It's nice that the boards started to arrive. Now it's interesting who will assemble and test(listen) to the amp first.
BR Damir
BR Damir
Hi Dadod,
What is the current setting for the 2n5457/100r ccs?
I would like to replace this ccs with a current regulating diode, as 2n5457 is difficult to find.
Thanks
What is the current setting for the 2n5457/100r ccs?
I would like to replace this ccs with a current regulating diode, as 2n5457 is difficult to find.
Thanks
It's about 2 mA and it's not critical. You can use other jfet as BF245 or similar. Idss should be higher then 2 mA but not to high, let's say between 3 and 5 mA. Of course you can use a current regulating diode, but then you have to do some acrobats on the PCB.
BR Damir
Hi dadod,
Two questions:
1. About electrolytic capacitors: low ESR type for all ?
2. Are some components to be matched (and how to do that) ?
Nicola
Two questions:
1. About electrolytic capacitors: low ESR type for all ?
2. Are some components to be matched (and how to do that) ?
Nicola
I used Panasonic FC type, but any good ESR type will do. Of course you can use your preferred brand.
I first test BJTs for Hfe, and then from similar groups do Vbe matching, 5% difference is OK.
List of Vbe matched transistors and thermally connected transistors below:
Vbe ............ thermal contact
Q11-Q12 ....... Q11-Q3
Q3-Q4 .......... Q12-Q4
Q15-Q16 ....... Q15-Q13
Q13-Q14 ....... Q16-Q14
BR Damir
Anything new here? Did anyone start to assemble the board?
If you have any problem, please ask!
I suggest that you first assemble the shunt regulators and test it(adjust the voltage with the trip pot) and the pre amp part.
BR Damir
If you have any problem, please ask!
I suggest that you first assemble the shunt regulators and test it(adjust the voltage with the trip pot) and the pre amp part.
BR Damir
Dadod, did you not at some stage design a non-feedback voltage gain stage capable of larger voltage swings...?? something like 50-60 V
You can use this test setup (Richard showed it in CFA thread).
Damir
ps. with BC550C/BC560C from the same batch all transistors were inside the 5%
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Not yet, this is next on the build list. Been getting the parts together. Just got a few resistor values missing and the IRF MOSFETs to obtain.
Going to make some minor changes. Bigger decoupling caps and using 1N916B diodes instead of the 1N4148. These changes are purely because I already have them and they fit. Don't think they will have a negative impact.
Going to use Pansonic FCs, Welwyn resistors and polystyrene caps.
This is part of a bigger pre amp / DAC project.
I have so many .asc files(I simulated hundreds of different configurations) that is not easy to find what I seek.
Here is one with JFET at the input, if I find more I will send to you, pls send PM to me with your email.
BR Damir
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