Hacking The Teenage Engineering PO-80

[Damien86]

Great thread, I've had my Gakken for a couple of years and when I first got it I made a few somewhat decent cut discs using the provided plastic blanks. I tried my hand at embossing CDs with a flipped stylus but they were all pretty awful. My workflow seemed fine, folded mono and something resembling reverse RIAA but not exact.
I've just dug it out again and after some further experimentation I'm actually getting some decent results. The biggest difference has been made by driving it with the headphone output of a pair of powered computer speakers. Originally I was using the line out of a laptop and obviously it just did not have the grunt even when combined with the inbuilt amp. My original embossing attempts were probably just victims of SNR.
The stock motor is really not handling the additional weight required to emboss so the flutter is crazy but the discs are listenable.

If nothing else this has finally given me the push to go ahead with my long dreamed of DIY machine. I stupidly gave away a TT500 with a broken arm years ago and am kicking myself on that one.

[Komysh]

Hi, Mark. I am very inspired and amazed by your work on upgrading the po-80. I ordered the same one from Japan to Ukraine but I have a couple of questions and suggestions.
1. The DAEX13CT-4 emitter is quite inexpensive and available only in America. For Europe and especially Ukraine with delivery it will cost me more than $ 80. Maybe we could make a more affordable alternative? I have 44mm 25w vibration speakers for example.
2. Where can I find inexpensive local styluses for replacement? Maybe it is easier to make them yourself or is it fashionable to buy one but durable?

[kugelblitz]

Hi, Mark. I am very inspired and amazed by your work on upgrading the po-80. I ordered the same one from Japan to Ukraine but I have a couple of questions and suggestions.
1. The DAEX13CT-4 emitter is quite inexpensive and available only in America. For Europe and especially Ukraine with delivery it will cost me more than $ 80. Maybe we could make a more affordable alternative? I have 44mm 25w vibration speakers for example.
2. Where can I find inexpensive local styluses for replacement? Maybe it is easier to make them yourself or is it fashionable to buy one but durable?

here's a european source for the exiters:
https://www.audiophonics.fr/fr/vibreurs-exciters/dayton-audio-daex13ct-4-haut-parleur-vibreur-exciter-3w-4-ohm-o13mm-p-17028.html

[Komysh]

Hi, Mark. I am very inspired and amazed by your work on upgrading the po-80. I ordered the same one from Japan to Ukraine but I have a couple of questions and suggestions.
1. The DAEX13CT-4 emitter is quite inexpensive and available only in America. For Europe and especially Ukraine with delivery it will cost me more than $ 80. Maybe we could make a more affordable alternative? I have 44mm 25w vibration speakers for example.
2. Where can I find inexpensive local styluses for replacement? Maybe it is easier to make them yourself or is it fashionable to buy one but durable?

here's a european source for the exiters:
https://www.audiophonics.fr/fr/vibreurs-exciters/dayton-audio-daex13ct-4-haut-parleur-vibreur-exciter-3w-4-ohm-o13mm-p-17028.html

thanks,ill look to it. sadly they are not shipping to Ukraine but if no more options will left ill try to order to somebody in eu

[Komysh]

but anyway,is there a chance to mod it to even more powerful exciter ?

[Komysh]

i found a solution ! there are a lot 26 mm aliexpress vibration speakers and even 32mm 8W

[markrob]

Hi,

You probably don't need the higher power, but if you can make it fit, I'm sure it will work for you. You might want to start off using the driver that comes with the Gakken. I would also start using the supplied stylus but flip it in reverse to emboss. It will last quite a awhile. Just bypass the amplifier built in to the Gakken and drive it with you own higher power amp. That extra power is needed to improve the high frequency response. Just be careful. You only want the peak power for very short durations spikes. The average power to the driver has to be kept below a couple of watts or you will destroy it.

Mark

[Komysh]

thanks! ill print your upgrades soon and im waiting for a few dayton exciters but i will try to play with stock gakken first as you propose

[ninohapaura]

Hello markrob, I saw in this thread that you are using the Presto short shank stylus in your (awesome) build. If at all possible, could you share the dimensions of that part? Working on a solution myself but can't seem to find any drawings for it. The useful numbers would be overall length including sapphire, length of just the shank, and the shank diameter. Thanks in advance from a newbie

[markrob]

Hi,

Here are some page grabs form the Presto 1D and Grampian cutter head manuals with the info you need. The length of the sapphire was not standardized, I don't believe. Just the overall length is important.

Mark

1D Stylus.png

Short Shank.png

[ninohapaura]

Thanks! So the final measurement of 47/64" or 5/8" is from the tip of the sapphire to the end of the shank regardless of the individual sapphire size if I am interpreting this correctly. Makes sense, easier to cut thin aluminum rod down than make perfectly identical sapphires each time.

