Here鈥檚 a question I probably should have asked years ago:
They鈥檙e basically little speakers strapped to your head, right?
I mean, how hard can this be?
Apparently, pretty damn hard.
Fried Reim has been thinking about the question since 1986.
Reim is the founder of Lake People, and the engineering work he began there eventually developed into Violectric and Niimbus. Nearly four decades later, he has condensed a remarkable amount of that experience into something wonderfully titled the Headphone Amplifier Cookbook.
The innocent headphone jack turns into a system-design problem.
A conventional loudspeaker amplifier typically expects something around 4 or 8 ohms.
Headphones?
Reim describes a landscape running roughly from 8 to 600 ohms, plus enormous differences in sensitivity.
One headphone might require more than 250 times the power of another to reach the same sound-pressure level. High-impedance headphones can demand substantial voltage. Low-impedance headphones present their own demands. Sometimes the headphone amplifier needs to amplify the incoming signal.
Sometimes it actually needs to attenuate it.
Sometimes its most important job is simply providing an extremely low-impedance interface between the source and the transducer.
Suddenly that little headphone jack doesn鈥檛 look quite so innocent.
We obsess over speaker matching, then improvise with headphones.
We will spend hours talking about matching a loudspeaker and amplifier.
We discuss watts.
Current.
Impedance.
Damping factor.
Headroom.
Cables.
The room.
The position of the speakers.
The position of the chair.
Possibly the gravitational influence of Jupiter.
Then we can buy a pair of extraordinary headphones, stick a quarter-inch adapter on the end and plug them into whatever socket is closest.
Reim spends much of his book explaining why.
The boring-looking numbers are doing musical work.
Variable gain matters because wildly different headphones place wildly different requirements on the amplifier. Lake People and Violectric call their implementation PRE-GAIN, allowing the amplifier to accommodate everything from sensitive in-ear monitors to much less sensitive high-impedance headphones while controlling noise and preserving useful range in the volume control.
Voltage matters.
Headroom matters.
Damping matters.
Even the humble volume knob becomes an engineering problem.
Reim devotes an entire section to volume-control approaches, eventually making the case that relay-controlled attenuation, using carefully selected fixed resistors switched by relays, provides extraordinary precision and channel matching when the complexity and expense can be justified.
This is where the cookbook starts becoming philosophy.
In a conventional unbalanced headphone connection, left and right share a ground return. Reim explains how residual signals can therefore find their way into that common reference, producing measurable crosstalk and intermodulation.
A properly implemented balanced amplifier drives each voice coil from two amplifiers operating in opposition. The common ground disappears from the load path. Channel separation improves.
All very engineer-y.
Until Fried explains what that can mean to a listener.
There it is.
Get closer to the music.
Not because another box needs to be sold.
Not because audiophiles desperately need another specification to argue about on the internet.
Because somewhere underneath the voltage rails, damping factors, resistors and relays is a very human objective:
That connects directly to something else we鈥檝e been exploring at 26Eight.
Vinyl Discovery is partly about recovering the ritual of choosing music. Taking an album out. Looking at it. Touching it. Choosing a side. Dropping the needle. Listening deliberately.
Headphone Heroes is going to explore what happens after we press Play.
Who are the people who figured out how to eliminate another barrier between us and the recording?
What did they discover?
Why did they build things the way they did?
And perhaps most importantly: can understanding a little more about the technology help us hear a little more of the music?
Fried Reim seems like a pretty damn good place to start.
The source reference for this episode, Fried Reim鈥檚 Headphone Amplifier Cookbook, is now preserved in the 26Eight HUB Library as the first Headphone Heroes reference.