zz1fk@sdccsu3.UUCP (03/08/84)
-this line is for line eaters A friend and I were looking over the new Pioneer catalog, and noticed that they have a line of "non-switching amps". We assumed that this meant a DC amp, but we weren't sure. In fact, we weren't even sure what the advantage of a DC to an AC amp was. We had some discussion, but nothing conclusive turned up. Would somebody out there please enlighten us? (Especially about the DC-AC question). Thanx in advance fritzz the zebra :-)
parnass@ihuxf.UUCP (Bob Parnass, AJ9S) (03/09/84)
x
A recent submission asked about the meaning of "DC amplifi-
ers" as this term relates to the audio world:
A friend and I were looking over the new Pioneer
catalog, and noticed that they have a line of "non-
switching amps". We assumed that this meant a DC amp,
but we weren't sure. In fact, we weren't even sure what
the advantage of a DC to an AC amp was.
Isn't this term used to mean an amplifier which uses direct
interstage coupling rather than using capacitors or
transformers?
The point of avoiding the use of capacitors and transformers
is that they tend to act as filters, limiting frequency
response.
Audio gurus, is this correct?
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Bob Parnass, AT&T Bell Laboratories - ihnp4!ihuxf!parnass - (312)979-5760 pmr@drufl.UUCP (03/09/84)
AC coupling not only limits the frequency response at the low end but also is necessary in some types of amplifier designs to maintain the correct voltage levels (bias) for the next gain stage. The types of capacitors used also effect the quality of the signal passed to the next gain stage. Plastic dielectric capacitors have less reverse leakage and more linear impedances at higher frequencies than the commonly used non-polar electrolytic capacitor. Using plastic dielectric capacitors like polystyrene or metalized polypropylene, although debated by some as to their audibility, helps improve the overall sound. Yours for higher fidelity, Phil Rastocny AT&T-ISL ..!drufl!pmr
gregt@tektronix.UUCP (Greg Thomas) (03/11/84)
I believe that you're right; "DC" refers to "direct-coupled," not "direct current." Someone please correct me if I'm wrong.
emrath@uiuccsb.UUCP (03/13/84)
#R:sdccsu3:-163900:uiuccsb:5700028:000:765
uiuccsb!emrath Mar 12 13:00:00 1984
I haven't seen the catalog, but I would assume that "non-switching amp"
has nothing to do with whether the amp is AC or DC coupled. I expect
it means either: 1) the power supply is non-switching; or 2) the amp itself
is biased heavily into the class A-B region or is fully class A.
In case 1, the output of the power supply is not controlled by the audio
signal (such as in Carver's "magnetic field" amps), nor does it use a
"switching" regulator. It's just a standard old analog or unregulated supply.
In case 2, the larger bias on the output transistors means that they stay in
a more linear region of operation. I doubt that the amp is class A or they
would have said so. Without more facts.....
Perry Emrath, UofIL
...{decvax|inuxc}!pur-ee!uiucdcs!emrathrfg@hound.UUCP (R.GRANTGES) (03/13/84)
You are not wrong, but it could be either. Since a Direct Coupled amplifier has response to DC potentials, it is also a Direct Current Amplifier. It really doesn't make any difference which you use in the audio context. Incidently, in my opinion it's all hype. Given equal quality of design, an "AC" amp will be superior to a "DC" amp for audio purposes. More stable and less worry about blown woofers from dropped cartridges and the like. The search for advertising hype must go on, however. Dick Grantges hound!rtfg
frankj@dartvax.UUCP (Frank Jaffe) (04/07/84)
Bob Parnass is partially correct. DC used to stand exclusively for DIRECT COUPLED. However, in this crazy world we live in now, some manufacturers are claiming their amps to be DC even though they have capacitors in line with the output terminals. I can only assume that they must mean Direct Current.