3transistor spare parts Guitar headphone amplifier

[dave_j_fan]

 took a heapphone amp and added a preamp stage
 our basic guitar headphone  amp is here

 some restrictions : 4.5V operation  as in Vox amps
 this is working  but two issue

 1) a bit distorted
  2) weaker HP signal

 Please help

[NiHaoMike]

Read up about opamps and some simple headphone amplifiers based on them.

[Audioguru]

Of course it is distorted. The output transistor has no negative feedback.

[Audioguru]

Please translate "HP" into English.
I looked at the schematic and the datasheets for the battery and BC547 transistor. Then I did a little arithmetic and discovered that many bC547 transistors will clip badly or be completely saturated in that poorly designed circuit:

[dave_j_fan]

thank you,

i am thinking of this with first pre stage  of my amplifier
https://circuitszone.com/portable-headphone-amplifier-circuit-based-3-transistors/

what u think

[dave_j_fan]

Here is the  circuit  i modified

 - gain in stage one reduced
 - stage isolation with 680E
 -final power transistor usage : As per audioguru high gain transistor is removed 

 volume is vv loud .. working very well
  will upload recordings later

[mikerj]

That circuit puts a constant DC current through your headphones which isn't the best idea.

[Zero999]

Presumably you're talking about an inductive guitar pick-up?

A guitar amplifier needs no voltage gain, as the output level is quite high. Indeed, some voltage attenuation may be necessary.

What is required is an amplifier with a high input impedance >1M and a fairly low output impedance, perhaps even a unity gain buffer.

What impedance are the headphones?

Here's a design I've just done in LTSpice. It has a gain of under 1. No doubt it will need tweaking if build in real life. It uses bootstrapping to keep the input impedance high. The input impedance is over 1M for frequencies under 6kHz and over 300k up to 20kHz.

No doubt a simpler design can be made with a J-FET pre-amp or just a pair of MOSFETs.

[NiHaoMike]

The right solution is an audio opamp like the 4580.

[Zero999]

The right solution is an audio opamp like the 4580.

Except it's not specified to work below 4V, which wouldn't give much battery life out of three AA cells.
The bootstrapping configuration I posted has an almost rail-to-rail output. It would be better to only use two transistors in the feedback loop of an op-amp with a rail-to-rail output.

[NiHaoMike]

Then look for headphone amplifier chips that are rated to work from both 5V and 3.3V - there are truly a lot.

[Zero999]

Then look for headphone amplifier chips that are rated to work from both 5V and 3.3V - there are truly a lot.

I agree, the circuits posted above are more for educational purposes. Using a purpose designed IC is the right way to do it.

[dave_j_fan]

ic i dont prefer getting chips for many countries is real pain and expensive
for eg here in Asia digikey takes 40$ for  0.1$ part as shippping

i wanted a design that uses very low cost parts still sounds good 
Hero999, Thank u for the circuit but that bulky220ufs are and issue for small cases
i hope 22u will work

[Audioguru]

There are electronics chat websites in India that talk about parts that are available in India. On this website we talk about Western parts.
If the 220uF capacitors replaced with 22uF capacitors then the circuit will produce no low frequency bass sounds in music and not produce voice sounds from many men.