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GB for DC coupled B1 buffer with shunt PSUs

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#1,541
gabanyayaya said:
Is this what you mean...? Which is the wrong one?

An externally hosted image should be here but it was not working when we last tested it.
Click to expand...

There is NO "PCB error" as can be seen by looking at the photos of the prototypes. The screens are correct as are the orientations of the transistors.

I may be reading incorrectly but I believe that AndrewT is pointing out something he thinks is incorrect as he stated in Post 148. Please read the reply to this by Salas. The prototypes work well and sound great.
 
#1,544
jFET error

billyk said:
There is NO "PCB error" as can be seen by looking at the photos of the prototypes. The screens are correct as are the orientations of the transistors.

I may be reading incorrectly but I believe that AndrewT is pointing out something he thinks is incorrect as he stated in Post 148. Please read the reply to this by Salas. The prototypes work well and sound great.
Click to expand...
Hi,
please ignore my post148 and my references to it for this PCB. It works as drawn.

Now let's look at the 4devices inside the red rectangle.
The top is negative.
The bottom is positive.

The upper jFET (-ve side) has the Drain connected via a 10r to ground.
The Gate and Source pins are on a common trace and connected to the LEDs.
This is correct.

The lower jFET (+ve side) has the Source connected via a 10r to ground.
The Gate and Drain pins are on a common trace and connected to the LEDs.
This is wrong.

My suggested solution is wrong.
Do not rotate the jFET.
The trace joining Drain to Gate must be cut.
The Gate and Source pins must be soldered together. A long Gate pin under the board can be bent over and soldered to the nearby Source pin.

I am glad you all argued the point.
It made me look again and again to see that the real solution is as stated above.
 
#1,547
AndrewT said:
Hi,
please ignore my post148 and my references to it for this PCB. It works as drawn.

Now let's look at the 4devices inside the red rectangle.
The top is negative.
The bottom is positive.

The upper jFET (-ve side) has the Drain connected via a 10r to ground.
The Gate and Source pins are on a common trace and connected to the LEDs.
This is correct.

The lower jFET (+ve side) has the Source connected via a 10r to ground.
The Gate and Drain pins are on a common trace and connected to the LEDs.
This is wrong.

My suggested solution is wrong.
Do not rotate the jFET.
The trace joining Drain to Gate must be cut.
The Gate and Source pins must be soldered together. A long Gate pin under the board can be bent over and soldered to the nearby Source pin.

I am glad you all argued the point.
It made me look again and again to see that the real solution is as stated above.
Click to expand...

Its as such on the board on purpose. Look here for more and why.
 
#1,551
AndrewT said:
why is the modification the case for the universal version but not for the DCB1 version?
Click to expand...

I found that in the case of DCB1 by introducing some deliberate asymmetry to the Vref current (this having an impact to Vleds too) I could feel it subjectively more pleasing, plus it helped somewhat easier offset in audio parts Jfets pairs by rather grosser matching standards as far as I have checked on some couples. Of course it will work both ways. But in the case of using it as a pair of shunt regs for general use, I have shown the orthodox way in that psu only guide. I don't know what circuits could be supplying and if there will be any fortunate synergy or not. Back in this very thread I have referred again about the Vref current asymmetry, it was when discussing an Australian Hypno proto build if I recall correctly. So the Jfet orientations on the PCBs are as intended and further tested in the proto phase. Each PCB that T-Bag delivered is compliant to the circuits that were finally decided and proto tested. For the learned members that will like to change whatever in the orientations or in the way that the error amp of the reg sees the load, they are more than welcome to show alternatives in the build thread. Some may want to listen to alternatives and follow. As it is on the boards given, is exactly as intended to be from me, and as the proto team tested and liked enough.

Regards, and happy building / listening to all. Will be great to see your builds in the dedicated thread.
 
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