Cheapmondo

Came across the Quasimondo and Cheapmondo circuits to excite transformer/rectifier oscillations and tune in snubber and decided to implement it using junkbox parts:

• Mosfet: 05N03L
• Logic level gate
• Ron 4mohm @4.5Vgs Id=55A
• Id max 80A
• "gate driver" 
• transistor PNP 2N3906
• basis resistor 1k
• pulldown 150ohm
• Clock generator 
• 74LS14 hex inverter
• RC feedback
• 1uF
• 1kOhm

Simulated in LTspice (using 0.1uF to get higher oscilator freq and lower sim time)
got some LTspice help from:
https://www.mikrocontroller.net/topic/428100 on how to use schmitt trigger in ltspice
http://electronicsbeliever.com/how-to-sweep-resistance-in-ltspice-with-step-by-step-tutorials/ on how to sweep resistor values

Not pretty but it works well :-)

Here is a 500VA toroid oscillating at 1Mhz.

Here it is dampened out. 

NewClassD NCD1 (re)build. New case and snubber.

Decided to give my aging NewClassD NCD1 a new home. Its been living inside a Doxa 40 Power amp enclosure for 6 years.

I figured i could cram it into a smaller case. I went for the B2109 from Ebay

Had to split the amp alu thermal sink in 2. one on each case heat-sink. I put a 500VA 1x230V 2x36V toroid transformer in there powered trough a 20D thermistor for soft startup. I figured that as normal 500W PC power supplies can live with this in series at all times a ClassD amp might also.  Have no room for a full soft start PCB. The transformer should give me a theoretical Pmax=36V^2/8ohm=162W.

Had some faint noise in the speakers when listening at 50cm. 

Mounted Common mode ferrite filters on power harness into the boards and and on the speaker cable output. Also added ceramic capacitors from speaker terminals to copper tape on lower back chassi. This solved all the hissing noise in the speakers.

Tranformer snubbering

I made a "Quasimondo clone" using stuff in my junkbox. Squarewave generated by 74LS14 and a mosfet that came off a PC mainboard CPU DCDC converter. It is driven with a PNP transistor. and the rest is like the Quasimondo. The exiting works and the transformer rings at 1Mhz.

Here are some results with C_s=150nF Cp=10nF and different R values taken from Rigol DS1054Z. Saved as csv and imported to Libre Office.

Seems 14ohm is the right one. 

Finished 2 channel snubber. One for positive and one for negative supply. 150nF/100V and 10nF/400V film capacitors. Two 30ohm metal film in parallel gives 15ohm. 

Akai MPK225 in Reason 10

Autodetect surfaces creates 4 surfaces

Reason 10

• preferences > Control Surfaces 
• Autodetect surfaces (creates 4 of them)
• now i can play and tap on the tabs but transport buttons does not work

MPK:

• Edit button
• some transport button( play)
• Change type in the display from MIDI CC to MMC/MIDI

Now the transport start and stop buttons work :-)

Links:
http://community.akaipro.com/akai_professional/topics/im-having-a-hard-time-mapping-my-mpk-225-with-reason-8

Old Emu 1820m PCI on windows 10 desktop

Update 2019-11: After Windows 10 got updated to build 1903 and then it stopped working.
The good news is that there now is a workaround:
https://www.kvraudio.com/forum/viewtopic.php?t=529349



Installed an old EMU 1820m i had in a drawer.

At first it did not work. All LEDs was constantly lit on the external box. Opened up and found 2 blown capacitors i guess at the output of the power supply. Replaced them and now only the correct LEDs light up (like sample rate) and it has connection with the patchmix application.
I got windows sounds but no ASIO in Propellerheads Reason 10.

Stumbled across this:
https://answers.microsoft.com/en-us/windows/forum/windows_10-hardware/e-mu-e-dsp-soundcard-problem-after-installing/0b808069-8356-40b0-9715-e4d392ad5112

• Turned off computer
• Removed the card from the PC and booted into windows. 
• Uninstalled everything EMU/creative.
• Selected show hidden in device manager and uninstalled the EMU device under audio. 
• Rebooted. 
• Downloaded the files for emu 1212m pcie and patchmix for emu 1616m from this:
• http://support.creative.com/downloads/download.aspx?nDownloadId=12479
• http://support.creative.com/downloads/download.aspx?nDownloadId=11912
• Installed EmuPMX_PCDrv_US_2_30_00_BETA.exe and rebooted
• Installed EmuPMX_PCApp_US_2_20_00.exe and rebooted
• Now ASIO E-MU appeared as a card in Reason. Selected it and checked that it sent to ASIO channel 1-2
• Added Asio strip 1/2 in patchmix and i got sound in my headphones

The emu 1820m is not dead yet :-)

Replace cable on AKG K551

I use mostly android phone so the remote shipped on my K551 was not functioning great. I also was not fan of the big jack that would not fit my phone with bumper mounted.

Now that apple decided to remove headphone jack I don't need a reference headphone with apple remote :-)

I recently bought a few new cables from ebay and lunashop.com for my Sennheiser HD590 that included a remote compatible with both android and apple. The Sennheiser have a 2.5mm jack into the phones so i figured i could modify the K551 to the same connector.

Removed the pad

The black cable goes to the other driver. Keep that. De-solder the 3 wires going to the blue cable and remove that.

Solder on a 2.5mm stereo connector. I used this: http://no.rs-online.com/web/p/jack-trs-connectors/5051407/  (RS-online article 505-1407). 

Pin 1 is left, Pin2 is right Pin3 is ground. 

Add some double sided foam tape. (make sure to make a hole in the tape before placing, i didnt and had to do it again) 

Mount the 2.5mm jack and reassemble. 

Very happy with the results. Volume and play pause works nicely. Just set the selector on the back of the remote to android. It even release if cable is pulled to hard.