I know that a number of you reading this already know. That when Covid broke out in early 2020 I was dealing with something else that made Covid a walk in the park. Nothing in my life could have prepared me for this. The three Covid years happen to coincide with my son's condition, which is incurable but turned out in the end to be treatable, and now he is much better; he has a disability pension as a safety net, and since early this year has stabilised with medication and have been able to take up steady work this year. Those three years can only be described as harrowing! I also learned that this is far more common than most realise and that health services are very flawed and often made a bad situation worse. Despite this, I have still been active in audio and kept my business alive, just. A number of projects/jobs for private clients were fulfilled. As for that paper, it is coming along nicely and will feature a novel test that was conceived in March earlier this year. It will surprise a lot of people and force them to start measuring something that they are not doing, the effect that the driver has on the amplifier when the latter is a voltage source, it is supposed to behave one way except it does not. We must measure both voltage and current of the amplifier and this novel test will show why that is the case. It will be thoroughly proof read and reviewed by very knowledgeable persons before becoming released. There will be no fanfare here. Enuff said.
NBAC teaser: Barring the very slightest adjustment (unlikely) this is the final impedance, not simulated but actual hardware Clio measurement.
The lowest impedance where it drops down to 4.5 Ohm is around 8-9KHz.
Next the measured electrical current phase:
The next on is interest, but please note this is simulated in SoundEasy, but there is reasonable correlation between below and the actual hardware measurements above:
"PPDR = 4.5 Ohm"
(Peak Power Dissipation Ratio)
The key here is the Red line and (1) on the right. This line represents the minimum 4.5 Ohm = 1. Think of this as comparing with an actual 4.5 Ohm resistor and the current it draws versus frequency.
If the Black line stays below the Red (1) line, then the current drawn by the loudspeaker is less that the current that would be drawn by a 4.5 Ohm resistor. We can see that is the case from about 170Hz and upwards.
Some may have seen "EPDR" or Equivalent Peak Dissipation Ratio and PPDR is similar. The Black line is the same except it is rated to be specific resistor value. Clearly a 4.5 Ohm resistor draws a known current and the same current would be drawn if we saw 4.5 Ohm in an EPDR graph. At the moment PPDR is available in SoundEasy and basically provides the same info as EPDR, but in a less obvious way. I hope that SoundEasy will provide an EPDR option as that is much more intuitive.
I believe that REW does EPDR measurement and maybe need to look there and get hardware to do it.
It would be nice to find that there is a piece of (stand-alone?) software where you could import the actual measured impedance plot (usually converted to a text format) and that is will give you an EPDR graph. Does anybody know if there is such a thing?
The lowest impedance where it drops down to 4.5 Ohm is around 8-9KHz.
Next the measured electrical current phase:
The next on is interest, but please note this is simulated in SoundEasy, but there is reasonable correlation between below and the actual hardware measurements above:
"PPDR = 4.5 Ohm"
(Peak Power Dissipation Ratio)
The key here is the Red line and (1) on the right. This line represents the minimum 4.5 Ohm = 1. Think of this as comparing with an actual 4.5 Ohm resistor and the current it draws versus frequency.
If the Black line stays below the Red (1) line, then the current drawn by the loudspeaker is less that the current that would be drawn by a 4.5 Ohm resistor. We can see that is the case from about 170Hz and upwards.
Some may have seen "EPDR" or Equivalent Peak Dissipation Ratio and PPDR is similar. The Black line is the same except it is rated to be specific resistor value. Clearly a 4.5 Ohm resistor draws a known current and the same current would be drawn if we saw 4.5 Ohm in an EPDR graph. At the moment PPDR is available in SoundEasy and basically provides the same info as EPDR, but in a less obvious way. I hope that SoundEasy will provide an EPDR option as that is much more intuitive.
I believe that REW does EPDR measurement and maybe need to look there and get hardware to do it.
It would be nice to find that there is a piece of (stand-alone?) software where you could import the actual measured impedance plot (usually converted to a text format) and that is will give you an EPDR graph. Does anybody know if there is such a thing?
You should only need a resistor.
As you've gone ahead and reduced the impedance phase angle to around 0, what would be the point?
Yes, of course. No, I meant what would be the point in showing the EPDR when we can already guess what it's going to showThat is the point.
