Hi Jason
Took some doing, but "https://www.customanalogue.com" now works. It was just a matter of being persistent and finding a way.
I have just tested it and it works when posting new graphics using IMG command. So that sorts out future posts.
But the old ones, going back many years, they are still HTTP, like the one on Post #1 of this "Trans-Amp" thread, where the main schematic diagram of the amp was posted. For that to work, it needs the s added.
The main areas of concern is the Elsinore Project thread.
And of course this "Trans-Amp" thread.
Is there some kind of script that can be run on those two threads, or is that in the too hard basket? If that could be done, that would make be happy as other threads are not as important.
Thanks again. Cheers, Joe
Joe,
Can you please email contact@diyaudio.com to start a ticket with the helpdesk, and we'll work out a solution from there towards getting your previous posts' links updated to the new HTTPS ones.
Thanks!
Can you please email contact@diyaudio.com to start a ticket with the helpdesk, and we'll work out a solution from there towards getting your previous posts' links updated to the new HTTPS ones.
Thanks!
Excellent... I tried with 2*TDA7293 in parallell, +/- 48 Volt power supply, driving a 15" Subwoofer. Approx 140 watt max RMS output. I used them both as voltage feedback and current feedback. And current feedback gives clearly less distortion. I will use a Klippel system to do distortion measurement and comparison, nice piece of equipment.
Hello everybody .
I read these pages with great interest because everything that is not conventional and revolutionary turns something inside me.
I have to ask a question about the relationship between this amplifier and the elsinor speakers. I asked myself why there are so many low-frequency speakers.
are they all connected in parallel to make the inductance smaller and increase the pure resistivity?
I read these pages with great interest because everything that is not conventional and revolutionary turns something inside me.
I have to ask a question about the relationship between this amplifier and the elsinor speakers. I asked myself why there are so many low-frequency speakers.
are they all connected in parallel to make the inductance smaller and increase the pure resistivity?
There is an Elsinore thread where questions can be asked, but basically it is there for DIY'ers helping each other with construction as they are a challenge to some, it is a sizeable project.
I am unfortunately grown a bit unwary of entering into a deeper discussion because the Elsinore speaker does have some unusual features. For example, as the transamp proves, it can be equally well driven by both voltage source amps (low output Z amplifiers) and current source amps (very high output Z amplifiers). The Elsinores effectively cancels out the output impedance of the amplifier and that makes them compatible with amplifiers that have fixed output current. The output largely disappears.
One question that occupies me is the question: "What is a reactive load?"
With a voltage source, the current becomes reactive, with a current source the voltage becomes reactive. The fact that we use both series and parallel elements when we add a crossover, any series element makes the source more voltage reactive and any parallel element potentially current reactive. There are so many variables.
In the Elsinores there is a balance achieved and the transamp was designed as proof. But as for a deeper theory being discussed, the serious players are avoiding online discussion because of the prevalence of trolls, or those who say everything has already been figured out and that discussion is superfluous. But the truth is that the speaker reacts in ways that distort the current of the amplifier and we already have a stunning measurement that shows distortion on the current side that is not on the voltage side, so that the amplifier has two distortion profiles while connected to a single driver, so even before a crossover is connected and making the subject even more complex. So our attempts to understand better what is happening will go on.
The interface between the amplifier and a dynamic loudspeaker is the most complex interface in the audio chain.
Cheers, Joe
It is critical, but current measurements are necessary to see this. Most don't use current probes, and are unaware.
For example, you can run into audible current limiting much earlier than would be expected, on either music
or asymmetrical test waveforms.
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Well, one of the challenges could be-that the amplifiers people are none too familiar with speakers and the speaker people are none too familiar with the amplifiers so it’s not easy mixing it altogether like that.
The late Graham Maynard looked at the behaviour of his JLH inspired amplifier differently. He was concerned about the impact of a non-resistive speaker on the output stage of the amplifier. He investigated it and designed his amplifier accordingly.
And for some folk, amplifier technology is already fine and great speakers are available too. The challenge is what to do with the room interaction.
For me, it’s mostly academic interest, the Elephant In The Room is actually the difficulty of finding good recording quality. I got ‘ruined’ by a couple of Chesky CDs years ago and have yet to recover.
