Neurochrome Modulus-286: 65W (8Ω); 125W (4Ω) @ <-120dB THD Composite Amplifier Module

[tomchr]

Neurochrome Modulus-286: 65W (8Ω); 125W (4Ω) @ <-120dB THD Composite Amplifier Module

Key features:

• Mono construction.
• 65/125 W into 8/4 Ω, respectively @ THD < -120 dBc.
• Tested for stability with reactive loads up to 1.0 µF || 8 Ω.
• Multi-tone IMD residual: < -100 dBV.
• Damping factor: >560 @ 1 kHz; >225 @ 20 kHz (8 Ω).
• Integrated noise (20 Hz - 20 kHz): 17 µV (A-weighted); 22 µV (unweighted) @ 20 dB gain.
• Integrated noise (20 Hz - 20 kHz): 27 µV (A-weighted); 32 µV (unweighted) @ 26 dB gain.
• Balanced input (can be connected to unbalanced sources as well).
• Default gain: 26 dB for ease of use with other HiFi components. 20 dB available upon request. Higher gain possible by a simple resistor swap.
• Four-layer PCB, fully optimized for the highest performance.
• Designed, manufactured, and assembled in Canada. All components sourced from reputable distributors (Mouser, Digikey, et al.)
• Available for pre-order within the next few days with a significant early adopter discount. Expected in stock by the end of November, 2018, at which point the into sale will end.

The Modulus-286 is a composite amplifier, which uses an LME49720 to perform error correction on two LM3886 power amplifier ICs in parallel. This results in an amplifier which has the precision of the LME49720 and the power of the two LM3886es. This error correction is the central point of the Neurochrome Modulus composite architecture. The composite design will correct for many types of error, including distortion and power supply induced errors. It is due to this architecture that the Modulus amplifiers achieve their high performance levels as evidenced by their ultra-low THD, IMD, multi-tone IMD, etc.

Note that attached picture and measurements are of the prototype. I will follow up with a more comprehensive set of measurements once the production version is in.
The production version will be Neurochrome Blue and professionally assembled in Calgary on a gold-plated PCB made in Ontario, Canada. The finished module will include aluminum mounting hardware (also made in Canada), which allows the module to be bolted directly onto a heat sink. This mounting method greatly simplifies the mechanical work for the the DIYer (only three holes needed with ±0.5 mm precision in their location).

Fully assembled modules are in stock and available for purchase here: Modulus-286: 125W power amplifier achieving -120dB (0.0001%) THD – Neurochrome

Enjoy.

Tom

 

[HarmonicTHD]

Cool. Could you point out the major differences eg in performance to the Mod268 ver 1.1 in mono mode? At first glance it seemed pretty identical. Of course now with the benefit of not having to solder all the SMD parts and the inherent risk of something going not as planned.

Thx

 

[poseidonsvoice]

Sign me up!!

Best,
Anand.

 

[wcwc]

Now to choose between this and the Mod186.

 

[tomchr]

Cool. Could you point out the major differences eg in performance to the Mod268 ver 1.1 in mono mode? At first glance it seemed pretty identical.

At first glance, I agree with you. Rev. 2.0 provides higher output power (65/125 W vs 60/100 W into 8/4 Ω, respectively). It also offers lower noise. Rev. 2.0 is also quite a bit smaller. And slightly lower cost (Rev. 1.1 fully assembled was $400). The fully assembled Rev. 2.0 is also more robust mechanically and easier to use for the DIYer.

Of course now with the benefit of not having to solder all the SMD parts and the inherent risk of something going not as planned.

Indeed. The biggest advantage of Rev. 2.0 is probably a long-term one. As you point out, sometimes DIY builds don't go exactly as planned. Even the most competent DIY enthusiast (or professional for that matter) makes the occasional mistake. I know I do from time to time. Whether we like to admit it, SMD builds do cause more headaches than leaded builds. At the same time, the SMD builds are often very difficult and time-consuming to debug via email. While I do enjoy the personal interactions that come with debugging, I would much rather focus on growing my business and delivering cutting edge products. I also think that when someone spends a few hundred bucks per channel on my state-of-the-art products, the build experience needs to be state-of-the-art as well. So by offering only the fully built modules, I expect to be able to offer more positive build experiences while getting to spend my time more productively and grow my business. All of which will benefit everybody in the form of more and better products available at a good price/performance point.

