I would be very interested in this. I started a thread a couple of years ago about a supertriode PP amp using ECL85. I've now almost finished construction and have some distortion test results that I've been meaning to post. I will try and do that over the next few days.
+1
I don’t know about the sound (as i have not heard it), but i have seen this used in a proprieary phono circuiy by a very good designer.
dave
It is a finding consistent with what Joe is showing with his voltage vrs current measures.
dave
The load the amplifier drives is very germain to the conversation. The sound of the amplifier is diirecty related to the load. Headhones do not replace speakers. T
The listening test you do with amplifiers on headphones is only applicable to those headphones.
dave
Agreed that loads can be relevant to the topic, but it entirely depends on context. Are you loading the tubes with the load? Or are you simply using the triode as amplification? In a "properly" designed amp, the load (within spec) should not affect the signal that the amplifier produces, ever, Period. If it does then it is a faulty design IMO.
But for tubes I'll make an exception as the intent of design is different with tubes, we want it to alter the sound in some hopefully positive way.
If you are loading the tubes then yes, the load matters.
It also depends on what you are testing.
I prefer to do tests one level at a time so I know where the results are coming from.
For example, if I built an amplifier, or a sub-circuit in an amplifier I always isolate what I've changed and do test under ideal conditions before I start putting real loads on it, therefore I know what has changed under load.
In my experience, headphones are the perfect "ideal load" test device because they present a high impedance and don't introduce room effects.
If you then attach the amp to a loudspeaker and latch on the headphones at the same time you will be able to hear if there is any difference in voltage distortion compared to the previous test over the headphones.
After that you start doing tests with the loadspeakers themselves.
For me personally, I don't think tubes belong in the output stage without a transformer. In which case the transformer will take over most of the sonic qualities in my experience. (which is extremely limited with transformers, I've only used them once for a short time)
My direct drive tube experiments just didn't sound anywhere near as good as a good solid state output stage.
My main intent for the thread was to find out whether or not tubes can actually, own their own, make the magical euphionic sound, in whatever configuration.
I haven't been able to find a result that doesn't get matched or beat by solid state and have not found the euphonics yet.
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So what do you think people do who have to make a living out of recording?
Work with WW2 army equipment?
Not take the slightest interest in the very latest innovations which might affect their work???
I think the innuendo we've never heard "hi end" anything is one of the worst presumptions I have ever seen in writing!
Pot - kettle - black springs to mind.
The biggest problem with ALL high end "cans" is that they are almost all universally CRAP, and that is not my opinion, it's widespread knowledge in the industry, - also because it makes the stereo image invariably wrong and behind your head.
I might have opinions which seem a little hard hitting, but it comes from a lot of factual info, lots of it entailing blind testing, - "what did you just do there" stuff.
As I said, your methodology manifestly invalidates any conclusions you might personally like to draw,-
or how come the attraction of valve based classics such as Fairchild 660 or Pultek?
Sheer stupidity?
Once again you are presumptively and aggressively making accusations. I never officially claimed you have or haven't done anything which is why I said "I would opt to say" and I don't know what your experience is, I was making a potential observation. Quit being so uppity, it's not what you say it's how you say it.
Agreed that headphones are all crap. That's why I recently designed my own, they sound vastly better than all commercially existing high end headphones (I've heard all the best ones). Going to try to make them available for people here to purchase and/or build if they want.
Disagree that the image is placed "behind" the head. This depends entirely on recording and what system is feeding it (yes the system can have a pretty large affect here), and the headphones of course. Most of my recordings are placed in "front" or somewhat to the front on the sides.
Also with things like the smyth realizer now existing, that argument does not apply at all anymore if you own one. (if only I could afford it)
Agreed that headphones are all crap. That's why I recently designed my own, they sound vastly better than all commercially existing high end headphones (I've heard all the best ones). Going to try to make them available for people here to purchase and/or build if they want.
Disagree that the image is placed "behind" the head. This depends entirely on recording and what system is feeding it (yes the system can have a pretty large affect here), and the headphones of course. Most of my recordings are placed in "front" or somewhat to the front on the sides.
Also with things like the smyth realizer now existing, that argument does not apply at all anymore if you own one. (if only I could afford it)
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Sorry, a bit of a late response. It seems to me that when a loudspeaker (or any load for that matter) is driven by a voltage source (low Z) the current into the load is merely a consequence of the voltage. In the case of a current waveform lagging the voltage waveform, this is simply a voltage driving a load that is capacitive at that freq. I still don't understand why you say it produces two sinewaves, maybe this was done for illustrative purposes. If you're posing the question: does voltage or current correlate to acoustic output, the answer is that (assume a perfectly flat acoustic output) as you go from infinitely low output Z to infinitely high Z, the acoustic output will go from perfectly flat to an output that mimics the speaker's impedance.
A transconductance amplifier (current out, voltage in) has ideally infinitely high output Z, and acts like a current source. The output voltage will therefore be I*R and when driving a reactive load, the voltage produced will mimic the load's impedance vs freq. I've done this in a simple way when measuring a loudspeaker's Z vs freq. You hear all the peaks and valleys. The acoustic output seems to follow the applied voltage, not the current. So, conversely, when driving from a current source, the voltage is merely a consequence of the current and impedance. One just happens as a result of the other.
When a tube amp (high output Z) drives a speaker, the resonance points will likely produce a compressive effect because the amplifier runs out of compliance and will soft limit. This might sound 'good/better'. The speaker may produce a bump in the output near the low freq resonance and at the xo resonance, which might be good thing.
If we look back upstream, for example the output of a DAC, it is a voltage. You simply would like that voltage to be made bigger and applied to a loudspeaker. I'm assuming a given acoustic output is derived from a voltage, not a current.
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why not reduce your thoughts into a schematic that we can all look at, can help too...
"I don't have or even know of any test kit that measures current noise or distortion"
Really? Why should we take any off that post in the screen shot seriously?
that would be mighty fine better way to move forward than engage in an endless loop of blah blah blah i believe...
forgive my language....
It's actually very basic stuff, what the guy is saying is he doesn't even know how to measure what he's hearing. I don't see how that is relevant to what Joe is doing, he has shown measurements of the current distortion at the amplifier output.
Most amps yet (lets say 99% but that is likely rounded down), but a growing number are not. Typical SE amps (tube or SS — how many members have built ACAs?) and i see at least some PP amps that have similar outut impedance. And then we have current amps like the Firstwatt F1.
The point that concern over this only applies to those playing on the fringes jas been expressed in this thread many times, but it is useful to remind readers of how small (relatively) this population of hifi afficiandos is. But if you are one of those, only 1 person matters. You. And then it becomes germane.
dave
There are so many thngs peope say they hear that we can’t measure that you are surprised?
The bit in italics is a person trying to convey something he hears in words where the language is ill defined. I eagarly await the day we can test by actually directly measure what the brain is doing and bypass teh “squishy” interpretation step. Then we have a hope to find out if people are really hearing things or whether it is imagined (psycho-acoutics).
[/quote]...he has shown measurements of the current distortion at the amplifier output.[/QUOTE]
Did he not say exactly how he measured it. He used ohms law i believe.
dave
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