[markrob]

Hi,

Yes, that's correct. You might make the gem a bit longer if you intent to add heating wire, for example.

Mark

[zdenek]

Hi Everybody,

When the PO-80 came out a few weeks ago, I decided to grab one and see if it could be hacked to get better performance. I put the kit together and played with it for a bit and then went to work upgrading it. Rather than be stuck with buying blanks and cutting styli from Teenage Engineering, I decided that I would use it to emboss CD-R disks. To do this, I just turned the stylus backwards. I traced out the schematic for the unit and decided that although its a pretty nice design, the 5 watt amp did not provide enough headroom to really drive the head to EQ the highs. So, I rolled my own 3 Watt amp that has reserve power to push 100 watt short duration peaks to the head at 4 ohms. The supplied head design is based on a exciter speaker just like many of our DIY heads here. Rather than risk blowing it up during my experiments, I decided to roll my own based on a Datyon DAEX13CT-4. That way I can replace it if it pops. I was also concerned that the silicone tubing used to couple the stylus to the driver might lose efficiency at high frequencies. On my head design, I hard couple it to the stylus shaft. Here is a link to a short Fusion 360 animation of the head construction:

https://drive.google.com/file/d/1KYOLhktLab4Des2BRRzfQJRJnS3qnguB/view?usp=sharing

I modified my custom PC based DSP software suite I wrote my lathe for this machine. It allows for head EQ and calibrated power monitoring along with steep high and low cut filters plus some fast limiting.

See the link for a short video of the embossing process where you can see the DIY head, amp, and software running embossing a track.

https://drive.google.com/file/d/1THEBQbnJzlgY2P42ejTyOYmsjhbnvfVk/view?usp=sharing

Finally, here is a link to a playback of the embossing:

https://drive.google.com/file/d/13HqjmsrjrlCVd9b84Wzt5gx7GFBnkihr/view?usp=sharing

And the source file used:

https://drive.google.com/file/d/1V8RNJgP0GVv1AYb4C9Q687tQrRGR8cie/view?usp=sharing

All in all, I'm pretty happy with the results. You can hear that the drive motor suffers from quite a bit of wow and flutter and the playback is a bit fast due to the cutting speed being slowed due the mechanical load of the embossing head weight.

If there is any interest, I can provide more details of the mods. There are still more possibilities here.

Mark

Mark

A very well recorded album considering the device is cheap. It's the first time I hear such a good recording with this PO80 machine.

[Komysh]

here is the shaft model for custom cutting arm (6mm OD,1.5mm ID, 37mm l)

[Komysh]

the information was wrong. this part need 2mm ID so here is v2

[markrob]

Hi,

I just checked and you are correct. The shaft diameter is 2mm. Sorry about that. Thanks for the correction and the stl.

Mark

[zdenek]

Mark ,have you tried to make such a small head from two computer converters, 4W speakers maximum and press in stereo on cdr, dvd etc with this po80 device? Tell me also if any additional electronic audio device is needed to be able to extract the differences in the signals of the left and right channels to expand the stereophonic effect, to extract both channels. Something like in digital mastering MID and SIDE, or maybe you have ready-made for sale even made on foot, i.e. without printed circuits only a prototype board, because I came to the conclusion that factory printed circuits do not make a difference to those made on test boards, would you have something like that ready?

[markrob]

HI,

I have not tried to make a stereo head for the PO-80. Since it's really an embossing setup for me, stereo is iffy at best when embossing.

For my stereo cutting, I do the processing digitally in software in conjunction with an elliptic filter. I have a width control that boosts the gain of the Mid-Side channel to "widen" stereo image. Its useful with a head design that suffers from poor separation when cutting due to mechanical driver interaction or incorrect vertical angle. Not a complete fix for these issues, but still useful. An all analog design would be great, but I'm firmly into the DSP camp. All of Wayne's designs seem to be first class.

Mark

[Komysh]

hi again. thank you for markrob and all of you for this project. I’ve got mine few days ago. I got it work with custom cutter arm. nut I have a problem with torque. The belt is skipping and sometimes motor is slowing down. how can I fix this? I’ve tried to power arm weight and it’s partly working but depth of groove becoming too small.

[markrob]

Hi,

The stock motor is very marginal when used for cutting or embossing. I ended up retrofitting a NEMA 14 stepper and a shock mount that provides way more torque and lower wow and flutter. See below:

Motor Mount 4 Low Res.jpg

Along with that, I developed an Arduino based controller to drive the stepper via a TMC2209.

My PO-80.jpg