Burning Amp BA-3 - Page 76

Melon Head · 28th May 2012, 05:14 PM

You could also consider paralleling constant current sources with one of the output devices

buzzforb · 28th May 2012, 10:18 PM

As in Leaving Class A" article?

Melon Head · 28th May 2012, 10:29 PM

My memory is bad, but yeah I am reasonably sure Nelson discussed it in that article.

buzzforb · 28th May 2012, 10:35 PM

Little bit above my head, TBO. Interested though. Got to many pokers in the fire anyway. In about 2 months, it will be time to finalize my system, that will be on the agenda .

Melon Head · 10:47 PM

Well just compare BA3 front end with BA2 output stage vs BA1 output stage.
Then think BA1 output with more grunt is what you will get with BA2/current source. It is a bit of a compromise for difficult/reactive loads.
If you don't need the grunt, then BA1 output or Aleph output is all you need.
With or without these tweaks the amp will sound sensational.

buzzforb · 28th May 2012, 10:52 PM

I watch in earnest. No feedback naked F4/Ba output has a sweet sound to it. MOre musical than F5 for me. I havent messed with P3 on F5t yet. That will come when i get soundcard up and running. Too little time!

Backbones · 1st June 2012, 01:10 PM

Hi buzzforb,
We were talking about thermal drift on the BA-3 but I don't think we decided how much heatsink was enough. I was getting a variable dc offset, certainly not rock solid, using the same heatsink as in Nellson's picture in his build plans except mine had two more prongs.
Did you end up using something more substantial? Technical details or a picture would be appreciated.
Chris

buzzforb · 1st June 2012, 02:07 PM

If you are still getting drift and your fets are cool or at least warm to the touch, it is probably more circuit related than the heat related. I believe this is the primary reason for such a large cap. Mine is torn down right now, as I am in the midst of the F5T, but will be reinstalled on the sinks when I am done testing.

Kamel · 4th June 2012, 03:56 PM

Hi,

is there any issue in decreasing R10/R11 to 10Ohms, to double voltage gain? Are there Problems with oscillations?
Bias Point will be adjusted to 70mA per Device and R13 an 12W type will be used...

Best regards, Felix

Melon Head · 03:08 AM

Has anyone used panasonic FR caps? They look significantly better than panasonic FC. I am looking at ordering some for C1 and C2. However I have noticed 2 different part numbers for the same cap, but can't see what the difference is.

28th May 2012, 10:18 PM	#752
buzzforb diyAudio Member Join Date: Oct 2010 Location: Burlington, NC	As in Leaving Class A" article? __________________ \|F6 Kit/Trasnformer GB Sign up sheet Closed,\|Primrose GB Sign Up sheetClick Here ...Shape the sound , Man!

28th May 2012, 10:35 PM	#754
buzzforb diyAudio Member Join Date: Oct 2010 Location: Burlington, NC	Little bit above my head, TBO. Interested though. Got to many pokers in the fire anyway. In about 2 months, it will be time to finalize my system, that will be on the agenda . __________________ \|F6 Kit/Trasnformer GB Sign up sheet Closed,\|Primrose GB Sign Up sheetClick Here ...Shape the sound , Man!

28th May 2012, 10:40 PM	#755
Melon Head Banned Join Date: Nov 2006	Well just compare BA3 front end with BA2 output stage vs BA1 output stage. Then think BA1 output with more grunt is what you will get with BA2/current source. It is a bit of a compromise for difficult/reactive loads. If you don't need the grunt, then BA1 output or Aleph output is all you need. With or without these tweaks the amp will sound sensational. Last edited by Melon Head; 28th May 2012 at 10:47 PM.

28th May 2012, 10:52 PM	#756
buzzforb diyAudio Member Join Date: Oct 2010 Location: Burlington, NC	I watch in earnest. No feedback naked F4/Ba output has a sweet sound to it. MOre musical than F5 for me. I havent messed with P3 on F5t yet. That will come when i get soundcard up and running. Too little time! __________________ \|F6 Kit/Trasnformer GB Sign up sheet Closed,\|Primrose GB Sign Up sheetClick Here ...Shape the sound , Man!

1st June 2012, 02:07 PM	#758
buzzforb diyAudio Member Join Date: Oct 2010 Location: Burlington, NC	If you are still getting drift and your fets are cool or at least warm to the touch, it is probably more circuit related than the heat related. I believe this is the primary reason for such a large cap. Mine is torn down right now, as I am in the midst of the F5T, but will be reinstalled on the sinks when I am done testing. __________________ \|F6 Kit/Trasnformer GB Sign up sheet Closed,\|Primrose GB Sign Up sheetClick Here ...Shape the sound , Man!


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28th May 2012, 05:14 PM	#751
Melon Head Banned Join Date: Nov 2006	You could also consider paralleling constant current sources with one of the output devices

28th May 2012, 10:29 PM	#753
Melon Head Banned Join Date: Nov 2006	My memory is bad, but yeah I am reasonably sure Nelson discussed it in that article.

1st June 2012, 01:10 PM	#757
Backbones diyAudio Member Join Date: Sep 2008	Hi buzzforb, We were talking about thermal drift on the BA-3 but I don't think we decided how much heatsink was enough. I was getting a variable dc offset, certainly not rock solid, using the same heatsink as in Nellson's picture in his build plans except mine had two more prongs. Did you end up using something more substantial? Technical details or a picture would be appreciated. Chris

4th June 2012, 03:56 PM	#759
Kamel diyAudio Member Join Date: Sep 2008 Location: Mannheim	Hi, is there any issue in decreasing R10/R11 to 10Ohms, to double voltage gain? Are there Problems with oscillations? Bias Point will be adjusted to 70mA per Device and R13 an 12W type will be used... Best regards, Felix

14th June 2012, 03:05 AM	#760
Melon Head Banned Join Date: Nov 2006	Panasonic FR Has anyone used panasonic FR caps? They look significantly better than panasonic FC. I am looking at ordering some for C1 and C2. However I have noticed 2 different part numbers for the same cap, but can't see what the difference is. Last edited by Melon Head; 14th June 2012 at 03:08 AM.

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