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Old 19th April 2017, 04:39 PM   #3331
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by danielwritesbac View Post
Supply impedance of rather cheap filters aboard the SMPS, may vary off from expectations. It might not maintain good regulation while driving a load.
For sure. The supply impedance and load regulation is something one should look at when buying a power supply. That's in fact why I limit my recommendations to supplies I've tested or that are well specified by the manufacturer.

Quote:
Originally Posted by danielwritesbac View Post
In my experience, Good SMPS are available, they're not the majority and they're never the cheapest.
That applies in a lot of situations. You often get what you pay for. Except in case of many of the eBay vendors where I'd argue that while you don't pay a lot, you often don't get what you pay for.

Quote:
Originally Posted by BrianL View Post
Connex also sells assemblies that are a PCB with bunch of large-ish caps if you feel you need more capacitance between their SMPS and your amp.
True that. Some experimentation/characterization may be needed to find the optimal amount of capacitance, though. It all depends on the regulation bandwidth of the regulator and how the additional capacitance plays in.

Quote:
Originally Posted by AndrewT View Post
the pigtail connecting Pin1 to enclosure is far too long.
Is the shell of the socket electrically connected to the enclosure?
If not, then make it so. The more electrical connections you can ensure around the perimeter of the hole it pokes through the better.
I find it funny how you choose to worry about a short pigtail while ignoring all the RF that will enter through the long slots in the top plate. #perspective

Quote:
Originally Posted by AndrewT View Post
You can also attach 10pF to 47pF ceramic capacitors of NP0 type from pin2 to pin3 and from pin1 to pin2 and from pin 1 to pin3. These provide a bit extra RF attenuation before it enters the enclosure. The leads of the caps MUST be very short, 1mm to 2mm maximum.
Actually, by definition, they wouldn't. If you want to keep the RF outside the chassis, you'd need ferrite beads on the outside of the enclosure and feed-through capacitors as the various wires enter the enclosure. You'd also need an RF seal along all edges and no slots in the chassis would be allowed. These measures would be completely appropriate if you were building a satellite, space shuttle, or avionics but would be total overkill and completely unnecessary for residential audio applications.

While I do agree that the RFI filter could work more effectively if placed right on the connector, that complicates assembly unnecessarily. That's why the RFI filter is on the PCB.

Tom
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Old 19th April 2017, 04:40 PM   #3332
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by jrleadbet View Post
I finally got around to putting your amp into use and I just wanted to write to let you know how great it sounds. I'm using a Benchmark DAC1 HDR as source and ATC SCM11s as speakers. Great depth and imaging, really articulate bass.

Thanks again for the great amp.
Thanks for sharing. I appreciate it.

Tom
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Old 19th April 2017, 04:59 PM   #3333
KSTR is offline KSTR  Germany
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Yes, NC3FD-LX ist best for EMC (the unpainted version, that is). Chassis must be conductive (free from paint, etc) in the mounting area as well.
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Old 19th April 2017, 05:09 PM   #3334
KSTR is offline KSTR  Germany
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For private DIY creation I think if the amp passes the cell phone test "as is" then no need to worry about better connector and additional filtering at the point of entrance.
Put a dialing cell phone close to the amp, hovering around and getting close to any attached cables, unused connetors, switches/knobs etc. If you get the typical clicking noises at significant volume from the speakers, EMC could be bettered.
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Old 19th April 2017, 06:49 PM   #3335
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by KSTR View Post
For private DIY creation I think if the amp passes the cell phone test "as is" then no need to worry about better connector and additional filtering at the point of entrance.
Put a dialing cell phone close to the amp, hovering around and getting close to any attached cables, unused connetors, switches/knobs etc. If you get the typical clicking noises at significant volume from the speakers, EMC could be bettered.
I agree. In addition, switching sparks from heavy loads turning on (think furnaces, electric heaters, and refrigerators) should not cause clicks in the speakers either.

Tom
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Old 19th April 2017, 10:37 PM   #3336
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Thanks everyone for the feedback. I did spend way too long working out details, so it's nice to hear I caught most of them.

I agree the little pigtails aren't ideal for RF, but I had wanted to use a heavier bolt to make a really strong chassis connection. I noticed the XLR connector does have a pin to the shell, so I could make a direct connection by removing a some of the epoxy finish.

Otherwise, I was a bit careless about RF, as I had seen in Tom's notes there is a filter on the input. The long slots in the enclosure were the biggest compromise; using lots of little circular perforations does a better job, but adds a lot to the enclosure cost.

As is, the amp is super quiet: I can't hear any hiss from the speakers, and music really leaps out of nowhere when I hit play.
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Old 19th April 2017, 11:38 PM   #3337
Studley is offline Studley  United Kingdom
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I'm still working on the enclosures for my bridged Para 86 amps so currently they are completely open to the domestic elements. Despite that they sound fantastic, which is why I'm completely relaxed about the fact that the only metal in the finished articles will be the heatsinks.
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Old 20th April 2017, 03:08 AM   #3338
tomchr is offline tomchr  Canada
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I ran mine in prototype mode (bare boards on heat sink, out in the open) within two feet of my wireless access point right by where I normally put down my cellphone for quite a while. No issues for me either.

That said, I have had LM3886-based amps (P2P setup) where switching transients from the furnace and fridge kicking in would make the amp go 'click'. That's OK for a prototype but unacceptable to me in a finished product.

Tom
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Old 28th April 2017, 12:30 PM   #3339
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So while I have still been a following I have been getting some hours in with the amp and I love it! So much so that I'm confident that it is a solid building block allowing me to look at the speaker and pre-amp options.

My audio chain is currently a RPi with a BOSS DAC (while re-ripping my CD collection to FLAC). A passive preamp based on Arduino controlled LDRs. And the final element is a pair of Furgal Horn MKIIIs with MA Alpair 7P drivers. It does tend to bring out the best and the worst of the sources but I'm find new things in tracks which is what it all about.

Anyways a couple of things...

I'd like to remote power control the amp via the remote of the preamp and I'm thinking a solid state relay would be the ideal way to manage this as it maintains mains isolation and allows low voltage control for easy uP integration. Are there any drawbacks to this approach?

Second and it has been mentioned before, amplifier protection. I'd like to see the power up speaker pops gone (just does not seem profssional) and have the piece of mind that if I (most likely) do something wrong or the amp fails in some way that the speakers are protected while at the same time minimising any impact on the quality of the amp. Any suggestions?
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Old 28th April 2017, 12:37 PM   #3340
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Quote:
Originally Posted by garym999 View Post
I'd like to see the power up speaker pops gone (just does not seem profssional) and have the piece of mind that if I (most likely) do something wrong or the amp fails in some way that the speakers are protected while at the same time minimising any impact on the quality of the amp.
I don't have power-up pops on my amp. ??? I turn on my amp last and turn it off first and let it decay before powering everything else down.

I'm wondering what is different about our setups.
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