|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
68.114.92.175
In Reply to: RE: OTL amps rule! posted by groovy.guru on October 18, 2014 at 21:25:30
OTLs rule? Now that depends on what amp you are comparing them to and what speaker you are driving, doesn't it? Black and white situations are pretty rare.....
Coming form a guy with several OTLs who has been through at least a dozen.
Follow Ups:
Otl definetly rules, even better when OTL/OCL which larger amount of power to work even with difficult speakers.
I am using a GRAAF GM200 with 32 Pl504 (27gb5a) on Magnepan 20.1 and they can handle it with ease, alltough I also have a additional room heater.
"Otl definetly rules, even better when OTL/OCL which larger amount of power to work even with difficult speakers."
I certainly agree with the general sentiment. But I'm never quite sure about the OCL aspect. Presumably this refers to not having a big output capacitor that is directly in series with the loudspeaker. (All my OTLs are OCL, in fact.) But the capacitors in the power supply are just as much in the audio path as an added output capacitor would be, so I've never really seen why OCL or not is a big issue. All OTL amps have capacitors in the signal path.
Chris
Is that a cap in Series or parallel with the output? An what size cap is in your OTLs output? thanks
"Is that a cap in Series or parallel with the output? An what size cap is in your OTLs output? thanks"
In both cases (output capacitor or power-supply capacitors), the capacitor would effectively be in series with the output. I don't use an explicit output capacitor in my OTL amplifiers, but the power-supply capacitors in mine are something of order 4000 uF.
Chris
So are you saying all amps OTL are SS have a cap in Series at the output?
What an I missing?I see no cap at the output?
thanks
"So are you saying all amps OTL are SS have a cap in Series at the output?
What an I missing?I see no cap at the output?"
You need to look also at the other schematic in that Tim Mellow article, showing the power supply. The audio signal current passing through the output tubes also passes through the smoothing capacitors of the power supply.
Chris
Not with the Graaf gm200!
Here a small section:
"Not with the Graaf gm200!"
I'm not sure if you are suggesting it has no capacitors in the signal path in its output stage, but in any case it does. Just like any OTL, whether totem-pole or circlotron, the power supply capacitors form part of the signal path. I'm not saying that's a bad thing (and, in any case it is unavoidable); I'm just saying it is a fact of life.
Chris
But to most people,some OTLs output PS caps look like there in parallel not in Series
Now some OTLs have a big 4-6mf cap in series with the speaker right?
Is this Like, is there a real class A OTL amp?
thanks
"But to most people,some OTLs output PS caps look like there in parallel not in Series"I'm never entirely sure what people mean when they say that the power supply capacitors are "in parallel with the output." But if they find those words more satisfying than "in series with the output," then I suppose that is fine, although it seems to me to be a misleading way of saying what is happening.
But what is not in doubt is that the audio signal is passing through the capacitors. If we consider a circlotron, for example, then there are two "signal current loops" in the output stage. One loop comprises the upper tube (or bank of tubes), the corresponding power supply capacitor(s), and the loudspeaker, daisy-chained in series. The other loop comprises the lower tube(s), the capacitor(s) of their associated power supply, and the loudspeaker, again daisy-chained in series. Any signal current that passes through a given bank of tubes necessarily also passes through the capacitor(s) of the associated power supply in that daisy-chained loop.
So provided one accepts that the audio signal "passes through the output tubes" (which seems like an uncontroversial enough statement!), then one necessarily must accept that the audio signal also passes through the power supply capacitors.
As far as class A OTLs are concerned, there do exist rather low power single-ended OTLs, which are necessarily class A. (They are also super-inefficient, even by OTL standards.) Such an amplifier would almost certainly have to have an "explicit" output capacitor, to keep DC current from flowing through the loudspeaker.
For push-pull types of OTL, whether totem-pole or circlotron, they are essentially what one would normally call class AB. Of course, for sufficiently low output levels they are "operating in class A," in the sense that if the signal is low enough that the tube (or bank of tubes) that is being driven towards non-conduction in a particular half cycle is not being driven fully into non-conduction, then for such a signal level both banks of tube are conducting all the time. But once the signal becomes large enough to take the current in the conducting tube(s) to about double the quiescent current, or higher, the current in the other bank of tubes will have gone essentially to zero, and so the amplifier is then operating in genuine class AB. In practice, the OTL will only be operating in class A for rather low power levels compared with the power it is capable of delivering in its class AB mode.
Chris
Edits: 12/07/14
As we know, theses things you are saying have been said befor,
You have clear way of saying it.
As I have always said,if you know how thing relly work,you can explaine it to anyone.
thanks
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: