Adjusting
A Sumiko headshell will be used. Weight of the headshell
assembly alone is 14.6 grams. Most headshells for this tonearm weigh
in at around 10 - 10.5 grams. The heavier weight of the Sumiko will add
mass (weight) to the tonearm/cartridge assembly to help get the effective mass
into a range that works to the benefit of the DL-103. Incidentally, the
Sumiko is adjustable for azimuth.
Above two photos. The stock Denon DL-103 lies next to a Uwe solid Ebony headshell body. The Denon will be separated from its plastic shell and placed into the Uwe Ebony body.
Like this.
The Uwe Ebony bodied DL-103 weighs 11.5 grams
A brass head-shell weight weighs 4.6 grams.
The Jelco awaits.....
I can find no published rating for effective mass of the Jelco SA-370H. However we know that the Denon works well in arms with an effective mass higher than 16 grams and as high as 25 grams. So we are left knowing the weight of all the parts but we don't know the rated effective mass of the tonearm. Consequently the setup plan is to assemble the cartridge to the arm using all of the above pieces, to align the arm and cartridge using our arc protractor and to set vtf (tracking force) to the median suggested amount. If we can do this using the standard Jelco counterweight, so much to the good. If we can't, then the choice is; to either lose some weight at the headshell or gain some weight at the counterweight end.
Then after that the HFNRR test record will be used to measure the lateral arm/cartridge resonant frequency. This measurement will tell us much. The rule of thumb with the arm/cart resonant frequency test is that readings of between 8 - 12 hz are considered to be within an acceptable range. However my experience with the DL-103 is that it starts sounding good when the arm and cart resonate at between 9 - 10 hz. So lets proceed with the plan and then see what it does.
Above photo: Sumiko headshell holds Uwe Ebony bodied Denon DL-103 Note the Allen bolt at the base of the Sumiko. Loosen to adjust azimuth, then re-snug. The Sumiko also comes with a really nice set of headshell leads & clips.
12/29/2009
First result. The counterweight won't balance the arm to 2.5g of tracking force when assembled and using the 4.6 gram head shell weight.
The weight was removed.
Second result: The counterweight won't balance the arm to 2.5g of tracking force when not using the 4.6 gram head shell weight.
Hmmmmm.
And for the solution to this dilemma, stay tuned for additional installments.
ttfn.
12/30/2009
Still searching for a Jelco Heavyweight counterweight that fits this model (SA-370H)
Meantime:
I find that the "heavyweight" counterweight from Expressimo (nla) works on this tonearm. The two bolts extending out the counterweight are there to add mass. Like this it is possible to set vtf (tracking force) to the nominal requirement (2.5grams).
Here are the hfnrr test record results from this configuration:
brief summary:
side 1: tracks 1 through 5 were a pass.
tracks 6 throu 9 are the bias "torture" tracks that test tracking ability and can be used to adjust anti-skate.
 | track 6: clean |
| track 7: clean |
| track 8: clean |
| track 9: steady medium buzz right channel |
side 2: tracks 2 and 3
| Lateral arm/cart resonant frequency: 10 hz |
| Vertical arm/cart resonant frequency: 10 hz |
Clean on track 8 and only a medium loud buzz on track 9. That is the best score yet on this tonearm. Proof that the Denon DL-103 is an excellent tracker...and also that the counterweight is working well like this.
........more later when the correct counterweight is found.
Found! 1/6/2010
Above photo: The finished project.
We find an ebay seller that offers counterweights for the newer Jelco tonearm model, the SA-750L. At the time we did not know if the counterweight from the SA-750L would work on the SA-370H that we have, but the seller offers a no fuss return if it doesn't work for us. So the counterweight is bought.
As luck would have it, the heavier counterweight for the Jelco SA-750L functions correctly on this arm. On this tonearm, to adjust for vertical tracking force, the counterweight is rotated in one direction or the other to move it backward or forward on its shaft. Because of its "heaviness" it will be limited to counterbalancing the heavier cartridge and headshell setups. This counterweight weighs 167.2 grams. In order to adjust the nominal 2.5 grams of tracking force with this tonearm / headshell / cartridge combination, the counterweight is adjusted way up close to the pivot. It was possible to adjust for even heavier tracking forces (3.0 grams) but by then the counterweight is bumping into the pivot housing. That's ok. As it is we have the adjustment we need for setting tracking force to 2.5 grams. Now on to measure arm/cart resonance and tracking ability.
hfnrr test record session with the new counterweight:
Side 1:
Tracks 1 thru 5 = pass
Tracks 6 thru 9 bias adjust "torture tracks"
| track 6: clean |
| track 7: clean |
| track 8: clean |
| track 9: medium buzz |
Side 2:
| Lateral arm/cart resonance: 9 hz |
| Vertical arm/cart resonance: 9 hz |
Comments: The heavier counterweight has an influence on the arm/cart resonance. Now it is resonating at 9 hz. A full point lower than with the Expressimo "Heavyweight" cw. In my experience, this cartridge will sound its best with this much mass behind it. And the hfnrr test record is an excellent real world test to determine if an arm and cartridge are a good match. In this case I wanted the arm and cartridge to resonate at 9 hz. Previous experience with the Denon DL-103 has taught me that it sounds its best with enough effective mass behind it to measure 9 hz arm/cart resonance.
It is ready.