Going back to the original question, I think the mostb significant reason is habit and familiarity with a particular orientation in the schematic. If you learn about the subject from schematics showing it in a particular orientation you are likely just to continue the pratice.
I, too tried to see if Space gave any insight, I even tried combining each orientation with quasi-complementat outputs of each orentation for a total of four permutations. ( A waste of a rainy afternnon with nothing else to do!) There were no differences that effected significant digits.
This suggests a scheme to charge exorbitant sums in the high-end market: build and amp with R & L channels topologicaly inverse from one another and attribute magical properties to the concept. "Right vs. Left is an outdated Eurocentric concept, we should really be concerned with Yin and Yang channels . . . ."
I, too tried to see if Space gave any insight, I even tried combining each orientation with quasi-complementat outputs of each orentation for a total of four permutations. ( A waste of a rainy afternnon with nothing else to do!) There were no differences that effected significant digits.
This suggests a scheme to charge exorbitant sums in the high-end market: build and amp with R & L channels topologicaly inverse from one another and attribute magical properties to the concept. "Right vs. Left is an outdated Eurocentric concept, we should really be concerned with Yin and Yang channels . . . ."
Off Topic> "Medical Equipment"
Even when I said "don't go there"
In a nutshell, I have been told that NPN is more coudusive to being used in enviroments around the human body.
(Somthing about bio-feedback induced nano-currents, from ground loops when using PNP devices).
Remember, the electronic probes used on humans are MORE sensitive that an LNA / LNB in a satilite dish.
Even when I said "don't go there"
In a nutshell, I have been told that NPN is more coudusive to being used in enviroments around the human body.
(Somthing about bio-feedback induced nano-currents, from ground loops when using PNP devices).
Remember, the electronic probes used on humans are MORE sensitive that an LNA / LNB in a satilite dish.
Dimitri, be nice.
A lot of people have awaited the return of Halojoy, enignmatic
as his posts might be.
Elso Kwak has not disappeared at length, but he enjoys similar
affection.
Remember this is the entertainment industry. (Personally I
am waiting for Asia Carrera, Mensa member, to take an interest
in hi-fi and climb in here). We could use a non-male viewpoint.
Anyway, I think that PNP's were and are popular because the
original RCA manual used them that way, and they remain
vestigial design items, like output coils.
Cheers, as Goldfrapp says.
A lot of people have awaited the return of Halojoy, enignmatic
as his posts might be.
Elso Kwak has not disappeared at length, but he enjoys similar
affection.
Remember this is the entertainment industry. (Personally I
am waiting for Asia Carrera, Mensa member, to take an interest
in hi-fi and climb in here). We could use a non-male viewpoint.
Anyway, I think that PNP's were and are popular because the
original RCA manual used them that way, and they remain
vestigial design items, like output coils.
Cheers, as Goldfrapp says.
These French - always refusing to follow the herd, instead sticking to UNpopular principles.
Ok so who told the French that electricity itself is asymmetrical? Who gave it away? The fact that electrons and holes are not opposites was supposed to be a secret. What do you mean they worked it out for themselves?
Hey, what do ya know, these gents aren't just about brie and accordions after all!
Maybe we should try to do designs that use both matter and
anti-matter? Then we would have a perfect symmetry between
electrons and positrons. There will be some slight techincal
problems to make it safe and functional, perhaps, but on the
other hand, we probably won't need any external power source.
Come to think of it, maybe it will even be self-soldering.
anti-matter? Then we would have a perfect symmetry between
electrons and positrons. There will be some slight techincal
problems to make it safe and functional, perhaps, but on the
other hand, we probably won't need any external power source.
Come to think of it, maybe it will even be self-soldering.
I understand that dual differential (complementary differential to some people) gives push-pull action in the VAS.
Single diffential lead us to single transistor VAS, with CCS on the other side (like Mr.Pass' designs, but not A75)
What's the real difference between push-pull VAS and single transistor VAS+CCS? Open loop distortion? Final sound characteristic?
There are several things to consider:
Dual diff input pairs driving complementary Common Emitter/
Source pairs does give lower distortion by higher open loop
gain and cancellation of 2nd harmonic.
Single diff pairs, with a single Common Emitter/Source device
gives very solid DC stability because it's anchored by a constant
current source (keeping in mind that the current through this
circuit helps set up the bias voltage for the output stage), has
about 6 dB less open loop, and higher 2nd harmonic content.
Take your pick.
Dual diff input pairs driving complementary Common Emitter/
Source pairs does give lower distortion by higher open loop
gain and cancellation of 2nd harmonic.
Single diff pairs, with a single Common Emitter/Source device
gives very solid DC stability because it's anchored by a constant
current source (keeping in mind that the current through this
circuit helps set up the bias voltage for the output stage), has
about 6 dB less open loop, and higher 2nd harmonic content.
Take your pick.
Mr. Pass, I have looked at A75 paper again and again. In one part of the paper, the threshold voltage for N mosfet average=4.4V, while for P mosfet average=4V.
I looked at the sch of A75, you use IRF9510 and IRF610 for push-pull VAS. If the threshold of IRF9510 and IRF610 is quite different, will it be the total differential resistor (R6+P1 and R1+P2) will be different value? What happens if we do not use P to trim the resistors, will the differential+VAS working properly due to different threshold gate voltage?
I looked at the sch of A75, you use IRF9510 and IRF610 for push-pull VAS. If the threshold of IRF9510 and IRF610 is quite different, will it be the total differential resistor (R6+P1 and R1+P2) will be different value? What happens if we do not use P to trim the resistors, will the differential+VAS working properly due to different threshold gate voltage?
Vgs varies quite a bit not only between different device types,
but also within device types, and by itself is no big deal. It
is accommodated by either selecting Vgs from a population
or trimming the values of resistors. Without trimming both
ends of the VAS stage of the A75, you will see improper bias
of that stage and DC offset at the output. That's just the way
it is.
but also within device types, and by itself is no big deal. It
is accommodated by either selecting Vgs from a population
or trimming the values of resistors. Without trimming both
ends of the VAS stage of the A75, you will see improper bias
of that stage and DC offset at the output. That's just the way
it is.
John Curl made a joke!!!!!
Why does all the really good stuff happen when I am gone? Must be a conspiracy.
Anyway......another reason that some folks use PNP inputs is that it allows for a NPN in the second stage. The slightly lower capacitance (compared to the PNP compliment) will yield a higher unity gain frequency. Maybe not much, but sometime every little bit helps.
Jocko
Why does all the really good stuff happen when I am gone? Must be a conspiracy.
Anyway......another reason that some folks use PNP inputs is that it allows for a NPN in the second stage. The slightly lower capacitance (compared to the PNP compliment) will yield a higher unity gain frequency. Maybe not much, but sometime every little bit helps.
Jocko
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