Simple Headphone Amp

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Nico Ras

Nico Ras

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Joined 2005
and finally completed tested and about to go into its housing
 

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Nico Ras

Nico Ras

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Joined 2005
This the end result and was finished Thursday afternoon. I have been listening to it ever since and I am very pleased with the results. My friend should also be pleased I think.:angel:

Operating revision 4 with the originally designed ±15V supply it ran too hot for my liking and one only needs about 4V maximum swing at the output.

I have since reduced the supply voltage to ±6 V and run it off a very compact 7.2A/h NiMH rechargeable battery pack made up of 20 Panasonic HHR380A cells. Reducing the supply needed trimming of tail resistors in the LTP to 6K. R 5 & R6 changed to 2.7K and 3.3K respectively.

With the new supply voltage performance remained unchanged.

Below are two photos of the finished product that will be presented to my friend tomorrow. I wish I could keep it because it looks so much nicer than my first attempt.:bawling:
 

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Nico Ras

Nico Ras

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I have tested running it off the battery pack and it runs approximately for 45 hours continuously when the terminal voltage reaches 5.8 volts. I use a quick charger that can replenish the batteries to 100% in three hours.

Here is another view, BTW the batteries are in a separate ABS utility box with its charger (not shown).
 

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Nico Ras

Nico Ras

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nelsonvandal said:
While you're at it, couldn't you design a portable headphone amp for the use with 8 - 10 AAA's?
Click to expand...

This one is single ended class A which sounds great on head phones because of zero cross-over distortion. It will draw the AAA's down in no time. I would suggest class B for portable use and would look at using an op-amp. It sounds sounds totally different though.

Kind regards

Nico
 
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Gordy

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Joined 2006
MikeHunt79 said:
Hi, I'm a newbie when it comes to things like this...

This looks very nice. If I wanted to use this in a balanced set up, would it be as simple as making 2 amps instead of 1?

Also, could I build 1 +-10v power supply, and use it to power 2 amps?
Click to expand...

What do you mean by balanced? Don't be confused / mislead by the Headroom adverts: you do not need each ear to be fed by a balanced amp to get better performance. Just separating the grounds, and hence creating a dual-mono system, is all you need to do.

To do that just build two completely separate amps and power supplies. The only components common to the left and right channels would then be the volume control and the main transformer. (You need to rewire your headphones too, and not use the standard jack connector, but I guess that you already know that).

Actually you can share one supply between two amps, but *ideally* each should have a separate supply.
 
MikeHunt79

MikeHunt79

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Joined 2003
Gordy said:


What do you mean by balanced? Don't be confused / mislead by the Headroom adverts: you do not need each ear to be fed by a balanced amp to get better performance. Just separating the grounds, and hence creating a dual-mono system, is all you need to do.
Click to expand...
Well I'm running a dual Cmoy balanced setup right now, and simply use a quad-gang pot for volume control, and am using a modified HD-650 cable which has separated grounds. My source is also balanced (emu 1212m) so I'm trying really to upgrade from a better sound than the cmoys (which is essentially a portable amp). I figure building 2 of these shouldn't take much longer than building 1. :D
Gordy said:
To do that just build two completely separate amps and power supplies. The only components common to the left and right channels would then be the volume control and the main transformer. (You need to rewire your headphones too, and not use the standard jack connector, but I guess that you already know that).

Actually you can share one supply between two amps, but *ideally* each should have a separate supply.
Click to expand...
Ok, sounds good. I'll get all the parts for 2 x PSU's. Thanks. :)
 
Nico Ras

Nico Ras

Member
Joined 2005
Gordy said:


What do you mean by balanced? Don't be confused / mislead by the Headroom adverts: you do not need each ear to be fed by a balanced amp to get better performance. Just separating the grounds, and hence creating a dual-mono system, is all you need to do.

To do that just build two completely separate amps and power supplies. The only components common to the left and right channels would then be the volume control and the main transformer. (You need to rewire your headphones too, and not use the standard jack connector, but I guess that you already know that).

Actually you can share one supply between two amps, but *ideally* each should have a separate supply.
Click to expand...

Hi Gordy, the most important common thing you for got is the head:hphones:
 
Nico Ras

Nico Ras

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MikeHunt79 said:

Well I'm running a dual Cmoy balanced setup right now, and simply use a quad-gang pot for volume control, and am using a modified HD-650 cable which has separated grounds. My source is also balanced (emu 1212m) so I'm trying really to upgrade from a better sound than the cmoys (which is essentially a portable amp). I figure building 2 of these shouldn't take much longer than building 1. :D

Ok, sounds good. I'll get all the parts for 2 x PSU's. Thanks. :)
Click to expand...

I would like to humbly differ from your views simply because one actually would like some cross-talk using headphones simply because the sound stage falls apart completely and some kind of mixing and time delay is necessary else you will become very fatigued.

There has been a fair amount done on this topic and probably one of the simplest and very effective methods is three resistors and two caps shown below. If I remembered the chaps web page that did the research I would be happy to quote him but unfortunately his name escapes me, sorry guy.
 

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Nico Ras

Nico Ras

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Hi Mike,

Just try one of the earlier recordings 70's & 90's and even some recent recordings, especially on electronically generated music. The sound is so spatial it makes your eyes water. I read somewhere that to wide stereo have a psychological side effects and the reason you suffer fatigue is because the brain copes badly with sound that only exist in one ear, it is not natural that sound does not spill around your head.

I will try and locate the web-site, it is really very interesting, and it works.

I think that you may be suffering from this effect rather than anything else. Try it, you may just not have to build another amp.

Kind regards

Nico
 
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