The Neumann AM31 thread

[subkontrabob]

Hello folks,

I decided to open a thread specifically about the Neumann AM31 in pursuit of knowledge for a direct-to-disk recording project (corresponding thread in this forum: https://lathetrolls.com/viewtopic.php?t=1484&mforum=lathetrolls ).

I also posted a request for AM31 documentation in the appropriate forum: https://lathetrolls.com/viewtopic.php?t=1804.html

The reason I am doing this is because I have only very technical literature, that focuses solely on the physical principles of disk recording. I'm seeking knowledge about the actual process, how to set up the machine and adjust it, how to exactly operate it, what to do in which order etc. etc.

Let's pile up all there is to know about the AM31 in this thread!

[subkontrabob]

Alright,

it's been a while since I started this thread, here is finally some follow- up:

I shot a few pictures and edited them in GIMP so as to have a good reference for the discussion. First I want to focus on getting the terminology nailed down properly. As the discussion goes on I will go back to this post and edit it until it is complete and accurate. Contributions, please.....


Picture 1


1. Cutterhead suspension
2. Platter
3. Arm
4. Base
5.
6.
7. LPI fine adjustment gears ??
8.
9.
10.
11. Stopper
12. Playback tone arm mount

Picture 2


1. Cutting head
2. Cutter Release lever added by Simon
3. Microscope
4. Tension adjustment added by Simon
5. Cutter assembly height adjustment
6. Chip/Swarf suction

Picture 3


1. Dash Pot added by Simon
2. Tension Spring added by Simon
3. Cutter Arm added by Simon
4. a) Cutter Release lever added by Simon
b) Cutter arm rest ??
5. cutting head

Picture 4



1. Dash Pot
2. Tension Spring
3. Cutter Arm
4. a) Cutter Release lever
b) Cutter arm rest??
5. cutting head
6.

[Simon]

Wow well done with the pictures

I am sure they will all be filled in.

[subkontrabob]

Hi,

as I pointed out in the opening post, I don't have a manual for the actual lathe. So I would be really thankful for any advice on how to adjust the lathe.

I have some specific questions regarding the dash pot and the spring:

1. What are they exactly supposed to do?

2. What spring tension should the spring have? I suspect it might have bent and lost it's "springyness".

3. How do I adjust the dash pot and spring to interact?

When I release the cutterhead by pushing down the release lever (marked "4" in pictures 3 and 4), the pot rests against the lid. Is this normal? I would expect it to be in balance , so that the "seesaw" (part 3 in pics 3+4) can move either way.


cheers,

Bob

[Simon]

As I am Mod on the forum I have been able to add to your post.

[subkontrabob]

thank you for filling in Simon!

I added a few things that I'm not sure of, they are marked with question marks. I split part 4 into a and b, the lever and the egg-shaped part that the cutter arm rests on.

I hope someone will be kind enough to answer the questions in my previous post about the dash pot and the spring.

cheers,

Bob

[Simon]

Do you own this system?

[subkontrabob]

Do you own this system?

Unfortunately not

[bancho]

I don't know about the spring but I think the round disc (you painted the disc and the pot blue) should fit INTO the dash pot. You fill the pot with oil and it works as damping system. maybe then the mistery of the spring solves by itself... maybe not, you'll see. about the tension I don't know.
hope it helps

[mossboss]

Hey Bob
Ok If you where to read my post on another thread for mastering decision concrete man in regards to setting up it will apply to your setup as well
Now Bancho is right The post needs to be filled with silicon oil there is a thread here on this as well as the density of it on the Grampian head However If I was to take a guess It would not be to far out if at all if you filled it with Singer fine sewing machine oil
Just to point out a couple of things
The spring has an adjusting screw so as to take up the weight of the head and bring it parallel to the platter
you make check for linearity on any parallel surface under the head in relation to the platter
Since this is a simple slow adjustment the dash pot has no effect It only comes into play only on sudden movements like the shocks on your motor car
Once this is done the handle up the top no 5 is adjusted so as to move the whole assembly up or down to the right height
There should be a fine adjustment on it as a guess but be that as it may if you where to adjust the depth of cut as described in the concrete thread you should be fairly close
In other words just a very faint line on the lacquer with no signal input
It should be the same depth all around if not find the adjusting screws under the T/T apply corrective action
Also once there with that fine mark move the whole head assembly along the carriage by hand from left to right so as to scratch a straight line form the very outside to the center which should be dead center with the hole on the lacquer
Adjust accordingly
Hope this helps
Cheers
I am sure you will find that with signal input you will get a fair first cut

[subkontrabob]

Hi mossy, bancho and others,

thank you for your posts! Yes, I've followed concretecowboys mastering thread. Thank you moss for your instructions on cutting head aliginment. I have understood and will follow them.

