I'm doing the layout for a 2A3 Loftin White style amplifier. My question is pretty straightforward and probably obvious to those with any amount of experience. Is the circled section of the schematic (see attached) repeated on both channels? I would assume it does but I was looking over a Japanese audio magazine and saw some similar filtering in a different/unrelated schematic and that section appears to only be implemented once.
Thanks in advance!
Thanks in advance!
The first circuit power supply decoupling circuit (25k/100uF) would be duplicated for the second channel,
after the choke and second capacitor, where it is marked "Bch".
The second circuit appears to be an actual mono amplifier.
after the choke and second capacitor, where it is marked "Bch".
The second circuit appears to be an actual mono amplifier.
Please use English.
yes you must have 2 separate circuits
This is an ECC82 anode power supply.
and the passage of the alternative modulation into the other
c7 r13 right next to the ecc82 tube preferably
Thanks for the confirmation! I will proceed as intended with the filtering on each channel. The second schematic is for a stereo amplifier which was confusing. Perhaps it was a misprint...
While I'm working through that end of the power supply (PS)... I've attached a sketch of where I was imagining the bleeder resistor would go. I see them often on the last cap; however, in this instance would there be two bleeders? One on each channel? Or just one on the last 100uF PS capacitor?
As you can see I've modified the PS because 100uF for a first capacitor seems very high. I've put a 22uF in the first position, followed by a choke and two paralleled main 100uF filter caps.
The original and annotated schematics are attached.
Thanks again!
the 200k resistor on c7 allows c7 to be quickly discharged after switching off the amplifier
100k is good
modify the CLR network is measured in simulation
I wouldn't touch this but a good quality non-polarized capacitor can be added to the capacitor after the choke
we now find good capacitors of several tens of UF for a resonable price
100k is good
modify the CLR network is measured in simulation
I wouldn't touch this but a good quality non-polarized capacitor can be added to the capacitor after the choke
we now find good capacitors of several tens of UF for a resonable price
Thanks! Just to clarify, I'm referring to the 2A3 schematic (see previous post) and NOT the photos of the EL34 amplifier from the original post. I would like to know if the 200k resistor in position I've sketched would be good to discharge the entire power supply.
Again, referring to the 2A3 schematic... I've reattached it below.
Sorry for the confusion!
Yup! With the exception of adding a bleeding resistor and a smaller first capacitor in the power supply, it will be built as drawn. At this point, just curious to know if the position I've drawn it in makes any sense. It does to me as it's the last filter capacitor, but I've seen it in different positions.
here you already have them, why not?
the capacitor on the cathode of the 12ax7 must be of good quality, elna silmic II or oscon sanyo
alternative filament twist the wires well
and flat at the bottom of the chassis
the capacitor on the cathode of the 12ax7 must be of good quality, elna silmic II or oscon sanyo
alternative filament twist the wires well
and flat at the bottom of the chassis
https://storage.googleapis.com/prod...898/yfSRtibT/dbe9ba0f4be94f2db181fe24d91a8475
here is something similar with a good idea on the diagram
here is something similar with a good idea on the diagram
Thanks for this! It looks to be based on an old Isamu Asano schematic (see below)... I have it in a book of his from the 70s. Do you have a source for the schematic you shared (also below)?
I know the diagram well with the 2a6 as input
I made this montage in the 80s
it doesn't make me any younger
here is the site of the diagram
https://theaudiofeast.com/blog/tag/c3m
I made this montage in the 80s
it doesn't make me any younger
here is the site of the diagram
https://theaudiofeast.com/blog/tag/c3m
Just for comparison, here was the output stage of a radio I used to own from 1936, Paillard 70TR. The tube 6Q7 is the same as a 2A6. Back in the days before 'conventions' and 'best practices' there were some very interesting schematics.
Admittedly it is not direct coupled from the driver, but this radio did have battery bias on the driver tube - a Mallory cell.
The clever thing with those old radios was that they derived the negative rail for biasing the 2A3 from putting the choke on the negative side of the rectified supply, and grounding after that. (The other choke is the field coil of the loudspeaker).
Admittedly it is not direct coupled from the driver, but this radio did have battery bias on the driver tube - a Mallory cell.
The clever thing with those old radios was that they derived the negative rail for biasing the 2A3 from putting the choke on the negative side of the rectified supply, and grounding after that. (The other choke is the field coil of the loudspeaker).