Now coming to something completely different ... Today's topic is → "AC-Current-Source-Amplification"That's why it came as it had to come: The various self-proclaimed Audio "experts" at DIY-AUDIO immediately agreed that something like this could never work and that I should therefore refrain from coming up with it. I had the device in operation at my home, and like many of my colleagues who had already heard it, I was thrilled by its brilliant performance. Well, what shouldn't be, mustn't be ... I think today something like this is called a "shitstorm", although the term was not yet common in the 90s. It became clear to me even then that the so-called “experts” and "Audio popes" from whom you simply can't escape on DIY-AUDIO had once again absolutely not understood what it was all about. You can't look at an AC constant current source like a voltage amplifier. Then extend the shortcomings of the Voltage-Sourcing-Amp (VSA) to the Current-Sourcing-Amp (CSA) and state that this is precisely why it cannot work at all ... couldn’t stop laughing! For example, the internal resistance of a VSA has a negative impact on performance if its value becomes too large. In an CSA the internal resistance approaches infinity. Did everything go wrong? What is still missing here, however, is the fact that in a VSA a voltage is regulated at its output which is proportional and as congruent as possible in the curve form to the input voltage. However, the load is not a linear, ohmic resistance, but an impedance. However, this means that the resulting load current will never be congruent with the input voltage. But it has to be, because according to Hendrik Antoon LORENTZ, a theoretical Physicist from the Netherlands who established the “Lorentz-Kraft” and was awarded the Nobel-Price in 1902, said ... "The force acting on a conductor in a homogeneous magnetic field is directly proportional to the current across the conductor." Fres = Irms * B * l In addition, there are a few other factors that determine the force. These are the length of the conductor [l in m] and the magnetic flux density of the magnetic field [B in T]. However, these factors do not exert a direct influence during operation, as they do not change during operation. Thus, the current from the load alone (of course we are talking about the voice coil of the speaker here) remains the only determining factor in this game. This is also where the characteristic parameter for a speaker-driver "B*l – product" is derived, which is a key figure for the efficiency of a speaker-driver. So, what's different with a CSA? At its output, this one emits a current proportional to the curve shape of the input voltage, which value is independent of frequency and load impedance. This also means that the force applied to the voice coil is directly proportional to the input voltage – a fact, by the way, that is not achievable by any other technology. The main difference to the VSA, however, is that in the VSA the current through the voice coil is a result of output voltage, load impedance and frequency – while in the CSA the current is already predetermined and only the voltage at the load is a result. However, we know from LORENTZ that the voltage is insignificant, because only the current determines the force on the voice coil. As a further result, a loudspeaker will always emit usable sound as long as it is mechanically capable of doing so. And of course, this is the point, where the full range drivers (FR) jump in. At the same time, however, this circumstance must also be noted as the most significant disadvantage of the CSA: As a following, multi-way speakers with crossovers will only work to a very limited extent, especially those with acoustic optimization. If you don't want to part with these – possibly already existing speakers – I would have to seriously advise them against CSA. Basically, speakers that conduct current past the various voice coils and those that are optimized in phase will not really work satisfactorily. This results from the fact that the imprinted current from the CSA would have to flow through all voice coils and current parts that are passed by in crossovers are of course lost as a source of driving power. At the same time, the output current is basically in (the same) phase and therefore of course there is no need for runtime elements in crossovers. But of course, the most advantageous thing is to use an FR right at the beginning to cover the entire audio frequency range. Two mechanical construction methods are available here – the "Back-Loaded Horn" (BLH) and the "Cut (or Taylored) Resonator" (CR). But more on that later ... The result of this design philosophy is on the one hand the SEA power amplifier CABERNET and the miniature version of it, the BAROLO. This is a model of it, but with the same function for powering headphones. Please note the respective PDF articles on the projects listed. ############################################## But then almost all Audio amplifiers on this planet turn the wrong way 'round? Well – YES and NO at the same time. Why?
When I started a discussion on the principle of current source amplifiers once more at DIY-Audio at the end of 2025, the same shitstorm broke out again immediately, which I already knew enough about. It is significant that the majority of people persistently refuse to become wiser. And yes, the Spanish Inquisition has also become superfluous over the centuries ... unfortunately only after she was able to commit unspeakable cruelties and crimes and also only too late to be able to bring those responsible to justice. To date, a few hundred, maybe even a thousand (?) have built these devices according to the documents I published and I have not heard any complaints so far. On the contrary, I have received a myriad of praising but also very grateful letters. They were written mostly by Audio-aficionados’ who were searching for the perfect performance for all their life - and now found it ... |
... and what's that all about ...
The Back-Loaded-Horn-Speakers
The EXCEL-Calculator Spreadsheet
Horn-guide
The User Manual for this EXCEL-Calculator Spreadsheet
User Manual
Some pictures of my own Horn-Speakers
My Horns
The DAC-Project
DAC-Output Stage
El Cheapo PRO MkII
El Cheapo - Binder
El Cheapo - DAB-Calculator
The Pre-Amp Project
Phono-Pre-Preamp
CHARDONNAY
CHARDONNAY - Binder
CHARDONNAY - Plots
Coupling a MC-cartridge
to come!
Linestage-Preamp
TEQUILA-Mk3
TEQUILA-Mk3 - Binder
TEQUILA-Mk3 - Plots
Total Setup incl. Inputs and AUX-Supply on 1 PCB; Binder
Inputs, Tape, AUX-supply
Connection Diagram of the Total Setup incl. Inputs
Inputs, Tape, Supply
The Power-Amp Project
CSA - SEA-Poweramp
CABERNET
CABERNET - Binder
CABERNET - Data and Plots
The Headphone-Amp Project
CSA - Headphone-Amp
BAROLO
BAROLO - Binder