-edible zone-
-- Aligning the Dynavector DV20X Low and Jelco tonearm to the TD150
- Type: moving coil
- output voltage: .3mv
- vtf: 2.0 ±0.2 grams
- compliance: 12x10-6cm/Dyne
- Load impedance: >30 ohms
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-- Using the TAD Arc Protractor. The Jelco SA370H shares its alignment geometry with Rega RB250 thru RB1000 tonearms. TAD arc protractors are drawn for the individual tonearm and are --not-- interchangeable for other tonearms....... unless they happen to be designed for that particular geometry.
- Effective Length: 239mm
- Overhang: 17.3mm
- Mounting distance = Eff. Length - Overhang
- inner null: 66mm
- outer null: 120.89mm
- First, place a wedge under the platter so that it may not rotate. Note also that a "disposable record" is used as a "work surface" beneath the protractor. Secure the protractor so that it will not rotate when you don't want it to. In this session I used 3 Quarters to weigh down the protractor over the record surface.
- Adjust the protractor and arm so that point zero and point 1 at the outer boundaries of arc travel match to the stylus without moving the protractor.
- From this point forward the protractor remains stationary and it is the cartridge that is adjusted within its headshell so that it may precisely hit all the alignment points of the protractor. In fact the stylus should rest on top of the arc line at any point on it once correct adjustment is done.
- At the inner and outer nulls adjust "zenith angle" of the cartridge by swiveling it one direction or the other so that the alignment grids of the protractor run parallel to the cantilever.
-- (hint: click thumbnail to view image full size)
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point zero
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point 1
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point 2 (outer null) Cantilever is in line with grid marks
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point 3 (inner null) Cantilever is in line with grid marks
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wide sequence shot of the 6 alignment checks
-- Once overhang, zenith and vtf adjustments were finalized the HFNRR test record was used to determine arm/cart match-up and tracking ability.
-- Here is a brief summary of the notable results from that session:
-- Side One
- band 6, +12 db: clean
- band 7, +13 db: clean
- band 8, +16db: constant medium buzz
- band 9, +18 db: the Dyna 20x tracks the band completely thru without jumping out of the groove, all the while making loud buzzing noises both channels.
-- (anti-skate set to 2.0g)
-- Side Two
- track 2: lateral arm/cart resonance: @ 11 - 10 hz
- track 3: vertical arm/cart resonance: @ 10 - 12 hz
-- Comments: Damping fluid had previously been added to the SA370H and no amount of damping adjustments made any difference to the test readings.
-- VTA adjustments (vertical tracking angle)
--With this Jelco care must be taken when setting VTA adjustments.
The tonearm is adjustable at the base mounting for elevation by means of
two set screws that press the base pipe of the tonearm against the
opposite sides of the smooth inner bore of the base fitting. To adjust
VTA while changing from one cartridge to another the body of the tonearm
must be raised or lowered within its base mounting.
One set screw
digs into the pipe body and can work like a pivot point while the other
set screw attempts to press against the pipe from the 90 degree
angle....resulting in slightly tilting the entire tonearm out of square
to the turntable. Negatively affecting azimuth at the stylus/record
interface. I'm working on a set-up jig that will enable greater ease in
raising and lowering the tonearm within its base mount and assure
against tilting the tonearm out of square to the turntable. More later.
Suffice it to say that I did adjust vta into a "ballpark" range
where it appears to sing sweeter. With the arm tube closely level to the
record as the stylus tracks accross the disc. The usual starting point
before "listening for vta".
_____________________________________________________________horizontal rule
-- Some headshells that will hold different cartridges:
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A Sumiko headshell awaits fit-up with the Denon DL-103 with custom Uwe
Ebony body.
-- Please Note the DL-103 / Uwe setup process used on this arm is detailed here
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The standard Jelco headshell will be used to hold the Ortofon 2m Black.
_____________________________________________________________horizontal rule
-- Ortofon 2m Black (moving magnet type)
- Settings:
- vtf: 1.6g
- overhang per TAD Arc Protractor as detailed above
- initial vta set: arm tube sighted in as level of the record surface
--HFNRR test record results for the Ortofon 2M Black in the Jelco SA-370H
-- Bands 1 thru 5 check correctly for a pass
-- Bands 6 thru 9 are the bias torture tracks, results below:
- band 6: +12db: clean
- band 7: +13db: clean
- band 8: +16db: constant medium buzz located center between speakers
- band 9: +18db: the 2m tracks the band completely thru without jumping of of the groove all the while making loud buzzing noises in both channels
-- Comments: I've witnessed much worse with different arms and cartridges on this impossible to track band (band 9) It would have been nicer had the arm and cartridge passed band 8, but still this test is outside the realm of what is likely for the arm and cartridge to encounter while playing music on 'real records'. All in all, a positive test result.
-- Side Two:
- track 2: lateral arm/cart resonance: @ 11-10hz
- track 3: vertical arm/cart resonance: @10-12hz