Modulus-686: 380W (4Ω); 220W (8Ω) Balanced Composite Power Amp with extremely low THD

[asuslover]

Unfortunately, offering the SMD-only boards also increases cost for everybody and drives up the number of support emails. I do enjoy providing support, but it takes me away from growing my business, so I have to do what I can to limit the number of support calls. Also, when someone spends good money on a partially assembled board, they need the rest of the build to come together smoothly. The fully assembled modules facilitates this, thus, help me continue my business.

Tom

This is the time when you could think about neurochome.com/blog....

 

[tomchr]

This is the time when you could think about neurochome.com/blog....

For the support questions or more for my business musings?

It's indeed been interesting to go from hobby to business. The scaling appears to be rather nonlinear.

Tom

 

[Connex]

That said, I should also mention that while I used to recommend the Connex supplies, I've grown to be considerably less enthusiastic about them following a recent bulk order with them. The quality of some of the components is hit-and-miss depending on which batch you get. I was fortunate that my bulk order came from a good batch.

Strange to say that from two orders only. Though would be fair to admit that the quality is steadily increasing.

My initial order of two SMPS300RE arrived with rather cheap mains inlet connectors which I crushed just by turning the screws. I was prepared to have to replace the connectors on all the ones in my bulk order, but thankfully they came from a different batch. I've also had one SMPS300RE (ordered years ago) that needed rework as one of the quick connect terminals pulled out of the board. Neither of these things are show stoppers, they're just not quite production quality.

I've seen destroyed connectors and ripped off parts from boards few times before, and I was just wondering why would someone had to torture a board to achieve that. I don't think connectors or other parts simply fall of just by touching them.

In addition, Connex's customer service has always been a bit lacklustre and appears to have taken a turn for the worse. For example, I ordered my supplies configured for 120 V mains. They arrived configured for 230 V mains. This is likely due to a misunderstanding as I had asked if this was possible to do on my initial order of two supplies. I clearly specified that I wanted the supplies in the bulk order configured for 120 V. So I now have to spend a couple of hours soldering in wire staples. Again, not a show stopper but just not a production flow.

You were asking for a version capable to be used both with 120V and 230V mains, and you also said that you prefer to solder wires to a switch instead of a jumper on a PCB. I explained you again in the oct. 26 email and you said that you forgot about it. Next, if they were 230V version as you claim they wouldn't work at all with 120V with or without jumper. Do I have to explain again why ?

I could also swear they committed to a two-week lead time, yet spent nearly two months building my order with several promises of "shipment this week" along the way. I'm not asking for much. All I expect is that people follow through on their commitments. That's all.
That said, they were able to deliver the supplies in a 100x100x25 mm form factor, which I have not found elsewhere, so that's good.

I could swear 3x that you asked to use capacitors which I told you we have to order them and will take at least 2 weeks to arrive, because we have to import them and with the current trade war situation there is no definite time. I kept telling you the status from when we ordered them till when arrived and when we assembled the boards.
If you order customized boards and expect to fit your requirements, please be reasonable and don't complain about longer lead time or the fact that they don't look exactly like the non-custom ones. Or just don't order custom ones.
Shipping was done as soon as they were all tested, not this week or that week, and after we posted them we got the tracking info and sent it to you. You have to understand that it takes time for custom made boards, because they aren't made with the rest of the batch in the same time. There is no benefit for us to make a couple of customized boards, definitely not for few $ more because there is a lot of extra work / each board compared with the overall work on a large (200-500pcs ) batch. Not to mention if they are sold with discount.
Just curious, did you even check your emails or commitments before making these allegations ?

 

[tomchr]

Strange to say that from two orders only. Though would be fair to admit that the quality is steadily increasing.

Three orders, actually. I ordered an SMPS300RE about 4-5 years ago while I still lived in the US.

I've seen destroyed connectors and ripped off parts from boards few times before, and I was just wondering why would someone had to torture a board to achieve that. I don't think connectors or other parts simply fall of just by touching them.

