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2014-08-17

Simple attenuator for your home stereo

I have this nerdy problem that the output of my CD and MD player is too high and my amplifier volume halways has to stay in 7 o'clock position. To lower the volume of the CD and MD player, one can insert attenuators between CD player and amplifier.
Unfortunately those attenuators are quite expensive, ranging from 38 EUR to 55 EUR. To solve the issue, I build my own attenuators with simple RCA plug and sockets and a voltage divider consisting of a 6,8 kOhm and a 2,7 kOhm resistor, which creates approximately 10 dB attenuation. The resistors fit into the RCA plugs.
The solution works quite good. Unfortunately 10dB is not sufficient. Therefore I'm going to build 20dB attenuators soon. This requires 10 kOhm and 1,2 kOhm resistors. If you need some more information about these attenuators, here are some german forum posts: [1], [2] Approximate costs for one pair of attenuators: 2,40 EUR.
2014-04-23

Monitor a switchport on your dd-wrt router with iptables

If you want to monitor a device within your network (i.e. to check if your printer is talking with its manufacturer), you do not need a plain old hub. You can also use the firewall of your dd-wrt router. Access your router by web-interface (and browse to Adminstration -> Commands) or ssh or telnet, and execute the following code, where you replace $IPTOBEMONITORED with the IP-Address of the device which you want to monitor, and $MONITORIP with the IP of the device which is running wireshark or some other packet capturing software.
#Add Rules to monitor a Device
iptables -t mangle -A POSTROUTING -d $IPTOBEMONITORED -j ROUTE --tee --gw $MONITORIP
iptables -t mangle -A PREROUTING -s $IPTOBEMONITORED -j ROUTE --tee --gw $MONITORIP

				
This will modify your mangle-table (how this works is depicted here), and tee's all traffic from and to your $IPTOBEMONITORED to your $MONITORIP.
To remove the rules, just run the follwing code:
#Remove the Rules
iptables -t mangle -D POSTROUTING -d $IPTOBEMONITORED -j ROUTE --tee --gw $MONITORIP
iptables -t mangle -D PREROUTING -s $IPTOBEMONITORED -j ROUTE --tee --gw $MONITORIP
			
2013-09-05

Website Migration

After some work, this website is now running on a Raspberry Pi. The server is located in my flat and powered by solarpanels.
2013-07-29

NEW PGP KEY

I switched PGP keys and upgraded to a stronger encryption. My new key has the fingerprint: 666AB60B66E715636D54CE95B526D786882B9A80 (Key ID: 882B9A80). You can download the revocation of the old key (8E073D8A) here, and my new public key block here.
2013-03-02

FrankenDisc: use a PCGA-MDN1 MiniDisc over USB

Still I'm a MiniDisc fan. I shed some tears when Sony announced that their last device capable of using this superior medium will be produced end of this month. Recently I had the chance to aquire a Sony PCGA-MDN1 netMD player/recorder which was intended to be used in the multibay of Sony Vaio NV-Series notebooks. Some guys from minidiscforum.de already converted that device to a USB device[1]. I tried to do that myself now.

What do you need for that?
A calm hand, soldering iron and tin, USB-plug / cable, some THIN wire (I used old IDE-Connector wires, but coated litz wire is more appropriate).

Soldering
Open the device by removing the four screws. Pop off the top metal cover. You can see the net-MD Drive (MZD-N1) and a Vaio Interface Connector. Carefully solder the USB plug / cable according to that specification: http://www.nord-com.net/dglander/md/sony_pcga-mdn1_steckerbelegungen.pdf to the Vaio Interface Connector. When using this connector you don't risk ruinining your precious player, but only the Interface connector. You can find images of the soldering on the page of the guy who also provided the pin-settings: http://www.nord-com.net/dglander/md/

Drivers
After soldering you'll find it testing, that the normal netMD drivers are not working. Have a look on this FTP-Server: ftp://ftp.vaio-link.com/. You can find the drivers here: ftp://ftp.vaio-link.com/PUB/VAIO/ORIGINAL/NV1_DRIVERS.EXE. Unpack the exe file, you'll find a folder named NETMD. Install the drivers and enjoy your new, USB-Only MiniDisc Recorder.

Thanks to the authors at the minidiscforum for providing information on the possibilities of this modification.