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

tomchr

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#41
1 million point FFT is brutal in the way it digs deep to find even the tiniest hints of distortion/spurious response.
That's the whole point! You want to dig out those harmonics. Do note that both amps are quite close to clipping. It'd be insightful with a measurement, say, 3-6 dB down from clipping.

Interesting to note the difference in the harmonic structure between the two amps.

Here is the same measurement as above but with Audio Precision APx555 measuring itself in loopback mode:
Great... I have analyzer envy now. My APx525 is good ... but not this good. The 555 had just been released when I bought my 525 (and promptly lost a few nights of sleep).

Tom
 

tomchr

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#42
DIY designers aren't "hobbyists" if they have a wealth of experience in design. Still, what Tom has done is really exceptional. Everyone benefits from having a team helping out, if only to point out things that go unnoticed. It's a lot of hats to wear- designer, buyer, project scheduler, builder, marketer. Color me impressed.
Thank you. Don't forget to mention that I'm a full-time student (BA Psychology, honours) too. I'm adding some social skills to my engineering skills. :) After I graduate in April, I'll push on my business full time.

Tom
 
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amirm

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Thread Starter #43
That's the whole point! You want to dig out those harmonics.
I realize that and use 256 k point for my DAC FFTs. The issue with it is that the data "bothers the eye" much more than ear as I usually say. People see those spikes and think they are going to hear them and will be bothersome. So I tend to balance resolution of measurements to show issues but not go to the extreme. Of course when troubleshooting, then going all out is fine as I did in this case.
 

tomchr

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#44
I would say outsource the non-critical stuff such as the case work to some China factory [...]
And then assemble the complete system in Canada.
That's one option. There're some options out of Japan as well. And Italy for that matter. Finally, I'd probably check out Radison Ltd. in Toronto. It'd be nice with a domestic option to lower shipping cost and eliminate customs fees.

Tom
 
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Thread Starter #45
Do note that both amps are quite close to clipping. It'd be insightful with a measurement, say, 3-6 dB down from clipping.
They were but that is what you told me to do. :) I have taken apart the THX 789 for my tear down. I will put it back together tomorrow and run new tests after that.
 

tomchr

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#46
I realize that and use 256 k point for my DAC FFTs. The issue with it is that the data "bothers the eye" much more than ear as I usually say. People see those spikes and think they are going to hear them and will be bothersome. So I tend to balance resolution of measurements to show issues but not go to the extreme. Of course when troubleshooting, then going all out is fine as I did in this case.
Fair enough. In case of the HP-1 there isn't much to dig out, though. You just want enough spectral resolution that you can actually see stuff.

DACs and their spurs may be another animal.

Tom
 

tomchr

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#47
They were but that is what you told me to do.
I know. I'm not complaining. I just realized I'd asked for the wrong thing, that's all. I'm used to being the one turning the knobs... :)

Shocking concept: Ask for what you want. You'll improve your odds of getting it. Here's what I would like: 200 mW into 32 Ω and 200 mW into 300 Ω on 1M FFT, 8 averages. Please. No rush.

Tom
 
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Thread Starter #48
200 mW into 32 Ω and 200 mW into 300 Ω on 1M FFT, 8 averages. Please. No rush.
Will do tomorrow. Note that the AP only has 300 ohm built-in so for 32 ohm I use my dummy load fixture which may add a bit of noise to the analysis.
 
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#50
Totally agree. Those small Alps pots are terrible in terms of longevity. I replace them all the time in consumer level gear as they fracture, separate and get torn off the boards. Often the aluminium rivets in the corners split the plastic. I sincerely hope there is a nut and washer under that little knob.

The balanced headphone jack should have countersunk screws that match the other screws as a bare minimum.

The 6.35mm PCB mount headphone socket appears to eschew any type of physical mounting other than the PCB solder joints and perhaps some plastic spigots through the board? It's designed to utilize a nut to hold it to a metal sub chassis, behind the front panel- is there one? Bear in mind, those sockets get a hammering and dry joints will happen without adequately secured sockets. I know, I fix them all the time.

The PCB mount toggles are relying 100% on the solder joints for mechanical support (un-threaded collars and no nuts) and will fracture down the track. The single solder pin 'anchor' point at the front of those switches is manifestly inadequate IMO, the number of them I see loose in PCBs on modern gear- especially PbFree, makes me angry.

All these criticisms are justified. It is marketed and reviewed here as a USD$1249 retail product, let's not forget that.

Absolutely agree with this post, it shows technical experience on prehistoric mechanical potentiometers, but not only that...

I refuse to buy “any” gear that uses them. It’s a kick in the guts especially for high end with the mega dollars to go with it regardless of performance becuase using a prehistoric mechanical potentiometer will be the weakest link!

In today’s electronics there’s many ways to get around prehistoric components that exhibit wear and tear from day one! a lesson learnt over 30yrs of DIY. Even volume control chips such as Cirrus 3310 or the BB PGA 2310 will wiped the floor on any mechanical volume pots. That include all Alps, Allen Bradley, TKD and the like. Whether they’d be carbon or plastic film, they will all degrade from the initial physical turn regardless of what people claim.