I didn't rip anything off the board. The two boards you sent back in October (or so) used the blue leaf spring type of mains connector. It cracked when I tightened the screw. For my prototyping, I had to connect/disconnect 2-3 times and by the end the connector had cracked in multiple places. At that point I concluded it wasn't safe to use it, so I replaced it.
The green terminal blocks (rising cage type) you used on the bulk order are much better.

Tightening a screw should not be torture for any terminal block that requires the turning of screws to operate.

You were asking for a version capable to be used both with 120V and 230V mains, and you also said that you prefer to solder wires to a switch instead of a jumper on a PCB.

I asked if it was possible to deliver the boards like that. In my email of November 2, 2018, I listed my specs for the bulk order as:

Output voltage: ±36 V
AUX voltage: ±12 V
Mains voltage: 120 VAC

I explained you again in the oct. 26 email and you said that you forgot about it. Next, if they were 230V version as you claim they wouldn't work at all with 120V with or without jumper. Do I have to explain again why ?

You are correct that I had forgotten I'd asked if it was possible to have the boards 120/230 V switchable. The reason I forgot is that you never answered my question. You just delivered boards configured that way.

I could swear 3x that you asked to use capacitors which I told you we have to order them and will take at least 2 weeks to arrive, because we have to import them and with the current trade war situation there is no definite time.

It is entirely possible I misunderstood your email then. I'm sorry.

I kept telling you the status from when we ordered them till when arrived and when we assembled the boards.

That wasn't my experience. I followed up 15 days after ordering (Nov 25th) asking how the production was coming along. You didn't actually answer my question. Rather, you raged about a $40 address change fee that you claimed I had caused. I have provided my correct address with every order. This address is also my confirmed Paypal address. Somewhere between you and I, two letters were dropped off the address, which caused DHL to be unable to find it. So they called me and I provided my address. I do agree that charging $40 for that is outrageous, but that's not something I have control over.

At least the bulk order came to me without incident.

If you order customized boards and expect to fit your requirements, please be reasonable and don't complain about longer lead time or the fact that they don't look exactly like the non-custom ones. Or just don't order custom ones.

Then please be upfront about your delivery schedule. A statement such as, "It will take 2-4 weeks to order the caps. Once the caps get in, it will take another 2-4 weeks for us to build and test the supplies." would have prevented my anxiety regarding the lead time.

Even if you did feel like you had already provided all the necessary information regarding the lead time, why didn't you just let me know the lead time (again) in your email of Nov 26th? Sometimes customers forget, get stressed out, or what not. In those cases, I find it helpful to provide the information, even if I feel like I'm over-communicating it. And let's face it. Sometimes I do think I've told somebody something when in fact I haven't. I invite you to ponder whether that might be true for you as well.

You had another opportunity to communicate your delivery schedule on December 7th when I followed up again. In your email of Dec. 8th, you said the supplies were built but that you needed to test them. That they'd ship "next week" (which I interpreted as the week of Dec. 10th).

I followed up on Dec. 17th, which got a tracking number generated. That was my last communication with you.

By Dec. 21st, the tracking shows the package being accepted by your shipping aggregator. They shipped to me the following day via DHL.

Shipping was done as soon as they were all tested, not this week or that week, and after we posted them we got the tracking info and sent it to you.

I obviously want you to test your products before shipment. You have my full understanding there. However, all this debacle could have been avoided had you been open about your delivery schedule up front.

Just curious, did you even check your emails or commitments before making these allegations ?

Of course I did. I also waited a few days to write to allow my head to cool. I wanted my critique to be fair rather than guided by emotion.

My approach is pretty simple:
- Under-promise, over-deliver.
- Say what you do. Do what you say.
- If you are upset, wait 24 hours before posting/complaining about it. If your issue is still relevant, then post/complain.

