F5X -- the EUVL Approach - The Build Thread - Page 56 - diyAudio
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Old 22nd April 2013, 04:33 PM   #551
Horio is offline Horio  United States
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Tested my first (of four) amp boards over the weekend. JFET bias were all within 1%, and I threw in the output FETs. The output FETs all tracked extremely closely as the channel warmed up, and were within 5mV at the stabilized state (with no adjustments). Great job to Gerhard and Nic on the matching!

I aimed for 1.5A bias per Dave's recommendations and setup the Vgs accordingly. I ended up with about 1.6A on these initial adjustments (my +/- rails are about a 1V higher so maybe the little extra heat pushed the bias up slightly). After reading Nic's comments about the cased amp bias drifting up, I think I may shoot for bias of 1.8A or so uncased.

Last edited by Horio; 22nd April 2013 at 04:58 PM.
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Old 22nd April 2013, 05:15 PM   #552
EUVL is offline EUVL  Europe
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Congratulations.

Let it run first and test some signal, maybe even some music.
The bias you can still adjust later.
You need to anyhow when you float the X.


Patrick
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Old 22nd April 2013, 06:32 PM   #553
Horio is offline Horio  United States
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I think I will run some test signals and try playing a little one channel music before I float the X.

Speaking of bias, since my rails are a bit higher at 16.9V I'd expect the amp to run a bit warmer. In fact, I was measuring around 59 degrees C peak uncased at 1.6A bias. Connecting up the front and rear panels will add a little "heatsinking", but it still seems like my amp might run a little warmer than 62 degrees shown in the linear audio article. How hot would you feel comfortable running the heatsinks long term? 65 degrees?
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Old 22nd April 2013, 07:09 PM   #554
EUVL is offline EUVL  Europe
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Me ? 65~70C.

You should decide whether you want to go regulator eventually first.
If so you can set the regulator to 16V or even 15.5V.
And then you are free to choose.

16V 4A is optimised for 6R speakers.
So if your speaker impedance is lower, you don't want to reduce current.
If you have 8 ohm, then 1.6A per FET is plenty.


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Old 23rd April 2013, 01:42 AM   #555
heinz1 is offline heinz1  Europe
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Quote:
Originally Posted by Horio View Post
... Great job to Gerhard and Nic on the matching! ...
Thank you! I am indeed very happy to learn that our "in vitro" results are reproducible "in vivo" in your hands.
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Old 23rd April 2013, 03:52 PM   #556
ashaw is offline ashaw  Australia
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Hello all. I am making a brief post before I go offline again.

I have been horrendously buisy these last few months with more than I could handle. Not just study but other stuff too. I have sent Vitalica a refund and will send one to alazira shortly.

This is not me saying that you will not get your boards. Rather they are here ready for the first bit of testing to be done before more work is done soldering them. I want to make a testing video for them, however I do not have the time right now and do not know when I will (it could be a couple months). So please let me know which of the following options do you want:

1. I test the boards when I have the time and make up the documentation.
2. I send you them now and I still make documentation however I do it at a slightly later date and your boards and the boards have only had inspection and a cursory electrical check.
3. I send the boards and parts to the person that makes the documentation. They can keep the boards or send them on to you.

In all three cases you get to keep the refund. I will send you the only non standard part by express mail tomorrow. You should be able to sort out the rest at digikey. I have sent back more than the amount you sent me to compensate you in some way for your time.

I want to thank you for your patience so far and apologise for my lateness.

Alazira can you confirm for me how much I need to send you.

Bye for a little while. Alexis shaw.

Last edited by ashaw; 23rd April 2013 at 03:56 PM.
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Old 23rd April 2013, 06:55 PM   #557
EUVL is offline EUVL  Europe
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Alexis,

If anything, I feel sad that you are not with us anymore.
And it is obvious that you are not enjoying this hobby right now.
This is a real pity, for I above all still value your contribution to this project a great deal.


Sincerely,
Patrick
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Old 24th April 2013, 01:47 AM   #558
ashaw is offline ashaw  Australia
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I always enjoyed this hobby. Still do.

This hiatus has nothing to do with anyone here. I still want to build my amps and have a couple projects on the back burner that I will share once I have some time to get them just a little off the ground.
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Old 24th April 2013, 02:46 AM   #559
alazira is offline alazira  United States
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Quote:
Originally Posted by ashaw View Post

Alazira can you confirm for me how much I need to send you.

Bye for a little while. Alexis shaw.
Hi Alexis,
A refund in not necessary in my case.
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Old 4th May 2013, 05:16 PM   #560
Horio is offline Horio  United States
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So I'm getting down to the point where I need to start assembling the protection/control PCB. I know the protection/control board build article is in progress, but is it safe for me to start populating the boards per the latest BOM? Or would it be wiser/easier to wait for the build article for the fix?
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