I still need a clarification regarding the dash pot / spring combination.

I had the opportunity to talk to a very experienced mastering engineer (20+ years as a cutter), and he confirmed my assumption that the head assembly was not adjusted properly.

Conclusion (correct me if I'm wrong):

Head assembly (= spring) has to be adjusted so that it floats freely in equilibrium, and can be lifted higher with the red lever.

[mossboss]

Yeah He is right
Take the weight off it so as it is Parallel to the T/T It is not that hard The ajusting screw will allow you to do that If the spring has gone weak which is doubtfull it easy enough to replace it is not that critical really a bit of trial and error with another spring will see you through
chhers

[subkontrabob]

these questions may sound kind of stupid, but:

1. What is the right sequence to begin a cut? Coupling the cutter arm to the lead screw, then releasing the cutter, or the other way around??

2. How do I do the end groove? Just start manually turning the wheel when there is no signal anymore until the arm base hits the stopper?

3. How do I begin my cut when using 14" master (in order to produce a decent "lead in"- groove)

:

[Aussie0zborn]

You must couple the cutter arm to the lead screw first, otherwise you may end up cutting a very deep groove, cutting through to the aluminium base and ruining your stylus.

I have no idea how to do lead-in or lead-out grooves on this particluar model.

[subkontrabob]

I 've been cutting with the past two days with a Telefunken R12 b head with swiss steel stylii (standard). We had some serious problems on the first day, a diode in the power supply started to act weidly and had to be repaired. I also had some issues with chip suction (clogged pipes), had to improvise a tube cleaning rod out of a iron coat hanger. Nevertheless I was able to produce some decent results. Today and tomorrow we will hopefully be able to capture some magical performances by the artist.

Yesterday I used 54 year old Master Sound System lacquers (12 inch) Pyral masters (14inch, don't know the age), and brand new transcos (14 inch).

pre- heating a few minutes with a lamp did the trick, chip suction worked like a charm.

This is fun!!

[cpg]

Let's complete the list started in post #2 at picture #1:

1. Cutterhead suspension
2. Platter
3. Arm
4. Base
5. Gear for . Cutterhead suspension
2. Platter
3. Arm
4. Base
5. Gear for driving the spindle for lead-in/lead-out
6. manual adjustment handle for base (4) and arm (3)
7. LPI adjustment gears (3 positions per gear set, 5 different gear sets available)
8. Hand drive for lead-in and lead-out grooves
9. Lock-in to spindle
10. automatic lock-off from spindle at inner groove when touching stopper (11)
11. Stopper
12. Playback tone arm mount

Does anybody have any documentation or manuals related the AM31?


Some more pictures of another AM31:

AM31_2.jpg

AM31_cutting head carrier 1.jpg

AM31_cutting head carrier 2.jpg

AM31_cutting head carrier 3.jpg

[dubcutter89]

Hi Claus!

Looks like you finally found an AM31. Is it yours?
I don't know if there is any tech-documentation for the AM31, but I have a sales brochure and maybe some other things...

Interesting Detail: This is the 3rd diferent version of vakuum-chuck-platter i have seen.. Maybe you can take another pic of it?

Grüsse aus Wien,
Lukas

[subkontrabob]

wow, I never checked back on this thread, and failed to notice this post

those are some really nice pictures, thank you for sharing!

Does anybody have any documentation or manuals related the AM31?

I have asked a lot of people about AM31 manuals to no avail. It seems that no one has any.

Some more pictures of another AM31:

AM31_cutting head carrier 1.jpg

This is interesting stuff! Do you know what the switches/contacts of the cutter release lever do? I reckon the microswitch switches the microscope on? But what about the knife blade contacts?