Bee Power Ampifier to the test - diyAudio
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Old 23rd June 2003, 05:49 PM   #1
nanhifi is offline nanhifi  Malaysia
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Talking Bee Power Ampifier to the test

I have made my new power amplifier. After a long day night working hard on the research for a 2 month. I named it a '"Bee Power Amplifier".

The amplifier is a Class AB type. The result have make me a lot. The simple circuit with great sound is what I'm aiming.

I want to share it with the fan. Any idea or comment from the fan will bring me a lot of new information to me.

The value of the transistor soon will be publish at my own website.

The main porpuse of this is to get the comment from the expert amplifier maker if my design have anything wrong in the value and connection.

I have built the prototype and the end result have prove to worked well but the testing and tools I have cannot check all the result. What I done is a hours off hearing form the loudspeaker of mine.

regards

nanhifi
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Old 24th June 2003, 05:50 PM   #2
nanhifi is offline nanhifi  Malaysia
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Exclamation opps something wrong

The value for the R3 is 22k not 1k. The view is been drawn by me base from the ugly original copy sorry for this mistake.

Ok anybody have a comment?
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Old 24th June 2003, 09:42 PM   #3
red is offline red  Romania
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Nice!!!!!!!! I like it a lot.I am a newbie but as far as I know looks pretty good.I have only one question? Has this amplifier 60 watts on a 4 or on an 8 Ohm load?
Because I've build something that look like youre design and I have absolutely no ideea How much puts out.
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Old 24th June 2003, 10:01 PM   #4
Freddie is offline Freddie  Sweden
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Quote:
Has this amplifier 60 watts on a 4 or on an 8 Ohm load?
With +/-40V, 60W into 8ohm seem reasonable..
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Old 24th June 2003, 10:15 PM   #5
Freddie is offline Freddie  Sweden
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nanhifi,

You could place a capacitor between emitter and collector of Q8, so that the signal can pass through the capacitor instead of the transistor.

I have something quite similar, but no current mirror on the inputstage, boostrapped VAS (instead of current source), and two pairs of output transistors in parallel. It runs at +/-52V.

I wonder how you have come up with the value of R19 and R20. I'm not sure what the optimum value is? (I use 220R myself)

I would recommend you to mount Q8 on top of Q9 if you haven't done it already. The bias current got very stable when I did that.

/Freddie
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Old 24th June 2003, 11:08 PM   #6
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Will the capacitor C6 of only 220pf really be of any help decoupling the base of the current source? In other amplifiers i have seen values of over 100uF! Maybe you should decouple the LED too?
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Old 24th June 2003, 11:20 PM   #7
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C1 and C5 are the wrong way around.
Cap across Q8 desirable, as mentioned already.
Otherwise looks ok.
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Old 25th June 2003, 11:34 AM   #8
PWatts is offline PWatts  South Africa
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Default P3A similarity

There's nothing wrong with C1 and C5's orientation. Remember C5 is for the inverted feedback signal.

Not implying anything, but this amp is very similar to Rod Elliott's P3A (especially component values). The only difference is a PNP diff amp, current mirror and some small other refinements.

I suspect it should sound quite good considering the quality of the P3A (I've already built 12, progressively changing the design as I go along). Especially the current mirror instead of the normal resistor should be a great improvement. Maybe a Wilson current source could further improve matters. The emitter degeneration resistors can also be reduced a bit without penalty (in fact several diff amps omit them).

All in all a fine amp.

Pierre
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Old 25th June 2003, 11:50 AM   #9
Jennice is offline Jennice  Denmark
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PWatts,

You mention that some omit the reducing resistors in the long tain pair.

This will increase open loop gain. If the designer doesn't have that many tools to check the signals with (other than listening) then it can lead into problems.

Considering that the input pair's current is (as usual) low, I'm surprised about the small values (100ohm) of the resistors leading to the current mirror. Wouldn't an increase improve dynamic range/gain for the next stage?

Mvh,
Jens
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Old 25th June 2003, 11:58 AM   #10
PWatts is offline PWatts  South Africa
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Hmmm, haven't thought about it that way. You are of course correct. I'll do some SPICE simulations to check the overall effect. Now that you mention it, I've seen values in the kohm range for some. I suspect that simulations should be used to find an optimum value, and then fine tune it by ear.
Pierre
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