Another advantage of Rev. 2.0 is that it's positioned very well for OEMs. Building relationships with OEMs will allow me to further grow my business. (Why do I suddenly feel like I'm writing the quarterly earnings statement for a Fortune-500 company here? Must be getting ahead of myself. )

Now to choose between this and the Mod186.

The struggle is real, man...

Let me throw this into the mix: I'm seriously contemplating putting a kit together with two channels of Modulus-286 in a ModuShop Mini Dissipante 2U x 230 x 200 mm chassis and power them with a Connex SMPS300RE (±36 V). This should result in a stereo amp that can deliver 2x 65 W (8 Ω) 2x 125 W (4 Ω). It should also be possible to bridge the two channels for 1x 100-120 W into 8 Ω.
I have all the CAD drawings done and all the chassis bits (power switch, connectors, mechanical bits) selected. I just need Connex to deliver the supply so I can test the prototype.

The chassis will be super nice. It'll feature digitally printed front and rear panels. It'll have all the necessary holes for connectors, standoffs, power switch, etc. All the hardware will be included with the kit right down to the wiring harnesses.

I should be able to offer the kit at a price point that's lower than the sum of the parts if ordered at QTY = 1. The pricing isn't etched in stone quite yet, but a total kit cost of $1249 seems realistic. I will offer the kit to the early adopters at a significant discount. I'm currently thinking something like $899 for the first six and $999 for the next 12 or so. I'll announce the launch in this tread as well as through my newsletter (signup: Sign Up to Stay Informed) and Facebook feed (Neurochrome - Home | Facebook). Intro sale aside, I'm not planning any other sales.
I'll also offer the kit as a fully assembled product. I haven't decided on the pricing there.

Tom

 

[wcwc]

How big of a heat sink would you need for two bridged channels?

 

[tomchr]

Around 0.44 K/W if you put both channels on the same heat sink. Twice that if you have them on separate heat sinks.

For reference, the 3U x 300 mm heat sinks from ModuShop (available separately if you need just the heat sinks) are 0.40 K/W.

You'll want a 2x25 VAC @ 200 VA transformer and a Power-86 (or -686) to go with it. Or a suitable SMPS.

Tom

 

[wcwc]

What is involved with bridging the amps? Do we need to make any changes to the board or just to the wiring coming to/from the board?

 

[tomchr]

If you build the amp for bridging, you just connect the inputs of the amp to the same XLR connector in opposite phase and take the output across the two Speaker(+) terminals.
If you already have the amp built, I find it easier to make an "inverter" (XLR cable with the signal conductors swapped). Use an XLR Y splitter and put the "inverter" in one of the branches. Take the output across the Speaker(+) terminals.

I'll include drawings of this in the documentation.

Before any of this happens, I need to get a prototype going. I'm still waiting on the power supply from Connex.

Tom

 

[tomchr]

The introductory sale has started: Modulus-286: 125W composite amplifier achieving <-120dB THD
The sale will end by 23.59 Mountain Time (GMT-7) on November 30th. This will be the only sale on the Modulus-286 so get 'em while you can.

I expect to launch the intro sale for the Modulus-286 Kit (chassis + amp modules + supply + etc.) in about two weeks. I should have the parts necessary for the prototype by then.

Tom

 

[miero]

Tom, these new modules are very nice!


Is this module suitable also for 4Ohm or 2Ohm loads? If yes, what kind of performance could be expected?


BTW: I miss measurements into a capacitive load for your amplifiers -- Measuring Power Amplifiers with Reactive Loads - Audio Precision

 

[tomchr]

The Modulus-286 is suitable for 4 Ω operation. It's 2 Ω stable, i.e. will not misbehave or self-destruct if loaded with 2 Ω.

If you limit the supply voltage to ±20 V, you can drive a 2 Ω load. For 2 Ω headphones (there are some wicked ribbon drivers out there), the MOD286 would be a good option. For 2 Ω speakers, I think you'll find the ±20 V to be a limiting factor.

You didn't miss the reactive load measurements. I haven't gotten there yet. Let me get through today (exam tonight), then I'll get those measurements in for you. To start, I look at stability into a reactive load (8 Ω || 1 uF). That AP box looks super cool, though. I'll see if I can get something similar going. It won't happen right away, but it's something that's been on the back burner for a while. Stereophile publishes a frequency sweep with a simulated speaker load that I'd like to reproduce also.

You can find the THD+N vs power and THD+N vs frequency for 4 Ω in Post #1.

