# Amplifier Load Box Project **URL:** \ **Category:** DIY Audio & Modifications\ **Created:** [February 20, 2020, 9:18pm UTC](https://forum.headphones.com/t/amplifier-load-box-project/5420 "2020-02-20T21:18:43Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![angstorms](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.headphones.com/angstorms/32/9017_2.png) [@angstorms](https://forum.headphones.com/u/angstorms)\ **Post date:** [February 20, 2020, 9:18pm UTC](https://forum.headphones.com/t/amplifier-load-box-project/5420/1 "2020-02-20T21:18:43Z")
Well, this is the start of my Headphone Amplifier load box project, Mouser just delivered all the parts. ![IMG_9937](https://us1.discourse-cdn.com/flex016/uploads/headphones/original/2X/e/ee308b0927e4c76d616481854bfaf38ec10371b3.jpeg) Will have an 8 load values - 12 Ohms Aeon Flow Open (13 Ohms) - 25 ohms Ananda ( 25 Ohms) - 30 Ohms. Rad-0 (29 Ohms) - 40 Ohms Close to Arya( 41 Ohms) & HEDDphone (42 Ohms) - 75 Ohm Close to ELEX (80 Ohms) & Utopia ( 80 Ohms) - 120 Ohms. ( used in SPL Phonitor x mesurements) - 200 Ohms LCD -4 - 300 Ohms Vertie & HD-6xx Inputs - 4 wire XLR - 6.5 mm Stereo Headphone Jack - 3.5 mm Stereo Headphone Jack Output - two BNC outs for test equipment Needed to 2 x 1 pole 10 selection pots to do selection for left and right load channels The case i am going to use ![IMG_9938](https://us1.discourse-cdn.com/flex016/uploads/headphones/original/2X/0/0927991aa319c06c22c4db6746e50976c4a35495.jpeg) ---
**Author:** ![ValentineLuke](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.headphones.com/valentineluke/32/9729_2.png) [@ValentineLuke](https://forum.headphones.com/u/ValentineLuke)\ **Post date:** [February 20, 2020, 9:22pm UTC](https://forum.headphones.com/t/amplifier-load-box-project/5420/2 "2020-02-20T21:22:32Z")
Very cool. This will be a fun thread to follow. 👍🏽 ---
**Author:** ![jb77](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.headphones.com/jb77/32/6168_2.png) [@jb77](https://forum.headphones.com/u/jb77)\ **Post date:** [February 21, 2020, 8:01am UTC](https://forum.headphones.com/t/amplifier-load-box-project/5420/3 "2020-02-21T08:01:10Z")
Looks like an awesome project, looking forward to your updates! ---
**Author:** ![stoN\_Cold](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.headphones.com/ston_cold/32/7858_2.png) [@stoN\_Cold](https://forum.headphones.com/u/stoN_Cold)\ **Post date:** [February 21, 2020, 2:44pm UTC](https://forum.headphones.com/t/amplifier-load-box-project/5420/4 "2020-02-21T14:44:12Z")
Nice, but box is fugly, my sg. is Hammond 1455N1602. ---
**Author:** ![jnorris](https://avatars.discourse-cdn.com/v4/letter/j/73ab20/32.png) [@jnorris](https://forum.headphones.com/u/jnorris)\ **Post date:** [February 21, 2020, 5:03pm UTC](https://forum.headphones.com/t/amplifier-load-box-project/5420/5 "2020-02-21T17:03:25Z")
I’m not sure what you are trying to accomplish here. Ideally, the amp output impedance should be less than 1/8 the headphone impedance. I built a box that provided a 3 ohm output impedance that worked well for all my headphones. Output was taken from the speaker terminals of the amp. ---
**Author:** ![Torq](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.headphones.com/torq/32/16384_2.png) [@Torq](https://forum.headphones.com/u/Torq)\ **Post date:** [February 21, 2020, 5:12pm UTC](https://forum.headphones.com/t/amplifier-load-box-project/5420/6 "2020-02-21T17:12:19Z")
A load box like that is to allow you to **measure** amplifier performance under a known, static, load - not to increase the effective output-impedance when using headphones. ---
**Author:** ![jnorris](https://avatars.discourse-cdn.com/v4/letter/j/73ab20/32.png) [@jnorris](https://forum.headphones.com/u/jnorris)\ **Post date:** [February 21, 2020, 7:01pm UTC](https://forum.headphones.com/t/amplifier-load-box-project/5420/7 "2020-02-21T19:01:40Z")
I see - you’re emulating the impedance of specific headphones for measuring, not trying to match the output impedance of an amp to the impedance of a headphone for listening. Makes sense, but what about the frequency-dependent impedance variations that most headphones exhibit? ---
**Author:** ![MazeFrame](https://avatars.discourse-cdn.com/v4/letter/m/e95f7d/32.png) [@MazeFrame](https://forum.headphones.com/u/MazeFrame)\ **Post date:** [February 21, 2020, 7:09pm UTC](https://forum.headphones.com/t/amplifier-load-box-project/5420/8 "2020-02-21T19:09:24Z")
Nice project. I got something similar for general use in electronics projects. Will you switch by replugging or by rotary switch? ---
**Author:** ![angstorms](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.headphones.com/angstorms/32/9017_2.png) [@angstorms](https://forum.headphones.com/u/angstorms)\ **Post date:** [February 21, 2020, 9:52pm UTC](https://forum.headphones.com/t/amplifier-load-box-project/5420/9 "2020-02-21T21:52:32Z")
Plan on using Rotary switch, I thought about building a toggle bank like on old PDP-11 just for fun. @Torq thank you for answering, work is a little crazy today, getting ready to fly out to see customer in Chicago. @jnorris For this type of testing, you normally look at fixed-resistance but remember I have a pretty wide swing in resistance that would cover most state you see. Now I could put 475 Ohm resistor for the peak of HE-6xx for the issue you raise, also put in 600 Ohm resistor. ---
**Author:** ![MazeFrame](https://avatars.discourse-cdn.com/v4/letter/m/e95f7d/32.png) [@MazeFrame](https://forum.headphones.com/u/MazeFrame)\ **Post date:** [February 25, 2020, 1:58am UTC](https://forum.headphones.com/t/amplifier-load-box-project/5420/10 "2020-02-25T01:58:15Z")
Toggle bank sounds like a good (and expandable) setup. Circuit would be like so: ![image](https://us1.discourse-cdn.com/flex016/uploads/headphones/original/2X/1/13d76c835a4ff63be723e245635b55d8034bd32d.png)