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Old 27th April 2010, 08:34 PM   #511
udailey is offline udailey  United States
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International shipping is 15 for each pair of amps. If you ordered 4 amps, buy International shipping two times, etc.
Canadian Shipping is 8 for each pair of amps. If you ordered 4 amps, by Canadian shipping two times, etc.
Its up on Uriah Dailey
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Old 28th April 2010, 09:40 AM   #512
shark70 is offline shark70  United Kingdom
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Hi Udailey great work thanks ,Iv payed 1 international shipping for 2 kits and 2 pcbs is this sufficient or should I buy another shipping fee thankyou.
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Old 28th April 2010, 12:16 PM   #513
udailey is offline udailey  United States
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No need to buy more. One is enough unless you are feeling particularly generous
Uriah
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Old 29th April 2010, 10:46 AM   #514
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Default Pictures of Lightspeed PSU for MyRef_C

Well, I have finished the PSU I will be using to integrate the Lightspeed attenuator that Uriah kindly offered to us at a very reduced price in the kit.
I managed to fit it in...an square centimeter! It's amazing how small you can make a regulator. You just have to take +35v from any of the MyRef_C boards. Attached is the schematic.
It may seem a bit messy and filthy, but it works as a charm, steady and clean voltage. It has a very robust construction, and being light can be directly attached to a big heatsink and hold it just hanging. Blue wire is input, white wire is output ant the bare grey is ground.

Another thing I have finished are the GROUND BREAKING devices. I am very concerned about electrical security, so I REFUSE to keep untied protective earth and GND from the amp. Just imagine what will happen if the live from the mains hangs out and touch an RCA socket. You will have 220v on the RCA; not really my concept of security. Especially if you have kids around with their (sometimes) wet fingers and their unavoidable neccesity to touch everything they see.
I have used this little devices in other designs, and they work really well. Here in the link you have a technical explanation, but resuming it, the diodes will not conduct if voltage is not at least the diode breakdown voltage. So, in a non-failure situation, diodes will not conduct and the capacitor will allow to pass ONLY high frecuency interference, thus allowing the case to act as a RF shield. The resistor will mantain PE and ground tied, but reducing circulating currents caused by ground loops to a minimum.
In case of failure, like the example with the RCA, the diode bridge will allow high current faults to pass, thus tripping the breaker from the house electrical panel, and derivating those currents to earth.
Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
Attached Images
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File Type: jpg IMGP1750.JPG (180.9 KB, 247 views)
File Type: jpg lightspeed regulator v1.1.jpg (68.5 KB, 122 views)
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Old 29th April 2010, 10:56 AM   #515
AndrewT is offline AndrewT  Scotland
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Default Disconnecting Network

Hi,
the ground loop breaker or Disconnecting Network can use a low wattage resistor, 250mW is suitable. Similarly the cap can be quite small and low in voltage. 100nF, 50V or 100V ceramic would do just fine.
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Old 29th April 2010, 11:03 AM   #516
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I forgot to say that, as you can see, I have made small variations in the selected components. Input bypass cap is not a tantalum one, but a polyester one. Just because it was hanging around my closet.
I have not used an electrolytic in the output. Two main reasons:
-It may not be neccesary. As the datasheet from the regulator says, it doesn't need more than 1uF tant or film at the output to perform well. Do we really need that amount of capacitance to supply 4 leds, plus some resistors voltage drops? After all, it is a 5A (with 12A current peak :O ) regulator, a device made to provide current without dropping voltage. I think it will cope with the current demands. This way, I can avoid some of the called "electrolytic distortion".
-Space wise. I wanted it to be very small. Though, an electrolytic won't take up to much space...
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Old 29th April 2010, 11:06 AM   #517
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You are right Andrew, we don't really need a high wattage resistor. In a normal usage it will produce very few heat. And in fault condition, resistor doesn't matter as all of the current will pass through the diode bridge. The same happens with the capacitor.

Maybe making the cap bigger than 0.1uF will have a lower HF attenuation, thus making it more effective?
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Old 29th April 2010, 01:16 PM   #518
udailey is offline udailey  United States
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Regi,
They will want to be careful that their regulator tab is either well insulated or NOT attached to the heatsink as it may interact with the LM3886 if THAT is improperly insulated from the sink.
Since the max that will ever be flowing though this circuit is about 40mA then a 30V drop will actually get that regulator pretty hot. Sinking is a necessity when the LDRs are at max and min volume. Any other volume and this is not a problem, but obviously we will use these settings so there will need to be sinking and it will need to be safe.
Another thing to consider is the on/off switch of the LDRs. If we dont use a switch then the LDRs will power up when the amp is turned on. Fine since there is a delay while the relay decides to kick in and during that delay the LDRs will hit their desired settings. However when we turn it OFF we want to make sure that the LDRs turn off AFTER the amp does because if the shunt LDRs go high resistance before the amp decides to turn off (capacitance will keep it going) then we get max volume for a second or two. It would be annoying. So we could put a diode from the amps power supply + to the regulator and then after the regulator give it a decent sized capacitor so that we get some extra time on the LDRs. Yes, we could simply connect to the amps power supply caps and while voltage goes low the relay might shut the amp off while enough power is left to keep the LDRs going for a while, but I dont recall. Just something to think about and I am sure we will figure out a good and easy solution.
Uriah
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Old 29th April 2010, 01:20 PM   #519
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Just FYI, there are JRC 7805 regulators available in isolated plastic tab versions, but I don't know about LM338.
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Old 29th April 2010, 10:50 PM   #520
udailey is offline udailey  United States
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Picasa Web Albums - Uriah - Ultimate MyREF
Starting to piece it together. Still waiting on OnlineComponents. I remember last group buy we used them for some parts and its just a long long wait with them. If I had remembered at the time of the order they would not have got the order.
Heilind sent me HEY1287 instead of KEY1287.. so fixing that to.
Anyway I hate deadlines for this reason.
On a lighter note I am working on the amp. I want to get it fired up and measure the heat on that Caddock with both heatsinks to see which is best. I spoke to Aavid today and their engineer was not sure if their datasheet was right for the second sink of 6.4C/W, so I guess its up to me to find out. Bought one of those laser thermometers. I am sure it will come in handy a lot over the years.
Uriah
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