Tom

 

[tomchr]

The Modulus-286 Kit is shaping up. The Connex SMPS300RE power supply is a good match for a stereo pair of Modulus-286. That'll allow me to specify:

2 x 65 W into 8 Ω
2 x 125 W into 4 Ω
1 x 140 W into 8 Ω (bridged mono)

The amp is stable into 2 Ω, but I don't recommend driving 2 Ω loads with the MOD286 as it'll overheat rather quickly. There's no way around physics. Sorry.

The 140 W in bridged mode is limited by the output current of the SMPS300RE power supply. On a beefier supply, the Modulus-286 will deliver 240 W into 8 Ω. With the kit, I'm aiming for an affordable small package, hence have settled on the SMPS300RE and the smallest ModuShop 2U Mini Dissipante.
Observant readers will note that the THD+N vs output power for bridged mode goes past 200 W. That's at 1 kHz, where the on-board supply capacitance provide the peak current. At 20 Hz, where the SMPS300RE will have to sustain the peak current for longer, the supply starts to brown out around 140 W, hence, I spec the amp for that.

Note that in bridged mono, the gain of the amp is 32 dB in the default configuration with each MOD286 providing 26 dB gain. If you configure the modules for 20 dB gain (pluck a resistor off the board), you can get 26 dB gain (and a bit lower noise floor) in bridge mode.

I'm about to start the prototype run of the MOD286 chassis bits. I expect to be able to show build pictures in 2-3 weeks and will open up for pre-orders of the kit around then.

Tom

 

[BrianL]

Looking forward to it.

 

[tomchr]

Inching closer to project completion. All the mounting hardware bits have arrived. Attached shows the prototype Modulus-286 module. The final version will feature a Neurochrome Blue circuit board but otherwise be identical.

All the mounting hardware and the PCB is manufactured in Canada. The modules will be assembled by a professional assembly house right here in Calgary.

I will deliver all the parts to the assembly house early next week and expect to have the modules in stock by the first week of December. The intro sale is on until the end of November.

Tom

 

[tomchr]

The prototype Modulus-286 Kit chassis have arrived from Italy.

I continue to be amazed how efficient ModuShop's packaging is. I suppose it's a small business owner's geek moment when you get excited about packaging, but good packaging often differentiates the good vendors from the rest of the pack.

I'm also amazed by how tiny these 2U Mini Dissipante chassis are. I hope all the electronics will fit. I included a hockey puck in the picture so you can get a sense of scale.

Now for the build. I expect to be able to open up for pre-orders of the kit by the end of the week. I'll have the kit available at steeply discounted intro prices: $899 for the first four kits to sell; $1099 for the next eight. After those have sold, the price will settle at $1399. I will announce the opening of the sale in my newsletter, on my Facebook page, and here (in that order).

Tom

 

[wcwc]

I was just trying to fit my build in the 2U Mini Dissipante. It is pretty small, but it looks like I should be able to make it all fit. 2 Mod286 should be easier to fit than 4 Mod86 boards.

Looks like there is room on the heat sink to stack the boards 2 high. I also think I am going to mount the boards on the right heat sink upside down to make the wiring job neater.

I got the 330mm width. Is that the 220mm width mini.

 

[tomchr]

Yep. 2U x 230 x 200 mm Mini Dissipante.

There is not enough room to stack the MOD286 boards on one heat sink. The module is 1.25" tall and you need to allow some room for the wiring to exit from the connectors.

Tom

 

[wcwc]

One of the pluses of the side exit on the Mod86 boards.

 

[tomchr]

It fits! Now I "just" need the wiring. The power supply is a Connex SMPS300RE in ±36 V. For the production kit I am getting a custom version of the supply made with 25 mm tall supply caps. That'll allow the supply to fit in the chassis and leave enough clearance to the chassis to meet electrical safety requirements.

In the first picture, I included the cover for Mark Knopfler's latest album. Yes. It's a CD! That gives you an idea of how small this amp is.

The outputs are Neutrik speakON and binding posts. The binding post are placed 3/4" (19.05 mm) centre-to-centre, thus allows for the use of banana plug adapters - even for balanced operation where the output is taken from the two "+" terminals.

This amp will provide 2x125 W into 4 Ω (2x65 W into 8 Ω). 1x140 W into 8 Ω if you bridge the two channels. Bridged operation into 4 Ω is not recommended.

The amp weighs in at 3100 g.

Tom