F5 power amplifier - Page 152

h_a · 25th July 2008, 03:56 PM

Quote:

This place is called DIY Audio ??

Ja!!

C'mon! One fetish piece of his Passness is a must!

The other zillions of pcbs I've still to do myself.

Have fun, Hannes

By the way: maybe somebody wants to work out a nice jfet only JLH with LU1014 in the output? I have such a feeling that mine will never be finished....

h_a · 26th July 2008, 11:12 AM

By the way, could somebody tell me what the limiting factor for the F5's power into 2R is?

Fig. 10 in the article shows clipping at 50W into 2R - at this power the F5 already left ClassA (5 A output current), but didn't not yet approach the rail (10 V output voltage).

What's happenin here?

Have fun, Hannes

MEH · 26th July 2008, 01:15 PM

Safe Operating Area limits of the MOSFETs. At least that's what I take it Papa means when writing: "The amplifier with 24 supply rails should be good for a 50 watt peak into 8 ohms, or about 2.5 amps. For a 4 ohm load we would want 5 amps, and for a 2 ohm load, we want 10 amps. Since we only have two output devices, we probably are best off stopping there."

h_a · 26th July 2008, 02:29 PM

No, the current limiting has nothing to do with clipping, the abrupt onset of large distortion.

It's current limited to 10A, so with 5A far away.

Have fun, Hannes

sandstorm33 · 26th July 2008, 06:18 PM

Quote:

Originally posted by jacco vermeulen
Actually, i was thinking of using the F5 boards as body jewelry at the nudy beach.
Single Ended, of course.

Hardly expeditious......all that wasted space!

Nordic · 26th July 2008, 08:48 PM

Has anyone come up with replacements for te 2sk170 and 2sj108... and the one alternative given for each by Nelson?

My boards are 55mm x 130mm, virtualy fully semetrical, with the outputs about 100mm appart.

The 2sj108 and its alternative specificaly seem to be hard to find...

Nordic · 26th July 2008, 10:21 PM

oops left out the decoupling caps and Ground, hahaha

Traces were slightly optomised again...

Nordic · 26th July 2008, 10:23 PM

and of course the PCB for comments

EUVL · 27th July 2008, 05:52 AM

I would perhaps move the power supply connections to the bottom left and right corners to aviod any voltage difference between the common nodes of the MOSFET source resistor and the JFET drain resistors. Also makes it easy to double up to a balanced on one PCB. And for that matter perhaps use a soldered jumper to connect the 10R (for which I use 3x 33R 0.25W in parallel) JFET source resistors to Gnd, which allows you to convert to an X-Balanced later. All options then open.

Otherwise quite well done, I thought.

Patrick

Nordic · 27th July 2008, 07:22 AM

Hi thanks for the reply...

I thought about cornering the two power points, but decided to stick with the stared layout giving all components accesing those nodes, connection at a single (reference) point, in the same way you might be used to seeing ground stars. It has the benefit of not makeing high and low current paths shareing the same tracks... (Quieter operation)

I do not see myself going balanced soon, but I will try to find the balanced schematic in this long thread, to get a grasp of what you intended wit the 10R's.

Also, I still need to sim the boards to check dissipation etc, so it will likely still change a little...

26th July 2008, 11:12 AM	#1512
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	By the way, could somebody tell me what the limiting factor for the F5's power into 2R is? Fig. 10 in the article shows clipping at 50W into 2R - at this power the F5 already left ClassA (5 A output current), but didn't not yet approach the rail (10 V output voltage). What's happenin here? Have fun, Hannes __________________ fresh matched IRFP240/IRFP9240 fets \|\| AlephJ/JX-kits F5 transistor kits \|\| Burning Amp BA-1/2/3 transistor kits

26th July 2008, 02:29 PM	#1514
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	No, the current limiting has nothing to do with clipping, the abrupt onset of large distortion. It's current limited to 10A, so with 5A far away. Have fun, Hannes __________________ fresh matched IRFP240/IRFP9240 fets \|\| AlephJ/JX-kits F5 transistor kits \|\| Burning Amp BA-1/2/3 transistor kits

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26th July 2008, 01:15 PM	#1513
MEH diyAudio Member Join Date: Feb 2007	Safe Operating Area limits of the MOSFETs. At least that's what I take it Papa means when writing: "The amplifier with 24 supply rails should be good for a 50 watt peak into 8 ohms, or about 2.5 amps. For a 4 ohm load we would want 5 amps, and for a 2 ohm load, we want 10 amps. Since we only have two output devices, we probably are best off stopping there."

27th July 2008, 05:52 AM	#1519
EUVL diyAudio Member Join Date: Oct 2003	I would perhaps move the power supply connections to the bottom left and right corners to aviod any voltage difference between the common nodes of the MOSFET source resistor and the JFET drain resistors. Also makes it easy to double up to a balanced on one PCB. And for that matter perhaps use a soldered jumper to connect the 10R (for which I use 3x 33R 0.25W in parallel) JFET source resistors to Gnd, which allows you to convert to an X-Balanced later. All options then open. Otherwise quite well done, I thought. Patrick

27th July 2008, 07:22 AM	#1520
Nordic diyAudio Member Join Date: Sep 2005	Hi thanks for the reply... I thought about cornering the two power points, but decided to stick with the stared layout giving all components accesing those nodes, connection at a single (reference) point, in the same way you might be used to seeing ground stars. It has the benefit of not makeing high and low current paths shareing the same tracks... (Quieter operation) I do not see myself going balanced soon, but I will try to find the balanced schematic in this long thread, to get a grasp of what you intended wit the 10R's. Also, I still need to sim the boards to check dissipation etc, so it will likely still change a little...

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