• 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 Modulus-286 Amp

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
21,448
Likes
29,446
Location
Seattle Area
#61

tomchr

Technical Expert
Technical Expert
Manufacturer
Joined
Nov 5, 2018
Messages
248
Likes
702
Location
Calgary, Canada
#62
According to the data sheet for the Hypex NC252, the Hypex is 14 dB higher distortion than the MOD286.

Tom
 

rebbiputzmaker

Addicted to Fun and Learning
Joined
Jan 28, 2018
Messages
751
Likes
127
#64
Yes you did. You said it was a garden variety DIY amplifier.
Not what I said at all. If you misunderstand my comment, please ask for clarification.

My comment. "This amp is a fancy gain clone. Have built several, they were popular maybe 10 years ago. "

Gain clones were not necessarily ever "garden variety" amps, some can be sophisticated like the one you tested. This is what I was saying. As far as diy, Tom and his designs have been part of diyaudio.com for years. He has advanced the concept and quality of these amps a great deal.
 

tomchr

Technical Expert
Technical Expert
Manufacturer
Joined
Nov 5, 2018
Messages
248
Likes
702
Location
Calgary, Canada
#65
By your definition, I guess a Ferrari is a fancy Lada as both have four wheels.

My Modulus-series of amplifiers uses the LM3886. That's the only thing they have in common with the Gainclone. The power output comes from the LM3886, but the precision from an LME49720. It's a completely different architecture than a Gainclone.

Tom
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
21,448
Likes
29,446
Location
Seattle Area
#66
Not what I said at all. If you misunderstand my comment, please ask for clarification.
The day I misunderstand your comment or better said, your intent, is the day I forget my own name. Your comments are not constructive, and disrespectful. Move along please.
 

VeerK

New Member
Joined
Jan 29, 2019
Messages
4
Likes
7
#67
Been following Tom's work casually for a while, and when I found out ASR was going to review a Neurochrome, lets just say I've been anticipating this review.

From what I could understand, it seems that most of the "issues"in this review are caused by the SMPS perhaps due to its location, etc. I can't claim to understand the specifics of mains leakage. My original plan has been to build a pair of 686s due to the price being lower DIYing it, and I was going to build the lower power 28V version with the Antek transformers. Would there be any discernible benefit going that route vs SMPS, at least in the context of this review?

On a side note, big thanks to Amir for making a tangible shift in the audiophile review world, I was introduced to ASR through Reddit and I've been a fan since. Additionally, big thanks to TomCR for being a present figure in the DIY community, and submitting his work to be reviewed here. I'm a speaker guy, so Neurochrome amps have been on my to-do list for a while.
 

tomchr

Technical Expert
Technical Expert
Manufacturer
Joined
Nov 5, 2018
Messages
248
Likes
702
Location
Calgary, Canada
#68
From what I could understand, it seems that most of the "issues"in this review are caused by the SMPS perhaps due to its location, etc.
Yeah. The power supply and its location are the limiting factors in this build. That said, the 'issues' are all well below audible and the amp is a stellar performer. But if one is willing to give up on the compact form factor, you can make different compromises and get the last bit of mains hum below the noise floor.

My original plan has been to build a pair of 686s due to the price being lower DIYing it, and I was going to build the lower power 28V version with the Antek transformers. Would there be any discernible benefit going that route vs SMPS, at least in the context of this review?
For Burning Amp 2018, I put together four Modulus-686 amps in ModuShop 3U x 330 x 300 mm chassis powered by Mean Well RPS-400-27-C power supplies. You can see pictures of the first one below. The supplies provide ±27 V when used with my Mean Well Control board. The amps provide 2x130 W into 8 Ω and 2x200 W into 4 Ω. I needed to be able to transport two of these amps in a suitcase without hitting the 21 kg weight limit, so transformers were not an option. I also find that the Modulus amps provide the same or better performance on an SMPS as they do on a transformer-based supply. The only exception would be short-term overload, where the transformer-based supply acts more gracefully. The SMPS will shut down when the over-current limit is reached whereas the transformer-based supply will just sag. I don't recall ever hitting the over-current limit on the MOD686 build, except with 2 Ω load. I don't recommend operating the Modulus-686 with a 2 Ω load as the power dissipated gets insane. The amp is stable with a 2 Ω load, so I have no concerns aside from the power dissipation.
I have no concerns with using a transformer-based power supply. My Power-686 will happily feed a stereo pair of Modulus-686. If you'd like more capacitance than the 4x22000 uF my Power-686 provides, you can use one Power-686 per channel.
I really like the ±27-28 V operating point. It makes for an amp that provides good power with a thermal system that is still manageable. I call it the safe-n-sane build. Those who want to push it to the full 240 W (8 Ω), 360 W (4 Ω) will need ±36 V and 4U heat sinks.

