F5X -- the EUVL Approach - The Build Thread - Page 52 - diyAudio
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Old 17th March 2013, 07:19 PM   #511
Horio is offline Horio  United States
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I'm trying to calculate the output voltage of the CRC power supply, and I think I'm missing something. I'm calculating out the CRC PS output voltage to be higher than +/-16V per Dave's biasing article:

Transformer secondaries = 15Vac
Rectified voltage = (15V x 1.41) - 0.9V = 20.25V
Vdrop across fuku resistors = 4A x 0.67ohm = 2.68V

PS voltage = 20.25V - 2.68V = +/-17.5V

Is there something I'm missing, or does the CRC power supply just have a slightly higher output voltage?

Thanks
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Old 17th March 2013, 08:33 PM   #512
AndrewT is offline AndrewT  Scotland
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I thought we were aiming for a +-18Vdc supply (but my memory is terrible).
Your +-17.5Vdc is might close.
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Last edited by AndrewT; 17th March 2013 at 08:49 PM.
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Old 17th March 2013, 08:46 PM   #513
EUVL is offline EUVL  Europe
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You forgot that you have a full bridge per secondary, or two full bridges per channel.
The two rectified secondaries are only connected at the star point on the amp PCB, and not before.
So your voltage drop for the rectifier needs to double, and you are now close to +/-16V.


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Old 27th March 2013, 12:38 AM   #514
NicMac is offline NicMac  Italy
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I have received the new regulator sinks and mounting hardware from Mark and as expected the build quality is top-notch (like all the stuff from XEN audio).

I have tested the CregC circuit with the new hardware and it seems to work flawlessly and a lot cooler that the CRC that I have in the amp right now. It will however take quite some time until I will be able to report on (possible) sonic difference as I will not be able to enter it into my amp(s) in the near future.

I think this will be a "must" upgrade for all Batch 1 F5X subscribers and I suggest that we start some kind of collective order with XEN audio to get this last piece of the puzzle in place.

Did anybody else finished their F5X or am I still the only batch 1 subscriber to have heard the sound of heaven? Was the last chapter on the protection board published?

Cheers,
Nic
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Old 27th March 2013, 05:35 AM   #515
EUVL is offline EUVL  Europe
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a) You can still test the regulator by running long wires between C Reg & C.
The location of the last C is guaranteed by the layout, so long wires in between is no issue.
Also since it is not a feedback circuit, so no stability problems.

b) The purpose of sending you the hardware to you now is for you to test & listen. So please kindly do, for the benefit of all.

c) Those who actually built and finished include of course fitzfish and smyslow. Uwe also built the regulator.

d) I tried to contact Alexis but no reply at all. If nothing comes in two week then I shall write at least a test chapter.
SMD soldering instructions are easily found on the net.


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Old 27th March 2013, 03:36 PM   #516
Horio is offline Horio  United States
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Thanks Nic for the update on the CRegC, and I'm looking forward to your comparisons. Was the new regulator heatsinks/regulator board just a straight swap out, or did you have to do some adjusting/re-biasing of things afterward? I'm trying to decide if I should just hold off on completing my second build for the new CRegC heatsinks.

On a side note, Nic what did you come up with for your control/protection board setup? Were you able to get it running like you wanted with the CRC PS, or were you forced into controlling the power to the PS via the real panel switch?
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Old 30th March 2013, 02:40 PM   #517
NicMac is offline NicMac  Italy
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Default To regulate or not......

I have now tested the new regulator hardware kit I purchased from XEN audio. The voltages after the CregC supplies are a bit different than those with CRC, so I had to adjust the bias a tiny bit, but otherwise it was a straight swap.

The top of the amp is notably cooler with CregC, and for me this justifies the "upgrade". I will be taking a second kit once XEN puts it up for sale.

Out of memory, I don't find any major sonic difference between CregC and CRC. It was very, very good with CRC and it is very, very good with CregC. Maybe very, very, very good with CregC, but that would take A/B testing to find out and I do not have the time for this.
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Old 30th March 2013, 02:59 PM   #518
EUVL is offline EUVL  Europe
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The resistors (MPC74s) are specified for 5W at 70C ambient. But they do get very hot.
In our own example, they are over 140C at the resistor body.
This is not surprising as a free standing MPC74 in 20C ambient and 5W will get to 170C in our measurement.
So the resistors will work properly under those conditions.
Because the top plate is not more than 40% perforated, it does receive quite a bit of that heat locally.
A wire grid as originally proposed will be better in that sense.

Of course the problem is solved by the much larger heat sinks in the CRegC.

If my memory is correct, Uwe likes the regulator more.
But I hope the feedback will come from the testers directly.


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Old 31st March 2013, 02:10 AM   #519
Horio is offline Horio  United States
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Do you have a rough idea when the CRegC heatsink group buy will run? I think I'm going to build one CRC and wait for the new regulator sinks to finish my second build.
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Old 31st March 2013, 08:17 AM   #520
EUVL is offline EUVL  Europe
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You get organised and tell us how many, then we need to find a production lot.
Finish date probably later summer to autumn. Factory is busy, so is Mark.




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