There is a lot of buzz in the MOX and related threads. All the suggested discrete opamps use JFETs like SK389 and J113 for the input stage.
I tried J111 in moamps circuit but it fails to work on the bench although the sim results are excellent. Other JFETs are very hard to come by except BFW10 and BFW11 and I wonder whether these would be suitable.
Hence, I have been trying various versions of bipolar discrete circuits. They sound very good with the only disadvantage of requiring input and output capacitors. Trimming offset has proved to be nearly impossible.
Does anyone here have any variant of bipolar discrete opamps (either 2 stage or 3 stage) which do not require input and output caps and have inverting and non-inverting inputs. I am asking since I have seen Class A buffers, but they have x1 gain and single inputs. I require some gain in the scheme that I would like to follow.
Any help would be appreciated and I think this would also help many of the forum members who are not able to obtain JFETs in their countries. Thanks!
I tried J111 in moamps circuit but it fails to work on the bench although the sim results are excellent. Other JFETs are very hard to come by except BFW10 and BFW11 and I wonder whether these would be suitable.
Hence, I have been trying various versions of bipolar discrete circuits. They sound very good with the only disadvantage of requiring input and output capacitors. Trimming offset has proved to be nearly impossible.
Does anyone here have any variant of bipolar discrete opamps (either 2 stage or 3 stage) which do not require input and output caps and have inverting and non-inverting inputs. I am asking since I have seen Class A buffers, but they have x1 gain and single inputs. I require some gain in the scheme that I would like to follow.
Any help would be appreciated and I think this would also help many of the forum members who are not able to obtain JFETs in their countries. Thanks!
Simplest discrete opamp you can see on pages of firm Bryston, where is used as input amp of power amps 😉 .
discrete op amp
hi samuel. In the wireless world jan 1985 john linsley-hood describes a stunning symmetrical discrete op-amp,which should sound better than most i.c. op-amps.I hope that helps. Pierre
diy audio veteran.
hi samuel. In the wireless world jan 1985 john linsley-hood describes a stunning symmetrical discrete op-amp,which should sound better than most i.c. op-amps.I hope that helps. Pierre
diy audio veteran.
Samuel Jayaraj said:
Hi Samuael,
The complementary part of the 2SK389 is the 2SJ109.
But you can also build a discrete folded cascode opamp with a non complementary frontend as Sonnya and I did:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=1794&highlight=
I do not use any input and output coupling caps for my line stage.
I dont think there is such as DIY audio veteran. Audio is hobby for life.
I'm diy audio beginner, so I dont have that copy. Where can I see the design?
discrete op-amp
I dont know if the jan 1985 discrete op-amp is published on the web. When i say veteran,i mean i have built most amp circuits that have been published over the last 20yrs or so,seeking the"perfect" amplifier!
I dont know if the jan 1985 discrete op-amp is published on the web. When i say veteran,i mean i have built most amp circuits that have been published over the last 20yrs or so,seeking the"perfect" amplifier!
WAW. Which is the perfect SS amplifier from your opinion (the nicest sounding one, not the best measurement one)
Or are you still seeking?
Samuel Jayaraj said:
Hi,
I just tried this opamp with J111 and it will work good with few changes: R7 to 100ohm, R5 to 750ohm, R6 to trimmer 10k (setting DC offset).
Regards
Milan
The only problem with the WW 1985 Linsley Hood design is that it also has an FET input and that is what Samuel is trying to avoid.
Brston OpAmp schematic
Upupa Epops had a good idea: consider the OpAmp Bryston uses in its amps. The schematic can be found in http://www.bryston.ca/pdfs/38bschem.pdf on page 21. It is dead simple, and works well.
Norman
Upupa Epops had a good idea: consider the OpAmp Bryston uses in its amps. The schematic can be found in http://www.bryston.ca/pdfs/38bschem.pdf on page 21. It is dead simple, and works well.
Norman
lumanauw said:
See http://www.diyaudio.com/forums/showthread.php?postid=360365#post360365
post #15
Fab
The tutorial about small FET from Mr.Borbely suggested that if we use FET it has to have source degeneration (about 100ohm) and cascode in the Drain. I can understand the function of cascode, but some designs just tied the sources together in differential without any R.
Is this R really needed?
Is this R really needed?
Thanks everyone for your suggestions thus far. I am going to try out moamps suggestions of resistor values with J111 input pair. I have also completed a PCB design for the Bryston input module. This is only for trial and hence, is single sided roughly measuring 2"x2.5". I know that is big for modules; but maybe double sided boards may shrink the size a bit and I have reserved that for post-auditioning.
I am also waiting for some schematics from Jonathan Bright. Will keep everyone posted on the progress and the sonics, of course.
I am also waiting for some schematics from Jonathan Bright. Will keep everyone posted on the progress and the sonics, of course.
I am proposing to use BC550C and BC560C for the input pairs, 2N5401/2N5551 for the VAS stage and MJE340/MJE350 for the output stage. I will try with +-24 volt rails, reducing the input transistor collector load resistor to about 12k and the emmitter resistor to about 22k. Simulation with these values show very good results but I may need to change them as I experiment.
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