jacco vermeulen said:
Thank you very much. A lot more information than the two page version I had.
Peak Ft should be another consideration. For lower current drivers, h(re) can be interesting to consider. (Put that in your pipe and smoke it, Scott and Bob)
jacco vermeulen said:
How about MJE171/MJE181? I have couple ten pairs ordered from Mouser ready to use.
john curl said:Peak Ft should be another consideration. For lower current drivers, h(re) can be interesting to consider. (Put that in your pipe and smoke it, Scott and Bob)
Unfortunately most datasheets do not tell much about the "h" parameters, except for hfe. But I will continue looking.
The 2SA1209/2SC2911 have their highest ft in the 20-50mA range (almost like a plateau) and hfe is linear and begins barely to drop at 50mA, this is why I think they might be usable here.
GK7, I offered h(re) as a 'one up' jest to Bob Cordell and Scott Wurcer. You don't have to worry about it in this example, just peak beta, and peak Ft.
Thank you for clarification, this makes it a lot easier.
It was very interesting to learn about the history of this circuit (Post #138),
the only thing I did not understand was: What does the "HP" in
"HP type additions" stand for, Hewlett Packard ?
It was very interesting to learn about the history of this circuit (Post #138),
the only thing I did not understand was: What does the "HP" in
"HP type additions" stand for, Hewlett Packard ?
I see. I will omit the HP type additions (I will need the relatively small space for the heatsinks anyway).
Attached is the schematic in it´s latest version (for now ;-) ), each Fet will run at 12mA, and the BJTs at about 50mA.
Next thing will be to change the capacitors to polypropylene types and to master Eagle PCB which is new to me (last time I used such a program it was running on DOS in the early 90ties ). I will report any progress here but it will take some time.
@HKC Did you already start with the phono stage ? Maybe we could discuss it here.
Attached is the schematic in it´s latest version (for now ;-) ), each Fet will run at 12mA, and the BJTs at about 50mA.
Next thing will be to change the capacitors to polypropylene types and to master Eagle PCB which is new to me (last time I used such a program it was running on DOS in the early 90ties ). I will report any progress here but it will take some time.
@HKC Did you already start with the phono stage ? Maybe we could discuss it here.
GK,
your choice of 20r for R4 is almost correct.
You need some adjustment to balance the front end currents, otherwise this balance will vary with component parameters.
22r//500VR will give a nice range of adjustment.
your choice of 20r for R4 is almost correct.
You need some adjustment to balance the front end currents, otherwise this balance will vary with component parameters.
22r//500VR will give a nice range of adjustment.
gk7 said:
Hi gk7
I am about to send the pcb document to factory for boards fabrication. I decided to use my own layout for the phono and RIAA sections. I will post photos once the boards are finished.
gk7 said:
It's annoying to see you still don't show the inverting input as externally connectable.
Yes,
I've read the thread, but not made any attempt to memorise it.
I am commenting on your latest schematic and reminding you to design in some adjustment to allow for parameter variations.
I've read the thread, but not made any attempt to memorise it.
I am commenting on your latest schematic and reminding you to design in some adjustment to allow for parameter variations.
AndrewT said:
The original does not use such an adjustment and later Designs with this type of circuit (Parasound) do not use it. It´s obviously superfluous.
HKC said:
Did you design an entirely new schematic or are you referring to the pcb layout only ? In the latter case what did you substitute for the Fets ?
