I am assuming that the Carverland (you refer to) was originally USA.
Do you possibly think that those habitants really know the difference between Schadenfreude and
shut the front door???
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Carver Crimson 275 Review (Tube Amp)
- Thread starter amirm
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Do you possibly think that those habitants really know the difference between Schadenfreude and
shut the front door???
mhardy6647
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Oh, I dunno... but I am honest enough to admit to deriving somewhat perverse enjoyment from watching certain train wrecks occur.I am assuming that the Carverland (you refer to) was originally USA.
Do you possibly think that those habitants really know the difference between Schadenfreude and
I expected better, too. I almost hope they goofed it up on purpose to get a warm, fuzzy sound. Better that than incompetence.
solderdude
Grand Contributor
specs for the BM25:
SPECS (my emphasis)
Gain: 29 dB
Power: More than 24 Watts Per Channel, both channels driven at eight ohms with no more than 1% Total Harmonic Distortion. Distortion decreases at lower levels
4Ω Power 25 watts
8Ω Power 25 watts
16Ω Power 25 watts
Noise: Better than 100 dB below 25 watts, A-weighted
Frequency Response: +0, –2 dB from 20 Hz to 20 kHz
Distortion Less than 1%
Source Impedance 1.7 ohms
Input Impedance 100 kΩ
Vacuum Tubes: EL-34 (optional 6550, KT88, KT120) 12AX7, 12AT7
AC Power:
120 Volts, 60 Hz (US)
240 Volts, 50 Hz (EU
Weight 19 lbs / 8.61 kg
Color: Satin Textured Black, Chrome, Natural Aluminum
Country of Origin: USA
I wonder, is that 1.7 ohms Source Impedance the output impedance to the speaker?
Almost certainly.
mhardy6647
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I assume that's the amp's output impedance. If so, then, heck, that's
That would actually be a pretty remarkable engineering achievement* on the part of Dr. Carver!
__________________
* engineering achievement, of course, being a vector quantity. I.e., the Gothic Cathedral at Beauvais (which collapsed several times during construction and ended up being more or less an outrageously glorified chapel, see Hartt's History of Art, vol. 1) and the "Galloping Gertie" bridge over the Tacoma Narrows were remarkable engineering achievements (just not in a good way).
Your 2A3 anode resistance is probably pretty small compared to an EL34. Maybe if you opt for say, the KT88 output tubes the impedance is a bit lower. Maybe...I assume that's the amp's output impedance. If so, then, heck, that'slower(EDIT) higher than that of my zero NFB single-ended 2A3 amp (with output impedance of a hair less than an ohm)!
That would actually be a pretty remarkable engineering achievement* on the part of Dr. Carver!
__________________
* engineering achievement, of course, being a vector quantity. I.e., the Gothic Cathedral at Beauvais (which collapsed several times during construction and ended up being more or less an outrageously glorified chapel, see Hartt's History of Art, vol. 1) and the "Galloping Gertie" bridge over the Tacoma Narrows were remarkable engineering achievements (just not in a good way).
mhardy6647
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Yeah, but I don't want no steenkin' tetrodes, kinkless or otherwise. (Power) triodes FTW!
If I just had to use tubes, push-pull triodes would be it. Luckily though they made those scratchy old silicon carbide JFETs.Yeah, but I don't want no steenkin' tetrodes, kinkless or otherwise. (Power) triodes FTW!
You mean like NO 'local' or 'global' feedback at all?
Are there many such beasts that do not rely on NFB?
They are probably all tube amps...
I always thought that (such stability w/o FB) was an audio fantasy.
There are a few SS designs. Some I know of:
FIRST WATT
www.firstwatt.com
FIRST WATT
www.firstwatt.com
Et cetera.
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FWIW negative feedback is a destabilizing design feature. If you want to see a stable circuit condition, apply positive feedback.
Amps without feedback can be quite stable; very resistant to oscillation, since negative feedback and phase margin issues don't play well together.
Class D amps can be built with zero feedback as well.
solderdude
Grand Contributor
It is actually worse than 1.7ohm as it is load dependent due to the current feedback.... ahem... 'the back EMF and room sensing feedback circuit'.
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tonycollinet
Major Contributor
You know what a nuclear detonation is? Positive feedback. As is any explosion - explosives not often described as being stable.
Anything you apply positive feedback to goes to limits.
My room is getting hot - feed back that positively to the heating systme so that it puts out more heat. That is postive feedback.
Ever heard of thermal runaway - that is positive feedback also.
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For any competent designer, stability is absolutely no issue- stability criteria have been well-understood for nearly a century. To quote Klaatu, "I find it works well enough to get me from one planet to another."
You’ve got it backwards mate.
Turn in your EE degree.
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The statement was meant as humor; I was using the Chaos Theory definition of the term
You know what a nuclear detonation is? Positive feedback. As is any explosion - explosives not often described as being stable.
Anything you apply positive feedback to goes to limits.
My room is getting hot - feed back that positively to the heating systme so that it puts out more heat. That is postive feedback.
Ever heard of thermal runaway - that is positive feedback also.
So, or 'but', depending on how you look at it:
A stable state is one that does not change. An amplifier in oscillation is in a stable state insofar as its output is concerned. FWIW positive feedback is the basis of self oscillating class D amps (like the Purifi) although at audio frequencies that feedback is negative. This BTW is why self-oscillating class D amps cannot be induced to oscillate when subjected to a strange load like one that is heavily capacitive. Its already oscillating... and therefor stable...
Of course there's more to it; apparently you missed this comment, perhaps when you did your facepalm:
(Emphasis added)
The reason negative feedback is destabilizing is due to phase shift. Phase shift is responsible for a design aspect all amplifier designers of amps with feedback must face, which is called 'phase margin'. If you exceed the phase margin of said amplifier, oscillation occurs. So it would appear that the amp is stable if that isn't done... except when the load on the amplifier's outputs messes with the feedback loop, which is a critical design in any amplifier with feedback (a simple resistor is rarely good enough...). Far too many amplifiers have been produced that can oscillate and fail when subjected to a slightly odd load, for example a Quad ESL57.
tonycollinet
Major Contributor
You know what phase shift does to negative feedback?The statement was meant as humor; I was using the Chaos Theory definition of the term
So, or 'but', depending on how you look at it:
A stable state is one that does not change. An amplifier in oscillation is in a stable state insofar as its output is concerned. FWIW positive feedback is the basis of self oscillating class D amps (like the Purifi) although at audio frequencies that feedback is negative. This BTW is why self-oscillating class D amps cannot be induced to oscillate when subjected to a strange load like one that is heavily capacitive. Its already oscillating... and therefor stable...
Of course there's more to it; apparently you missed this comment, perhaps when you did your facepalm:
(Emphasis added)
The reason negative feedback is destabilizing is due to phase shift. Phase shift is responsible for a design aspect all amplifier designers of amps with feedback must face, which is called 'phase margin'. If you exceed the phase margin of said amplifier, oscillation occurs. So it would appear that the amp is stable if that isn't done... except when the load on the amplifier's outputs messes with the feedback loop, which is a critical design in any amplifier with feedback (a simple resistor is rarely good enough...). Far too many amplifiers have been produced that can oscillate and fail when subjected to a slightly odd load, for example a Quad ESL57.
Turns it into positive feedback.
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