Neurochrome HP-LOAD Review (Headphone Dummy Load)

[jtwrace]

If they added a 100MOhm option with 100pF load you could even create a dummy electrostatic. Easy mod I suspect...

You buying one if it's added?

 

[Dan Clark]

You buying one if it's added?

Probably no since we make the "loads" not the test source, but for the vendors who make stat amps it may be useful. It'd also require a different 5 conductor stat jack which may add a little more complexity than my first "oh cool" thought indicated.

We now have some decent electronics lab gear so we can profile our test equipment and listening gear and I already made our own stat dummy loads to check the amps we have, so it's not needed for us at this point. There are only a handful or amp makers so the vendor market is small but there is also a DIY community that's seriously into the hobby, they might be a target as well.

 

[gvl]

So, what's a poor and lazy man's (i.e. myself) version of this load? A set of headphone cables with 5W resistors of different values soldered on?

 

[Dan Clark]

So, what's a poor and lazy man's (i.e. myself) version of this load? A set of headphone cables with 5W resistors of different values soldered on?

Stats are balanced devices so for each leg + connects to - with a 100Mohm resistor and a parallel 120pF cap. That simulates a 2m cable and a large electrostatic driver... In this case VOCE, which at 88mm is a higher capacitance load due to size than any other headphone I know of, so consider that a worst-case load, unless you want to drive 2 in parallel then you use 50Mohm resistors and 240pF.

 

[3125b]

A set of headphone cables with 5W resistors of different values soldered on?

Kinda. Here's a scematic of mine (as carefully made as the device):

You could choose other resistor values, depending on the use case. Mine are E12, so there wasn't too much choice, and with that tolerance, you definitely need to measure them. This is an unbalanced load* and not for use with an AP or anything.
All I bought were four resistors, a switch and a cable, used an old lunch box for the case. Works well for casual measurements and costs <10€/$.
*Edit: well, using individual conductors for the return you could make it balanced, but I'm not sure if that makes sense given the kind of accuracy you'd want to measure a higher end amp/system like that? I used Wago 221 connectors internally, those make for flexible and safe connections with any kind of wire.

 

[gvl]

Kinda. Here's a scematic of mine (as carefully made as the device):
View attachment 144554
You could choose other resistor values, depending on the use case. Mine are E12, so there wasn't too much choice, and with that tolerance, you definitely need to measure them. This is an unbalanced load and not for use with an AP or anything.
All I bought were four resistors, a switch and a cable, used an old lunch box for the case. Works well for casual measurements and costs <10€/$.

And for "balanced" cables I just load each channel like this, less the switch? Must be.

L+ ---- Rl ---- L-
R+ ---- Rr ---- R-

As far as the analyzer connection, it just gets connected in parallel to the resistors I suppose? @tomchr, in your load the balanced outputs for the AP, do you convert voltage taken at the resistor to proper differential signal?

 

[AudioSceptic]

Thanks. Fixed.

Sorry, but same applies in the 3rd para.
"A year ago Tom approached me and asked if I was interested in a properly built dummy load for headphone amp testing".

 

[AudioSceptic]

$1500 for a well-designed headphone dummy load that interfaces with the AP box? That's fantastic. This is one of those things that's an annoying PITA to build, but very necessary for those who are designing headphone amps.

I use water heater elements for testing big power amps, and they're better behaved than I would have expected. I'm still able to measure distortion down in the 0.001% range with them, which is the limit of my current analyzer. For precise distortion measurements I have some better load resistors, but they're limited to 300 watts.

For super big power, I use a 4" diameter tube of water with an electrode at each end and an appropriate amount of salt added. What's nice is that this type of load can take enormous pulses without dying.

