I see now the connection in 6L6's SE diagram between -in and V- that completes the loop. Thanks again.
Hi there, sorry if naive question or off topic.
I wondered if the brillant simplicity of the HFE could work for non differential DAC ic curent output for a transimpedance task ?
Shunt resistor at the output and Ti JFE2140 (quiet enough ?) for the ones being far from DIYAUDIO store (for matched Jfet) like europeans and to avoid the mess of purchasing many J113 (or better) and sorting out them ?
I know there is the D1 with Hexfet iirc but it is made for dual and differential dac ic...
I often wonder on how to avoid a dc blocking cap for such a job ?
I wondered if the brillant simplicity of the HFE could work for non differential DAC ic curent output for a transimpedance task ?
Shunt resistor at the output and Ti JFE2140 (quiet enough ?) for the ones being far from DIYAUDIO store (for matched Jfet) like europeans and to avoid the mess of purchasing many J113 (or better) and sorting out them ?
I know there is the D1 with Hexfet iirc but it is made for dual and differential dac ic...
I often wonder on how to avoid a dc blocking cap for such a job ?
I've been brewing a FE2022 linestage in my own thread over here:
https://www.diyaudio.com/community/...-to-fit-a-specific-space.413744/#post-7724830
I had some oscillation that was fixed with the addition of lag compensation cap C6.
I would not have expected to need C6 for a simple linestage implementation.
I thought from the documentation from Papa that this should only be required for driving difficult loads etc.
If it isn't normally needed, is this likely due to my layout not being less optimal than the boards from the store?
https://www.diyaudio.com/community/...-to-fit-a-specific-space.413744/#post-7724830
I had some oscillation that was fixed with the addition of lag compensation cap C6.
I would not have expected to need C6 for a simple linestage implementation.
I thought from the documentation from Papa that this should only be required for driving difficult loads etc.
If it isn't normally needed, is this likely due to my layout not being less optimal than the boards from the store?
Very likely. A PCB is not just FR-4 and conductive paths, there is capacitance and inductance that interacts with the circuit that lives within it. Hence my warning awhile back "it may oscillate". (Remember papa is a circuit wizard)
Inputting a square wave can tell you a lot.... a picture example here (20khz input, 40V p-p output)
Inputting a square wave can tell you a lot.... a picture example here (20khz input, 40V p-p output)
Am I correct that the value of c6 should be as low as possible while still ensuring stability?
Specifically, 22pF made things stable. Is there much point trying to lower the value when Papa said 33pF should have no effect on distortion?
Specifically, 22pF made things stable. Is there much point trying to lower the value when Papa said 33pF should have no effect on distortion?
Last edited:
My understanding is.... too high = affects open loop bandwidth and THD20 gets worse, too low = stability margin gets worse. Trust Pa when in doubt. 20kHz square wave looks good with 33pF?
There may be a person or two on the planet of the opinion that the type of miller cap can affect the subjective result... silvered mica, polystyrene, NPO/COG ceramic (at higher frequencies, almost all signal current from the input stage flows through this miller cap)
There may be a person or two on the planet of the opinion that the type of miller cap can affect the subjective result... silvered mica, polystyrene, NPO/COG ceramic (at higher frequencies, almost all signal current from the input stage flows through this miller cap)
Ah it is designed low voltage input circuitry in mind (only voltage gain for the few I understand). Humm sorry for the question above. 
I ran some more tests last night.
With a 10k load and the 22pF caps I have on hand. Square waves look good right out to 40kHz where I stopped testing.
I think I will just call it done rather than fluff about ordering more caps in lower values and potentially damaging traces.
Just goes to show: The circuit is so good it still works despite my ham fisted, midwit layout.
Newcomer to this thread. I've bought the kit and now sourcing the other components.
C4 & C5, these are 1000uF 25v.
Left over from another project I have 3300uF 25v. Can I substitute or is the 1000uF specified critical ?
Thanks..Bob
C4 & C5, these are 1000uF 25v.
Left over from another project I have 3300uF 25v. Can I substitute or is the 1000uF specified critical ?
Thanks..Bob
Many thanks for the confirmation.
Box is big enough that if they don't fit on top I can fit from below.
Box is big enough that if they don't fit on top I can fit from below.
I meant if they physically fit on the PCB, is the footprint the same as with the original caps?
I have assembled a FE 2022 pre-amp but I am facing some issues: I would appreciate any input diagnosing the issue. I have added my wiring diagram and a picture of the assembly below.
I have measured the 48V the power filter and it is fine. The two main issues I have are:
Thanks,
Adrian
I have measured the 48V the power filter and it is fine. The two main issues I have are:
- I tried to measure with the Picoscope using a signal generator at input (Ain, Acom) and a probe at output (Out, V-) which caused a spark at Acom & V- as the picoscope has a common ground.
- I then used the signal generator at in input and a fluke volt meter and measured if I can measure a sinus amplified which also did not work.
Thanks,
Adrian
DO NOT CONNECT NEUTRAL TO CHASSIS!!!! Electrocution will follow.
Connect AC earth to chassis.
Connect AC earth to chassis.
Do not connect IN ground wire to VG. With a V+ power supply, V- on the board becomes Ground (and R10 is replaced by a jumper). So connect IN ground wire from RCA to V- on the board.
Also connect IN- on the board to V- (Ground).
Hopefully there was no damage to the attached equipment. With a unipolar power supply VG on the board has half of the power supply voltage.
Also connect IN- on the board to V- (Ground).
Hopefully there was no damage to the attached equipment. With a unipolar power supply VG on the board has half of the power supply voltage.
Last edited:
Watching adrianrw's build with interest (I'm hoping to do something similar, hopefully in the next several months).
Adding to the 2 comments above, I found 6L6's very helpful illustration for PS wiring in post #454: https://www.diyaudio.com/community/posts/7283612/
(Apologies if the post is a little redundant.)
Adding to the 2 comments above, I found 6L6's very helpful illustration for PS wiring in post #454: https://www.diyaudio.com/community/posts/7283612/
(Apologies if the post is a little redundant.)
Has anybody tried the circuit with jfe2140 yet?
From the looks of it, aside from a new layout being required, it looks to me like a drop in replacement.
From the looks of it, aside from a new layout being required, it looks to me like a drop in replacement.
