{"id":1405,"date":"2025-05-22T15:28:43","date_gmt":"2025-05-22T14:28:43","guid":{"rendered":"https:\/\/marzocchi.net\/wp\/?p=1405"},"modified":"2025-08-29T15:04:40","modified_gmt":"2025-08-29T14:04:40","slug":"output-impedance-of-nexus-5x","status":"publish","type":"post","link":"https:\/\/marzocchi.net\/wp\/2025\/05\/output-impedance-of-nexus-5x\/","title":{"rendered":"Output Impedance of Nexus 5X"},"content":{"rendered":"\n

Estimation of output impedance of the final audio stage<\/h4>\n\n\n\n

In general, audio headphones should have an impedance of at least 6-8 times<\/a> the output impedance of the final stage of the audio amplifier used to power them. Since my Nexus 5X is known to have a limited output power<\/a> (up to 0.286 Vac) and my KNS-8400<\/a> have an input impedance of 36 ohm, I decided to measure the actual output impedance of the Nexus 5X.<\/p>\n\n\n\n

I tried to load the Nexus jack output with one or two fixed 35.9 ohm resistors, about equivalent to the nominal and measured<\/a> impedance of my headphones (KNS-8400). The impedance may vary with the frequency, but not in my case (check the link).<\/p>\n\n\n\n

I used a Victor VC9808+ to measure the amplitude of the output in AC mode while playing a 1 kHz sine wave at the various output levels. I used the left channel but I also did one measurement with two channels loaded. The results are:<\/p>\n\n\n\n

Volume<\/th>Unloaded [mV]<\/th>SX [mV]<\/th>SX+DX [mV]<\/th><\/tr>
0<\/td>0<\/td> <\/td> <\/td><\/tr>
1<\/td>0<\/td> <\/td> <\/td><\/tr>
2<\/td>0<\/td> <\/td> <\/td><\/tr>
3<\/td>0.8<\/td> <\/td> <\/td><\/tr>
4<\/td>3.2<\/td> <\/td> <\/td><\/tr>
5<\/td>6.2<\/td> <\/td> <\/td><\/tr>
6<\/td>10.3<\/td> <\/td> <\/td><\/tr>
7<\/td>15.6<\/td> <\/td> <\/td><\/tr>
8<\/td>24.9<\/td> <\/td> <\/td><\/tr>
9<\/td>39.9<\/td>36.4<\/td> <\/td><\/tr>
10<\/td>53.5<\/td>48.8<\/td> <\/td><\/tr>
11<\/td>75.4<\/td>68.9<\/td> <\/td><\/tr>
12<\/td>108<\/td>98.6<\/td> <\/td><\/tr>
13<\/td>145<\/td>132<\/td>130<\/td><\/tr>
14<\/td>203<\/td>186<\/td>182<\/td><\/tr>
15<\/td>286<\/td>261<\/td>258<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

I then calculated the output impedance using only the left channel:<\/p>\n\n\n\n

impedance = (Vunloaded<\/sub>\u00a0– Vloaded<\/sub>) \/ Vunloaded<\/sub>\u00a0* Rload<\/sub>\u00a0=
= (0.286-0.261)\/0.286*35.9 = 3.1 ohm<\/p>\n\n\n\n

Using the case with both channels loaded, the resulting impedance is 3.5 ohm.<\/p>\n\n\n\n

The Nexus 5X has a weak output level and requires sensitive headphones, but its output impedance will not distort normal headphones with at least 24 ohm impedance (minimum value measured for the chosen headphones).<\/p>\n\n\n\n

\n\n\n\n

First revision: 2016-11-10.
Last revision: 2016-11-10.<\/p>\n","protected":false},"excerpt":{"rendered":"

Estimation of output impedance of the final audio stage In general, audio headphones should have an impedance of at least 6-8 times the output impedance of the final stage of the audio amplifier used to power them. Since my Nexus 5X is known to have a limited output power (up to 0.286 Vac) and my KNS-8400 have an input impedance of […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[76,77],"class_list":["post-1405","post","type-post","status-publish","format-standard","hentry","category-electronics","tag-headphones","tag-smartphone"],"_links":{"self":[{"href":"https:\/\/marzocchi.net\/wp\/wp-json\/wp\/v2\/posts\/1405","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/marzocchi.net\/wp\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/marzocchi.net\/wp\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/marzocchi.net\/wp\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/marzocchi.net\/wp\/wp-json\/wp\/v2\/comments?post=1405"}],"version-history":[{"count":2,"href":"https:\/\/marzocchi.net\/wp\/wp-json\/wp\/v2\/posts\/1405\/revisions"}],"predecessor-version":[{"id":1572,"href":"https:\/\/marzocchi.net\/wp\/wp-json\/wp\/v2\/posts\/1405\/revisions\/1572"}],"wp:attachment":[{"href":"https:\/\/marzocchi.net\/wp\/wp-json\/wp\/v2\/media?parent=1405"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/marzocchi.net\/wp\/wp-json\/wp\/v2\/categories?post=1405"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/marzocchi.net\/wp\/wp-json\/wp\/v2\/tags?post=1405"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}