Sunday, August 23, 2009

3 kits in a day!

Shown here the 3 digit counter being powered by the PSU kit.. Everything works the first time! What a day...!

Finally, the timer. Shown here powered and the timer started by pressing the 'START' button. The LED is powered and after a certain time, will go off. The relay during this time will also be energized and deenergized when the timer ends. There's a small pot on the board for small timing adjustments and a switch for Low or High timing schedules.

The completed digital counter. Should be of use in the future projects. For 5 bucks I ain't complaining!

I started with the PSU. A switchable between 9V and 12V. It had a PP3 battery clip terminal which is good as I can use it to replace the PP3 9V battery, which coincidentally is required to power the other 2 kits!
No big deal straight forward construction.

I bought 3 electronic kits last friday because it was on sale and its dirt cheap at RM5! Not that I really need them but heck, the parts alone cost more than that! The 3 kits were; 9V/12V PSU with transformer, 0-100 sec/min timer and 3 digit counter. I am always fascinated by digital circuits with seven segment displays so I'm kinda glad to have bought one.

I finished the first 2 kits within the hour on saturday morning. The last kit was finished in the afternoon..

3 kits in a day! A first!

Monday, August 10, 2009

My headphone - the Sennheiser HD201

Naturally the previous headphone amp was purposely built to drive this, the HD201.
I'd say the HD201 would be the best bang per buck headphone. Of course there are 'better' headphones out there.. and obviously more expensive. I paid RM120 (equiv. to USD36, early figureof 54 was wrong..)
I do not use headphones all the times, rather occasionally when I need the privacy and this is where the HD201 shines.. mostly it is used with my Sony's S7000 DVD player which being the flagship model during it's heyday, has the best built-in headphone amp…
To really enjoy the dynamics and the potential of the HD201, a headphone amp is really recommended, DIY or otherwise!

Here's a review of the HD201, and here.
More info here. Very interesting read.

Light weight. You can wear them for hours at length!
Very neutral sounding with slightly bright overall but not too 'fatiguing'..
Very good sound esp. the bass.
Cheap. Best bang per buck

The cable can be a tad too long and can tangle things..
May required amplification to realize full potential if your puny little mp3 player don't have enough juice.. but that’s being critical. ;)

Monday, August 3, 2009

Headphone amplifier using TDA2822M

The kit with all components installed.. 'standard' stuffs without any exotic components.. we'll 'see' how it performs later.. Have checked the datasheet. Not bad data and performance figures... if you check ebay, there's a headphone amp kit using the same IC!

The amp powered by a 9V PP3 battery, powering up the first time and using a SONY's PCDP as the sound source. The trimmer pot is shown there installed on the board.. more like a preset to me than volume control! Have to check if I have a spare dual/stereo 10K pot to be used as a volume control (checked, I have!)...

Was on leave today.. and feeling a little 'bored' and nothing interesting to watch on TV, went through my spare parts stuffs and I found a 1W stereo amplifier kit that I have bought 'eons' ago but not built for unknown reasons.. well one reason actually, I have no use of it, yet! Meant for 'bench amp' I decided if it's good enough to drive my Sennheiser's HD201.


I have been listening to it now (housed in a proper casing), which took about an hour to do. Total listening sessions is about 5 hours... just the Sony's CDP as the source (did connect to my notebook for a while). Will update with the finished product soon.

After using a shielded cable for the input connections, a slight hiss which was noticeable earlier during testing has somewhat gone.. very good bass, imaging and depth.. midrange(voice) was breathtaking (Diana Krall CDs) and highs were very well reproduced without overboosting too much.. which should minimized fatigue on extended listening session. At the time of writing I am still listening to it.

All in all.. this would be the best bang per buck headamp! The kit is cheap and listening satisfaction is fantabulous! Two thumbs up. I had a great monday this week... ;)

Sunday, August 2, 2009

LDR attenuator, the passive preamp update.

This is actually version one of the project! I was using a multitude of LEDs with different colors and burnt several due to overvoltage! I had a bunch of light green colored ones and it works without much noticeable difference! This version 1 prototype did not last long enough... ;)

This is the two excellent DC voltage controllers(using MOSFET) that I acquired. Working voltage is from 6VDC to 15VDC.. I see a multtude of applications here ;) Suffice to say, it works beautifully in this project!

This is my second prototype I have built to investigate the performance of the LDR preamp. Suffice to say, the initial sound quality that I got was really promising! It had all the SQ that was mentioned. The only quirks that I encountered was the non-linearity of the LDR itself. Evenhough I managed to control the intensity of the light proper but the LDR did not response as linear as I want it to be.. something for me to look into.. The shroud used to isolate the LDRs is not shown here for clarity of the unit.

As earlier mentioned, I was thinking of using alternate source of light instead of the LED which I think did not give linear light control as per original circuit.
After much thinking and hunting.. I found a DC controller based on PWM(Pulse Width Modulation) which would work better than linear control eg. variable voltage control.

The LDR preamp works great. No wonder diyparadise resorted to digital volume control on their LDR volume control to properly managed the attenuation.
If you don't have any preamp and itching to build one.. go for this one. It is cheap and simple!