Logic DM-101 turntable

jdjohn

One of Britain's better efforts, the Logic DM-101 turntable:

The suspended sub-chassis is 8mm thick by my measurements I have a Grace 704 tonearm en route...should be an interesting combo.

P.S. I love the industrial look of this...blemishes and all.

nooshinjohn

A little bit of love, polish and elbow grease and you have a gem on your hands. Nice piece of kit there mate.

dromunds

What’s the difference between the Grace 704 and a Grace 707? PM me if they are similar, and use the same phono cable Don

dromunds

I sent you a PM with photos of the custom made phono cable. Don

jdjohn

Here are some more pics of this British tank.
The plinth/base has several layers of MDF:


The suspended sub-chassis is several mm of solid aluminum, with three suspension screws, whose ends rest in rubber grommets suspend by springs (see above pic for springs and grommet):

The motor seems a little puny:

But the pulley is substantial and more than adequate - look, another set of suspension springs and grommet for the sub-chassis in the background:

I went with a Grace 704 tonearm, but had to fabricate a homemade armboard from 3/8" MDF...yes, it looks amateur:


Cartridge is a Technics EPC-205C-II.

Speed is still a tad slow, so I'm researching a thicker belt, and I want to fine-tune the suspension a bit more. This has a two-piece platter design of cast/milled aluminum, with the belt driving a sub-platter, and the main platter sitting on top. Yes, that is felt incorporated into the main platter, so no platter mat per se. I believe the whole design was meant to compete with the Linn Sondek LP12 back in the day.

The noise floor is non-existent with this deck...everything emerges from black.

joecoulson

Nice

jdjohn

I want to report that in the US, the best belt replacement for this turntable is the FBM20.0 from turntableneedles.com https://www.turntableneedles.com/Flat-Belt-Medium-200-Inch_p_239.html The specs for the belt show that it has the greatest thickness, and I can report that the speed is spot-on with this belt. I tried two of their other 20in belts, and the speed was off a bit. The FBM20.0 maintained speed better than the others.

halo

@SCompRacer - any insights here?

Nice looking deck John

SCompRacer

halo wrote: »

@SCompRacer - any insights here?

Nice looking deck John

Nice table! Back in the day, it was cheaper than the Linn LP12 and had a heavier plinth.

The Linn suspension springs had to be messed with quite a bit to get it working right. That is, springs have a starting and ending coil. The orientation of that edge of the spring was important. You had to turn the three suspension springs until the arm board was squared in the opening and the suspension worked properly without binding. I learned that from an old post at Pink Fish Media.

Not sure if the DM-101 was as touchy as I've never had one. I have owned a Linn LP12.

The Linn underwent many, many upgrades in its life that changed the presentation and cost. The DM-101 was only available for few years IIRC.

joecoulson

Jody - are you still enjoying the Clear Audio deck?

mhardy6647

The words logic and turntable do not go together*.
Just sayin'.



___________
* Note that I am speaking as someone who never gave up on records

jdjohn

But Mark, the inconvenience and high cost make up for it

Thanks for the input, guys. I enjoyed my first one so much that I got a second one This second one came with a dustcover and the stock feet instead of spikes like on the first one. Here it is with another new-to-me toy, a Micro Seiki MA-707 tonearm.

So far I've only installed the arm and checked the mechanics...haven't hooked it up yet.

On my first one, I took the Grace 704 arm off and installed a Micro Seiki MA-505 arm (mentioned in another thread).

As usual with suspended chassis, tuning the suspension is essential. You can see in my earlier pics that there are metal rings with rubber grommets in them, and springs on each side. There are three of these, and the long screws on the chassis rest in the grommets. A couple of the springs on my first deck were tired, so I found some suitable replacements at the hardware store; I did have to trim them a bit, and TBH is was kind of a pain, but I like to tinker on such things

Joe, I do still have the Clearaudio Concept, but as you can see, these vintage decks (and tonearms) currently have my attention

jdjohn

So this happened today:

Same turntable (except for feet), same cartridge (AT13EX w/0.2x0.7mm nudie)
Micro Seiki MA-707 arm on the left, MA-505 on the right
PS Audio Sprout integrated w/phono-stage and headphones

My idea of fun

displayname

jdjohn wrote: »

So this happened today:

Same turntable (except for feet), same cartridge (AT13EX w/0.2x0.7mm nudie)
Micro Seiki MA-707 arm on the left, MA-505 on the right
PS Audio Sprout integrated w/phono-stage and headphones

My idea of fun

This is awesome! So few people get to A/B a tone arm. Fun day indeed.

mhardy6647

jdjohn wrote: »

So this happened today:

Same turntable (except for feet), same cartridge (AT13EX w/0.2x0.7mm nudie)
Micro Seiki MA-707 arm on the left, MA-505 on the right
PS Audio Sprout integrated w/phono-stage and headphones

My idea of fun

Did ya spin some Beck?

https://youtu.be/EPfmNxKLDG4

jdjohn

Headphones, Mark...not Microphones

mhardy6647

Headphones will work as microphones -- and vice versa.

