F5X -- the EUVL Approach - Page 31 - diyAudio
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Old 13th July 2011, 11:36 PM   #301
EUVL is offline EUVL  Europe
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So some tipps about the matching:

You need only one point match at Id = 4A, with Vds = Vgs.
The Vgs at 4A is somewhere between 2.4 to 2.9V, so assume 3V max.
Connect drain to the 4A current source output, and the gate to the same but via a 1k resistor.
Connect source to the return path of the current source.Obviously reverse polarity for 2SJ618.
Mount the Device Under Test (DUT) on a large block of aluminium, or you will not get a stable reading.
(due to high tempco)

We used LT1084 as current source, but it has oscillations which needs taming.
If we do it again we would use 4x LM317 in parallel, each giving 1A.
(See NS datasheet P.16 1A current regulator)
Power supply current limits at 4A might be OK if it remains stable enough over time.
You need to monitor current as well as Vgs in any case.
I would set power supply to 8V or so.
You need good heatsinks for LM317s, best to fan cool.


Patrick
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Old 14th July 2011, 02:04 AM   #302
EUVL is offline EUVL  Europe
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We have sent to qusp as small packet registered today.

Disclaimer :
We cannot be held responsible for postal losses.
Happened to us twice in 2 years, both times with the USPS.
So the HK Post was not at fault.


Patrick
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Old 14th July 2011, 04:21 AM   #303
pchw is offline pchw  United States
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Thanks for the tip, Patrick.
I will mount all LM317 in one big heat sink (all insulated) with a blower on the side. I have a regulated power supply that can feed up to 40V/5A. Hopefully, that will do the job.
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Old 14th July 2011, 05:02 AM   #304
qusp is offline qusp  Australia
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Thanks Patrick, dont worry i know the drill, i think we'll be fine, but i realize sometimes stuff beyond our control just happens. will let you know when it arrives
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Old 14th July 2011, 06:52 AM   #305
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Great news Fred. Many thanks indeed.
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Old 14th July 2011, 11:07 PM   #306
EUVL is offline EUVL  Europe
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Payment received from AndrewT. Will send MOSFETs in next days.


Patrick
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Old 15th July 2011, 08:50 AM   #307
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Quote:
Originally Posted by pchw View Post
Thanks for the tip, Patrick.
I will mount all LM317 in one big heat sink (all insulated) with a blower on the side. I have a regulated power supply that can feed up to 40V/5A. Hopefully, that will do the job.
would you show setup / schematic
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Old 15th July 2011, 03:49 PM   #308
EUVL is offline EUVL  Europe
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Mosfets for AndrewT, fitzfish & smyslow sent.
Only pending John & "400". Both on holiday.

Patrick
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Old 16th July 2011, 08:09 PM   #309
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Quote:
Originally Posted by Studley View Post
Patrick
just as an aside and to keep us bobbing along, apart from having more power, how does the F5X compare to the F5 sonically?
I did Aleph5, Aleph2, AlephX, F3, F5.
With the help of Patick, I did F5X.
In my system I now Aleph2 (bass) and F5X for Supravox (full range)
F5X for me is the - BEST!!
It's very quiet, neutral and voices are incredible.
I love F5 balanced ,I want to make one

Thank you Patrick for that my system is this great amplifier!
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Old 16th July 2011, 11:42 PM   #310
EUVL is offline EUVL  Europe
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You should consider following the approach here and make a pair of new ones based on Toshiba MOSFETs.
As mentioned the test team will go through a few circuit variations and make comparison.
So you should wait until that has been reported before choosing one that suits your taste.

The modules you have still have Fairchild MOSFETs.
IMHO Toshiba sounds even better. More refined.

As usual, I am totally biased.
But that's the spirit of Class A, right ?




Patrick
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