I don't think the class of the amplifier mean anything sound wise
My humble opinion : high quality technics delivers good music. I have one its not hifi at all but it is good.
Unfortunately you can buy some hifi amp ( more 3d etc) wich doenst sound as good as the technics
iow : buying a denon , or panasonic technics is fine. I go sometimes at futureshop and it sounds all fine.
My humble opinion : high quality technics delivers good music. I have one its not hifi at all but it is good.
Unfortunately you can buy some hifi amp ( more 3d etc) wich doenst sound as good as the technics
iow : buying a denon , or panasonic technics is fine. I go sometimes at futureshop and it sounds all fine.
Class A is confused with First Class.
In the reality a very intuitive way to bias amplifiers...one of the first methods used.. ancient tubes used the method into the earlier days of radio... searching for lower distortion and better linearity they use to advance the "operational point".... interesting as you go distant from the cut side...but goes very near the saturation side.
Impossible to use into hot countries alike mine.... a suicide!
Marketing uses are there to reinforce this idea.... as first class...this appeal sells a lot.
Carlos
In the reality a very intuitive way to bias amplifiers...one of the first methods used.. ancient tubes used the method into the earlier days of radio... searching for lower distortion and better linearity they use to advance the "operational point".... interesting as you go distant from the cut side...but goes very near the saturation side.
Impossible to use into hot countries alike mine.... a suicide!
Marketing uses are there to reinforce this idea.... as first class...this appeal sells a lot.
Carlos
anyone interested in overseeing how 2diodes +4resistors are able to achieve so called non switching class-B without recoursing to exotic topology while keeping regular outputs in T or EF configuration, pls see:
http://www.diyaudio.com/forums/showthread.php?s=&postid=1727650#post1727650
Cheers
http://www.diyaudio.com/forums/showthread.php?s=&postid=1727650#post1727650
Cheers
annex666 is on the right track
new class A is an innovative bias circuit that keeps the output transistors in the ready state, eliminating crossover distortion, though keeping idling current low in order for more efficiency
- some models had computer drive which had an onboard microprocessor controling Icq of the output stage based on thermal and signal parametrics.
the sound of them?...
fantastic to say the least (well the amps from '78-91) - i should know by now - i have around 75 or so Technics amplifiers in my collection now (some models including SU-V2,V3,V4,V5,V6,V7,V8,V9,V1X,V2X,V4X,V6X,V8X,V40,V50,V60,V90D,V460,SE-A3MK2,SE-A5,SE-A7,SE-M100,SU-500,600,700,800,810,SU-G50,70,90,SU-Z22,Z400,Z600,Z780(SU-V78),SU-Z980(V98),SU-Z65 - a few recievers SA-TX50,SA-R430,R377 Hi Density SU-X90 SU-X101,X102
the best bits being clean sound, lots of current, wide dynamic range & loads of good bass - their bad point is they run quite warm and some models heatsinks leave a bit to be desired
http://www.geocities.com/technicshifi/Bias.html
the SU-V series is Technics Full width Integrated Amplifier series
not all were fully discreete and in fact some of the best sounding werent... (SU-V4X) - the SVI Hybrid ICs were infact excellent (now before the solid state buffs groan `bout the ICs - a few things bout them) Being a Hybrid IC they're infact discreete components on 1 substrate - much like the STK series BUT! better than the STK, the SVI features Complimentary Symmetry & all the resistors are ALL SMD rather than the film resistors in STK
http://www.geocities.com/technicshifi/SVI2004A.JPG a typical output stage design of Technics
a look at the internals
Keep listening
any Questions? - Email
-Baily
do you know a good technics amplifier 150-200w rms ?
Yes, there is Single Ended ClassA and Push Pull ClassA. I cannot see any other ClassA that meets my defintion of the active devices always actively controlling the output over the full waveform of the signal.
The Aleph, if done poorly, has the problem that activating the CCS introduces output offsets that will be added to the signal, i.e. what comes out is not a copy of what goes in. Yes, variable CCS meets the "active devices remain actively controlling" throughout the waveform, but that to me seems insufficent when other distortions could be introduced by the variable CCS.
If you are having difficulty in understanding the offset problem, take any Push Pull ClassA output stage. Set it up carefully to have zero output offset when quiescent. Adjust the temp comp to exactly cancel for variations in temperature (I will assume this has been achieved perfectly).
Now change the output bias current. Is the output offset still exactly zero?
Probably not, due to the slight difference in transconductance of the upper and lower halves.
Let's poke in a guesstimate of the output offset created by changing the output bias from 1A to 1.5A. Assume 10mV of offset.
Relative to a maximum power of 36W ClassA (3Apk into 8r0), this 10mV error is equivalent to a -67dB error. If one were listening to a -20dB average level, then that same 10mV error would be only 47dB below the average signal level. Is that hypothetical offset allowing a good copy of the input signal to emerge for a ClassA amplifier?
What if the offset were 50mV at the increased CCS controlled bias current?
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When the signal was in the negative (or positive region) the stabistor diode pack across the resistive feed bridge to the output transistor ensured wherever in the sine wave the output stage was that the output transistors never turned off... (Say output was -40V, conventionally the 2SC transistor would be in a nonlinear region as base voltage would be in that zone.... With the resistor bridge and stabistor even when in other territory the base-emitter voltage was sufficient to keep it forward biased, hence the output transistor never switched off (kept in its linear region (technics called the ready state) and eliminating output switching as the polar opposite is kept in this same state)
This discussion brings to light a common misunderstanding about what it means for an output stage to be in class A. This circuit merely makes sure that the transistor that would otherwise turn off never sees its current go to zero, but rather to some small dc static amount. In fact, even though that transistor can be said to be in a "ready" state, that transistor is not contributing any transconductance to the output stage; i.e., it is not contributing any signal.
An output stage is in class A only when both transistors are contributing signal (i.e., transconductance) to the output. Both transistors must be DYNAMICALLY on, not just statically on. Indeed, switching in fact does occur in these circuits when the control of the transistor's current changes from being governed by the signal to being governed by the circuit that enforces the minimum current when the transistor would otherwise be in the off state.
Even the definition above of class A is a bit loose, since there is the issue of how much transconductance is being contributed to the output by the transistor that would otherwise be off. In a true classical class A amplifier, both transistors are contributing very substantially to the total transconductance of the output stage (at least in a push-pull arrangement) and the amplifier stays in a push-pull regime throughout virtually all of the cycle.
When we say that a class AB output stage is in its class A region, we are loosely referring to operation when the peak output current is less than twice the idle bias current. During that interval, both output transistors are contributing substantial gm to the output stage, albeit non-equal at different points in that class A region.
Cheers,
Bob
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