Today I put this simple op-amp headphone amp together. http://diyaudioprojects.com/Chip/CM...2134PA-CMoy-Headphone-Amplifier-Schematic.png

Has anyone built it before and have any idea on it's specs, such as power output? What would be the best output resistor to use for a given headphone impedance(32ohms, and 16ohms). Also, what about the input capacitor, what would be the best to use? I tried a .15 uF and it seemed to work but dosn't capacitance reduce low frequency and increase treble?

Any notes as to how I can tweak the circuit for given results would be great...thanks.

 

Input capacitor does not increase treble.
It attenuates the bass response. If you want to get better bass response you can increase the value of the capacitor.

The output 38Ω resistor is to prevent blowing out your amp or your headphones.
However it also reduces the output by 6dB. You can try reducing the value to say 10Ω for a bit more volume.

 

Input capacitor does not increase treble.
It attenuates the bass response. If you want to get better bass response you can increase the value of the capacitor.

The output 38Ω resistor is to prevent blowing out your amp or your headphones.
However it also reduces the output by 6dB. You can try reducing the value to say 10Ω for a bit more volume.

Okay, you said the capacitor attenuates the bass response but how does increasing it give better bass response? Perhaps it gives a sharper rolloff but a punchier, peakier, higher Q?

 

There is an easy fix to this. High Powered Studio Headphones...designed specifically to provide a Musician monitered sound to allow them to hear themselves play or sing over any other musician or even their own amp output...use a PASSIVE CROSSOVER as such headphones have seperate Bass and treble mini-speaker and mini-horn which would be crossed over at about 1100 to 1800 cycles...or are using a three way...Bass, Mid-range, High End Mini speakers and horns that require two crossover points at 800 and 2500 cycles.
This solves your issue but any capaciter as it takes charge...will build heat and thus change sound...there are solves for this as well.
Split Infinity

 

Any ideas on a simple bass-boost stage for my small headphone amp? Rightnow I have contructed a simple non-inverting op amp amplifier. I got the schematic from the "grado RA1", why the heck do people name simple open amp designs after a name? I don't see how the "ra1" is propriety or anything special seeing as hwo it's a simple few component technique to amplify.

 

Op amps usually supply very little current but I have designed my own using two op amps, one each driving each speaker. I used this on a disco and the sound level was acceptable.

 

Okay, you said the capacitor attenuates the bass response but how does increasing it give better bass response? Perhaps it gives a sharper rolloff but a punchier, peakier, higher Q?

The input capacitor is a high-pass filter. A higher value capacitor will lower the frequency of the high-pass characteristic. The impedance of a capacitor is 1/(2*pi*F*C). Larger capacitance "C" gives a lower impedance at a given frequency "F". In the input coupling role, a larger C will improve the low frequency response.

 

I believe the Feb 2012 issue of EDN magazine has a simple circuit for a "tilt" tone control. It might work for you.
Google "Baxandal" and find nice tone controls too.

 

I've seen schematics of a simple .1uF cap in paralell with the output resistor, does this work?

 

I've seen schematics of a simple .1uF cap in paralell with the output resistor, does this work?

It will boost treble, but only at a frequency that is above the range of human hearing.

How much bass boost do you want? At what frequency do you want the boost to fall off?

 

Any ideas on a simple bass-boost stage for my small headphone amp? Rightnow I have contructed a simple non-inverting op amp amplifier. I got the schematic from the "grado RA1", why the heck do people name simple open amp designs after a name? I don't see how the "ra1" is propriety or anything special seeing as hwo it's a simple few component technique to amplify.

Although this reply is not specific to your question...I would add that even a medium to low quality amp can give you a good Bass response by adding a few Sound Processing electronic features.

Although such electronic processors are used mostly for High Output systems...there are now available software which you would run on a laptop and put your signal through first before it get's to the amp. This is of course if you can't seem to build an amp that get's you what you desire.

Compressor/Limitor...I have many Rack Mounted versions of these...some designed for studio work...some for live. But now...you can just by this software off the Internet. The compressor aspect in effect...can be adjusted to not allow the imputed signal of sound to be amplified immediately but rather a few Milla or Micro-Seconds after the signal is recieved. The same thing at the back end as it can be adjusted to cut off the signal a few Milla or Micro-Seconds before the signal ends.

This allows a Compression of Sound Imput and allows the amp to concentrate upon the strongest time code of the imputted signal.

The Limitor prevents dangerous peaks of inputted signal that might be able to blow speakers or horns. This is a MUST when using expensive equipment as well as when used with the Compressor....allows a fantastic Bass Punch to be amplified as it is created.

So...even if you build what you want....I would still make sure you run these software effects if you don't have a rack mounted unit.

If you do have either an Electronic or Passive Crossover system....remember....any crossover point below 400 for Large Speaker Systems and 800 for Headphones is spinning your wheels.

Split Infinity