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Burning Amplifier BA-3
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Old 27th September 2018, 10:26 AM   #41
dodovouk is offline dodovouk
diyAudio Member
Join Date: Sep 2017
Default BA3 Gain and Output boards

I a building the single-ended version from DIYAUDIO. It appears they gain board does not output enough to drive the power boards hard enough. The gain board clips at 19v and the output board only amplifies current, not voltage. Has anyone else experienced this? Is there a solution?
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Old 6th May 2019, 04:40 PM   #42
cyliew is offline cyliew  Malaysia
diyAudio Member
Join Date: Jul 2003
Location: Penang
Default matched JFET selection for BA3

Good day,

I understand this thread was started many years ago and hopefully members will still reading my post.

I am building BA3 to drive F5 in my recent project, and I bought 2 sets of LSK170/LSJ74 double matched pair from DIYAudio store since I am building two sets of them together with my friend. Upon receiving the parts from store, I performed one round of VI curve tracing using Keysight IV Measurement software on all of them.
Burning Amplifier BA-3-lsj74-iv-plots-png
Burning Amplifier BA-3-lsk170-iv-plots-png

The original matched pair is labelled as LSK170/LSJ74 & LSK170_3/LSJ74_3 in one group, then LSK170_1/LSJ74_1 and LSK170_2/LSJ74_2 in another group.

Below is the measured Idss value.
Burning Amplifier BA-3-ids-10vds-0vgs-png

And this is the default matching suggestion.
Burning Amplifier BA-3-default-matched-pair-png

Below is another table showing the delta of each LSJ compared to all LSKs.
Burning Amplifier BA-3-delta-lsj-lsk-png

And from the delta above, I notice that if I rearrange it with yellow color matching, I can get a more balanced on left and right channel of each BA3 as shown below.
Burning Amplifier BA-3-matched-pair-png

My question is, how I should choose the best matching pattern for a balanced Left and Right system? Is my new matching pattern make sense? Or is there anything that I should consider on selecting the matched pair?

Attached Images
File Type: png LSJ74 IV plots.PNG (159.9 KB, 212 views)
File Type: png LSK170 IV Plots.PNG (208.0 KB, 213 views)
File Type: png Ids at 10Vds 0Vgs.PNG (8.9 KB, 208 views)
File Type: png Default matched pair.PNG (5.4 KB, 208 views)
File Type: png New matched pair.PNG (5.2 KB, 206 views)
File Type: png Delta of LSJ to LSK.PNG (4.7 KB, 209 views)
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