Can amplifier speed and resolution be measured?

[Mad_Economist]

Not forgetting that the impedance values of headphones such as the HD650 and HD800 varies with frequency too.
And as far as I recall, the HD650 hits a peak somewhere north of 500 Ohms, while the HD800 in the 650-700 Ohm range.

So dynamic range aside, the power for an amp probably has to cater for these transient peaks in voltage too?

Peaks in headphone impedance are not peaks in voltage, for headphone measurements (and music playback, unless you happen to own a Bakoon) are conducted with (nearly) constant output voltage. When a headphone's impedance swings up, what occurs is that output current drops, in accord with Ohm's law. Thus, the "hard load" comes in a case where headphone impedance swings downward, demanding more current for the same voltage level (this is very uncommon).

There is a case where a rise in headphone impedance results in a significant rise in output voltage, of course - if the amplifier's output impedance is sufficiently high to meaningfully reduce the headphone's share of the output voltage. However, this is not often a significant factor, as most amplifier designers know not to put 100+ ohm resistors on their amplifier outputs, and most headphone amplifiers are solid state designs without substantially high output impedance when not deliberately raised.

 

[rebbiputzmaker]

And when you're all done, at best you have something which performs significantly less well than a conventional potentiometer. And is more expensive and fiddly.

It's the perfect audiophile solution to a non-existent problem.

Some people are just not smart enough to listen to "experts".

 

[solderdude]

It depends on what each individual feels is an 'expert' in certain areas.

 

[SIY]

It's much worse, IMO, when people "believe" things with a lack of evidence and in the presence of contrary evidence.

 

[rebbiputzmaker]

It's much worse, IMO, when people "believe" things with a lack of evidence and in the presence of contrary evidence.

IMO when people make their general "expert" statements they actually loose credibility with knowledgeable people which is the exact reverse of what they intend. Example generalizing and using the word "tubes" as one word fits all. Just because one built "some" tube amps, they do not become an expert on every active vacuum device ever made.

It is good that the ldr pre is being tested, and then some proper listening tests can be done.

 

[hetzer]

At human hearing perspective, the amp needs to have low residual noise, flat frequency response and low distortion that most people will agree that it is inaudible. Other elements are not important except for safety and price.
But if we should also consider the emotion of people when they purchase, install, turn it on and listen to music. Visual, tactual experience, convenience and even the advertising phrase are crucial factor for the user's experience.

The price of amplifier is enough to quantify the 'resolution' of amplifier. But the resolution gets better as there are some phrases like 'state of the art' or 'DSD512 support' on advertisement. The unique, patent-pending technology of the manufacturer with abbreviated words is essential.

The speed of amplifier is determined by the color of the case, the number of word "fast" or "digital" on review, the picture of oscilloscope on advertisement and SMPS. But the sound gets harsh if it is too cheap or too small. So the manufacturers should use big and heavy case with 'mechanical grounding' to reduce distortion caused by vibration.

This is the reason we should buy €9600 Goldmund Telos 2 headphone amplifier with significant noise.

 

[tomchr]

It's much worse, IMO, when people "believe" things with a lack of evidence and in the presence of contrary evidence.

Never let facts get in the way of a good opinion.

Tom

 

[Sir Sanders Zingmore]

I’d add to the other interesting things to potentially measure (if possible)
3: temperature sensitivity

Many of the devices used to make these end up having strong temperature sensitivies (carrier_generation(T), resistance(T), and noise(T), which can also change V and other sensitivities). Maybe 20C - 40C difference (stacked unit in a garage with poor ventilation, compared with inside desktop in AC)... Maybe only do this if the initial measurements look reasonable at 25C? Just an idea... ;-)

It would be interesting to see how Amirs test results compare with those of the person who makes these...

 

[SIY]

It would be interesting to see how Amirs test results compare with those of the person who makes these...

You're making an assumption.

 

[tomchr]

Tortuga makes measurements available? That's news to me... Or are we back to talking about amplifier speed and resolution?

Tom

 

[rebbiputzmaker]

Tortuga makes measurements available? That's news to me... Or are we back to talking about amplifier speed and resolution?

Tom

You really can't figure out these are two different units made by different people, or you just don't want to?

 

[tomchr]

Oh. You're right. I did miss the subject change. My bad. Thank you for pointing it out to me so eloquently and politely.

