Burning Amp BA-3b (Balanced)

[lhquam]

Just use a 2 pole switch or even a regular switch.
You don't necessarily need 2 wires at the output. You can just have one wire linking the ouput of BA2 to the dual feedback of F5. Then just switch it open and close.

With the feedback switch open (not grounded?) the output would see the open-loop gain of the amplifier. I think it would be far easier to compare the 2 different configurations as separate builds.

 

[Melon Head]

NO
The front end (ie F5) still has feedback.

I am saying extending a link from f5 output to BA2 output and just open and close that.

Maybe I should draw it

 

[Melon Head]

Actually I need to think about this now
I'll come back
I need to work on my project

 

[lhquam]

NO
The front end (ie F5) still has feedback.

I am saying extending a link from f5 output to BA2 output and just open and close that.

Maybe I should draw it

Here is what I simulated. I was lazy - only one output FET per rail and IRFP parts, just to get an estimate of the circuit.

 

[Melon Head]

Here is just to show you the feedback and where to place the switch.
The amp is not complete.
Just want to show you local and global switching idea

Something like that

 

[lhquam]

Here is just to show you the feedback and where to place the switch.
The amp is not complete.
Just want to show you local and global switching idea

Something like that

OK, I understand your switch idea. Good, but it doesn't do a comparison with the BA-3/BA-2 without any global feedback.

 

[Melon Head]

That is correct
I thought you were interested in F5 + BA2 with and without global feedback

 

[lhquam]

That is correct
I thought you were interested in F5 + BA2 with and without global feedback

OK I understand the confusion. Apparently you misread the earlier post:
http://www.diyaudio.com/forums/pass-labs/201281-burning-amp-ba-3b-balanced-24.html#post3054133 were I asked

Has anyone sonically compared such an amplifier with the BA-3/BA-2 or equivalent balanced versions?

.

 

[Melon Head]

OK I understand the confusion. Apparently you misread the earlier post:
http://www.diyaudio.com/forums/pass-labs/201281-burning-amp-ba-3b-balanced-24.html#post3054133 were I asked .

Yeah. I didn't read your question properly

 

[Zen Mod]

smaller mosfets in first mosfet stage ?

 

[Itsmee]

There is something similar going on in the Solid State forum.

http://www.diyaudio.com/forums/solid-state/125466-zenquito-variants-sk170-sj74-drive-2sk1058.html

 

[Melon Head]

smaller mosfets in first mosfet stage ?

Yeah 2sk2013/2sj313. I am just lazy

 

[lhquam]

smaller mosfets in first mosfet stage ?

Of course, they are only driving a small resistive load and the gates of the output MOSFETs, just like the BA-3 driving the BA-2.

 

[buzzforb]

Melon Head and Ilqam,
Perhaps the UGS thread would help. Chef goes through a similar thought process in it.

Also, Juma has an F5 Preamp circuit tha could be put in front of the BA output stage.

Just couple things to look at on your journey

 

[Melon Head]

I did all this stuff about 2 years ago. I have moved on to other things now.
Just trying to help where I can.

 

[buzzforb]

Cool. Thanks.

 

[lhquam]

Melon Head and Ilqam,
Perhaps the UGS thread would help. Chef goes through a similar thought process in it.

Also, Juma has an F5 Preamp circuit tha could be put in front of the BA output stage.

Just couple things to look at on your journey

Thanks for the pointers. I will study those threads.

 

[Melon Head]

Juma is very helpful

 

[Melon Head]

Starting my BA-3b

 

[Melon Head]

Just measured 12 x 100 Ohm vishay dale cmf50 resistors at random and got the following values:
99.98
99.98
99.97
100.00
99.98
99.97
99.98
100.00
100.01
99.98
99.98
99.98

They have definitely got their manufacturing process right