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-   -   Hafler bias current (http://www.diyaudio.com/forums/solid-state/11005-hafler-bias-current.html)

Fritz 10th February 2003 11:46 PM

Hafler bias current
 
Does anyone have suggestions on DH200 bias current?
Or even the factory spec?
Fritz

george a 11th February 2003 12:39 AM

I think from memory it is about 1 or 200mA from factory with up to 400mA for Pooge refit- I will need to check pooge article.

Nelson Pass 11th February 2003 12:42 AM

I recall that its only about 100 mA per device, certainly
not a lot more.

This is one place where a higher bias will really make a
difference, IMHO. I say crank that bias up to until the
heat sinks run at 50 deg C, which I would bet is about
300 mA per device.

Better yet, put a fan on them and take them up to 500 mA.

:devilr:

george a 11th February 2003 12:49 AM

While you're mucking around with the bias , try adding some regulators to the main boards It makes a huge difference for minimal cost and effort

Fritz 11th February 2003 01:04 AM

Ill start at 125-150 and fine tune to a higher bias by smell. On the other hand I should get it back to my sister in one piece if possible. I see there are thermo switches, they must be there for experimentation.

I put in the ESL speaker protection circuit so now it doesnt throw my subwoofer cone out of the box at startup. It was passing a large 10v + DC at powerup.

Thanks for the input.

Fritz

Fritz 11th February 2003 01:05 AM

Thanks George,

Unfortunately I probably dont know enough to fit regulators. Which voltage would I want to regulate?

mlloyd1 11th February 2003 01:40 AM

Re: Hafler bias current
 
The schematics in the manuals say 100mA per device. That's right on with the databook recommendation to run at the zero temperature coefficient operating point for the devices ...

However, my amps that use these devices (or similar lateral technology parts) benefitted sonically from having more. I think right now I'm running about 400mA per MOSFET.

Be concerned about the heatsinking if you are doing this in a Hafler with +/- 65V rails! Or as Nelson says get a fan.

mlloyd1

Quote:

Originally posted by Fritz
Does anyone have suggestions on DH200 bias current?
Or even the factory spec?
Fritz


Fritz 12th February 2003 03:44 AM

So 100mA per device and there are 2 in parallel so Id measure 200mA through the fuse?

mlloyd1 12th February 2003 12:21 PM

Depends on how precise you want to be. Technically speaking, you should also add the bias current of the current/sink for the diff stage and the driver stage. I don't have the schematic in front of me at the moment but i thinking adding about 20mA is reasonable. So, I'd look to measure about 220mA through the fuse.

Make sense?

mlloyd1

Quote:

Originally posted by Fritz
So 100mA per device and there are 2 in parallel so Id measure 200mA through the fuse?

jam 12th February 2003 12:27 PM

Mr.Pass is right.

I used to run my Hafler at 450ma per channel. It is amazing how much better it sounds. Keep amplifier in a well ventilated location though.

Jam


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