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

[tomchr]

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?

The mechanical feel of the volume knob doesn't have anything to do with the sound quality. The size of the pot or the volume knob have noting to do with sound quality either. Aesthetics also have no impact on the sound quality. Yet, these are the main points of critique of the HP-1 (including in this thread). Humans are not rational critters. That's one of the reasons I'm studying psychology.

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!

About 10-12 years ago, I designed a preamp that used the PGA2320. I still have it. It works quite well. The PGA2320 is a bit noisy, but better options are available that I could use instead.

If you're going for an electronic volume control, I think it makes sense to take a full step and include a remote control. That opens up another can of worms. I have yet to find a manufacturer or vendor that offers a nice remote control handset. Again, the quality of the remote has nothing to do with the sound quality but everything to do with the user experience (which will impact their perception of the sound quality).

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.

Not really. Have you looked at the performance of the Pass gear? JFET buffers with 0.1-1% THD at line level. Not my cup of tea. Then again, he's made a small fortune selling that gear and I haven't, so what does that tell you?

Also, the argument that volume pots degrade sound quality doesn't hold water. As you can see from Amir's measurements, it's perfectly possible to get good performance even with a volume pot in the signal path.

Tom

 

[restorer-john]

What has the quality of “feeling” ie rotational mechanical dampening has to do with SQ and the way it last?

Clearly you don't understand the term 'last'. Analogue volume pots last for many decades, in fact I have plenty of 30, 40 and 50 year old Alps pots inside gear that are as good as the day they were made. Die cast Alps Black beauties in TOTL integrated and preamplifiers that still exhibit their 'guaranteed error' of a fraction of a dB. Alps blues last for decades too.

Rotary encoders on the other hand are rubbish. I've got all sorts of gear with encoders on it. There's only one I like and that uses twin PD array interrupters and a large flywheel on a lubricated sleeve bearing and a heavy knob. That's on a TOTL digital tuner and it feels perfect.

In general, rotary encoders are cheap plastic. They fail prematurely and you can almost guarantee total mechanical and electrical failure in 10-15 years. They wiggle and have zero precision feel to them. And, they need a micro with all the associated crap that goes with that. Those micros are bespoke and unrepairable down the track. The Muses chip is just the latest flavour-of-the-month volume chip with nice specs. It too, will be gone soon enough and gear that uses it, will be unrepairable.

I looked at a (AU$1999) Onkyo two channel integrated amplifier just the other day with pretensions to quality. The big volume knob was wiggly, lacked feel and used an encoder. Under the flap were a few plastic buttons. My partner thought it looked and felt cheap too.

 

[restorer-john]

Also, the argument that volume pots degrade sound quality doesn't hold water. As you can see from Amir's measurements, it's perfectly possible to get good performance even with a volume pot in the signal path.

100% true. Your headphone amplifier's performance, particularly the pot's channel tracking is amazing. The gang error is virtually non-existent at a max of 0.5dB through the travel.

Proponents of switched attenuators and Muses driven complexity haven't ever built or repaired such devices down the track. Switched attenuators, regardless of the exotic contact material used, end up giant intermittent switch arrays, in time IME.

 

[JJB70]

The mechanical feel of the volume knob doesn't have anything to do with the sound quality. The size of the pot or the volume knob have noting to do with sound quality either. Aesthetics also have no impact on the sound quality. Yet, these are the main points of critique of the HP-1 (including in this thread). Humans are not rational critters. That's one of the reasons I'm studying psychology.

Indeed, yet these things often make the difference. There is a pleasure of ownership, in my case I'm not the golden eared type and find that most DACs and amplifiers are transparent (although even my cloth ears can appreciate good headphones and speakers), despite that I would buy something like an Accuphase amp simply because I just find something beautiful about the craftsmanship and absolute quality of gear like that. One reason I'm loathe to change my Sony amplifier is that to get anything like the level of quality that Sony built into their ES products in the 80's and early 90's would cost me serious money and the perfectly weighted feel of the controls, the finish, the materials used etc still makes me smile and feel a sense of satisfaction that may sound silly but is real to me.
At this price point you are above the level of the cheap n'cheerful sort of product where good performance at low price excuses a cheap feel (even then, personally I'll be interested to see if JDS suffer any push back for using plastic for the case of their new amp despite it's tremendous performance - cost). If I was going to buy a headphone amp for this price I'd really expect it to have the feel of my beloved Sony ES gear, or Accuphase or other high quality gear (although really, if you want to sell to me put some analogue VU meters on it ).
Hopefully this is seen as helpful, as I really am impressed by the measured performance here, it is clearly a splendid design.

