HAL SYMFET

OnAudio · 2011-12-21 7:13 pm

Hi RSK,

Here it is. Let members comment for a while then you can build.

kind regards,

Harrison.

OnAudio · 2011-12-22 4:07 pm

OnAudio said:
Here it is.

The statement in the schematic that reads "Replace R37 and R38 with a 2k precision trimmer" should read "Replace R37 and R38 with a 1k precision trimmer".

OnAudio · 2011-12-22 5:50 pm

a few more graphs inorder

dadod · 2011-12-22 10:08 pm

OnAudio said:
a few more graphs inorder

Strange way to do square wave test, only positive swing???

OnAudio · 2011-12-23 2:57 am

dadod said:
Strange way to do square wave test, only positive swing???

Hi Dadod,

Not so strange :rofl:

kind regards,

Harrison.

OnAudio · 2011-12-23 2:59 am

gate protection diodes

I wonder how much heat the gate protection diodes on these output devices can take ?

Nico Ras · 2011-12-23 5:08 am

dadod said:
Strange way to do square wave test, only positive swing???

Is it not? I mentioned it in his previous design.

Nico Ras · 2011-12-23 5:19 am

OnAudio said:
I wonder how much heat the gate protection diodes on these output devices can take ?

Why? the device is rated at 150 degrees centigrade, it would be silly if they rated the diodes at any less.

Nico Ras · 2011-12-23 5:27 am

Why use a Vbe multiplier with Lateral Mosfets, that whole arrangement including precision pots can be replaced by a single resistor.

What are the purpose of D9 & D10, the double diode Vdrop will remain the same regardless of the additional noise introduced by the zener.

dadod · 2011-12-23 7:35 am

OnAudio said:
Hi Dadod,

Not so strange

kind regards,

Harrison.

OK show us +- swing, or you don't know how to do that?
Use of the bias spreader with laterals is recommended because when trimer loses conntact there is no danger of possible distraction of laterals. Trimer should be connected between base and emitter and bias transistor should not be thermaly bonded with laterals.
dado

homemodder · 2011-12-23 12:01 pm

OnAudio, why a new thread for this amp ??

You should show THD and FFT s at higher powers than 1 watt, then things dont look so rosy anymore. Show a 10 or 20 volt swing so members can better compare to other designs on the forum.

OnAudio · 2011-12-28 4:37 am

Nico Ras said:
Why? the device is rated at 150 degrees centigrade, it would be silly if they rated the diodes at any less.

Hi Nico,

Thanks about the heat.

Apologies for that meant wattage. Could they handle say 4 watts ?

kind regards,

Harrison.

OnAudio · 2011-12-28 4:55 am

Hi Nico,

Nico Ras said:
Why use a Vbe multiplier with Lateral Mosfets, that whole arrangement including precision pots can be replaced by a single resistor.

That could work. However I prefer this setup or a zener or string of diodes and it has noting to do with heat tracking

Nico Ras said:
What are the purpose of D9 & D10, the double diode Vdrop will remain the same regardless of the additional noise introduced by the zener.

There is a thread in this forums that could explain that. I have lost track of it. With rail modulation the current isn't firmly held, thus the applied measures. The Goldmund clone features one of the sinks discussed there.

kind regards,

Harrison.

OnAudio · 2011-12-28 4:59 am

dadod said:
OK show us +- swing, or you don't know how to do that?

dado

Hi Dadod,

Could you show me

OnAudio · 2011-12-28 5:16 am

Hi Homemodder,

homemodder said:
OnAudio, why a new thread for this amp ??

This amplifier isnt the one you think it is. With those FETs on the output, lets say its a different animal.

homemodder said:
You should show THD and FFT s at higher powers than 1 watt, then things dont look so rosy anymore. Show a 10 or 20 volt swing so members can better compare to other designs on the forum.

The first watt is the most important

. Exactly what do our ears perceive ?

kind regards,

Harrison.

Nico Ras · 2011-12-28 7:10 am

OnAudio said:
Hi Nico,

That could work. However I prefer this setup or a zener or string of diodes and it has noting to do with heat tracking

There is a thread in this forums that could explain that. I have lost track of it. With rail modulation the current isn't firmly held, thus the applied measures. The Goldmund clone features one of the sinks discussed there.

kind regards,

Harrison.

Very likely it will not be held by a zener either. So your reasoning is hearsay?

OnAudio · 2011-12-28 4:04 pm

Nico Ras said:
Very likely it will not be held by a zener either. So your reasoning is hearsay?

Hi Nico,

Really

?

How it works is that we take the first voltage. This voltage will have some variation, then we take a fraction of that variation by using a voltage divider. Resulting in better regulation.

How would you go about it ?

Kind regards,

Happy new year, hope your having a great time

Harrison.

RSK · 2012-01-19 2:56 pm

SYMFET - pcb first try

Hi Harrison,
I am not very good at pcb layout.
But at least I try to make the best I could. Q2 and Q17 has its individual heatsink. Output mosfets are mount under pcb.
Please commend any improvement.

Kind regards,
Raj

OnAudio · 2012-01-19 8:54 pm

Hi Raj,

Nice Job. I took a quick peek. I saw two pairs of mosfets instead of three. I found the ground slightly thin. The feedback looks ok to me since you took it from a stub.

I hope PCB domain experts will give their insights.

kind regards,

Harrison.

RSK · 2012-01-20 3:17 am

OnAudio said:
Hi Raj,

Nice Job. I took a quick peek. I saw two pairs of mosfets instead of three. I found the ground slightly thin. The feedback looks ok to me since you took it from a stub.

I hope PCB domain experts will give their insights.

kind regards,

Harrison.

Hi Harrison,
Can it work with two pairs of mosfet? What maximum rail voltage to use?
I will alter the thin tracks accordingly.

Regards.

HAL SYMFET

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