Bee Power Ampifier to the test

[PWatts]

Another thing on C1's polarity- the electro's polarity is for the 0V input DC offset at the diff amp's base. It's not possible to orient C1 for potential DC offsets from the preamp, as DC offset can be both positive & negative. Another reason to rather change them to poly or bipolar at least.
Pierre

 

[nanhifi]

A big change done

thanks jennnice, PWatts and traderbam fot the suggesttion only a few change I made.
The Bee Amplifier was in a pcb a big of jumper now for the modification.

I manage to get rid of the C5 at the moment bye using a preset for the R8 and adjust to get the DC offset near zero. Then have to split the R12 into dual of 10K at the center of connection
I put a Caps of 100uF to prevent any oscillation and un stabile condition in the power amplifier. The value of R3 also change at 10K and the R11 into 12K. Then the result comming in a big smile
of my face. A very mid range details (vocal) and middle smooth treble. I like it. But the supply for this experiment is only 12V PP. I do not want anything to get burn. I cancel this type of modification because I affriad when the 40Vpp get in something must get burn if the DC offset get to high when i
switch on it. Any comment on this?

I have change the C1 with an non polar that is 3.3uF. I found that it make a big smoother in the treble. I put a Caps of 47uF at the Q8 collector and emitter. The result also make the voice more open wider. yes a great positive result. This change made using a original Basic circuit of bee Amplifier.Then I put the 100nF parrallel with C5 and notting change very much form my listening test. Mybe it change something but I cannot hear it. I sometime see a 1N4148 put there and wonder what are the use of this diode????

A get a few more experiment I then bias it to class AB and change the power transistor with a fast switch one of 30Mhz that is A1943 and C5200.Bias at 100mA. The result that the treble
really get into very-very smooth and lost a lot of details sound. Juzzz I cannot accept this sound. It make the treble respond gone out somewhere. I then started to change the C1 back into 10uF of electrolit and change the pole that it positif connected for the base of Q1. well it get into a deal now. Not very smooth treble put extra live back in my sound. I then have to set the bias current higher of 150mA that make it better now. I still love the sound of the 3Mhz power transistor a BD911 and BD912 type. Any comment on this condition. The slow 3Mhz even better then the 30Mhz at a same 100mA bias..

I have a few mesurement tool. That is the Digital multi meter and a spice simulation. A test from spice to check the logic of the circuit. Then a hours of listening comparing with a Original
P3A power amplifier. At full blass of listening that is very tired process I need a oscilliscope. Ooops I cannot afford it.

Ok for jennice

What I mean for "The major problem is still under moderated when I drive it at higher level" is I found when I increase the volume the sound of a vocalist seems to un controllable over voice. The bass get on whoompa like not enough power from the supply. I get it run P3A of 300VA dual toroidal transfomer with 50,000uF of 4 power caps. This make me unhappy. It only work well at a middle of the volume. That why I get on design an amplifier base from the P3A. I change and put a current source insted of bootstarp. I think this is the problem because of non linearity of a Caps. It just an experiment. Maybe the saturated of the VAS???

You said to get an emiiter follower for the VAS transistor, I have big problem to do that. This is because of it PCB hardly to get connected. I found that blameless amp use a 2 of transistor but you suggest a 3 will make it more linear correct. Maybe I will buil it, but not for now.

Anywhere a big change in the overall performance form the 1st version. Thanks guy.....