Tom

 

[BrianL]

Mr/Ms Connex

I don't want to get involved in a discussion between you and Tom. However, since you are monitoring this thread, I would like to point out the following about your SMPS products:
1 - They look promising for amps such as Tom's and similar DIY amps
2 - Your web site and product numbering make it difficult to determine which supplies are appropriate for an application. It would be wonderful to have a 'decoder ring' to allow one to easily distinguish between single-output vs +/- outputs, regulated vs semi-regulated, and older versions vs new/improved versions.
3 - Some of the pages for each supply have a link to a .pdf datasheet/manual and some don't. I find it difficult to make a decision on suitability of a supply with just a picture and a couple paragraphs' worth of description.
4 - In general, more detail on specs and measured performance would be useful to your customers. People are reluctant to buy without some confidence that the product is safe, reliable and performs as expected.
5 - Prompt and complete communication (even "over-communication") instills customer confidence.

My inputs for what they are worth...

 

[chrisb]

Small businesses like Neurochrome have far better things to do with their time than to conduct public bladder emptying contests such as these.

 

[tomchr]

+1

 

[Enochrome]

noob question

This amp looks really interesting.I have little electronic experience. If purchasing the fully assembled boards of both amp and power supply, can a beginner be able to construct? Also, is it one power supply board per mono 686 board?

P.S. The preamp looks very interesting as well. Have you considered making a phono stage?

Thanks

 

[tomchr]

One Power-686 will power two Modulus-686 modules. If you order the assembled versions of both, I can assemble the power supply wiring harness for you. In that case, it's plug-n-play once you've connected the power transformer. I provide instructions for how to do that with the Antek brand of transformers. Should you choose a different brand, I'll be happy to help via email.

I have considered a phono stage. I have yet to have time to work on one.

Tom

 

[BrianL]

Somewhat generic question: If one wants to use an SMPS for a DIY amp in the 2x50 to 2x100W range, does anyone know of options? The +/-36V Mean Well '400W' units seems to have the buzz/whine problem (acoustic and electrical). There seem to be some concerns about Connex (at least the SMPS300). Years ago I purchased some surplus toroidal transformers for a project I'm just getting to, but in the past year or so have warmed up to the idea of a more compact chassis that doesn't take a body-builder to move. What I see at distributors do not appear practical -- enclosed industrial-duty supplies with (likely noisy) fans at prices that get too high for my DIY budget.

 

[RobSoet]

Hi Brian,


I'm using connex and I'm satisfied with them. It came supplied with flimsy and naked fastons. Replaced those with isolated and better quality.



I think the 'issues' are mainly related to availability and having a commercial flow.



Alternatively I think there are some 36V hypex smps-es.


Rob

 

[BrianL]

The Hypex I see available on their DIY site put out higher voltages than +/-36; The SMPxxxxA100 version appears to be closest to +/-36V, but isn't offered for sale, at least on the DIY site. Also, they appear to be unregulated as Vout is proportional to Vin, which means that even the xxxA100 version might be risky for LM3886 as it's skirting the AbsMax supply specs at high line voltages. Given the unregulated behavior, I would expect the output voltage to be a function of transformer winding ratios -- i.e., one can't tweak the output voltage slightly by tweaking a resistor value.

 

[tomchr]

Unless Hypex has released a new supply since I last looked (a few months ago), they don't have anything that'll work with the LM3886. Their supplies are unregulated, so at high mains, their output voltage will exceed the ±42 V ABS MAX of the LM3886.

In the Mean Well lineup, the RPS-200 and RPS-300 are interesting for low powered amps, however neither is available at 36 V. One day I'll try a Modulus-186 or -286 on a pair of RPS-200-24-C. That'd be a pretty nice and compact desktop amp. For the Modulus-686, my favourite SMPS remains the Mean Well RPS-400-27-C. You'll get 130 W (8 Ω) with a pair of those.

Tom

 

[Davey]

Unless Hypex has released a new supply since I last looked (a few months ago), they don't have anything that'll work with the LM3886. Their supplies are unregulated, so at high mains, their output voltage will exceed the ±42 V ABS MAX of the LM3886.