I'm looking forward to Amir's measurements of the other LDR volume control. Meanwhile, if the manufacturer of it would drop a link to a product page, I'd be interested.

Tom

 

[SplitTime]

It would be interesting to see how Amirs test results compare with those of the person who makes these...

I think that’s the great irony of the LDR discussion here... the proponents of LDRs don’t make any measurements themselves. Furthermore, If anyone contest their (LDR proponent’s) claims then they (LDR advocates) ask for lots of data and measurements to back up the opposition to LDR designs. When data is produced (as has been done in this thread) then it’s a “poor design” and/or “Basic electronics sadly does not work sufficiently well with LDR's” comments. (That comment really captured my attention as we have extremely good SPICE simulators, and device characterization techniques that have been available for many decades. Heterojunction BJT, Tunnel Diodes, ... all quantum mechanical effect devices & semiconductor devices can be simulated effectively.) So, I’m really looking forward to the measurements of this latest LDR design proposal. I have my own prediction of what the outcome will be; but I’m open minded to measurable data to convince me otherwise. So lets see if this LDR design is measurably good or if it is just another another Oswald Bates skit (In Living Color) being played out in real life.

 

[maxxevv]

It's much worse, IMO, when people "believe" things with a lack of evidence and in the presence of contrary evidence.

That sounds like how "religion" works though.

 

[tomchr]

“Basic electronics sadly does not work sufficiently well with LDR's” comments. (That comment really captured my attention as we have extremely good SPICE simulators, and device characterization techniques that have been available for many decades. [...])

Indeed. If you include the voltage coefficient and temperature coefficient in the SPICE simulation, you should see the THD in the simulation as well. It also makes perfect sense from a theoretical point-of-view. If the resistances of the two resistors/LDRs vary as function of the voltage across them (and voltage-squared in case of the temperature coefficient) they will introduce a signal dependent error (= distortion).

These effects aren't limited to LDRs. I've seen the same with some thick film SMD resistors that happened to have high voltage coefficient and, thus, high distortion (although still in the <0.01% territory). Switch to a thin metal film type with low TC and low VC and suddenly the THD is below the measurement floor of my AP (<0.0002 %/-112 dB.).

What also surprised me with the Tortuga LDR volume control was the change in frequency response as function of the volume setting. It'll be interesting to see how the other design fares in this regard.

Tom

 

[rebbiputzmaker]

Oh. You're right. I did miss the subject change. My bad. Thank you for pointing it out to me so eloquently and politely.

I'm looking forward to Amir's measurements of the other LDR volume control. Meanwhile, if the manufacturer of it would drop a link to a product page, I'd be interested.

Tom

Well forgive me but there is no mention of tortoga, and even when the poster who wanted to submit his preamp corrected the error, it did not take. So much for science and accuracy.

 

[tomchr]

Tortuga was mentioned earlier in this thread. See Post #59.

Tom

 

[amirm]

Well forgive me but there is no mention of tortoga, and even when the poster who wanted to submit his preamp corrected the error, it did not take. So much for science and accuracy.

Please lower your tone. We have some serious designers and engineers in this thread. You can present data as a challenge but I want to make sure we don't create an unfriendly atmosphere for them to participate.

 

[stereo coffee]

Indeed. If you include the voltage coefficient and temperature coefficient in the SPICE simulation, you should see the THD in the simulation as well. It also makes perfect sense from a theoretical point-of-view. If the resistances of the two resistors/LDRs vary as function of the voltage across them (and voltage-squared in case of the temperature coefficient) they will introduce a signal dependent error (= distortion) Tom

Probing for resistance with signal voltage present can create distortion in itself, as the meter despite its high impedance is a parallel in the case of the series pairs input to output. A basic set up would assess the attachment of measuring equipment by having music playing to see said equipment
and its many settings was not the actual distortion contributor, caused by being a parallel.

 

[rebbiputzmaker]

Please lower your tone. We have some serious designers and engineers in this thread. You can present data as a challenge but I want to make sure we don't create an unfriendly atmosphere for them to participate.

Yes friendly is important. I hope this applies to everyone.

post 54 "If this is the Chris Daly stuff, he is notoriously ignorant of basic electronics, so I would not hold out much hope that there's any actual engineering or performance involved. "