There are no dumb questions

[fonogabor]

Hi Guys!

I am Gabriel from Budapest. I did built a recording lathe from scratch- you can see some photos about it in my "from screatch" topic. The machine became ready. It runs well. The cutterhead also functional. BUT: I use HSS stylus and polycarbonate blank disc. The stylus is grinded from a 2 mm HSS drillbit.Its form was as a typical cutting needle.

The problem that I got a very very loud screatching noise without modulation too.

I tried to heat the blank discs but they became warped.
I tried to grind the stylus to conical: also without any result.
I changed the polycarbonate to PVC. Also not any result.
Applied some WD 40:Nothing

Noise,noise,noise.... It covers my recorded audio.

Please give me some advice!

Thanks!

Gabriel

[ilovedrums247]

Hi Gabriel, how much weight are you applying to the cutter head? I also had this problem but resolved it somewhat when I backed off to 30-40 grams.

[Fela Borbone]

Hello,
Noise also comes when the stylus is too sharp, tearing the bottom of the groove.
You can dull out the point by letting it emboss for a while, (5-15 minutes). To avoid spoiling many blanks, I usually do it in a locked groove.
Hope it helps.

[fonogabor]

Thank you very much for your advice! Now I try to use a "Thermo Stylus"...

[fonogabor]

Thank you very much for your advice! Now I try to use a "Thermo Stylus"...

[Dogtemple]

I have a silly question here. How do you measure frequency response of a head?

[markrob]

Hi,

There are several ways. Below are a few.

Make a cut using pink or white noise (depends on the analyzer type used) in place of normal program material. Playback the cut and capture the results to a file or view in real time using an analyzer (FFT or RTA). Use white noise with an FFT based analyzer and pink noise with an RTA. That will give you the response of the head. If you are capturing with a standard phono pickup and pre amp, you will need to pass the noise source through an IRIAA filter to get correct response. This can be done up front or after playback. You could eliminate the need for the IRIAA curve if you capture playback with a flat preamp that does not have the RIAA included. You should record and capture some silence to establish the system noise floor so that you do not mistake this for signal. This is most apparent at the high and low frequency extremes. Rumble is the enemy at the low end and and surface noise at the high end. Setting a good level is important. Too low and you will lose the response in the noise floor. Too high and you can damage the head, cause overcuts, and increase harmonic distortion.

You can also do a series of spot frequencies over the range or generate a linear or log sine sweep. This gives the best signal to noise ratio, but you need to be very careful if you intend to pass the sweep or tones through an IRIAA prior to cutting. The IRIIA curve has some extreme boost at the high frequencies and if not taken into account will fry the head. Using a flat preamp or apply the IRIAA post capture is the safest approach here.

One other way is to use use the light band test to see the response optically right in the cut grooves. See the attached PDF.

Meyer.pdf

[Dogtemple]

Thanks for that markrob. I’ve read this forum from cover to cover and your posts are up there with the best, if not the best! Thanks for your input, you’ve definitely helped a lot of people out, me included.

[apoklis]

Are there any moving magnet preamps that don't invoke a riaa curve ?
I record some 78 for old jukeboxes that don't have a curved preamp built in. When i cut, or emboss (depending on the machine, some play vertical) I like to play it while i cut it. This way I can color it a little as its test cut. I have done this but it involves changing the mm cartridge to a Ceramic Cartridge and using tube amp with a different monitor speakers. Real pain to setup ,then put things back to right. So i was looking for a way to use the mm cartage and get line level out to the amp.
No dumb questions seemed like the right form . Any input would be appreciated .Thank you

[markrob]

Hi,

A few years ago, I needed the same thing and came up with a simple mod to an off the shelf BBE phono preamp to make it switchable from flat to riaa. Attached are schematics of the unmodified pre-amp and another with my mods.

BBE_Schematic.pdf

BBE_Schematic_Mod.pdf

I did a quick search and see that the model is still available. You might be able to find used for less.

https://www.guitarcenter.com/BBE/FJB-200X-Phono-Preamp.gc

I used to have some pictures of the mod, but I can't seem to find them. I drilled a hole in the from and added a DPDT switch to allow selection of flat and riaa. I assume that the current BBE shown in the link has the same circuitry. If so, its a pretty easy mod if you are handy with a soldering iron. If you just want it flat, you could just cut C7 and C9 from the board and jumper (or replace) R7 and R10 with a 100K resistor. You might not need to remove the PCB from the chassis in that case.

Hope you find this helpful.

MArk

[apoklis]

Wow, over the top helpful, the model , the schematic , and a schematic with mods. WOW thank you very much. I order one this morning.

[sinkopated]

I am a newbie who wants to know about a cutter that a customer of mine has. He knows nothing about it and showed it to me today in his garage, piled with boxes. Is there a way to post a picture here?

[farmersplow]

Hello and welcome. Posting a picture is easy (if you have done it before).
1. log in
2. open a post (as you have already done) and write text
3. scroll down and click on the file attachments button
4. click the "Attach file" button

A1.png

5. select the file from your hard disk
6. the bar shows the loading status and at the end time the status has a green checkmark

A2.png

7. use the cursor next to your text to select where the image should be displayed
8. click (at the bottom of the files) on the image you want to add and click on the "Show in post" button

A3.png

I hope this helps

[CoastToCoast8]

Hi there!

I'm looking for a replace for the cutting needle of a Gakken Record Maker, but it's sold out everywhere. Can I use another kind of needle?

Thanks a lot!