Loading adjustment only. Does not apply to MC Loading due to completely different parameters.


As a parting note, I muse on the genre of High Output MC cartridges. They are interesting animals. because of their high output, they are almost always used with 47K ohm MM stages. Most of the time, results are satisfactory. Consider Denon's own DL-110, which I rate very highly, and it works very very well with MM phonos (despite some voices to the contrary). But there are times when one senses something can perhaps be improved. The case of the Denon DL-102 illustrated here points out that.

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