Hello,
I am going to make my ownn bassguitar headphone amp( for my graduation project).
I have concluded the scheme of my project with this message.
I have also concluded the last version of my project in LTSpiceXVII, but it still shows some misbehaving.
My goal is to run the whole project on a 9 Volt battery and having the ability to listen to the outgoing signal with a pair of nominal 32 Ohm headphones.
I also like to listen to my drum tracks, which are on my mp3-player, so I wanted an extra aux input.
So far, I chose some JFET's as the pre-amping part and two LM386 chips for the amplifiying part.
I hope to be working in the right direction, maybe someone has a bit more experience with these kinds of projects?
I'd like to hear your opinions!, of course I need to do all the work and thinking myself, but I would just like to hear if I'm going into hte right direction or not...
Greetings from Holland,
S.
I am going to make my ownn bassguitar headphone amp( for my graduation project).
I have concluded the scheme of my project with this message.
I have also concluded the last version of my project in LTSpiceXVII, but it still shows some misbehaving.
My goal is to run the whole project on a 9 Volt battery and having the ability to listen to the outgoing signal with a pair of nominal 32 Ohm headphones.
I also like to listen to my drum tracks, which are on my mp3-player, so I wanted an extra aux input.
So far, I chose some JFET's as the pre-amping part and two LM386 chips for the amplifiying part.
I hope to be working in the right direction, maybe someone has a bit more experience with these kinds of projects?
I'd like to hear your opinions!, of course I need to do all the work and thinking myself, but I would just like to hear if I'm going into hte right direction or not...
Greetings from Holland,
S.
Attachments
Looks good and will work properly as is. 
Would add just a couple small details:
1) add DC discharge resistors (to ground) after C14/C15 so headphones do not pop when pluggedn into a just turned on preamp. anything from 100 to 1000 ohm will be fine.
2) add a 220k to 1M resistor from Q2 gate to ground, so it does not depend *only* on pot wiper helth for ground reference.
No difference with new pots, but after wear and dirt they easily become scratchy, a separate fixed ground reference resistor minimizes that.
3) *maybe* you have too much gain, if so add a couple 4k7 to 10k resistors from IC1 and IC2 pin 3 to ground.
4) remember R15 volume pot must be Log taper for smoother control, a Linear taper control there will be harder to adjust to desired volume level.
And 30k is not a normalized value, choose between 22(25)k and 47(50)k .
But in general a very good first design, congratulations.
Would add just a couple small details:
1) add DC discharge resistors (to ground) after C14/C15 so headphones do not pop when pluggedn into a just turned on preamp. anything from 100 to 1000 ohm will be fine.
2) add a 220k to 1M resistor from Q2 gate to ground, so it does not depend *only* on pot wiper helth for ground reference.
No difference with new pots, but after wear and dirt they easily become scratchy, a separate fixed ground reference resistor minimizes that.
3) *maybe* you have too much gain, if so add a couple 4k7 to 10k resistors from IC1 and IC2 pin 3 to ground.
4) remember R15 volume pot must be Log taper for smoother control, a Linear taper control there will be harder to adjust to desired volume level.
And 30k is not a normalized value, choose between 22(25)k and 47(50)k .
But in general a very good first design, congratulations.
@JMFaley, sorry for my very late response, but I was very busy with my graduation and final internship.
I am glad to tell you that the project works, and the scheme I used worked for the biggest part.
You were absolutely right about all the points you put out to me, I used a very old 30K Log resistor, since my school has only very old components. Though, I am very sure it would work the same with a 25K POT.
Thank you again for your message, I will definetely post my project on this site in the future.
I am glad to tell you that the project works, and the scheme I used worked for the biggest part.
You were absolutely right about all the points you put out to me, I used a very old 30K Log resistor, since my school has only very old components. Though, I am very sure it would work the same with a 25K POT.
Thank you again for your message, I will definetely post my project on this site in the future.
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