There is a compact downloadable software app for the QA403, probably having nothing to do with Linux.
Hi Rick,
Thanks for this good information.
Jan's review of the QA403 has been published in AudioXpress.
I wrote a fairly large tutorial for the QA403 and I will be putting it up on my site in the next few days. The tutorial walks the reader through a complete set of measurements on the BC-1 power amplifier.
Cheers,
Bob
Version 1 of my Tutorial for the QuantAsylum QA403 is now up at my site at cordellaudio.com. I is under the Audio Instrumentation tab.
Cheers,
Bob
Cheers,
Bob
Version 3 of my Tutorial for the QuantAsylum QA403 audio analyzer is now up on my website and is discussed in the QuantAsylum User Forum. The tutorial walks the reader through all of the pertinent tests for an audio power amplifier, in this case my BC-1 design, which is also described in detail on my website.
The QA403 is an outstanding piece of equipment, especially at only $600. It has pretty much all of the functionality and performance most people could need. It is just as valuable for use with small-signal circuits as well as power amplifiers. One nice feature is that it includes selectable inverse RIAA respnse shaping for measuring phono preamps. It also includes selectable A-weighting for noise measurements. Further, it includes optional user-entered weighting responses. It can usually see distortion products below -120 dB or better, and report THD down to -120 dB or better. It can sample at up to 192 kHz, allowing one to see FFT products up to at least 80 kHz. Sampling to 384 kHz may be available soon. It is powered from its USB connection to the PC on which its software resides, and it is galvanically isolated from the PC side. It has balanced I/O.
Cheers,
Bob
The QA403 is an outstanding piece of equipment, especially at only $600. It has pretty much all of the functionality and performance most people could need. It is just as valuable for use with small-signal circuits as well as power amplifiers. One nice feature is that it includes selectable inverse RIAA respnse shaping for measuring phono preamps. It also includes selectable A-weighting for noise measurements. Further, it includes optional user-entered weighting responses. It can usually see distortion products below -120 dB or better, and report THD down to -120 dB or better. It can sample at up to 192 kHz, allowing one to see FFT products up to at least 80 kHz. Sampling to 384 kHz may be available soon. It is powered from its USB connection to the PC on which its software resides, and it is galvanically isolated from the PC side. It has balanced I/O.
Cheers,
Bob
As many of you know, the KSA1381 and KSC3503 have been my favorite VAS and predriver transistors, but are now both EOL and essentially not available, especially the KSA1381 PNP transistor. They have high voltage, very good beta and low capacitance, plus a high Early effect figure of merit. What substitutes are you guys using now and what has been your experience with their performance and availability?
Cheers,
Bob
Cheers,
Bob
Hi Bob,
Profusion in the UK (same guys as the Exicon mosfets) recently signed a deal with KEC and are going to stock the KTA/KTC devices. I have an account set up so when they show stock I'll get some for us to try out. A bonus is that they are selling the same hfe graded "Y" devices.
https://us.profusion.uk/int/catalogsearch/result/?q=kta1381
Rick
Profusion in the UK (same guys as the Exicon mosfets) recently signed a deal with KEC and are going to stock the KTA/KTC devices. I have an account set up so when they show stock I'll get some for us to try out. A bonus is that they are selling the same hfe graded "Y" devices.
https://us.profusion.uk/int/catalogsearch/result/?q=kta1381
Rick
Hmm... where is the "QuantAsylum" User Forum? Obviously not in here.
Bob, can you provide the link?
Thanks
,sreeehC
ynoT
Bob, can you provide the link?
Thanks
,sreeehC
ynoT
The Version 3 of the tutorial and a ZIP folder of all of the settings files is also on my site cordellaudio dot com under the Instrumentation tab.
Cheers,
Bob
@Bob Cordell - thank you very much for these excellent tutorials. As each has become available, I've printed them out and studied them repeatedly. I also have an AP SYS-2722, and your test procedures and recommended settings have actually helped me with performing better tests with that unit as well!
Thanks for the kind words. Matt Taylor deserves great credit for bringing the QA403 to us and for continuing to improve the software and add new features. Version 4 of the tutorial is currently a work in progress and I welcome comments, suggestions and pointing out of errors.
Cheers,
Bob
Cheers,
Bob
Hi Bob!
I am thinking og reviving your 50W HEXFET amplifier project that I started 30+ years ago. I did the layout of the boards, bought components, even built the box and had a custom ordered transformer. But I never came to actually producing the PCBs. So my question is this: Is it worthwhile in your opinion, to make this amp now? Will it compare favourably to the DH-220C? Which btw,I already have made a PCB for, but not started building.
A second question about output transistors: In my schematic I have doubled the output tranistors. Is this possible? To balance the transistors, maybe I would need to add source resistors to the HEXFETS?
My original PCB layout and box:
Today's schematic:
I am thinking og reviving your 50W HEXFET amplifier project that I started 30+ years ago. I did the layout of the boards, bought components, even built the box and had a custom ordered transformer. But I never came to actually producing the PCBs. So my question is this: Is it worthwhile in your opinion, to make this amp now? Will it compare favourably to the DH-220C? Which btw,I already have made a PCB for, but not started building.
A second question about output transistors: In my schematic I have doubled the output tranistors. Is this possible? To balance the transistors, maybe I would need to add source resistors to the HEXFETS?
My original PCB layout and box:
Today's schematic:
Is that the original circuit?
Considering you loose all the voltage headroom for mosfet and cascode, 50W is really inefficient. I suggest to stretch it to near 100W for 8 Ohm. Those IRF mosfets are beasts, I won’t bother to double them even for 4 Ohm.
I have copied from the original article but there may be errors (hope not). Not having to double the output is a good thing! Seeing Bob is using cascodes and CCS's, would it be OK to rise supplies by 10V? I.e 60V & 45V?
Here are the original drawings:
Here are the original drawings:
Hi @m0rten , if I am not wrong, this output/bias network is so called MOSFET with Error Correction. If that is only thing you need, please check out my new post. https://www.diyaudio.com/community/threads/rail-to-rail-mosfet-buffer-with-error-correction.426869/
Hi @jxdking!
Thanks for your comment! This project is more about nostalgia and fun - if I believe the end result is good enough. I did enjoy reading Cordell's application note in those days and I camo SO close to finishing the project. To make a completely new amplifier is not an option, since I have at least 10-15 projects in different states of (un)completion, and they are all begging for more attention.
But if you can give any advice on raising the supply voltage and maybe the comparison with the DH-200C, it would be great!
Thanks for your comment! This project is more about nostalgia and fun - if I believe the end result is good enough. I did enjoy reading Cordell's application note in those days and I camo SO close to finishing the project. To make a completely new amplifier is not an option, since I have at least 10-15 projects in different states of (un)completion, and they are all begging for more attention.
But if you can give any advice on raising the supply voltage and maybe the comparison with the DH-200C, it would be great!