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I’m too high

friendlyvolc

friendlyvolc

Active Member
Or maybe my tonearm is...

I just built a plinth for my newly acquired Technics SP-10 Mk2 and EPA-100 arm. The plinth is a solid 3” thick layered birch ply affair. I’ve found an original Obsidian armboard which I’ve mounted next to the deck. The aluminum armboard is mounted on the same level as the deck. I’ve very carefully fabricated through CNC the armboard insert so that it lies flush with the top of the insert.

So far so good. Unfortunately, I feel that no matter how low I drop the EPA-100 in its column and lower the VTA adjustment to its lowest point, the arm still rides a little high.

Can anyone with an Obsidian plinth tell me if the bottom of the armboard is flush with the bottom of the deck? I might have to fabricate a new armboard if I can’t get the arm low enough. AE2954D2-2428-4FCA-96A9-982EF81B865E.jpeg1925486A-F7D0-4AF9-A141-F51A1E417112.jpeg
 
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friendlyvolc said:
So do you think it’s cartridge specific as to whether I can get to level?
Click to expand...
Cartridge, table, arm and maybe the mat.
It all depends it's all geometry. Lets say everything was stock factory with the plinth, they don't know what arm and cartridge your using. Not all arms are the same hight, nor do they all have the same VTA adjustments. Not all cartridges have the same dimensions either so we have to work things out as to have adjustments.

Your arm is bottomed out, and even if you can make the board lower, your arm looks pretty low now as it is. So you have two choices here to get the arm wand level, lower the board, or raise the head shell. Adding a spacer between the cart and head shell, will rase it, in turn effectively lowering the back of the arm.

Actually three choices, a thicker mat will raise the head shell, and might be the best option. Do you have a felt mat you can add under the factory mat to try out?
 
I guess I was surprised because I’m using a Technics arm, armboard and deck that would have been spec’ed all together in the Obsidian plinth. From what I could tell, I matched the relationship of the armboard to the deck as Technics did. So you’d think there would be more travel options on arm height.

Your suggestions are all sensible. The mat idea would be the easiest to try. I have a cork mat that would probably fit well under the rubber pad. I also have the original Technics headshell which might have different geometry than the Ortofon headshell I’m using with the Decca Gold cartridge. There’s a big rubber washer that’s under the retention disc of the tonearm which might not be vital.
 
That Decca 'Gold' cartridge body does not seem so high. That headshell 'roof' in the pic is definitely at a standard height. Mind you some other headshells can have higher 'ceiling'...

Uses of spacers between cartridges and headshells are a common practice that can also have interesting sonic coloration depending o the material used.

Eccentric maniacs of the second decimals of their VTF might feel not at ease with such proposition though... The extra mat is also a good VTA compensator proposition.

One can even have another mat surface in contact with the record and chose from different fabric or material according to it's preference. I wouldn't worry, on the contrary.
 
friendlyvolc said:
Can anyone with an Obsidian plinth tell me if the bottom of the armboard is flush with the bottom of the deck? I might have to fabricate a new armboard if I can’t get the arm low enough.
Click to expand...

Yes, it’s flush. Attached pic of the SH-100S may help. Looks like the cartridge mounting surface of your headshell is ~ 3-4mm higher than what the stock headshell would be.

9CA2DA99-5B85-4BBA-B4C5-356A53E7989B.jpeg
 
You need the arm board to be flush with the plinth, otherwise all other efforts will be makeshift. Get a Router and machine out a recess so that your arm boards will be flush with the top of the plinth.

Don't waste your time with the temporary fixes others are recommending, you have a great table, arm combo, do it right.

By doing it right you have the capability of using your adjustable VTA.
 
Ken Boyd said:
You need the arm board to be flush with the plinth, otherwise all other efforts will be makeshift. Get a Router and machine out a recess so that your arm boards will be flush with the top of the plinth.

Don't waste your time with the temporary fixes others are recommending, you have a great table, arm combo, do it right.

By doing it right you have the capability of using your adjustable VTA.
Click to expand...

He has it as designed, Ken. This is a combination of a bit lower cartridge and a headshell with different geometry than was intended. If he drops the arm mount to the deck of the plinth he’s likely to have problems the other way. EPA-100 doesn’t have a lot of VTA range.
 
Ken Boyd said:
You need the arm board to be flush with the plinth, otherwise all other efforts will be makeshift. Get a Router and machine out a recess so that your arm boards will be flush with the top of the plinth.

Don't waste your time with the temporary fixes others are recommending, you have a great table, arm combo, do it right.

By doing it right you have the capability of using your adjustable VTA.
Click to expand...

Ken is right I had the same problem with my Acoustand plinth . The tonearm mounting has to be level with the plinth surface
 
Surprised that the EPA arm has such limited range. Couldn't he machine a bit to allow the arm board to sit lower if he plans on using that cart most of the time. It seems to me all the other recommendations are temporary fixes.
 
Ken, I had the same thought. I could use a slightly larger Forstner bit than the one that cut the hole and and kiss a countersink a few millimeters below the surface. That would nestle the retaining plate of arm into the surface of the armboard. I’m not sure how that would look aesthetically but I have a few inserts made from my build to test with.

I’m general, I guess I’m curious if other official Obsidian/EPA-100 owners have had this problem with non Technics headshell or cartridges.
 
Ken Boyd said:
Couldn't he machine a bit to allow the arm board to sit lower if he plans on using that cart most of the time. It seems to me all the other recommendations are temporary fixes.
Click to expand...
It's not a case of a temporary fix, it's all to get what he has there together work right. To me in the photo, the back of the arm is already very close to the record, lowering the board will make this even worse, but has elevation of the arm but that's not the direction he needs to go.

I see a P mount cartridge and adapter that looks like the cantilever is collapsed. The body of the cart looks like it could bounce of the record with the slightest bounce.

The head shell looks out of proportion and I'm sure with that cart is a really bad match. I see the head shell bottom very close to the record as well as the head shell coupler on the arm wand.

If it was me, I'd use a more appropriate head shell and cartridge. But a spacer for the cartridge or a taller mat will give better geometry with what he has there.
 
Right now, the deck and armboard are sitting flush bottom on the same surface, as original Obsidian design. I think what’s confusing about the Obsidian design is that there are raised areas around the deck and armboard that obscure the fact that the deck bottom and armboard bottom are level. Once you strip away those raised areas, they rest in the same plane. Not sure why Technics did it that way unless I’m missing some important functional or aesthetic tweak.
 
Ken, from my angle, as the guy that took the photo, the arm is close to level but still a little high. I’m bottomed out. I have only to go but up. Maybe it’s “level enough”.
Ken that is a Decca Gold cartridge as designed. It is a Garrott brothers model. They have vertical cantilevers that puts the diamond very close to the cartridge body. There’s no p-mount stuff. It’s in a current vintage Ortofon LH2000 headshell. I will look at other headshell designs or wedges first as that seems the most minimally invasive fix.
 
I'm leaning toward what 4-2-7 is saying - the bottom of the headshell looks closer to the record surface than I'd like, though that may just be perspective of the photo. I'd go with a friendlier headshell, or shim the cart if it really is that close.

@Ken Boyd, sure, if married to this headshell, etc. I've not had an issue with the stock setup and OEM headshell, though I understand others like to use different headshells. Just have to pick the compromise that fits his particular goals the best.
 
This cartridge is a cantileverless design that's why it rides so low.

My advice would be to use a spacer between the headshell and the Decca cartridge mount. Or get a Micro Seiki H-303 headshell which sits several millimetres lower relative to the armtube.
 
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