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luvdunhill

What Are You Building Today

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On 2/5/2018 at 12:45 AM, lkong said:

I paused my SS Dynalo project for almot 2 years because I'm too lazy to drill holes

Story of my life, and probably most DIYers... casework is the worst :( which 3d printer do you have?

Here is version 1 of the hamster cage, needs a few more improvements before I'm willing to try to machine everything :) 

bda2c48982.jpg

 

 

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2 hours ago, mypasswordis said:

Story of my life, and probably most DIYers... casework is the worst :( which 3d printer do you have?

Here is version 1 of the hamster cage, needs a few more improvements before I'm willing to try to machine everything :) 

bda2c48982.jpg

 

 

I'm using a Monoprice/Duplicator D6 at home. For bigger and more detailed builds I can use objet and carbon from work.

Having a 3d printer at home really helps with my procrastination problem. My builds always die during waiting for new parts.

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On 2/5/2018 at 9:50 AM, bjarnetv said:

Finished up a 6 channel Anaview AMS0100 to use with my horns, as the old amps were to noisy.

A pretty plug and play build by DIY-standards, but since it was my first try that suited me just fine.

Only had the time to plug it in and check the channel routing using test noises, so i haven't tried playing music on it yet, but hopefully everything will be ok when i try it out later today.

 

I still have a Holton NXV500 to build, which is a bit more difficult, so having this as a warmup to get rid of my cabinet-drilling fright was perfect ;)

DSCN6144.thumb.jpg.eae12c17b13dba252c37de0802cf0134.jpg

Looks really good!

Minor point on the XLR wiring. You've got pins 1 chained together and then via a wire to chassis. And yes - pin 1 absolutely has to go to chassis, but by the shortest possible route - a separate thick wire from each pin 1 to a ground solder tag at the nearest XLR screw. With the arrangement you have, any RF intercepted by the balanced cable screens goes into a tuned radiative loop (from the dimensions, several hundred MHz) and spray it inside the chassis. And conversely any radiative interference from those class D power amps gets coupled onto the XLR cable screens.

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Thanks for the good advice!

i was kind of confused on what was the best way to ground them, as it seems everyone online has different preferences and advices.

is that something that will be audible as noise, or is it just generally bad for the audio signal?

 

This is by far the most silent amplifier i have ever heard, and the background is completely black, even with horns as sensitive as 108db

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It is just that it can give rise to difficult to understand problems. Like a phone doing a cell search on maximum power, and suddenly zzt zzt zzt.

The best papers I'f found on this are the Rane Notes http://www.rane.com/note151.html and http://www.rane.com/note110.html  and http://www.rane.com/note166.html 

The nub of it is: connect each pin 1 to chassis ground as directly as possible in heavy gauge single strand wire - the goal being zero length. Even a very short direct connection inside the box is not ideal. Many professional amplifiers use a two terminal tagboard on the rear panel for + and - signal, and a screw terminal to the case. So pin 1 is grounded outside the case and shield current never penetrates the case. Pain in the ass for domestic gear where you want to disconnect it easily, but OK for permanently installed studio gear.

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Very nice work bjarnetv. 

Just to add on to what Craig has correctly pointed out in regards to pin 1, and your query if it’s something that may be audible. In my opinion a correctly implemented (as per rane notes) balanced line is all about “potential”, in other words one scenario may differ greatly from another, influencing environmental factors are all very different. The only way to test whether a certain environment has audible RFI, would be to dissconect pin 1 from the chassis and listen for hum, in a quiet rural country area you may not hear any as opposed to a city area where RFI is obviously greater.

And then there’s house hold wiring, appliances and fluorescent lights that all add to that “potential”.

 

Edited by johnwmclean
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Seeing as i live in the middle of the capital, i suppose i am in a high RFI area,  but the amps are still completely hum free.

But i guess i better fix it sooner rather than later, if only just to sleep well at night ;) 

 

would it be enough to get rid of the "ground bridge", and just connect pin 1 to the solder tab on the XLR body?

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The solder tab on the body connects through to the cable connector shell. Unless the body of the connector is connected to chassis that gains you nothing. You need to connect pin 1 to chassis as directly as possible.

Reducing the loop area is the aim of the game. To do individual grounds at each XLR you have to clean the paint or anodizing off around the fixing screws so the solder tabs at that point are shorted to chassis metal. I do that with a Dremel before I start installing hardware, so it is easy from there. It also ensures that the shell of the XLR (and hence the shell of the cable connector) is tightly grounded too.

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Thanks Craig and John! This is really very helpful and critical information to have.

I've followed John's KGSSHV wiring scheme on all my builds to great effect (thanks John).

I am now finishing a Soekris DAM1021 DAC build and have a question:

In the headphone amps with the XLR input connectors, I have the pin 1 of the XLR connectors tie to chassis, only pin 2 and 3 are wired to the non-inverted and inverted inputs of the amp board. 

For the DAC's balanced output, should I follow the same practice - that is, tie pin 1 of the male XLR connectors to the chassis and only wire the inverted and non-inverted output from the DAM1021 board to the pin 2 and 3 of the XLR connectors?

EDIT: Also, what about RCA connectors?

  

Edited by mwl168

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Not today, but very soon my buddy Milo (some of you may remember him from my trip to Lake Michigan recently, and he looks remarkably similar to Al) and I will be building this configurable router table together...

download.jpg

Should be a really fun project, and quite useful for our little shop we're assembling. Milo is a handy guy!

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Looks serious, nice copper bar. Did you do all of that metalwork? Sony eh? Very nice!


Yeah, working non the other side this weekend. I have a good set of counterbore bits now and can show off the results when I am done.

That first MOSFET logo is one for KG and Craig - not one you see these days - Harris. The rest are indeed the Sony VFET, similar design to this one, which uses a small fortune of devices:

http://www.firstwatt.com/pdf/art_sony_vfet_40yr.pdf

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That Harris brings back memories..........:)

...and I should still have some  Hitachi mosfets in the same package when I was building 100w and 140w power amps back in the '90s before Hitachi stopped producing them.....B)

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12 hours ago, luvdunhill said:

 


Yeah, working non the other side this weekend. I have a good set of counterbore bits now and can show off the results when I am done.

That first MOSFET logo is one for KG and Craig - not one you see these days - Harris. The rest are indeed the Sony VFET, similar design to this one, which uses a small fortune of devices:

http://www.firstwatt.com/pdf/art_sony_vfet_40yr.pdf

What set of counterbore bits? I could probably use something like that myself.

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What set of counterbore bits? I could probably use something like that myself.


Something like this, in various sizes. I have just bought them one-off in the exact sizes I need:

https://www.mcmaster.com/#2919A34

I use them to sink socket head screws and in this case to ensure no contact between portions of the PCB (through hole plating) and the bracket.

I think I am specifying no through-hole plating, but I guess the fab won’t honor it. What I want is odd - exposed copper pad on the bottom of the board (which I call out with a copper pour) and no through-hole plating with no copper on the top of the board. (So a pad with only copper on the bottom).

For my production run it will be a requirement that likely I will have to ask specifically about.

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Yeah, I think the fabs try to protect you from your "mistakes", when in this case it is intentional.

For your one-offs, do you just do ebay or something? I've bought some machinists tools (used) from ebay with good results (Starrett auto punch, some taps, etc.).

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