 

[amirm]

Having had the unit in person, I don't see it as feeling cheap. It is not luxurious but that I consider a property of gear costing thousands of dollars.

From the pictures, the sturdy feel of the unit does not come across.

 

[graz_lag]

A jewel of this caliber in the hands of the mktg gurus of some esoteric brands, after working it out a bit in terms of manufacturing ... We would see it at twice the price, if not more ...

Thank you so much for sharing with us the passion you have for your work and the knowledge you clearly put into it.

 

[restorer-john]

If I was going to buy a headphone amp for this price I'd really expect it to have the feel of my beloved Sony ES gear, or Accuphase or other high quality gear

My Accuphase C-11 preamplifier ($3500 in 1991) uses a motorised Alps Blue pot and a heavy solid aluminium knob. All my Sony ES preamps/integrateds use the Alps Blue. Even the headphone level controls on the TOTL CD players use the same pot. Marantz used it in their PM-94 ($3500) and PM-95 ($6000) statement amplifiers. All of those pieces have that 'feel' we are talking about.

It's so much the standard, that reviewers mention it, and the Chinese copy them in vast numbers. Have a look on eBay for Alps RK-27 pots- they are mostly all fakes. They even fake the RK-271xx motorised units.

Noble was another Japanese maker of superlative performance die-cast with conductive film pots in the 80s and 90s. I don't know what happened to them.

 

[tomchr]

Proponents of switched attenuators and Muses driven complexity haven't ever built or repaired such devices down the track. Switched attenuators, regardless of the exotic contact material used, end up giant intermittent switch arrays, in time IME.

I looked at the MUSES72320. Like many of JRC's components, it's decent but not fantastic. 0.001 % THD (1 kHz, 1 V, 30 kHz BW) and 10 uV RMS (A-weighted) noise is good but not excellent. The CS3318 is better spec'ed, tighter production tolerances, and about the same price.

Douglas Self notes in his Small Signal Audio Design book that relay-based attenuators are great on audio performance, but customers tend to complain about the clickity-clack of the relays when they change the volume.

Tom

 

[solderdude]

I have a 30 year old (DIY) pre-amp and it has been in use for the last 30 years continuously.
Had to replace 1 op-amp (got noisy) and 1 small signal relay over time but the ALPS Blue pot is still working perfectly, scratch and noise free for all that time.

Nice (electronic) design Tom, would have liked to see a 'nicer' front layout and volpot-knob.

Have built quite a few devices with RK097 over the years and found that some were not well matched (L and R) in the lower volpot range and 2 have gone scratchy on me. Not a bad pot but it's size is the reason for channel imbalance at the bottom of the volpot range.

 

[restorer-john]

If you're going for an electronic volume control, I think it makes sense to take a full step and include a remote control. That opens up another can of worms. I have yet to find a manufacturer or vendor that offers a nice remote control handset.

But it's a headphone amplifier. The user is only going to be 3 to 5 ft away from it and surely wouldn't need remote volume? Are people really that lazy?

If you put a back mounted line out on it, then you've got a preamplifier, and your remote controlled can of worms alright.

I agree with remote handsets, why can't anyone make really nice ones? Look at Sony, regardless of price, they haven't made a nice one in...forever. Apple made ones so small even kids hands were too big for them. A few anodised satin finish ones that get wrecked the first time they slip of the arm of your sofa.

In an effort to make remotes 'feel' more substantial, many of the big names resorted to 'tricks'. Even Accuphase were not immune. They put scrap steel weights in the otherwise lightweight remote handsets to give 'weight' which is associated with quality.

Here's one I prepared earlier (a Cambridge Audio Azur 751BD)

Reviewers commented on the 'feel of the substantial remote'. I was suspicious, as I know that molding is a cheap-ass Chinese standard remote. So here's the truth, 181 grams total, of which 61 grams (over a third) is scrap steel used as ballast.

 

[restorer-john]

10 uV RMS (A-weighted) noise is good but not excellent.

You have an order better at 1uV. 1uV is really SOTA.

 

[Addicted to music]

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


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

Here’s SMSL M9 that uses a PGA 2311 at $402 US. And look at its size and the way they have implemented. Not hard to do to look away from that old fashion mind set and move on.

