Sound Issue relating to stylus pressure/inconsistency

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Rob-NYC
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Posts: 1844
Joined: Sun Sep 25, 2011 3:05 am
Location: Manhattan, NYC USA

Re: Sound Issue relating to stylus pressure/inconsistency

by Rob-NYC » Sun Feb 01, 2015 9:37 am

Ok Goat, I see I'm in your crosshairs if this doesn't work out.

The cart you ordered should be fine, it's output will be a bit lower than the 400 but that may be an advantage in eliminating the need for a pot between the preamp and amp input. We'll see.
Some points here:

1) The mag cart will be a few grams heavier than the typical ceramic so you will need to adjust the lateral balance via the screw on the rear end of the arm. These arms are not well balanced to begin with and will bias either slightly upward at the start of a record, and downward toward the spiral. Do the best you can and don't worry about it. Bear in-mind that the tonearm wires will add weight if the arm is just in free space> So it is probably best to anticipate slight rebalance once it is mounted.

2) tonearm wire drees is important to reliable tracking at relatively low pressure.

3) Make sure the arm pivot bearing are neither too tight, nor sloppy. these ain't great bearing points so good enough is good enough.

4) Trip switch. On this pic you can see the trip switch and it's L-shaped keeper:
http://s1192.photobucket.com/user/Rob-N ... ort=2&o=69
The purpose of that keeper is to prevent the trip switch from loading the arm and stylus till it gets to the spiral at the end of a record. It is a significant load and a drop of light oil on the bronze switch bearing might help a bit. In the past I usually flipped the keeper out of the way and let the trip whisker ride the arm tail continuously. I then rebalanced the arm to compensate for this,

5) Long pickup wire to the preamp. You can use the existing coax lead from the arch to the preamp, however this does create a ground loop which will induce a certain amount of hum since the shield touches the arch assembly. If the hum bothers you simply run an isolated wire. You may need to run a ground wire from the preamp case to either the mech or amp chassis as you would with a turntable.

Be careful removing and replacing the flea clips of the new cart, the tiny wires can break. If they do, do not try to solder them with the clip on the cart. the plastic with deform and ruin the cart (I know).

Keep us informed.

Rob
"If we believe absurdities, we shall commit atrocities" -- Voltaire


Topic author
Old Goat
Regular Member
Posts: 96
Joined: Wed Nov 26, 2014 4:27 pm
Location: Charlotte, North Carolina, USA

Re: Sound Issue relating to stylus pressure/inconsistency

by Old Goat » Sun Feb 01, 2015 6:33 pm

Rob-NYC wrote:Ok Goat, I see I'm in your crosshairs if this doesn't work out.
But only if it doesn't work out...remember, I get the credit/glory if it does :D

The cart you ordered should be fine, it's output will be a bit lower than the 400 but that may be an advantage in eliminating the need for a pot between the preamp and amp input. We'll see.
Some points here:

1) The mag cart will be a few grams heavier than the typical ceramic so you will need to adjust the lateral balance via the screw on the rear end of the arm. These arms are not well balanced to begin with and will bias either slightly upward at the start of a record, and downward toward the spiral. Do the best you can and don't worry about it. Bear in-mind that the tonearm wires will add weight if the arm is just in free space> So it is probably best to anticipate slight rebalance once it is mounted.

Yes, I noticed this with the ceramic cartridge upgrade. Drives me crazy, but glad to hear a little bit of variance should be OK

2) tonearm wire drees is important to reliable tracking at relatively low pressure.

This also drives me crazy as the weight and lack of flexibility of the wire definitely plays into the equation. After a lot of fiddling with it, it seems to be fairly neutral right now; although I'm sure I'll mess it up when I replace the cartridge. Is there an optimal way to route and mount the wire?

3) Make sure the arm pivot bearing are neither too tight, nor sloppy. these ain't great bearing points so good enough is good enough.

I've not checked this before, but definitely will


4) Trip switch. On this pic you can see the trip switch and it's L-shaped keeper:
http://s1192.photobucket.com/user/Rob-N ... ort=2&o=69
The purpose of that keeper is to prevent the trip switch from loading the arm and stylus till it gets to the spiral at the end of a record. It is a significant load and a drop of light oil on the bronze switch bearing might help a bit. In the past I usually flipped the keeper out of the way and let the trip whisker ride the arm tail continuously. I then rebalanced the arm to compensate for this,

Makes sense

5) Long pickup wire to the preamp. You can use the existing coax lead from the arch to the preamp, however this does create a ground loop which will induce a certain amount of hum since the shield touches the arch assembly. If the hum bothers you simply run an isolated wire. You may need to run a ground wire from the preamp case to either the mech or amp chassis as you would with a turntable.

I figured I would need to ground the preamp

Be careful removing and replacing the flea clips of the new cart, the tiny wires can break. If they do, do not try to solder them with the clip on the cart. the plastic with deform and ruin the cart (I know).

Thanks, definitely something I would do

Keep us informed.

Rob


I'll let you know how it goes. Thanks for all your help
Brooks

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