Tom
 

Attachments

tomchr

Technical Expert
Technical Expert
Manufacturer
Joined
Nov 5, 2018
Messages
248
Likes
702
Location
Calgary, Canada
#70
Amplifier modules: Currently on sale at $449/each
MW Control PCB: $199 if you have me assemble it. $80-90 if you assemble it.
Chassis: $400ish (I modify all panels except the top, which drives up the cost)
Power supplies: $80/each
Connectors, wire, etc.: $80ish
TOTAL: $1740ish (less if you DIY everything)

I'll be happy to share the CAD drawing for the chassis when you place your order.

Tom
 

Toku

Active Member
Joined
Apr 4, 2018
Messages
248
Likes
158
Location
Japan
#71
Although it may be cheap for rich in USA and Canada,
It is not a price that I can buy very much.
 
Joined
Nov 18, 2018
Messages
34
Likes
36
#74
Amplifier modules: Currently on sale at $449/each
MW Control PCB: $199 if you have me assemble it. $80-90 if you assemble it.
Chassis: $400ish (I modify all panels except the top, which drives up the cost)
Power supplies: $80/each
Connectors, wire, etc.: $80ish
TOTAL: $1740ish (less if you DIY everything)
Obviously the chassis is a non-trivial component of the cost. Tom, you're using the Mini Dissipante 3U 300x330, right? If so, note the base price is $179, so over half the cost Tom quoted above is for custom machining. You can save a lot by doing the machining yourself, or, just go with less machining. I'm using the 2U version of that chassis for my Mod86 build, and I had them machine only the back panel (XLRs, speakers, IEC). That minimal machining was only an extra $50.

Note that if you use the Mini Dissipante chassis with a transformer-based power supply, I highly recommend getting the steel base plate, as it adds a much-needed amount of strength and rigidity to the case.

I haven't looked, but I'd be willing to bet you could get an even cheaper case from China (ebay/aliexpress). Cheaper still would be to simply buy the required heatsinks, then build a wooden chassis around those (somewhere on diyAudio someone did that with a Mod86 build).
 
Joined
Nov 18, 2018
Messages
34
Likes
36
#76
If you have all the tooling and know what you're doing. Otherwise you'll likely spend hundreds on tools, mess it up and have to fork out for more casework to replace the stuff you ruined! :D:D:D
No doubt there, that's a general risk for any kind of DIY.

I've personally found that drilling aluminum cases isn't too terribly hard, though, especially simple circles. I just use a regular hand-held drill and standard drill bits. I first cover the aluminum with masking tape. This prevents scuffs and scratches during drilling, and also gives me something to draw on. I draw and annotate all the cuts I intend to make. Measure thrice, cut (or drill) once! I just clamp the aluminum to a piece of scrap wood so the aluminum doesn't bend while I'm drilling it. Then I use a deburring tool (here's an example) to clean up and smooth over the rough edges of any cuts. This results in pretty decent holes, and any remaining imperfections get covered up by whatever goes in the hole anyway.

As you get over 1/2" or so in size, drill bits get expensive. So, for XLR hole cutouts, I spent the money on a punch. I build enough audio electronics that it's paid for itself.

If you want to machine non-circles, it does get trickier. For me, the only non-circle I need is the IEC cutout. What I've found is that the cheap Chinese chasiss almost always come with the IEC cutout. Also, if the aluminum is thin enough, you can use a cheap handheld nibbler tool to make non-circular cutous. However, if I'm going for something a bit nicer, I'll spend the cash to have it machined professionally (e.g. diyAudio store, Front Panel Express). But I've also gone without an IEC completely, and just had the power cable permanently attached, going through the chassis via simple circular cutout with a grommet (and an internal cable clamp).

If you have zero chassis-working experience, you probably don't want to make your first attempt at metalwork on something as nice as the Mod-686. In that case, either pay for someone to do it for you, or first spend some time practicing on cheaper builds.

Oh, there is yet another way to really save on the chassis: hit up thrift shops on a regular basis, and wait for some cheap/old used components that have an appropriate chassis you can re-use. I see people on diyAudio doing this fairly often. If you have the heatsinks, you could even use something like an old PC chassis!
 

rebbiputzmaker

Addicted to Fun and Learning
Joined
Jan 28, 2018
Messages
751
Likes
127
#77
No doubt there, that's a general risk for any kind of DIY.

I've personally found that drilling aluminum cases isn't too terribly hard, though, especially simple circles. I just use a regular hand-held drill and standard drill bits. I first cover the aluminum with masking tape. This prevents scuffs and scratches during drilling, and also gives me something to draw on. I draw and annotate all the cuts I intend to make. Measure thrice, cut (or drill) once! I just clamp the aluminum to a piece of scrap wood so the aluminum doesn't bend while I'm drilling it. Then I use a deburring tool (here's an example) to clean up and smooth over the rough edges of any cuts. This results in pretty decent holes, and any remaining imperfections get covered up by whatever goes in the hole anyway.

