Denon DP80 & DP75 Owner's Thread

[bimasta]

When I got my DP80, all 5 screws were tightened down hard, on each of the 3 springs. It came like that, so I assumed it was right. Now I'm sure it's not right.

What is the point of using springs if they're all adjusted tight, with no give? It's like joining the 2 parts of the platter like a single piece of metal — Might as well just use one piece of metal for the entire platter, in the first place. Why 2 parts?

The 2 parts have different functions — the bottom fits onto the bearing-and-motor, it's heavy and has most of the mass.

The top part is much lighter: it's just a surface for the LP to rest on.

And it's supposed to be de-coupled from the bottom piece. That's why the springs are there. The bottom-platter gets all the Bearing Rumble and Motor Noise, which will resonate through the Vinyl and be picked by the Stylus. The upper-platter is supposed "to float above it all", and present a non-resonant surface for the LP — that's why the foam pads are added: to damp residual resonance that makes it through the leaf springs.


I adjust the leaf springs as follows. The middle screw is tight (Screw 3). As Legrace notes, it came from the factory with an "alignment seal". It was, and must be kept tight.

But should the other 4 screws also be tight?

The two outer screws (1 and 5) must be loosened in order to center the Upper Platter within the mass of the Lower Platter, or else the platter will spin "wonky". Once centered, then 1 and 5 are tightened hard so it remains centered.

I leave Screws 2 and 4 loose, so the springs can act like springs, and "give". They can damp some of resonances excited in the lower platter by the bearing and motor.

The DP80 platter is designed like a "sprung" turntable, e.g. Linn and Thorens, which bounce a little — the springs in a belt-drive isolate the Platter+LP+Stylus from the noise of the Motor.

You can't isolate a DD's platter from its motor (like you can with a belt-drive) because a DD's platter is part of the motor. So Denon designed it all into the Platter — and the top part of the platter is supposed "give".

 

[Legrace]

And it's supposed to be de-coupled from the bottom piece. That's why the springs are there. The bottom-platter gets all the Bearing Rumble and Motor Noise, which will resonate through the Vinyl and be picked by the Stylus. The upper-platter is supposed "to float above it all", and present a non-resonant surface for the LP — that's why the foam pads are added: to damp residual resonance that makes it through the leaf springs.

Thanks for the explanation, makes total sense. I am inspired to try your adjustment idea with screws 2 and 4. Also pretty certain I need new foams on the upper platter.

 

[bimasta]

Thanks for the explanation, makes total sense. I am inspired to try your adjustment idea with screws 2 and 4. Also pretty certain I need new foams on the upper platter.

Given the age of all DP80's, you definitely need to replace the foam: it has decomposed.

If you try my adjustment, you only need to loosen screws 2 and 4 enough that the top platter can sink down when you press on it — again think of the "floating" suspension of a Linn or Thorens TT — but it can only sink just so far, and there's no point loosening 2 and 4 any farther. If you loosen them too much, you'll exceed the maximum benefit, so it's pointless, and the screw-heads will protrude so far they'll hit the tape read-head when the platter is spinning.

With a Linn or Thorens, you can make the suspension go bouncy-bouncy — but the Denon's top platter doesn't move that much, those leaf-springs aren't as "springy" as the coil-springs on a Linn/Thorens.

As an aside, in the early '90s Thorens changed to leaf-springs for the suspension in a new range of TTs — they eliminated the sideways "rocking" the coil-springs allowed, and movement was restricted to up/down, and didn't move as much — the DP80s leaf-springs are much the same: limited up/down "give".

 

[fiddlefye]

Alignment, in this context, means centering, so the 2 parts of the platter are balanced. But what about "adjustment" of those leaf-springs? I'm introducing "adjustment" as a new idea here.

But first, a question — How do all you guys, who have a DP80, adjust your leaf-springs? There are 3, and each has 5 screws. When I got mine, all 5 were tightened down hard, on each of the 3 leaf-springs.

Is that how yours are? Did you get the TT untouched from the Factory? Did you get it serviced by a Tech? Have you adjusted the springs yourself?

A lot of DP80 owners never even knew that foam pads lurked within that sandwiched platter because they're hidden — and didn't know the foam rotted and had to be replaced.

Denon's two-part platter conceals a few mysteries, and the Service Manual doesn't say a word about it —so how should those springs be adjusted?

As you might recall, my DP-80 was professionally serviced by Peter Noerbeck as it had issues beyond rotted foam and such I might have dealt with myself. Peter has rebuilt many of these drives so perhaps I will send him a message and ask him about spring adjustment in the platter. My drive was "virgin" when I got it, if electronically-challenged.

 

[bimasta]

As you might recall, my DP-80 was professionally serviced by Peter Noerbeck as it had issues beyond rotted foam and such I might have dealt with myself. Peter has rebuilt many of these drives so perhaps I will send him a message and ask him about spring adjustment in the platter. My drive was "virgin" when I got it, if electronically-challenged.

Good idea (and hello again). I thought of a new analogy, and you might use it with Peter — there are 15 screws in total, securing the 2 parts to each other, and if all 15 are torqued-down hard, you might as well WELD the 2 parts together... in which case, why not just use a 1-part platter, a single piece of metal? Why have those leaf-springs at all?

