Burning Amplifier BA-2 - Page 68

Backbones · 18th February 2011, 01:03 PM

Quote:

Originally Posted by Zen Mod

I really can't remember how this ended in this thread

Sometimes you've just got to go where the mood takes you.

Backbones · 10:06 PM

In spite of my uncertainty on the previous page I have gone ahead and I have been running the amp (one monoblock) on full mains power and nothing is smoking.
However, Nelson refers to setting P201 to adjust the Drain voltage of Q203 to 0 volts.
Do I measure across resistor R215 for this?
Regards,
Chris

nightrush · 25th February 2011, 09:50 AM

If I understood Nelsons instructions right, you want to measure the voltage between the drain-pin and GND actually. However, this adjustage isn't very critical, as any dc will be blocked by the cap anyway.

EDIT: We want some pictures, instantly

Best Regards, Florian

Backbones · 25th February 2011, 12:28 PM

Thanks Florian,
I'll measure that anyway.
Here are some photos. If my chum doesn't come through with the other chassis then I'll have to transfer the whole thing. At the moment I have 250mV across the source resistors and the heatsinks are barely warm after 15 minutes.
Regards,
Chris

Tea-Bag · 25th February 2011, 01:11 PM

Let it run for 4 hrs like this and see where it goes. If it can take it, double the bias, or order another set of outputs!
Nice work!

Backbones · 25th February 2011, 04:03 PM

I've pushed the bias up to 400mV and the heatsink temperature is rising to comfortable heat, however, the ambient temp in my workshop is about 12 deg C so I'm it's going to be running hotter in the house.
Regards,
Chris

joda · 27th February 2011, 08:28 AM

Hi friends
A simple question:
You can make a power supply to a BA2 +40-0-40 V?
can be dangerous?
I have at home a pair of transformers 28 0 28 AC,,,,,
any input?
rgds

Tea-Bag · 27th February 2011, 12:15 PM

Not with the default input boards....There is a cascoded design Jim M made, that uses this, although he is using around a 36-40v tranny. I am using the same boards and tranny range.

Nelson Pass · 28th February 2011, 01:54 AM

Quote:

Originally Posted by Backbones

Any reason not to use 47K resistor instead of 47.5K on BA-2 front end at resistors R203 and R204?

A wide range of value is OK. The false precision of 47.5K
is simply the result of using my favorite resistor type.

Backbones · 05:22 PM

Strange question to ask but how loud should the amp be? I've turned the pre-amp volume control to 3/4 of the way round and I'm just getting a reasonable output. The exposure amp on the other channel is too loud to listen to. Heatsinks are warm to hot at 410mV across the output resistors. Nice sound when I can hear it though! Running it in single-ended mode.
Any thoughts?
Regards,
Chris

24th February 2011, 10:02 PM	#672
Backbones diyAudio Member Join Date: Sep 2008	In spite of my uncertainty on the previous page I have gone ahead and I have been running the amp (one monoblock) on full mains power and nothing is smoking. However, Nelson refers to setting P201 to adjust the Drain voltage of Q203 to 0 volts. Do I measure across resistor R215 for this? Regards, Chris Last edited by Backbones; 24th February 2011 at 10:06 PM.

28th February 2011, 05:17 PM	#680
Backbones diyAudio Member Join Date: Sep 2008	Strange question to ask but how loud should the amp be? I've turned the pre-amp volume control to 3/4 of the way round and I'm just getting a reasonable output. The exposure amp on the other channel is too loud to listen to. Heatsinks are warm to hot at 410mV across the output resistors. Nice sound when I can hear it though! Running it in single-ended mode. Any thoughts? Regards, Chris Last edited by Backbones; 28th February 2011 at 05:22 PM.

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25th February 2011, 09:50 AM	#673
nightrush diyAudio Member Join Date: Mar 2010 Location: Kulmbach	If I understood Nelsons instructions right, you want to measure the voltage between the drain-pin and GND actually. However, this adjustage isn't very critical, as any dc will be blocked by the cap anyway. EDIT: We want some pictures, instantly Best Regards, Florian

25th February 2011, 01:11 PM	#675
Tea-Bag not politcally affiliated diyAudio Member Join Date: Feb 2006 Location: Kennebunk Blog Entries: 5	Let it run for 4 hrs like this and see where it goes. If it can take it, double the bias, or order another set of outputs! Nice work!

25th February 2011, 04:03 PM	#676
Backbones diyAudio Member Join Date: Sep 2008	I've pushed the bias up to 400mV and the heatsink temperature is rising to comfortable heat, however, the ambient temp in my workshop is about 12 deg C so I'm it's going to be running hotter in the house. Regards, Chris

27th February 2011, 08:28 AM	#677
joda diyAudio Member Join Date: Feb 2005 Location: roma	Hi friends A simple question: You can make a power supply to a BA2 +40-0-40 V? can be dangerous? I have at home a pair of transformers 28 0 28 AC,,,,, any input? rgds

27th February 2011, 12:15 PM	#678
Tea-Bag not politcally affiliated diyAudio Member Join Date: Feb 2006 Location: Kennebunk Blog Entries: 5	Not with the default input boards....There is a cascoded design Jim M made, that uses this, although he is using around a 36-40v tranny. I am using the same boards and tranny range.

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