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And 'current measurements' is the key and right now looking at a series of such measurements that will show results that will be surprising: That amplifiers can have two different distortion profiles at the same time, one on the voltage side and another on the current side - and the current side will have more distortion than on the voltage side. The first two measurements have already been done, not just by me but also by somebody else. Take a typical 2KHz sinewave into a single driver, put that on Channel 1 on your scope. Now fit a 0.1R current sense resistor on the return side, a small voltage that represents the current. Now put that small signal through a low distortion amplifier with a gain around 60. Since the DC resistance of the voice coil is 6R, you have now the Vre of the driver. Multiply the Vre by the current of the amplifier and you will have the dissipation of the voice coil. Only this part of the impedance dissipates heat, the rest of the impedance above 6R does not. I have been attacked for calling this part of the imepdace the "back-EMF impedance" and yet I stand by it. Now put Vre on Channel 2 of the scope. It's amplitude will be less that the voltage of the amplifier, but typically delayed by 30 degrees with most drivers.
Since we now have the voltage sinewave of the amplifier and we also have the current sinewave of the driver, and that there is a difference in time, the question must be asked: WHICH sinewave are we listening to? We cannot be hearing two sinewaves at the same time and we are not. The answer is simple, we are listening to the current, as represented by the Vre of the driver.
What if I was to tell you that you will measure distortion on the Vre (putting it through an analyser) that you won't measure on the voltage side of the amplifier? Well, I am here to tell you that there is, And since we have admitted that we are listening on what we see on Channel 2 is the sinewave we hear, then were are listeining to that distortion.
What causes this distortion? The multitude of imperfections of the driver, that distorts the "back-EMF impedance" and hence corrupts the current of the amplifier. And it can be backed up with measurements.
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Absolutely right and doing the same here, based on the legacy work of the late Allen Wright a new amplifier is being developed over the last three years, with the help of another friend of Allen's, Brian Gurr in Auckland, New Zealand.
This amplfier has effectively negative gain (-24dB) in the output stage, this makes it highly immune to current corruption caused by the "back-EMF impedance" of the speaker, that which makes the driver non-resistive.
Got no beef with you about room problems, but can't agree about the speakers and amplifiers.
If you get amplifiers that cope with back-EMF issues (or current issues, as it is the same thing), you get an extraordinary soundspace, openness and clarity and the sound seemingly coming away from the confines of the speaker box. Also, EQ the current of the speaker and once again you get the same sort of thing. It seems that current management at the interface and you get an audible clarity that seems so less Hi-Fi sounding, textures of instruments so much more realistic in space. Sadly, not the sound that you hear in Hi-Fi shops and shows.
But agree 100% about the room, but to me, that is one of three to get right.
Hi James
Down in Tasmania for a break, so late this evening catching up...
Absolutely, but these show up as imperfections and modulating the "back-EMF impedance" of the driver and hence as actual current distortion of the amplifier. This is measurable, that is what makes it so interesting, but work in progress...
They may actually prove a good thing. We think of an output transformer as a step-down device, but it is as much a step-up device when it comes to current. But in reverse they are step-down devices when it comes to current that is caused by the back-EMF of the speaker. Now try get the output tubes as close to unity gain as possible, and voila! This is not just theory, we got working amplifiers doing just that. Being 'local' I think you will be hearing more about that.
There is now a new world-wide interest in this topic, that saying "follow the money" means "follow the current" will get us a much better understanding of what is happening.
Hi, Joe,
We haven't corresponded in some time, so I just thought I would drop in here to say hello. I hope all is well with you and your family.
I see from your Custom Analogue website that you are still developing unique approaches to obtaining good sound. I check the site from time-to-time to see what new ideas you are currently about. I've always appreciated your rejection of rigidly doctrinaire thinking, which, as you well know, entails enduring slings-and-arrows from the self-righteous, who, with minds closed, reflexively defend orthodoxy.
Recent topic on other threads Bob Cordell's Amp Thread and JC's BT Thread.
Cyril_Bateman/Bateman_Speaker_Amp_Interaction.pdf
Cyril_Bateman/Bateman_Speaker_Amp_Interaction.pdf