Tag Archives: monica

i stole your i2s-eiaj convertor design?

there has been allegations that i copied someone’s i2s to eiaj convertor and passed it as my own. and according to the accuser, this scheme was posted on my forum in 2009.

so i was the criminal who copied a schematic posted on my forum, then made a pcb and sold it as my product. hmm…

i see… but first thing first, why would i want to copy someone else’s design when i already have an i2s to eiaj convertor myself?

first thing first, i2s and eiaj are just digital analog convertor (dac) chip’s input format standard. i2s is the most popular but the dac chip i like, tda1545a, uses eiaj, so i got to use eiaj.

now way back in 2007, i did a usb monica.  this design uses the pcm2706 usb receiver and i used its i2s output to  convert it to eiaj, then feed the tda1545a dac chip. so i already have an i2s to eiaj convertor. because if i didn’t have such a convertor, i would not be able to make a usb dac using tda1545a.

i was even bold in 2007 to make this claim that my usb monica is the first usb dac in the world to use a non-i2s input dac chip. in my case — tda1545a.

(i2s input chips like tda1543 and tda1541 can be hooked to the pcm2706 directly, thus no need for any data conversion.)

so if you just apply some logic thinking…

2007, i introduced the usb monica, which has an i2s-to-eiaj circuitry in it.

2009, this accuser posted his version on my forum.


does it make sense?

besides i have been selling online since 2002 and built up a reputation. would i be so stupid to soil my name, built over almost 10 years, for a product selling for  sgd43 (~usd30)?

if you look at the pcb module above, there are 4 chips. 3 chips to handle flip flop duties and 1 as a buffer.

the accuser’s design uses 6 chips.

besides, i made a mistake in my i2s-to-eiaj convertor which makes it stand out from the rest. the Left/Right channel is supposed to be swapped as this is one of the difference between the 2 data formats. i forgot to do this. this mistake is seen in usb monica as well as this module above, named black crow.

so based on time line,  mine came first by a good 2 years.

based on motive, i hope you could give me a bit of a credit and not regard me to be so stupid to sell out my good name for such a low priced product!

based on the number of chips alone, it’s different!

i rest my case.

i have no further comments on this. if you still think i’m a rascal who stole someone else’s design, after all this explanation above, nothing further i write could convince you.

Buffer Tweak on all Monicas

One of the highest recommend tweak for all versions of Monica is the JFET buffer tweak. This tweak has been described on this page using 2N3819 JFETs.

Since I finally got the 2SK170s, thought it’ll be beneficial to show how it’s done to your Monica. Note that the tweak on the main site uses 2N3819 and had the output caps soldered out. This tweak here does not remove the output caps but involves cutting PCB traces.

FIrst off, solder your 2SK170s like this.

You then need to cut the trace linking the I/V resistor to the output Black Gates caps. Shown here is for one channel. Confirm with a multimeter the trace is open before proceeding with the next steps.

Installed the pair of 2SK170s. VCC (24VDC) could be tapped from upper most end of the trim pot.

Another view with both channels installed.

This view shows the cut trace for both channels.

After everything’s soldered. Power her up. All LEDs should light up as before and confirm voltage across I/V resistor measures about half of your power supply. Then play music!

If there’s no sound, you have made a mistake somewhere. Don’t blame me.  🙂

As usual, with all mods, you are on your own. So be careful!