• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Review and Measurements of Neurochrome HP-1 High-Performance Amp

tomchr

Addicted to Fun and Learning
Technical Expert
Manufacturer
Forum Donor
Joined
Nov 5, 2018
Messages
523
Likes
1,594
Location
Calgary, Canada
The HPA-1 circuit boards have arrived from the assembly house. The first one will be in a prototype chassis and underway to Amir for review and measurements within the next hour or two. The only difference between the prototype chassis and the final chassis is that the final will be anodized after machining, whereas the prototype chassis was anodized before machining. Basically, this means all metal surfaces will be black in the final version whereas the prototype shows raw aluminum around the RCA connectors and inside the various cutouts.

Electrically the sample Amir will receive is identical to the final revision.

I will need to hang onto the sample after Amir is done with it, unfortunately. I need the demo version around for the various remaining tasks, including:
  • Getting a Performance Measurements tab going on the HPA-1 product page.
  • Getting foam inserts for the shipping box manufactured.
  • Other sundry tasks (like preparing for the Florida Audio Expo in February).
I am still expecting the final version to start shipping towards the end of January (probably 3rd week).

Tom
 
Joined
Dec 15, 2018
Messages
83
Likes
294
Location
Fremont, CA
Excellent news! I'm looking forward to seeing this under the scrutinizing gaze of Amir's APx555 =D
 

Yviena

Active Member
Joined
Jun 5, 2019
Messages
117
Likes
32
Just curious but is there any reason you decided to use 6.3mm jack instead of making space for 4-pin XLR, I know the only difference would be crosstalk/contact resistance, and it's probably not audible but it will still limit your total crosstalk to -95.
 

Schackmannen

Active Member
Forum Donor
Joined
Aug 6, 2018
Messages
163
Likes
215
Location
Tucson, Arizona
Just curious but is there any reason you decided to use 6.3mm jack instead of making space for 4-pin XLR, I know the only difference would be crosstalk/contact resistance, and it's probably not audible but it will still limit your total crosstalk to -95.
I'd imagine that only having a 4-pin XLR output would severely limit the amount of potential customers.
 

Yviena

Active Member
Joined
Jun 5, 2019
Messages
117
Likes
32
I'd imagine that only having a 4-pin XLR output would severely limit the amount of potential customers.
Hmm true but at the price point of the amp 899$ + 20% tax (if in EU) I think we can assume that most people would have adapters, or headphones with 4 pin input not that it would really matter much as long as the headphone cable itself is 4 conductor.
 

solderdude

Major Contributor
Joined
Jul 21, 2018
Messages
7,086
Likes
13,788
Location
The Neverlands
Would a crosstalk of 95dB be a real world problem ?
 

solderdude

Major Contributor
Joined
Jul 21, 2018
Messages
7,086
Likes
13,788
Location
The Neverlands
The real world problem is in the 3 wire cable and depends on common wire cable resistance vs headphone impedance.
It will be worse than -95dB
This issue is not resolved for any TRS headphone connected via an XLR to TRS adapter, only for balanced headphones.
 

Yviena

Active Member
Joined
Jun 5, 2019
Messages
117
Likes
32
The real world problem is in the 3 wire cable and depends on common wire cable resistance vs headphone impedance.
It will be worse than -95dB
This issue is not resolved for any TRS headphone connected via an XLR to TRS adapter, only for balanced headphones.
Hmm do you know if HD6xx/HD800 uses 3 wire or 4, if 3 wire would a new cable with 4 wires help?
 

Julf

Major Contributor
Forum Donor
Joined
Mar 1, 2016
Messages
2,044
Likes
2,585
Location
Amsterdam, The Netherlands
I would love to see proof that 4 wire makes an audible difference over 3 wires.
 

solderdude

Major Contributor
Joined
Jul 21, 2018
Messages
7,086
Likes
13,788
Location
The Neverlands
Hmm do you know if HD6xx/HD800 uses 3 wire or 4, if 3 wire would a new cable with 4 wires help?
Not with 300 Ohm headphones. Also the dual entry headphone cables usually have 4 wires where the returnwires are connected in the TRS plug.
Single entry (certainly those with a 3-wire connection to the cup) have a 3 wire cable.
 

solderdude

Major Contributor
Joined
Jul 21, 2018
Messages
7,086
Likes
13,788
Location
The Neverlands
I would love to see proof that 4 wire makes an audible difference over 3 wires.
Something I wrote about AQ Nighthawk cables where folks report audible differences:

Only the resistance remains. This is where the cables differ.
For the silver cable each conductor is 0.5Ω (so each driver has 1Ω in series with it)
For the gold cable each conductor is 1.6Ω (so each driver has 3.2Ω in series with it)
The driver itself has a DC resistance of 22.9Ω (left channel) and 22.1Ω (right channel)
Because the impedance of this headphone is quite linear over the entire frequency range the voltage division that occurs will also be linear over the audible frequency range.
Each cable attenuates the applied signal.
The output resistance of the test amplifier (Kameleon with 4x gain flat module) is 0.2Ω.
When the gold cable is connected the source will see 0.2Ω + 3.2Ω + 22.1Ω and the voltage across the 22.1Ω load thus is 0.866 x the source voltage. That is – 1.24dB attenuation.
When the silver cable is connected the source will see 0.2Ω + 1Ω + 22.1Ω and the voltage across the 22.1Ω load thus is 0.948 x the source voltage. That is – 0.46dB attenuation.
A difference of 0.8dB.