I won’t buy products with any mechanical volume pots, I’ve moved on so if Nelson Pass wants me to buy that he either needs to modify it and use what me uses in his top of the line Preamp... it’s not hard!

Hence this Pass Lab head amp won’t be on my shopping list....

 

[danadam]

I learned about Tom in chasing a review he had done of a passive volume control.

Did you catch the review? Link maybe

 

[Addicted to music]

But it's a headphone amplifier. The user is only going to be 3 to 5 ft away from it and surely wouldn't need remote volume? Are people really that lazy?

If you put a back mounted line out on it, then you've got a preamplifier, and your remote controlled can of worms alright.

I agree with remote handsets, why can't anyone make really nice ones? Look at Sony, regardless of price, they haven't made a nice one in...forever. Apple made ones so small even kids hands were too big for them. A few anodised satin finish ones that get wrecked the first time they slip of the arm of your sofa.

In an effort to make remotes 'feel' more substantial, many of the big names resorted to 'tricks'. Even Accuphase were not immune. They put scrap steel weights in the otherwise lightweight remote handsets to give 'weight' which is associated with quality.

Here's one I prepared earlier (a Cambridge Audio Azur 751BD)

Reviewers commented on the 'feel of the substantial remote'. I was suspicious, as I know that molding is a cheap-ass Chinese standard remote. So here's the truth, 181 grams total, of which 61 grams (over a third) is scrap steel used as ballast.

View attachment 17810

View attachment 17811

View attachment 17812

View attachment 17813

The problem with remote controls is that the buttons wear out!

 

[jsmiller58]

I am sure I am missing lots of stuff in this whole knob brouhaha... but I have to admit it is some fun to see what I assume are mostly grown men so passionate about a knob... kind of reminds me of watching Zeos... now there is someone with serious issues with knobs. Anyway, I will sit back, watch, and eat some popcorn...

Oh, and Tom, in my very uneducated opinion, nice product. You should be commended for your creativity and the courage to put yourself out there and offer your creation for others to decide if they like it or don’t, will buy it or won’t. And I am impressed with the mature and good spirited way you seem to be taking the passionate feedback.

 

[tomchr]

But it's a headphone amplifier. The user is only going to be 3 to 5 ft away from it and surely wouldn't need remote volume? Are people really that lazy?

Given that a remote is one of the most common requests, I'd say yes. Also, I'm about 2.5 m away from my headphone amp. My arms aren't quite that long.

Tom

 

[tomchr]

Did you catch the review? Link maybe

Probably this one: https://www.neurochrome.com/tortuga-audio-ldr3/

"Passive" should be taken with a grain of salt. There're no active parts in the signal path but the device does consume power.

Tom

 

[tomchr]

I am sure I am missing lots of stuff in this whole knob brouhaha... but I have to admit it is some fun to see what I assume are mostly grown men so passionate about a knob... kind of reminds me of watching Zeos... now there is someone with serious issues with knobs. Anyway, I will sit back, watch, and eat some popcorn...

Welcome to Audio. I must admit that the first time this was brought up with me, I'm pretty sure I developed some serious bruising from the face-palms. Then again, market says, "we want pretty knobs that feel right". It would behove me to listen rather than to argue.

Oh, and Tom, in my very uneducated opinion, nice product. You should be commended for your creativity and the courage to put yourself out there and offer your creation for others to decide if they like it or don’t, will buy it or won’t. And I am impressed with the mature and good spirited way you seem to be taking the passionate feedback.

Thank you. I do my best to listen to criticism, even if it isn't presented constructively. It seems like the culture here is mostly constructive, though, so all is well.

Tom

 

[restorer-john]

...Here’s SMSL M9...

It looks like a cheap Chinese iPhone dock. At 397 grams, you couldn't plug a headphone plug into it without it skating across the desk.

I actually prefer the look of Tom's headphone amplifier to that SMSL thing, knob and all.

 

[jsmiller58]

Welcome to Audio. I must admit that the first time this was brought up with me, I'm pretty sure I developed some serious bruising from the face-palms. Then again, market says, "we want pretty knobs that feel right". It would behove me to listen rather than to argue.



Thank you. I do my best to listen to criticism, even if it isn't presented constructively. It seems like the culture here is mostly constructive, though, so all is well.

Tom

Oh, I agree. The culture here is great. But this seems to have really touched a nerve. And I’m not beyond enjoying watching a little food fight now and then...