I built 2 identical Preamp 9mths apart. The 2nd destroyed the 1st on SQ after initial turn on. All components are the same. Replacing the volume potentiometer on the 1st Preamp brought the SQ up to matched the 2nd Preamp. I spent the next 30yrs playing with different types of potentiometers. Even bought a NAD M51 and used that to control volume on a power amplifier. Today anyone who design preamps without considering digital control volume chips are not even in the race. Today I use a Preamp that uses a BB PGA 2310 and will never look back! The advantages are all there, last the life of the product with perfect balance throughout the entire volume range, everytime!

Even Elector Magazine had a project to replace all mechanical volume pots in the mid 80s in studio recording consoles.
 
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tomchr

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#51
Absolutely agree with this post, it shows technical experience on prehistoric mechanical potentiometers, but not only that...

I refuse to buy “any” gear that uses them. It’s a kick in the guts especially for high end with the mega dollars to go with it regardless of performance becuase using a prehistoric mechanical potentiometer will be the weakest link!
That could be. However, how do you get an encoder to "feel" right? How do you move users past the experience of the "infinite turns" volume knob? Life as we know it will never be the same. :)

From a DIY perspective, using the volume control chips means the project now requires a micro controller, which adds another layer of complexity. The programming and digital design is trivial. Making it a turnkey DIY solution is much harder.

Tom
 

JJB70

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#52
A tremendous amplifier design for sure but I am with those who have recommended giving more attention to the case and industrial design. At that price point you're mixing it with products from manufacturers such as RME, Spl and Violectric who put a lot of effort into the tactile touch quality of their products and very high standards of casing design and construction. This amp is clearly a superb design, it would be sad if it lost out just on the basis of alternatives feeling more expensive.
 

andymok

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#53
To be fair AAA 789 spec changed in mid way, it could have been even more powerful

But I'm very happy to see both such high performance designs available at low cost / DIY. At work, I have the chances to play with Pyramix and Hapi interface, but I've never been able to do proper headphone monitoring on them. It would be such a waste not to drive these amp with those wonderful D/A, even better if these amp can turn into a distribution amp for musicians :p

Such small footprint is also great for location recording/monitoring too!
 
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tomchr

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#56
LOL. There's too much individual variability in bananas for them to be used as a reliable scale indicator. I usually use a hockey puck. :)
 
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#57
I'd like to take the opportunity to ask you folks here: If I was able to make a headphone amp available in a prettier case, with a volume knob that felt right, and that would provide the same performance (except likely lower output power) for around $500-600, would you be interested?
I think $600 is a good price point that while still expensive is more accessible than +$1k offerings. While I kinda like the looks of the amp as is I do think the appeal would be much greater if the look and feel was improved. Peoples perceived value is tied very closely to aesthetics.

Design the casework and controls to look and feel like something really special. Make it beautiful. Make it so people want to touch it, take it home and show it to their wife.
I can't agree more with this. I think if you can pull this off you'll be golden. Of course pulling that off with quality internals at a lower price point is the tough bit...
 
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#59
That could be. However, how do you get an encoder to "feel" right? How do you move users past the experience of the "infinite turns" volume knob? Life as we know it will never be the same. :)

From a DIY perspective, using the volume control chips means the project now requires a micro controller, which adds another layer of complexity. The programming and digital design is trivial. Making it a turnkey DIY solution is much harder.

Tom
An excuse to Getting over the “feel” of rotory encoder is a false sense of security. What has the quality of “feeling” ie rotational mechanical dampening has to do with SQ and the way it last? 100% of your signal will flow through that control! What you do here colours the sound big time!

I’ve been to Hifi show where there is a smorgasboard of headphone gear including some of the exotic sort after Amps to drive electrostatic. Mega dollars worth of equipment. Way beyond my pay grade! When you plug a Beyerdynamic T90 or a AT50THX into an iPhone * that “has no expensive quality rotation”. I questioned myself as to why should I purchase any of these gear on display. I took a friend who was just getting into HiFi and was 20yrs younger, his words “ the iphone is pretty good! “.

I was about to engage in coding a micro for the BB PGA 2310 but that got canned becuase I was offered a Preamp at a 1/3 of the cost! Yes, it’s a PITA and you need a separate regulated supply to run it, additional layer of complexity in my opinion well worth the take up. Today there are many products using the PGA2310 as volume control, and you’ll see many dac manufacturers introducing all sorts getting around this PITA primitive component. If you Google digital volume you’ll see a stack of volume control products and they are not expensive. However you can pay $300-500 for a stepped attenuators with gold contacts!

You have to wonder why Greats like Nelson Pass uses a Muse volume control chip in his top of the line Preamp. That speaks volumes.
 

restorer-john

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#60
You have to wonder why Greats like Nelson Pass uses a Muse volume control chip in his top of the line Preamp. That speaks volumes.
Nelson Pass uses an Alps Blue analogue volume pot in his $3500 hpa-1 headphone amplifier. That is what we are talking about here in this thread.

https://www.passlabs.com/amplifier/hpa-1

616passlabs.inside.jpg


"The volume control is a top-line Alps potentiometer, and the board is replete with metal-film resistors and other premium parts."
 
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