Advice Please On this amp design

[john121]

Hi And thanks for reading.
I have just put together my very first amp and would love some feedback on the circuit. The sound quality is disappointing, works ok, but is there anything you can think of to improve performance. Please see attached image. Thanks!

 

[HarryA1]

Using what I could find for similar transistors in the simulator I used your  circuit:

 

Green trace is the current through the NPN and yellow the PNP. The current through the 8 ohm load looks good inspite of the asymmetry in the transistor currents.



Connecting the PNP  between the two diodes removes the asymmetry but changes the output current:

 

[john121]

Thanks!

What do you think, any way to improve the circuit, improve the sound quality.

 

[HarryA1]

The output looks good in the simulator at 120mv(peak to peak) the current through the 8 ohm resistor is about 500ma pp which is about 1 watt. At 150mv the output is starting to clip on the bottom. This is do to the PNP Q3 having more base current than Q2. Q3 is directly connected to Q1 while Q2 is off from Q1 by the two diodes or 2 * 0.7 volts  I would think. The base currents; green is Q3 and yellow is Q2.



I like this  circuit better as it is symmetrical; both transistor get the same amount of base current I would think.

 

[john121]

Thanks for the reply,much appreciated.

The new circuit you posted is brilliant,

i would like to try and improve the amplifer circuit i posted up, is there anything that can be done to address the problems you mentioned.

 

[HarryA1]

Making your R1 2000 ohms from 1000 ohms improves the output with slightly  less output power. What do you expect for output power and what do you have for input voltage?

Also the transistors are large current perhaps some thing smaller? The circuit you are using has a base current of about 1.8 ma for the 2SC5200 at 150 mv peak input that is quite low.

 

[HarryA1]

This works well in the simulator using the transistors shown:

 

[Guest]

empezando por R6, el valor es bajo

 

[john121]

Thanks for the reply

This works well in the simulator using the transistors shown:

View attachment 44204

Thanks for the reply. Sorry for the massive delay in responding.

What impedance value speaker do you think i could use in the amplifier design right at the top of the page, the first post. I have a 4 ohm speaker which has a nominal impedance of 4 ohms and a minimum impedance of 1.8 ohms, do think the impedance is safe, or too low.

Many thanks.

 

[M Salman Sarwar Khan]

Decompensated operational amplifiers have improved noise, slew rate, harmonic distortion, etc., but required external compensation for stable operation. This report shows how to compensate such an amplifier and achieve the performance enhancement it provides in a unity-gain configuration.