I also refined my "instructions" a bit — loosen 2 and 4, and push down on the rim — the upper platter will sink down just a bit (maybe 1mm) and it should have a "soft landing" on the foam pads. The foam is there to damp vibrations at the rim, which is most prone to vibrate.

If your foam pads are rotted, you will feel a metal-to-metal contact when you push the upper-platter down.

You'll let us know what he says, won't you Fid?

 

[totem]

If a vintage plater had torqued down screws what does that say about Denons thoughts on having more
isolation between the patters?
Makes one wonder.

 

[bimasta]

If a vintage plater had torqued down screws what does that say about Denons thoughts on having more
isolation between the patters?

Not sure I get your question. By "vintage platter" do you mean other makes and models? If so, I can't think of any that use leaf-spring "suspensions" for isolation.

 

[Legrace]

I think what was meant is if an unmolested unit has all screws torqued that implies it was Denon’s original intent. Have to think on that one.

 

[bimasta]

Yes it would imply that. Does anyone have a guaranteed-factory-New DP80 to inspect?

 

[BillWojo]

I suspect that they were tightened down as well. Can someone post a picture of these mystery springs? I suspect they are used as compliant drive links between the upper and lower platter, not as levitating springs. The isolation being done mainly by the cushions.
But never having seen the design before I could be full of speculating BS. LOL

BillWojo

 

[totem]

Less than succinct but yes unmolested OEM platter.

 

[Bkphoto]

Platter molester, the worst kind of people...

 

[bimasta]

I suspect that they were tightened down as well.

I think most used DP80's had the screws tightened down by over-eager owners. It's human nature — 1) If a platter can come off, take it off — 2) If a screw is loose, tighten it.

I suspect they are used as compliant drive links between the upper and lower platter, not as levitating springs. The isolation being done mainly by the cushions. But never having seen the design before I could be full of speculating BS. LOL

"Compliant drive links"? They are unrelated to the drive mechanism, if that's what you mean. And wouldn't "levitating" be nice? Total isolation from the world. But I think you mean "lifting" or "raising".

And just between you and me, most of us on AK are speculating most of the time.

A photo wouldn't do much good — you'd need a 3D rendering.

 

[BillWojo]

"Compliant drive links"?

By that I mean using the springs to directly drive the upper platter from the lower platter so there is no angular movement between them.
Do the springs also serve to lift the upper platter at all? Like I said, without photos I'm only speculating. I don't think I need a 3D model, just a few photos of the springs and attachment points. Been designing, making and repairing machinery all my life, not much I haven't seen.
Have you seen the armboards I built on the "JVC QL-?? owners thread" starting on page 11? Just a little Covid project.
https://audiokarma.org/forums/index.php?attachments/img_1351-jpg.1979198/

BillWojo

 

[Legrace]

So installed new foam today. The old foam disintegrated into tiny pieces, definitely rotted. The sound improvement afterwards struck me immediately. Lower noise floor for certain. Anyone with one of these decks, check your foams!!!

 

[fiddlefye]

Good idea (and hello again). I thought of a new analogy, and you might use it with Peter — there are 15 screws in total, securing the 2 parts to each other, and if all 15 are torqued-down hard, you might as well WELD the 2 parts together... in which case, why not just use a 1-part platter, a single piece of metal? Why have those leaf-springs at all?

I also refined my "instructions" a bit — loosen 2 and 4, and push down on the rim — the upper platter will sink down just a bit (maybe 1mm) and it should have a "soft landing" on the foam pads. The foam is there to damp vibrations at the rim, which is most prone to vibrate.

If your foam pads are rotted, you will feel a metal-to-metal contact when you push the upper-platter down.

You'll let us know what he says, won't you Fid?

I sent Peter a message, will let everyone know what he says.

 

[matteos]

I think I might have had a duh moment before.... Are the leaf springs the piece of metal attached to the bottom on the underside of the bottom platter? I thought they were a fancy washer or something. I had just assumed the springs were on the inside and I was looking for them. But I sort of see how they work in this configuration as there is some give in the middle bolt that is tightening the rest to the inside.

Also the foam weatherstrip I bought worked very well. Seems like it is the right size. The old foam was so brittle that even though it was mostly still whole just broke apart when I started touching it.

https://www.amazon.com/gp/product/B0025KUSWI/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

 

[Legrace]

Yes. Although not sure I would formally call them leaf springs as normally leaf springs are curved and these are not. But in tension against the foams I can see them acting as springs. Since replacing my foams I am so pleased with the improvements.

 

[matteos]

Yes. Although not sure I would formally call them leaf springs as normally leaf springs are curved and these are not. But in tension against the foams I can see them acting as springs. Since replacing my foams I am so pleased with the improvements.

When I heard leaf springs I was looking for something like a truck suspension on the inside or something.. The foam does make an improvement and is well worth taking the platter apart for.

 

[Legrace]

Also the foam weatherstrip I bought worked very well. Seems like it is the right size. The old foam was so brittle that even though it was mostly still whole just broke apart when I started touching it.

Mine just disintegrated as well. Replacement wise I used a high density 1/4 inch thickness foam.