Learned that as a kid (with inexpensive transducers, thankfully).

jdjohn

Well done!

And as you probably know, step-up-transformers can be used for microphones and moving coil cartridges.

joecoulson

jdjohn wrote: »

Headphones, Mark...not Microphones

jdjohn

Oh my...this is getting ugly...

joecoulson

Lol.
After speaking yesterday, since you fabricated the msg plate for the one tonearm, can one be made to work with the other? Therefore eliminating as many differences between the two decks for the best comparison of just the arms.

jdjohn

Not sure what an msg plate is, other than a dish at a Chinese restaurant The two arms had different mounting plates (to cover the SME holes), so I decided to try and make them more comparable.

Here's the 505 arm, which I mounted originally with 7/16" MDF board:

And the same 505 arm now with a thin piece of laminate:

I can detect a (very) slight difference in sound between the two materials. I used Audacity and an ADC to record WAV samples. Phono pre-amp for this is a Dynavector P75 MkII.
MDF sample: https://drive.google.com/open?id=12JRkRIEBghVCLwA9tD3bkwmGq7SubjrJ
Laminate sample: https://drive.google.com/open?id=1lD0pIi3Oadr3Vlb7r19turDEMoUgYddx
Maybe not the best song to use, but I already had it spinning. After listening to the opening of the song, there is also a transition starting near the 2:45 mark that is interesting. IMO not a clear 'winner' here. I find the laminate a little crisper and cleaner overall, albeit a little leaner (yet tighter) in the bass. The MDF provides a fuller sound in the bass, yet perhaps a thin layer of cushion in the mid and treble. YMMV

Of course there can be a whole discussion about armboard/plate mounting materials (i.e., exotic woods, co-polymers, aircraft grade plywood, etc.). But now, at least, I have matching materials for these two arms, so can give them another listen.

joecoulson

So interesting that small of a variance can have such a profound effect. Very cool Jody

verb

joecoulson wrote: »

So interesting that small of a variance can have such a profound effect. Very cool Jody

Very interesting. Question @jdjohn - how did you account (if it matters) for the difference in the MDF vs the laminate adapter plates?

jdjohn

Hi Verb,

Do you mean the difference in thickness? Both of these tonearms have adjustable height (for setting VTA), so it's just a matter of loosening a set screw (or two), sliding the pillar up or down, and then re-setting the screws.

Does that answer your question?

verb

jdjohn wrote: »

Hi Verb,

Do you mean the difference in thickness? Both of these tonearms have adjustable height (for setting VTA), so it's just a matter of loosening a set screw (or two), sliding the pillar up or down, and then re-setting the screws.

Does that answer your question?

Yep! Thanks! I was thinking there had to be an adjustable height provision, angle of the stylus, ya know, the engineer in me!

jdjohn

Uh-oh...Verb is getting curious about vinyl

verb

jdjohn wrote: »

Uh-oh...Verb is getting curious about vinyl

Dude I already have 2 TT's ! Hooked up my Micro-Seiki for a bit, played with it, but not lately!

jdjohn

Oh, ok...I didn't see any in your sig. I picked-up another one last Friday, so now up to 17, I think. I really need to purge. It's a shame for them to just sit.

verb

Nothing wrong with a collection my man!

jdjohn

Fast-forwarding a few years here, but I have since acquired a third Logic DM-101 deck, but this, most recent one, got beat-up during shipping. I came to an amicable settlement with the seller, and pressed on.

Cosmetics aside, the condition of the spindle bearing was quite concerning.

With some judicious application of heat with a propane torch, I was able to get the old, scratched bearing out.

I found a suitable replacement bearing at my local Ace Hardware store, and used some epoxy to secure it. After installation of the fresh new bearing, I was able to get 20 more seconds of run-out from the platter, which was a huge win in my book!

Next, I was looking for a tonearm to mount on this beat-up turntable, and decided to go with a Rega RB900, pulled from a Basis Audio 1400 turntable.

A while ago, I fabricated a home-made mounting board from 3/8" MDF for a Grace 704 tonearm with a three-point mounting scheme, which had a 222mm pivot-to-spindle distance hole drilled. Turns out this worked perfectly with the RB900, including the resulting VTA. (Notice the hardware store hex-nut instead of the stock knurled thumb nut.)

I wanted a lower-compliance cartridge, so went with a Technics/National Panasonic 270C.

I procured one of the 'new' black diamond nude elliptical styluses for this cartridge, and it sounds quite good. This is overall a wonderful combination of turntable, arm, and cartridge/stylus. It's not the most handsome setup, but it sounds great!