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Modulus-86: Composite amplifier achieving <0.0004 % THD+N.

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I thought this would be a straightforward build but I guess not:

FYI - Mouser is completely down today. System-wide. They don't know what happened. No ETA on any orders (including mine) for right now. If privacy is a concern you may want to inquire if any personal info has been compromised. Just sayin'.

My Connexelectronic PS has been lost. It's been 2 months. It ain't gonna show. That's $110 wasted and $140 extra spent on Meanwell replacement. Connex was sketchy 10yrs ago and is still sketchy now. He really shouldn't be recommended.
 
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"Mouser.ca is working for me. Tested seconds ago."

I'm not talking about their website, I'm talking about internal. My entire order from the weekend was mysteriously shifted to backordered for no reason. I spoke with them on the phone. They said something happened system-wide and they have no idea what but no info on any orders, no ETA on when they'll know, maybe in the afternoon. It wasn't a 'there's a minor delay' vibe. It was 'we have no idea what's going on everything is down' vibe.
 
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That’s really unfortunate. The last two times I ordered Connex supplies, I got them from HiFiMeDIY, since they show US warehouse stock per item. The SMPS are good quality, but problems ordering direct from the manufacturer have come up.
https://hifimediy.com/product-category/power-supplies/

Yep, that's what I used to do after the first time I ordered direct, but Hifimediy doesn't have the lower voltage dual supplies in stock anymore.
 
Mouser.ca is working for me. Tested seconds ago.
The Mouser website loads and I can log in just fine. But both orders I placed yesterday show with all items backordered and a delivery date of "will advise". So something is broken. All items were in stock at the quantities I needed yesterday.

If Mouser is unable to take, process, or ship orders I would imagine that they're working as fast as they can to fix it. It's not fun to run a business when the revenue suddenly drops to zero because of some software update that sh*t the bed.

Tom
 
FYI - Mouser is completely down today. System-wide. They don't know what happened. No ETA on any orders (including mine) for right now. If privacy is a concern you may want to inquire if any personal info has been compromised. Just sayin'.
I'm pretty sure that if any personal information has been compromised they're legally obligated to tell you.

My Connexelectronic PS has been lost. It's been 2 months. It ain't gonna show. That's $110 wasted and $140 extra spent on Meanwell replacement. Connex was sketchy 10yrs ago and is still sketchy now. He really shouldn't be recommended.
I'm sorry to hear that, but it doesn't sound like the fault was on Connex's end. Apparently the USPS has its issues these days. It's also not unheard of that items go missing in the mail. My dealings with Christi at Connex have been pretty smooth. I did have one order of 25 SMPS300RE a few years ago that arrived with some of the supplies damaged in shipping. I think Connex skimped a bit on the bubble wrap there and the box took a beating in transit.
But that seems to be an issue that's in the past. My recent orders of SMPS300REh have all arrived with the supplies individually boxed and wrapped in bubble wrap. I always have Connex ship using a tracked service. I think they use DHL these days, but I forget. I usually order a small handful of supplies at a time so the shipping cost gets diluted some.

My only annoyance with the Connex supplies is that their assembly house trims all the leads of PTH components so they're flush with the PCB. This means those components don't always get heated sufficiently during the wave solder process. I've had a couple of cases where I could pull the 1/4" spade tabs right out of the board leaving a neat rectangular hole in the solder joint. Clearly the solder hadn't bonded to the tab. Now I just solder those tabs manually from the top of the board before using it.

I used to strongly recommend Connex but because of these issues - especially the pull-out tabs - I'll mention them as an option rather than give them a full-throated recommendation. It's a budget product and you get what you pay for. They do work well with the Modulus amps, but they're still a bit 'DIY'. Mean Well provides a commercial quality product at a higher price. I recommend those.

The latest iteration of the Modulus Chassis supports the Connex SMPS300REh. This should be viewed as a recognition that many DIYers use these supplies and not so much as a strong recommendation from my side. I'd rather that you support me and use the Power-86 or Power-686 instead. ;)

Tom
 
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I'm sorry to hear that, but it doesn't sound like the fault was on Connex's end. Apparently the USPS has its issues these days.

