[Elecraft] Yamaha CM-500 (was Heil Elite thread)

[Jim Brown]

On Fri, 27 Aug 2010 20:03:50 -0700 (PDT), ussv dharma wrote:

>the yamaha cm500 are 120 ohms...is this ok with the K3

YES. Pardon my frustration, but how many times must we repeat this? 

AUDIO SYSTEMS HAVE NOT BEEN IMPEDANCE MATCHED FOR NEARLY 50 YEARS! 
Audio output stages have very low output impedance, and are 
designed to drive load impedances that are much higher (a rule of 
thumb is about 100 times higher. 

A speaker output stage typically has an output impedance of a tiny 
fraction of an ohm, and is designed to drive any impedance from 
about 4 ohms up, and will give its highest output with a load of 
about 4 ohms, and its best performance with any load above 4 ohms. 
Headphone amps are simply small versions of this, and typically 
have an 4-8 ohm resistor in series to protect the output stage from 
a short circuit as a headset is plugged in, or is wired improperly, 
but the impedance of the output stage itself is typically a 
fraction of an ohm.  

Likewise, the output impedance of line level output stages is 
typically 100 ohms for a pro product and 200-300 ohms for a 
consumer product. Pro products are rated to drive a 600 ohm load, 
but they give their best performance with a 10K ohm load. Consumer 
output stages are designed to drive about 47K ohms. 

Pro mics typically have output impedances between 100 ohms and 300 
ohms, and are designed to drive impedances at least 5X their rated 
impedance. Many condenser mics specify a minimum load impedance of 
1,000 ohms. 

73, Jim K9YC