Aren't you converting water to hydrogen and oxygen doing that? ;-)

 

[P_M]

just like amp loads - 4ohm , 8ohm, or higher or lower headphones have different but standard

Kinda. Here's a scematic of mine (as carefully made as the device):
View attachment 144554
You could choose other resistor values, depending on the use case. Mine are E12, so there wasn't too much choice, and with that tolerance, you definitely need to measure them. This is an unbalanced load and not for use with an AP or anything.
All I bought were four resistors, a switch and a cable, used an old lunch box for the case. Works well for casual measurements and costs <10€/$.

right , and my point earlier was that if this $1500 dummy load is offering the same thing then ... what exactly is it offering for $1487 more ?

 

[Doodski]

just like amp loads - 4ohm , 8ohm, or higher or lower headphones have different but standard


right , and my point earlier was that if this $1500 dummy load is offering the same thing then ... what exactly is it offering for $1487 more ?

I thought the answer to that question has been laid in good detail in this thread. It's all there.

 

[doug2761]

Meanwhile this is how Chord's $1500 preamp selects its impedance... sigh...

Lights are pretty

 

[3125b]

Aren't you converting water to hydrogen and oxygen doing that? ;-)

I'd be more worried about the fact that using table salt in electrolysis produces clorine gas - not great indoors.
Soda is the better option.

 

[restorer-john]

what exactly is it offering for $1487 more ?

If I was in the business of measuring/manufacturing headphone amplifiers and interfacing with an AP for automated measurements, this is a brilliant product. In the scheme of things, not expensive and would pay for itself in no time.

I also like how @tomchr has made it look like it matches the AP. I can see this becoming the defacto standard test-rig for all manufacturers to present their performance curves.

 

[Helicopter]

If I was in the business of measuring headphone amplifiers and interfacing with an AP for automated measurements, this is a brilliant product. In the scheme of things, not expensive and would pay for itself in no time.

I also like how @tomchr has made it look like it matches the AP.

agree. it looks great for AP. Not bad with some of the RME stuff either.

 

[Doodski]

clorine gas

That stuff is deadly and damages lung tissue. I know, I've been accidentally gassed. My lips turned gray, fingernails blue and I had so little energy that I could not get up to help myself or even reach for the telephone to call for help...

 

[Helicopter]

That stuff is deadly and damages lung tissue. I know, I've been accidentally gassed. My lips turned gray, fingernails blue and I had so little energy that I could not get up to help myself or even reach for the telephone to call for help...

I ran through a galley filled with Chlorine to make sure it had been evacuated once while holding my breath. Probably not the best decision in retrospect.

Hydrogen can certainly be deadly too, but it seems it would be pretty safe with AC electrolysis, i.e., already mixed with the right amount of oxygen, if you just burned it off continually.

 

[Doodski]

I ran through a galley filled with Chlorine to make sure it had been evacuated once while holding my breath. Probably not the best decision in retrospect.

I inhaled a small amount and realized immediately that something in the air was toxic. So a partial inhalation was all that was required. It took a little more than a hour for me to regain proper breathing. I won't detail how I accidentally made the stuff but it was with common household cleaners and sanitizers.

 

[Helicopter]

I inhaled a small amount and realized immediately that something in the air was toxic. So a partial inhalation was all that was required. It took a little more than a hour for me to regain proper breathing. I won't detail how I accidentally made the stuff but it was with common household cleaners and sanitizers.

Someone was consolidating gallon jugs of stuff on the ship where I was. One jug wasn't labeled correctly.

 

[Doodski]

Someone was consolidating gallon jugs of stuff on the ship where I was. One jug wasn't labeled correctly.

You're lucky you never inhaled because it would have laid you out and maybe all alone in the galley breathing that stuff. It took cohoonas to run through there though. It's good to have peeps around that can do that sort of stuff.

 

[gvl]

I inhaled a small amount and realized immediately that something in the air was toxic. So a partial inhalation was all that was required. It took a little more than a hour for me to regain proper breathing. I won't detail how I accidentally made the stuff but it was with common household cleaners and sanitizers.

Every time I see a pool guy driving his truck with loads of chlorine and acid in the back next to each other I think that he should know better about occupational hazards.