The package never made it to USPS. It is with whatever courier he used, sitting somewhere in the region for the last 5 weeks. I've ordered from China for 15+yrs and Connex remains the slowest/least reliable shipper I've dealt with. I shouldn't have to ask for a tracking number a month after ordering. As for other issues, there's plenty enough in the search history going back to when he was active here and had his own board as well as more recent posts in other threads.
They do work well with the Modulus amps, but they're still a bit 'DIY'
Agreed. I would not recommend Connex as 'buy with confidence' but more 'risks may apply'.

I'm pretty sure that if any personal information has been compromised they're legally obligated to tell you.
This isn't Canada, they're in Texas lol! (kidding. sort of)
I'd rather that you support me and use the Power-86 or Power-686 instead. ;)

I was looking to avoid messing with transformers and having a nice light amp. Oh well.

Ordinarily I'd be more sanguine about the whole thing but I'm already ~$600 into this build so am a little frustrated.
 
Ah, yes. Christi is not good at letting you know if a product is out of stock and can be somewhat terse in his responses at times when you follow up about lead times, tracking numbers, etc. I usually ask up front about product availability.
I don't like the "middleman shipping" arrangement either. If I pay for DHL/FedEx/UPS shipping I should get DHL/FedEx/UPS shipping from his door to mine. Not China Post to a middleman and courier from there. But that may be the only way he can get reasonable rates from the couriers.

On the other hand he did help me out when I needed power supplies for the Modulus-286 Kit (Limited Edition) a few years back. Those were the 25 supplies I mentioned earlier. I had limited height available in the chassis and needed the supply to not exceed that. Christi made a custom run of supplies for me that used low profile capacitors so the supplies would fit in the chassis. That was pretty cool! He didn't even charge me extra for this.

Your frustration is understandable. Waiting sucks.

Tom
 
The Benchmark AHB-2 uses THX AAA technology (says the Benchmark website). AAA is THX's take on feed-forward error correction. It's used in quite a few headphone amps. As far as I know the Benchmark amp is the only power amp with AAA technology.

I can certainly license the AAA tech from THX but I doubt I'd be able or willing to afford the licensing fees. Usually license agreements and non-disclosure agreements go hand in hand, so I probably wouldn't be able to cater to the DIY market with anything that contained THX AAA tech.

Anyway. Feed-forward is one approach to error correction. Feedback is another. I use feedback and lots of it to get the stellar performance of the Modulus series of amps.

The Benchmark AHB-2 runs in Class-H with a tracking power supply (says the Benchmark website). That's how they're able to get relatively high efficiency and, thereby, a powerful amp in a small package.

Both feedback and feed-forward error correction can be applied to almost any amp, discrete or not. I think the main killer of discrete designs is that every time I look there are fewer and fewer discrete components available. Good audio BJTs are hard to find. There are some out there but would I want to hinge my business on them being available even a few years from now? I'm not so sure about that.

I already have the Modulus-686 available. It provides 240 W into 8 Ω and 360 W into 4 Ω. Those are the output power at <0.1 % THD+N. Most amplifier makers state the output power at 10 % THD+N. If I cook the books that way the Modulus-686 should probably be rated for nearly 300 W into 8 Ω and 400+ W into 4 Ω. Do you really need more power?

Speaking of the Modulus-686... I should have more in stock in about a week. Because of parts availability issues I'm only getting a pretty small batch made and I think I have six or eight committed at this point. If you want a Modulus-686 this year you'll probably want to order relatively soon.

Tom
 
My speakers are all just full-range single drivers of relatively easy load, and I do not intend to own speakers with crossovers in the near future. Is the inductor/resistor combo needed? I assume they are included for stability reasons. I am more of less-is-more person. Thanks!


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If you want the amp to remain stable with a reactive load, such as a speaker, I highly recommend that you keep the Thiele network (L||R) in place. It has no impact in the audio band, but great impact in the 0.5-10 MHz region that's important for stability with the LM3886.

Then again, maybe blown speakers = less speaker. Less is more... ;) :devilr:

Tom