I keep reading of the 1:10 rule with impedance matching where 1 is the output impedance and 10 the subsequent input impedance. But is this the ideal, the maximum or the minimum requirement?
Senior Member
Location: Bishops Stortford
Posts: 1,250
I'm Chris.
I keep reading of the 1:10 rule with impedance matching where 1 is the output impedance and 10 the subsequent input impedance. But is this the ideal, the maximum or the minimum requirement?
Source
SW1X Universal Music Server UMS I Signature with Power Supply Unit PSU I Signature
SW1X USB II
SW1X DAC III Special
Audiolab 6000 CDT transport
Amps
Pre amps -- Hi fi Collective twin mono ladder stepped attenuator, with Charcroft Z-foil and silver wired. And First Watt B1 active no gain buffer.
Power amps -- Welborne 45 SET monoblocks 1.8W / Decware Taboo 6W / Elekit 300B TU-8600SVK plus further improved components 9W / ICE Power 1000W
Speakers
Highly modified Endorphin P17 open baffle speakers containing both vintage and modern alnico drivers and paper cones. All silver wired - 8" Cube Audio FC8 full range drivers and vintage 15" Altec VOTT 416 bass drivers. All sat on Townsend Audio Podium seismic isolation platforms.
BK Electronics XLS400FF Sub.
Cabling
Silver mains cables, interconnects and speaker cables by SW1X
Headphones
HRT HeadStreamer and SennHeiser HD650 headphones
Captain Insightful
Location: Seaford UK
Posts: 1,861
I'm Dennis.
Impedance matching has largely been regarded as inappropriate in the audio world; the concept is taken from radio frequency engineering where considerations of maximum power transfer have been important, particularly in line transmission.
In audio voltage is used as the parameter to connect equipment, disregarding the power transfer theory which is regarded as of little consequence.
Sometimes a source is connected to numerous I/Ps of devices, and when so, the advantages of high I/P Zs becomes pronounced; they load the source to a lesser extent. From memory of my time at the BBC, even with signal transfer around the buildings the I/P Z and I/p Zs were 600 ohms, but I do not know the rational for this, probably noise reduction on long lines.
Consider the O/P Z of a power amp, which we all want to be as near zero as possible to transfer as much voltage as possible to the load into which it feeds. Damping factor is an expression of maximising this ratio. This whole scenario is completely unbalanced.
Some attempt to feed speakers with a constant current source, with various supportive contentions.
Senior Member
Location: The Black Country
Posts: 6,089
I'm Alan.
I would say minimum.
Fount Master & Moderator
Location: Essex
Posts: 32,042
I'm openingabottleofwine.
Dennis,
Impedance matching is still used for some audio amplifiers. That is why an output transformer is used in valve designs, to match the anode loading of a few kilohms to the ~ 8 Ohm load of the speaker.
Barry
Captain Insightful
Location: Seaford UK
Posts: 1,861
I'm Dennis.
My bad, yes of course Barry, my (internal context was one of the last47 years of SS equipment, I had forgotten the difficulties with matching with stages in valves. I built and used valve stuff from about '66 to '70.
Senior Member
Location: limerick
Posts: 223
I'm charles.
The 1:10 ratio should be regarded as a minimum. That is the source should feed into an impedance at least 10 X higher.
I sent you an email yesterday.
Captain Insightful
Location: Seaford UK
Posts: 1,861
I'm Dennis.
Yes Charles absolutely, so that the source amp doesn't 'know' that there is a load.
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