The audible differences between these cables, however, come from the 3-wire cable which is used. The resistance of a single return wire becomes important. Certainly for low impedance headphones as the ratio between them becomes smaller.

The difference in crosstalk between these cables is an audible 10dB. The silver cable has -34dB crosstalk and the gold one -24dB. These are audible levels and explain differences between the 2 supplied cables.
 

tomchr

Addicted to Fun and Learning
Technical Expert
Manufacturer
Forum Donor
Joined
Nov 5, 2018
Messages
523
Likes
1,594
Location
Calgary, Canada
I'd imagine that only having a 4-pin XLR output would severely limit the amount of potential customers.
Yeah. That's a non-starter. In my initial market analysis the vast majority of respondents said they didn't expect a 4-pin output on an amp at this price point. Granted, the price point in the survey was a bit lower, but still. In addition, there isn't enough room in the chassis to add another connector and I'm using the widest chassis available. I can go with a different series of chassis, but then the cost explodes. So I will save the 4-pin output for a future amp that'll be more expensive and in a larger chassis (and has yet to be even thought of in greater detail than what I've stated in this sentence).

Hmm do you know if HD6xx/HD800 uses 3 wire or 4, if 3 wire would a new cable with 4 wires help?
If the cable uses four wires, then the only shared resistance is that of the sleve of the 1/4" plug. On the Neurochrome HP-1, I measured 95 dB channel separation with the 1/4" plug and 115 dB with the 4-pin. The difference is negligible in my view.

As far as I can tell, all the HiFi Sennheiser headphones I've handled have had four conductors. This includes: HD414, HD580, HD650, HD800, HD820.

Something I wrote about AQ Nighthawk cables where folks report audible differences:
I can think of many psychological effects that would allow average humans to report hearing differences between two identical stimuli. Unless these reports of audible differences were statistically significant in a blind listening trial, I have a hard time taking them seriously. I do recognize that the individuals who report hearing the differences genuinely experience those differences. I just ask that we consider the possibility that the perceived difference may not be attributed to the stimulus. Rather, it could be attributed to cognitive psychology and humans being human.

Only the resistance remains. This is where the cables differ.
For the silver cable each conductor is 0.5Ω (so each driver has 1Ω in series with it)
For the gold cable each conductor is 1.6Ω (so each driver has 3.2Ω in series with it)
What blows my mind is that one could have achieved the same reduction in resistance by just using heavier gauge copper, which is considerably less expensive than gold.

Tom
 
Last edited:

HammerSandwich

Addicted to Fun and Learning
Forum Donor
Joined
Nov 22, 2018
Messages
765
Likes
869
What blows my mind is that one could have achieved the same reduction in resistance by just using heavier gauge copper, which is considerably less expensive than gold.
But that would be elegant, thoughtful engineering, and everybody knows that high-end is all about MORE IS MORE.
 

solderdude

Major Contributor
Joined
Jul 21, 2018
Messages
7,086
Likes
13,788
Location
The Neverlands
What blows my mind is that one could have achieved the same reduction in resistance by just using heavier gauge copper, which is considerably less expensive than gold.
The whole 'object of the AQ game' is to provide some 'proof' to the differences between the used cables. The goldplated connectors with copper cable inside is supposed to be the 'poorer' sounding one. The goal here is to 'promote' their silver cable as being the better one.
The 'gold plated' nice looking one is supposed to be as 'good' as the gold plated cables that are usually supplied with headphones.

If there are any audible differences they most likely come from bias but the 24dB vs 34dB channel separation might be audible.
Also the channel separation is not crosstalk but sort-of an inverse crosstalk where the mono parts are lowered relative to the stereo signal.
With normal crosstalk the signals of L and R are added/combined.
It is fun to make a small adapter with the common wire being a potmeter of say 100 Ohm and using a 300 Ohm headphone to explore the effect of the common return wire issue.
 
Last edited:

tomchr

Addicted to Fun and Learning
Technical Expert
Manufacturer
Forum Donor
Joined
Nov 5, 2018
Messages
523
Likes
1,594
Location
Calgary, Canada
But that would be elegant, thoughtful engineering, and everybody knows that high-end is all about MORE IS MORE.
Well, for some it certainly is. I prefer to back up my claims with measurements to show of the quality of my products. Some would rather back their claims up with exotic materials, marketing verbiage, etc. I'm sorta ok with that, though, I would prefer that marketing claims were based in fact. With accurate information available, the consumer can make the purchasing decisions that best suits them.

Tom
 

solderdude

Major Contributor
Joined
Jul 21, 2018
Messages
7,086
Likes
13,788
Location
The Neverlands
I agree.. but fear that most money can be made by bullshitting people in a believable way as people really want the flowery talk to be true..
Most ASR members don't want the BS but the rest of the world gobbles it up.
 

HammerSandwich

Addicted to Fun and Learning
Forum Donor
Joined
Nov 22, 2018
Messages
765
Likes
869
I'd much rather start the next Acoustic, not Synergistic, Research. I feel Tom shares the same philosophy. Which is why I'm more likely to buy his products.
 

Julf

Major Contributor
Forum Donor
Joined
Mar 1, 2016
Messages
2,044
Likes
2,585
Location
Amsterdam, The Netherlands
I'd much rather start the next Acoustic, not Synergistic, Research. I feel Tom shares the same philosophy. Which is why I'm more likely to buy his products.
Hear hear!
 
Top Bottom