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Old 19th June 2010, 06:11 PM   #211
udailey is offline udailey  United States
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Those transformers are great. You might consider a few more VA but they will do the trick and the Europeans seem to be happy with that brand. Us Americans are jealous because we wish we had nice encapulated trafos like that.
By the way, Antek now sells enclosures for trafos but you have to pot it yourself.
Uriah
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Old 19th June 2010, 08:40 PM   #212
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Quote:
where are your speakers?
Why do you need all the amps in the same chassis?
I plan on replacing my 5 channel amp that I use for surround sound with something more capable with music. The reason for the extra channel is the possibility of bi-amping the front 3 speakers in the future and then adding another 2 channels for the rears.

They haven't got to be in the same chassis, I just liked the idea of it and it seems more aesthetically pleasing. Also, Uriah's point about the work and cost is relevant as I'm trying to fund this project with the sale of my current amp.

Quote:
..I otherwise would prefer multiple cases. Grounding will be easier if you have a problem.
Hmm.. I hadn't thought too much about grounding yet, I was going to read up about it when I came to connect it all together, maybe I'll go and do some reading now and save a possible headache later. Thanks.

I know it will all be a tight fit, but my plan is to mount the boards vertically on their shortest edge with the LM3886 at the top and put them into the case like a row of dominoes along the back, with the trafos in a row along the front. Even with 10mm pcb mounts - to allow c21 to be fitted underneath - it will all fit into a case 430mm wide and only just higher than the length of the boards whilst still getting good access to everything. Also, I can then use a single heatsink for all 6 channels that will form part of the lid. It will be a bit hefty though.
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Old 20th June 2010, 03:33 PM   #213
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Quote:
Originally Posted by pengboon View Post
My previous power amp is 12x and it allowed me to listen with vol at 12 o'clock, with very nice sensitivity of the vol. In comparison, 31 times of the MyRefC is quite a lot more for me on 96dB speakers... All the resistors seem to be in the right places. I guess I won't be messing with anything, but the sensitivity is less than ideal for my application. I'll give it a propoer listen tomorrow.
Assuming your pot is being used simply as a potential divider of the signal (the 'standard' way) then placing a resistor in series with the pot should have the effect you are seeking. A value of about 1.5 times the value of the pot should reduce the effective gain from 30 to 12. For example, if you have a 20K pot then put a 33K in series.

signal -> 33K -> 20K pot -> ground; signal take off from the wiper.

Cheers
Geoff
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Old 21st June 2010, 03:48 AM   #214
troystg is offline troystg  United States
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[QUOTE=Stanphink;2221093]....when I suddenly thought that it might not be such a good idea to have all that stuff using just one 13A IEC?.....[QUOTE]

I would be concerned if you draw a continuous 13A @ 240VAC...

As for all in one case, if you take your time and carefully layout the parts you can do it.
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Old 21st June 2010, 04:53 PM   #215
AndrewT is offline AndrewT  Scotland
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Default from BOM Thread

you can re-form the black gate 220uF while in circuit, if both ICs are not in place.
There will be a small current flowing around R7, R8, R9, R10, dissipation of these <40mW @ 50Vdc reforming voltage and zero series reforming resistor.
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Old 21st June 2010, 08:37 PM   #216
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Quote:
Originally Posted by udailey View Post
Those transformers are great. You might consider a few more VA but they will do the trick and the Europeans seem to be happy with that brand. Us Americans are jealous because we wish we had nice encapulated trafos like that.
By the way, Antek now sells enclosures for trafos but you have to pot it yourself.
Uriah
I'm using one 225VA Nuvotem per channel. Should do the trick!! These are really nice quality and recommended!
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Old 21st June 2010, 08:58 PM   #217
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Originally Posted by jonclancy View Post
I'm using one 225VA Nuvotem per channel. Should do the trick!! These are really nice quality and recommended!
One of those on its own would be good to power both channels
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Old 21st June 2010, 09:38 PM   #218
billo44 is offline billo44  United Kingdom
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Default Questions about ground breaker

I have built a ground (loop) breaker Like the one Regi suggested from the ISP site Earthing (Grounding) Your Hi-Fi - Tricks and Techniques .

1) I don't understand how this device works or how I can test that it is working correctly?

2) I read that I should have used crimped connectors rather than solder, I understand the thinking here, but is it really necessary?

3) I should use one for each channel?

Can someone kindly point me towards a method to test this device and perhaps a little reading which might help me understand the principle of how this works? I have two decent DMM's, a dc bench supply to 32 volts, a variac, (and isolation transformer), and a bulb tester.

I don't understand how the amp works either but I can test that with my ears...this is a safety issue! I want to be sure my grounding is secure.

Thanks
Bill
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Old 21st June 2010, 11:57 PM   #219
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Originally Posted by westers151 View Post
One of those on its own would be good to power both channels
Now that would be handy.... nah, dual mono all the way!

I thought you needed 160VA per channel?
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Old 22nd June 2010, 12:22 AM   #220
Bill_P is online now Bill_P  United States
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Quote:
Originally Posted by AndrewT View Post
Except, I ordered chassis the day before the kit arrived. The smoothing caps + PCB thickness is only 1mm less than chassis height. Oops.
Sounds like that chassis is too tight. The Panasonic 10,000uF capacitors have a vent on top. An application note published by Panasonic specifies a minimum of 3mm space above the capacitor to avoid blocking the vent. Here is a quote from the application note: "If the space is smaller than the requirements, then the pressure valve may not operate
properly, leading to an explosion." That would make it a safety issue so I wanted to alert you (and others) not to block the vent. Here is another issue to consider: "Exterior sleeves or lamination covering capacitors are for indication purposes only and do not guarantee electrical
insulation."
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