AUDIO CIRCUITS

I have design some power amplifier and many more base on my own basic electronic knowledge. The aim for this circuit is to give DIY fan a chances in making own power amplifier. The circuit originally design by myself therefore some of the result may not satisfied the specifications of HiFi lovers. I use for very cheap material in building the circuit. Please BE CAUTION some of the circuit using our main 230V/110v, please get and advice from an authorize electrician.

• Power Amplifier
  • M25A - 25W Simple Power Amplifier
  • M45A - 45W Amplifier
  • M60B-60W Amplifier
  • P3A Modified Version
  • Bee Power Amplifier Class A-25W
  • Bee Power Amplifier Class AB-60W
  • Bee Power Amplifier MK II 
• Power Supply (Universal)

P3A MODIFIED VERSION

After a few month of extra diagnosis on original P3A project review from www.sound.au.com the result is still not satisfied me (sorry Rode this only my amateur idea). I then started to check the whole system of mine and a few upgrade have been made. The end result is better then original P3A. The overall modification is totally make me a small satisfied. A bigger and heat beat bass and clarity treble. I do not say that original of P3A is worse, overall my loudspeaker very null to do such great sound that the expensive loudspeaker like B&W, TANNOY, Mission, Warfdale  and many more. I still cannot afford it OK.....

Original P3A is using a monoblock alignment in a single box. It mean I using dual toroidal 32V/350VA transformers. It used a 700VA of total power in stereo. A quad of 13,000uF/50V capacitor to feed the ripple and a dual  35A bridge diode really a burn my money out. The result is very great stereo separation. The burn in process still terrible. A hish at high power test. A far away vocal also make me searching the singer voice??. I using a cheap speaker unit and that is my N1010A. The loudspeaker itself still very far from conventional high grade loudspeaker. Maybe this is all about I found the P3A not work well. I have tested with TANNOY MX3 mecury. This is a floor stander unit and the result is very great. A big an accurate bass with non over blown treble. Let forget about P3A in driving the MX3. I cannot afford it. I just borrow from my eldest brother. I just want the P3A to drive my own N1010A loudspeaker.

I just change only a few component value. A PCB have limited overall modification. I am very lazy to trace a new PCB.

1. Change the green LED1 to Red led. The red LED seems to more stable when I drive it into higher level. It do not blur when I drive it at high. I think it better then the green LED. I then change the R6 and R7 to 1k make DC offset at zero . I make a higher the CMRR of the input pair. The current is still enough for the input pair needed. I found that a higher current will increased the slew rate. This is a good to higher the current but at this modification I not used this theory. See my Bee Power Amplifier (high fidelity solid state power amplifier by nanhifi). 
2. Change the R2 to 220k. Input impedance now higher then usually that is 22k. This make the modified version of P3A can drive from a valve pre amplifier. The change of the R2 mean a same value in R5. R5 now also 220k. In order to get the same gain factor I change the R4 to 10k and the C3 to 10uF/50V. Overall this order of change make the treble boost.
3. The R13 and R14 change from 0.47R to 0.1R. This will minimize the class B distortion.
4. The power transistor change from 2SA1302 and 2SC3281 to 2SA1943 and 2SC5200. This is a new and a same type of original P3A. The original P3A power transistor is an old type therefore a lot counterfeit sold in the market. Using the new A1943 and C5200 will get rid of this.
5. Overall Set quiescent current is 100mA. A higher will provide the class A mode in higher output. The heat sink of mine is to small for a higher current. If you have a bigger heat sink better set the current from 150mA to 250mA.
6. I found that there will a big dc offset at the end output and it is at 100mV. This is because of the gain stage I have change before. To adjust the dc offset just change R6 to a multi turn preset.

PICTURES OF P3A MODIFIED

Pic1

Pic 2

Pic 3

THE END RESULT

After a few days or burn in process this modified version of P3A. I found that the bass is solid then original P3A. A Sarah brightman- EDEN the bass now more solid. I really like this. The bass seemly bigger then original P3A. The voice from the vocal is brighter now I can find the artist singing. The treble now is low hash when I drive it at higher volume. My ear detect many sound instrument now from my loudspeaker. It still have a lot of missing sound compared in a earphone set.

Now I playing into my Era-AMENO the church vocal and the guitar brighter and a big bass solid then ever. The lot of big bass with solid and a brighter vocal make my small N1010A like a big loudspeaker. Why needed a bigger loudspeaker if a small are enough. A subwoofer like BzII have to be tuned into 35Hz due to a big bass of the main speaker. The result now better mid-bass and sub sonic bass either. A small modification can bring a lot of changes at the result. Thanks god it is a positive result.

After a few hours in driving my N1010A loudspeaker I then change it to drive my N1000B. A big size and extra sensitivity gain the sound and vocal now open wider then ever. I found that the bass even now bigger and solid with low ruble dynamic bass. I turn off the subwoofer in this mode of test. Well the N1000B already have a big bass. 

The true result, I still under estimate the whole system to get the end conclusion. Well it just a small modification not a major therefore nothing change so much. I just stop it just like this. Now I will start my bee amp project.

SYSTEM USED DURING TEST 

Sound Track- Voyage 2

*Pulse Control Modulator (PCM) 44.1kHz 16 Bit will produce ultra low noise sound stage, therefore overall system better then expensive CD Player. Using Win Amp ver 2.05A PCM decoder. You will need a personal computer for this method.

*Conventional Coaxial 75 Ohm have been tested by me the result is really ultra performance in the sound carrier and it also cheaper. Actually coaxial is a core single cable. Detail with smooth Treble but RCA insulated with Teflon are far better then this. The worst is it will cost me near to $100 a pair.