Hi guys 
Testing period of the second generation of VSSA came to the conclusion, many important data gathered from assembly itself as well as from today's listening tests where both amplifiers were compared and carefully evaluated.
As I tought that VSSA with linear PSU showed all it can be squeezed from this topology, today's session clearly revealed that new VSSA channels with switching power supply SMPS400 can even go further, by far. It is not only the SMPS that made the difference, also the Nichicon ELCOs in a great portion. New stereo amp has more control over the lower spectrum, bass is perfectly controled, layered, all notes have nuances revealing bass instruments to the bone. Resolution is top notch, imaging is perfect, stage and atmosphere of the recording without limits in 3D sense, There's simply no amp present, because recordings differentiate among each other with ease, again totally no brainer, only music and positive energy. I have to praise reproduction of the vocals, they are so natural, distinct, surprisingly rich with harmonics and artefacts proper to each individual voice, presented in top resolution without any hiss in sibilants.
As I already said I expected the new VSSA amp to be closer, maybe a litlle "faster" beacause of the SMPS, but, on contrary, was faced with even bigger step towards ultimate audio reproduction.
Regards, Andrej
Testing period of the second generation of VSSA came to the conclusion, many important data gathered from assembly itself as well as from today's listening tests where both amplifiers were compared and carefully evaluated.
As I tought that VSSA with linear PSU showed all it can be squeezed from this topology, today's session clearly revealed that new VSSA channels with switching power supply SMPS400 can even go further, by far. It is not only the SMPS that made the difference, also the Nichicon ELCOs in a great portion. New stereo amp has more control over the lower spectrum, bass is perfectly controled, layered, all notes have nuances revealing bass instruments to the bone. Resolution is top notch, imaging is perfect, stage and atmosphere of the recording without limits in 3D sense, There's simply no amp present, because recordings differentiate among each other with ease, again totally no brainer, only music and positive energy. I have to praise reproduction of the vocals, they are so natural, distinct, surprisingly rich with harmonics and artefacts proper to each individual voice, presented in top resolution without any hiss in sibilants.
As I already said I expected the new VSSA amp to be closer, maybe a litlle "faster" beacause of the SMPS, but, on contrary, was faced with even bigger step towards ultimate audio reproduction.
Regards, Andrej
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Why you limited it at ~1MHz? Signs of ringing if left full open, or just general caution practice?
Because of RF picking from interconnect cables without completely concluded GND shielding, mostly used by audiophiles, also by me too hehe
I had at the begining 100 Ohm/100pF input low pass and noticed some MHz signals on the freq analyzer, plus more noise when cable with non complete shielding was connected, so I installed 1 k trimmer instead of input resistor and supression was sucessful beyond 470 Ohm, so 680 Ohm was chosen with safety margin included. Yes, audiophiles interconnects can also be just two plain wires 1 m long and that is nice antenna too. Have to be careful when GB takes place also the signal quality is not compromised with this -3 dB margin, clearly showed with squares plots.
P.S. If you ever test with single switching PSU common to channels so to measure spec and also evaluate the subjective compromise loss % many builders would be interested to know I am sure. Since such a single has the basic power at least and when used common offers enough budget saving if good enough.
Esperado, as always I can only agree with you. Your's experinces are greater than anyone's here and I am honoured to have you near. I think you'll be able to test VSSA too, since the decision was made that all VSSA PCBs will have ready installed SMD parts by default. Just have to check for how much costs per PCB, but regarding to requests many will be pleased with this decision.
Agree, really tried to get SMPS2000R from connex for single SMPS stereo operation, but unfortunately no response from them.
Do you have any suggestion for proper (current capable) single SMPS?
I don't understand anything about SMPS, but I suggest having a look at the DPS line from the recent Audio-Power (designed by forum member AP2).
Those supplies were tested on "The Wire" power amplifier with success, and may be a good alternative.
The DPS-500 and DPS-600 are fully regulated, btw.
You can contact AP2 directly by PM, he is very responsive.
http://www.diyaudio.com/forums/soli...-lme49830-lateral-mosfets-81.html#post2939487
Those supplies were tested on "The Wire" power amplifier with success, and may be a good alternative.
The DPS-500 and DPS-600 are fully regulated, btw.
You can contact AP2 directly by PM, he is very responsive.
http://www.diyaudio.com/forums/soli...-lme49830-lateral-mosfets-81.html#post2939487
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Are-you kidding ? YOU are the best audio designer i have met in my life. Because you are open minded and try always new tracks with no prejudice. Because you have some kind of "physical" sens of the electron's flow and the way parts behave. And, most of all, you use your ears in an objective manner, and get the right conclusions by a good technical analyze. I'm amazed by the accuracy of all your choices, witch always correlates the ones i made decades to figure out. And i discover a lot, looking at your work and reading your conclusions.
Salas, there is several reasons to try to build the faster amp you can, and to apply the slowest signal you can
First is to do not excite ringing, and get a coherency between low signals and high ones, yes. The other one, witch is a consequence, is to avoid TIM, dynamic phase distortion etc.
There is nothing interesting in Hf components, outside of the audio bandwidth, mostly distortion products from the previous stages. And, even if you do not ear them, they will produce distortion if the amp is at the limit to deal with. Let say that, if you have a flat phase curve at 20Khz (bandwidth 200kHz, including the input filter) and your amp is able to go 10 time faster, you are on the perfect way.
The last thing is the correlation between the slew-rate and the bandwidth of the signal. It was correlated by physical reasons (mechanical inertia of mikes or PU heads) )with analog sources. It is no more with digital, where you can have a bandwidth limited at 20kz (brick wall) while you can have incredible slew rates between two samples. It is good to limit them and recover a more natural coherency.
Always filter your inputs as low as you can, just at the limit to lose some trebles. And do this for all your stages, avoiding accumulations, of course.
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Esperado, as always I can only agree with you. Your's experinces are greater than anyone's here and I am honoured to have you near. I think you'll be able to test VSSA too, since the decision was made that all VSSA PCBs will have ready installed SMD parts by default. Just have to check for how much costs per PCB, but regarding to requests many will be pleased with this decision.
I am extremely pleased!!!
All hail the Cat!!!