Yeah, Hypex doesn't have anything that would work. I looked into this a number of years ago when replacing my Linkwitz Pluto modules (3886) with SMPS supplies. I ended up using Connex SMPS300RE. After purchasing six of them, I finally found three that worked well and continue to do so. The other three I threw on the shelf to collect dust.

I hope you don't have support issues with your 28 Modulus 286 amplifiers.

Dave.

 

[tomchr]

I ended up using Connex SMPS300RE. After purchasing six of them, I finally found three that worked well and continue to do so. The other three I threw on the shelf to collect dust.

50% yield. Wow. That's impressively bad. I wonder what happened there. Did you ever try to debug the supplies or contact Connex about it?

The SMPS300RE I bought years ago still works. The two I bought before my bulk order work as well.

I hope you don't have support issues with your 28 Modulus 286 amplifiers.

I do too. Perhaps I should test the supplies before I ship them.

Tom

 

[Mark Johnson]

Indeed, why NOT test the supplies before you ship them? It isn't exactly a new idea.

Maybe you can find other dimensions on which to compete besides price. If you don't yet own an electronic load for power supply testing, Keithley sells a good one at a nice price. And there are very low cost Chinese electronic loads on fleaBay and AliExplode. You can compete on thoroughness of testing and characterization, for example. Power-86 is unregulated, so line- and load- transient testing is irrelevant, but if you ever do start selling regulated power supplies, you could test the holy hell out of them and make that testing part of your unique selling proposition.

I already am [competing on thoroughness of testing and characterization]. I provide more test data and specs than any DIY person out there and more than the vast majority of commercial manufacturers of audio equipment.

Not on your Power-86 product. If you've ever connected Power-86 to an electronic load and monitored its temperature vs time vs load current, I for one haven't seen your measured data. But I have seen the measured data from at least one form, fit, and function compatible DIY PSU that has performed these tests. That's why I included a link to an electronic load instrument made by Keithley, so you could consider acquiring it as a way to compete on thoroughness of testing and characterization, rather than competing on price, in your Power-86 product line.

_

 

[tomchr]

Indeed, why NOT test the supplies before you ship them? It isn't exactly a new idea.

I wholeheartedly agree. However, I think it's very reasonable to rely on my vendors for the testing. Connex did mention to me that they tested the supplies before they shipped, so barring damage in shipping, they should still work, right?

Ultimately it becomes a matter of trust and selecting good vendors. As covered previously, that's not always a trivial task.

Tom

 

[asuslover]

This is the catch when you sell finished products, if I buy an "Modulus-286 Kit – Limited Edition" and the power supply( Connex SMPS300RE) is not doing that great, the whole amp is not gonna do great. As a customer is not my business to investigate what part of the amp is bad, so the whole amp is not a satisfying product.....

 

[tomchr]

I agree. Hence my comments about selecting vendors carefully. I'm glad I'm learning these lessons now rather than in the middle of a large scale production run.

I've never had a technical problem with the Connex SMPS300RE or I would not have used it for the Kit. Like any other electronic circuit, it has its limitations. Running the supply at twice its rated output power will fry the output diodes, for example. It would be nice with a more graceful shutdown, but I did operate the supply well outside its specified limits (which was entirely my fault, by the way).
I did find the mains connector used on the two SMPS300REs I ordered to start to be a bit flimsy and prone to cracking. That was easily remedied. Thankfully, the 26 I received on my bulk order used better connectors or I would have replaced them.

The five SMPS300RE boards I've had fired up so far have worked just fine.

I've run the Kit with the AP 32-tone "music" signal for an hour at clipping levels. The amp performed just fine.

Tom

 

[pinnocchio]

Here's a little update... Working slow since I'm assembling another project at the same time. I never liked the screw tab on the LM3886, they're pretty badly designed to give good uniform pressure. I added this pressure bar and good alumina pads. Still have the screws in the hole but it was for keeping proper alignment when tightening the pressure bar. I will remove them in the end. Added kapton tape on the bar on the PCB side to avoid any possible shorts.





All the best!
Do