Hello fellow DIYers!
So, a few days ago I was at the dump to ditch a few old computers and I came across a really beat up Philips AZ1202 boombox. I jumped on it repeatedly 😀 until it fell apart and I salvaged the small amplifier from inside it. Rest was just junk, so it flew back into the scrap pile 😀
Today I finally got around to testing it. After cleaning everything up, touching up some cracked solder joints and replacing some bulged capacitors, I gave it a test with my AKG K142HD headphones and a pair of old car speakers. When using speakers, this thing doesn't really have much power, but when I hooked up my headphones, I was pleasantly surprised. It actually sounds quite alright! I expected it to sound harsh, but it was smooth! A little bit lacking in high freq. detail and weak bass, but not too bad! It ran from the 12v rail of a PC power supply.
My next objective was to upgrade it with a few simple mods. The original 25v 4700uF filter cap got replaced with a 15000uF 16v cap with a .68uF film bypass, 10v 470uf output capacitors got upgraded to 16v 1800uf low ESR capacitors and bypassed with .22uF film caps. 50v 1uF input coupling electrolytics I replaced with .68uF Wima caps. And most old electrolytics that looked suspicious also got replaced.
For a power supply I used a very simple solution. A 10v 1A transformer with a filter choke at both input and output, and an X xap on AC input. Rectifier is a prefab.
Now for a proper test drive:
So much better than before! Much cleaner and more detailed, much better bass and high response. Sounds musical and enjoyable.
There are two issues, one is quiet 50 cycle hum and the other is slightly loose bass, but nothing too serious.
Overall, a very decent amplifier. Just needs a case.
What do you good people here think, any way to further improve on this amplifier? IMHO, this thing shows some pretty good potential.
I'm using my Thinkpad T420 as a music source, files are mostly .flac and 320kpbs MP3s.
Here is a link for the service manual:
PHILIPS AZ1202 AZ1602 SM Service Manual free download, schematics, eeprom, repair info for electronics
Thanks for taking time to read!
So, a few days ago I was at the dump to ditch a few old computers and I came across a really beat up Philips AZ1202 boombox. I jumped on it repeatedly 😀 until it fell apart and I salvaged the small amplifier from inside it. Rest was just junk, so it flew back into the scrap pile 😀
Today I finally got around to testing it. After cleaning everything up, touching up some cracked solder joints and replacing some bulged capacitors, I gave it a test with my AKG K142HD headphones and a pair of old car speakers. When using speakers, this thing doesn't really have much power, but when I hooked up my headphones, I was pleasantly surprised. It actually sounds quite alright! I expected it to sound harsh, but it was smooth! A little bit lacking in high freq. detail and weak bass, but not too bad! It ran from the 12v rail of a PC power supply.
My next objective was to upgrade it with a few simple mods. The original 25v 4700uF filter cap got replaced with a 15000uF 16v cap with a .68uF film bypass, 10v 470uf output capacitors got upgraded to 16v 1800uf low ESR capacitors and bypassed with .22uF film caps. 50v 1uF input coupling electrolytics I replaced with .68uF Wima caps. And most old electrolytics that looked suspicious also got replaced.
For a power supply I used a very simple solution. A 10v 1A transformer with a filter choke at both input and output, and an X xap on AC input. Rectifier is a prefab.
Now for a proper test drive:
So much better than before! Much cleaner and more detailed, much better bass and high response. Sounds musical and enjoyable.
There are two issues, one is quiet 50 cycle hum and the other is slightly loose bass, but nothing too serious.
Overall, a very decent amplifier. Just needs a case.
What do you good people here think, any way to further improve on this amplifier? IMHO, this thing shows some pretty good potential.
I'm using my Thinkpad T420 as a music source, files are mostly .flac and 320kpbs MP3s.
Here is a link for the service manual:
PHILIPS AZ1202 AZ1602 SM Service Manual free download, schematics, eeprom, repair info for electronics
Thanks for taking time to read!
