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Re: Informative questions before starting β24 build

PostPosted: January 14th, 2018, 4:43 pm
by amb
1. 2. Look at the schematic and you'll see the four quadrants. For every BJT in one quadrant, there will be a counterpart in the other quadrants. If you want to match hfes, then match them left side to right side, as well as upper to lower. Exact hfe numbers don't matter, just make them as close as possible to each other.
3. All this matching business (and trimpot tweaking) on the β24 is strickly to establish a well-behaved DC quiescent baseline. It has no impact on the performance of the amp, except output bias settings, due to the cascode topology of every stage.

The only thing you care about the CRDs is its forward current. Not voltage. The E-501 CRDs are spec'ed to have a tolerance of 10% which should be good enough. No matching should be necessary.

Re: Informative questions before starting β24 build

PostPosted: January 27th, 2018, 11:42 pm
by Pieterh
YESSSSSS, I have two working B24 boards now! With my second board I had an issue to get the dc offset right. Then made a mistake in the process of trail and error of that board. Now I made a new third board and i just set it up and that was very easy. So now i can continue with assembling everything in the dissipante chassis and i already made a design for my panels with front express software. Keep you updated!

Re: Informative questions before starting β24 build

PostPosted: January 28th, 2018, 12:38 am
by obee
Pieterh wrote:YESSSSSS, I have two working B24 boards now! With my second board I had an issue to get the dc offset right. Then made a mistake in the process of trail and error of that board. Now I made a new third board and i just set it up and that was very easy. So now i can continue with assembling everything in the dissipante chassis and i already made a design for my panels with front express software. Keep you updated!

Congratulations, I have started building beta24 since Nov last year and finished early this month. My build is a low power version which is capable to run in full class A.

Re: Informative questions before starting β24 build

PostPosted: January 28th, 2018, 5:20 am
by mpa2
Pieterh wrote:YESSSSSS, I have two working B24 boards now! With my second board I had an issue to get the dc offset right. Then made a mistake in the process of trail and error of that board. Now I made a new third board and i just set it up and that was very easy. So now i can continue with assembling everything in the dissipante chassis and i already made a design for my panels with front express software. Keep you updated!


Pieter, were you able to identify the problem with your foulty board?

Re: Informative questions before starting β24 build

PostPosted: January 28th, 2018, 10:38 pm
by Pieterh
I have send you a pm. For others, I just made a fatal error after I replaced some bc550 and 560's and E501's which were suspected. End of board. So unfortunately. Ordered new boards. Populated one and now i have two working boards.