I would like it in SoundEasy for a couple of reasons, first it is cool and also SoundEasy is of cause modeling (based on a strict set of measurements) and not an actual measurement. So you can look there as well whilst working on it. It is a challenge to do what I do. It is partly possible because the crossover is always lossy and all impedances go in one direction, up with frequency (above the LF motional impedance). Now that means that the current EQ (conjugate) can be pulled down in line and made flat. In modelling this is largely trial and error plus experience doing it many times before. Then you actually do it physically with the values indicated and see how close you came (Clio setup). Then there may or may not be some final tweaking. BTW, all of this is pointless if it made no difference to the sound. But it does.
Go get REW, make yourself a simple impedance measurement tool using this page: https://www.roomeqwizard.com/help/help_en-GB/html/impedancemeasurement.html
... and you're done.
... and you're done.
With tools like REW, X-SIM, Vituixcad etc. it actually became quite easy and available for anyone willing to try.
Hi Joe,
Impresive flat impedance for the nbac version !
https://kimmosaunisto.net/Software/VituixCAD/VituixCAD_help_20.html
Very simple to do, on impedance graph, crossover panel:
1. Right click : Open overlay
2. Right click : Show EPDR
Have fun !
Impresive flat impedance for the nbac version !
See the functionally described in Vituixcad 2 help (Search EPDR in the page)
https://kimmosaunisto.net/Software/VituixCAD/VituixCAD_help_20.html
Very simple to do, on impedance graph, crossover panel:
1. Right click : Open overlay
2. Right click : Show EPDR
Have fun !
That's a loaded question. You have really landed me in the deep with that one.
I have a problem, many who design loudspeakers do not design amplifiers. Mostly those who design amplifiers only design amplifiers and most who design loudspeakers only design loudspeakers. For example, it is well know that Brad Serhan and Michael Lenehan have been friends of mine for decades. But they only design speakers. That's a big topic on its own, so it is rare that you have people who design both. But I am one of those who do. My work and collaboration with the late Allen Wright was an interesting one, where early on he focused on the doing preamps which in those days had to have a phono stage in them, and in particular MC capable. That left me to play around with power amplifiers without any pressure (I am pretty sure I made the first amplifier in the world using IRF HexFet output devices). So when Allen eventually turned his attention to power amps, I had a lot of stuff ready for him to take note of and yet for him to do his own thing. I never tell others how to design things, I just bring things to their attention and leave it to them. Being generous has made me many friends, so I am rich there and less so in the pocket.
Around 2003 on, Allen was building the Vacuum State DPA-300B which was a collaboration where Allen had added something very original of his own, he forced a pair of 300B tubes into constant current. The amplifier could only work in Class A and even when it clipped it was in Class A and never Class B. You can read about it here with this link. I did a parallel amp design using EL34s.
https://www.enjoythemusic.com/magazine/viewpoint/0104/aachapter52.htm
The DPA-300B was around 20 Watt and that is certainly enough to drive Elsinores to a fair volume. But Allen then brought out the much more powerful DPA-150, which is simply the most crazy amplifier ever designed. I know of only six people who has seen the schematic. The output tubes were reduced in gain to about two, which made them pretty much impossible to drive. To get double the voltage swing he used the Anodes of the KT120 tubes to modulate the tube front end, to give 6dB more voltage swing. I will not even try to explain how Allen forced the output tubed down to near unity gain (not like a bog standard follower that would have been unity and not two).
The DPA-150 was a leap forward over the DPA-300B. But few have been made. They are a freakish design.
I consider the design as belonging to Vacuum State and I will not replicate it. But since late 2016, along with another friend of Allen's, Brian Gurr in Auckland New Zealand. In late 2016 I was visiting Brian and he wanted me to make an updated version of the DPA-300B because he knew I could be open to that, having been part of its development. I declined and said that the DPA-150 showed the way, where the idea of the tube being forced closer to unity gain was a way of "going beyond triode." I realised I had stumbled across the right words, Allen was the first one to go "Beyond Triode" with the DPA-150 and that I had to figure out a way to do the same without copying his design. I also wanted to use the EL34 instead (for a number of reasons, what I had in mind the EL34 is easily the most suitable.
It took six years!
Below is the schematic, but without the values etc that are critical. You can by all means make it work if you are clever enough, but there is values and info missing that means you will not hear anything like the potential values. Some of the resistor values are unlike anything you would expect and has a huge influence on the result. Also, no power supply schematic which is critical too.
I admit I am biased, but this amp was designed when 99% of the time it was connected to a pair of Elsinores. If any amp was ever designed to go with the Elsinores, this is it.