As you get over 1/2" or so in size, drill bits get expensive. So, for XLR hole cutouts, I spent the money on a punch. I build enough audio electronics that it's paid for itself.

If you want to machine non-circles, it does get trickier. For me, the only non-circle I need is the IEC cutout. What I've found is that the cheap Chinese chasiss almost always come with the IEC cutout. Also, if the aluminum is thin enough, you can use a cheap handheld nibbler tool to make non-circular cutous. However, if I'm going for something a bit nicer, I'll spend the cash to have it machined professionally (e.g. diyAudio store, Front Panel Express). But I've also gone without an IEC completely, and just had the power cable permanently attached, going through the chassis via simple circular cutout with a grommet (and an internal cable clamp).

If you have zero chassis-working experience, you probably don't want to make your first attempt at metalwork on something as nice as the Mod-686. In that case, either pay for someone to do it for you, or first spend some time practicing on cheaper builds.

Oh, there is yet another way to really save on the chassis: hit up thrift shops on a regular basis, and wait for some cheap/old used components that have an appropriate chassis you can re-use. I see people on diyAudio doing this fairly often. If you have the heatsinks, you could even use something like an old PC chassis!
All good suggestions. Greenlee punches are a good investment if you plan on doing more diy. I have had luck over the years with ebay for punches and other industrial type tools. Have also had luck finding heatsinks. I have not used an old pc chassis, but that is a good Idea. I have repurposed old audio equipment, dead amps etc, to build with.
 

invaderzim

Senior Member
Joined
Aug 30, 2018
Messages
320
Likes
508
Location
NorCal
#78
Although it may be cheap for rich in USA and Canada,
It is not a price that I can buy very much.
"Cheap" is a relative term. They are inexpensive compared to some similar offerings but that doesn't mean they are pocket change for most people.
 

DDF

Active Member
Joined
Dec 31, 2018
Messages
257
Likes
244
#79
When I built my NCore NC400 amp in a good quality Al chassis (reasonably thick), I found a Ti step drill bit to be a very worthwhile investment.

I used this very cost effective version and it produced high quality holes that were easy to debur with a hand file:
https://www.amazon.com/Neiko-10194A-Titanium-Drill-Speed/dp/B000FZ2UOY

Its a bit of a slow process and I can't say if this bit would last over a large number of chassis, but for a few chassis, it worked out well and was very economical.

I attached a picture of the results I was able to obtain with a hand drill and a vice only, as I didn't have access to a drill press. The notches in the large holes were added by hand on purpose later for the Neutrix connectors used.
 

Attachments

VeerK

New Member
Joined
Jan 29, 2019
Messages
4
Likes
7
#80
Yeah. The power supply and its location are the limiting factors in this build. That said, the 'issues' are all well below audible and the amp is a stellar performer. But if one is willing to give up on the compact form factor, you can make different compromises and get the last bit of mains hum below the noise floor.


For Burning Amp 2018, I put together four Modulus-686 amps in ModuShop 3U x 330 x 300 mm chassis powered by Mean Well RPS-400-27-C power supplies. You can see pictures of the first one below. The supplies provide ±27 V when used with my Mean Well Control board. The amps provide 2x130 W into 8 Ω and 2x200 W into 4 Ω. I needed to be able to transport two of these amps in a suitcase without hitting the 21 kg weight limit, so transformers were not an option. I also find that the Modulus amps provide the same or better performance on an SMPS as they do on a transformer-based supply. The only exception would be short-term overload, where the transformer-based supply acts more gracefully. The SMPS will shut down when the over-current limit is reached whereas the transformer-based supply will just sag. I don't recall ever hitting the over-current limit on the MOD686 build, except with 2 Ω load. I don't recommend operating the Modulus-686 with a 2 Ω load as the power dissipated gets insane. The amp is stable with a 2 Ω load, so I have no concerns aside from the power dissipation.
I have no concerns with using a transformer-based power supply. My Power-686 will happily feed a stereo pair of Modulus-686. If you'd like more capacitance than the 4x22000 uF my Power-686 provides, you can use one Power-686 per channel.
I really like the ±27-28 V operating point. It makes for an amp that provides good power with a thermal system that is still manageable. I call it the safe-n-sane build. Those who want to push it to the full 240 W (8 Ω), 360 W (4 Ω) will need ±36 V and 4U heat sinks.

Tom
Thanks for the quite in-depth response Tom, this just reinforces my decision to build the 686s. My biggest concern at this point is the custom chassis I want to make, I built my own speakers from scratch so I want to match their aesthetics, as well as my future headphone amp and DAC. I need to run some numbers, because I want my amps to be 300mm wide by 420mm deep, but unfortunately heatsinks will add another 80-100mm to the width. Another option is to build a pair of dual monos, if the heat cannot be managed. I wonder if anyone has shared their mono 686 build images with you?
 
Top Bottom