I used a similar chip, the TA8217P as my internal headphone amp for my stereo amplifier build found here (including schematics)..
http://www.diyaudio.com/forums/chip-amps/258418-my-first-chip-amp-tda7384-pics.html
The reason I did that was because the main power amp could not drive headphones directly because of the way my power IC was designed to run on a single rail power, so I gave the TA8217P a shot that I scrapped from a set of Kinyo PC speakers and was equally surprised like you.
Best of all I can run headphones at the same time as my loud speakers if wanted since they are on separate amplifier ICs inside my unit, which is useful for studio work.
These chips (TA8227P/TA8217P) can provide up to around 4 watts dissipation so you need to set the gain quite low in the circuit or else you will hear a lot of noise in headphones.
I believe these are class AB amplifier ICs and they do sound incredible on headphones with ample power to spare before THD gets high enough to be of concern.
Out of all my headphone amplifiers, including a few built into professional mixers, I actually prefer the sound of this IC and I can really crank it up to volume levels that most would frown at 😛
http://www.diyaudio.com/forums/chip-amps/258418-my-first-chip-amp-tda7384-pics.html
The reason I did that was because the main power amp could not drive headphones directly because of the way my power IC was designed to run on a single rail power, so I gave the TA8217P a shot that I scrapped from a set of Kinyo PC speakers and was equally surprised like you.
Best of all I can run headphones at the same time as my loud speakers if wanted since they are on separate amplifier ICs inside my unit, which is useful for studio work.
These chips (TA8227P/TA8217P) can provide up to around 4 watts dissipation so you need to set the gain quite low in the circuit or else you will hear a lot of noise in headphones.
I believe these are class AB amplifier ICs and they do sound incredible on headphones with ample power to spare before THD gets high enough to be of concern.
Out of all my headphone amplifiers, including a few built into professional mixers, I actually prefer the sound of this IC and I can really crank it up to volume levels that most would frown at 😛
Thanks for the reply! I really like that amplifier you built, I have been building similar amplifiers, also using ICs pulled from car stereos and PC speakers, and results have been fairly positive so far 😀
For the last two days, I have often found myself listening to music through this amplifier, because it really is that good, anyone who says otherwise has to hear it and would change their mind. In my opinion, it sound better than a lot of OP-AMP based headphone amplifiers.
Looking at the data sheet of this AZ1202 amplifier, I found that the transistors on this board are used as a pre-amplifier, which was a pleasant surprise. I also found more electrolytics in the signal path, a 1uF and a 4.7uF on each channel. So I'll try to find some film capacitors to replace them.
What happens when I replace the 1uF with, say, a 330nF film capacitor? because I replaced 1uF lytics' with .68uF Wima MKS and it's totally fine.
Today I changed two more electrolytic coupling capacitors with film caps, changed output bypass caps from 100nF to 220nF and just for fun added .047uF Russian PIO caps to bypass.
This amplifier now probably sounds as good as it could, no further changes can really be made, except for changing pre-amp transistors to FETs, but that's a bit too complicated for me, honestly 😀
The amplifier sound very detailed now and bass is tighter. I'm really happy with it, and I'm going to use it in my next chipamp/STK build, similar to darklife.
This amplifier now probably sounds as good as it could, no further changes can really be made, except for changing pre-amp transistors to FETs, but that's a bit too complicated for me, honestly 😀
The amplifier sound very detailed now and bass is tighter. I'm really happy with it, and I'm going to use it in my next chipamp/STK build, similar to darklife.
I have been listening to music through this amplifier, and the longer I listen, the more I like it. If anyone is looking to build a headphone amplifier that is cheap, simple and sounds amazing, the TA8227P is a great choice. I just compared it with my vintage, restored Samsung L4A solid state transistor amplifier (2x80W), and the TA chip sounds so much better with headphones. You have to hear it to believe it! 🙂
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