Brytt,
that information is always nice to know and to have confirmation from others that things work the way we think they do. At least on the microphone inductor you should be able to use a very small gauge wire as the current is so low, you don't have to use anything like you would have to do on a speaker where you are handling some real current requirement even though even there it shouldn't take much gauge as the CLR resonant circuit is in a shunt position.
that information is always nice to know and to have confirmation from others that things work the way we think they do. At least on the microphone inductor you should be able to use a very small gauge wire as the current is so low, you don't have to use anything like you would have to do on a speaker where you are handling some real current requirement even though even there it shouldn't take much gauge as the CLR resonant circuit is in a shunt position.
We tried Lazy cat's FODP (First One Dual Power supply) vs my FOSP (First One Single Power supply). FOSP was connected with cables in shape V which were split at the power supply connector. The earth from power grid was used to connect to ground at power supply only. Since only one point was earthed we could hear very natural, easy going sound. When compared to FODP there was less flow, less natural. Only with the ground cables disconnected we could get the same sound as with FOSP.
But, using only one power supply like in FOSP and then compare it to FODP you can clearly hear the difference. In high frequencies they are the same or very similar, the lower you go the bigger the difference. You can hear all the frequencies and there is no lack in amplitude in bottom octaves with FOSP. What you hear is lack of focus. Large instruments have less body. For correct presentation I would recommend 2 PS config with "lifted" ground.
Diodes need 0.7 Volt to conduct. Below that it is open circuit. If everything is O.K. the resistor has to keep the potential below that value. It should also be quite large in value, 1kOhm and above. The resistor can be low power rating, maximum voltage on it will be 0.7 Volts.
At 0.7 Volts the diodes step in and make a short to the ground. Since they have to endure more current I would go for 25Amps or bigger. This way the diode keeps the potential low and the house circuit breaker has the time to step in and trip the power to your amp.
hose4 very good post 3282, getting deeper into what was achieved. So time consuming to reveal if sonics is very natural and easy going or less flow and less natural by listening tests. We wish a cheap measuring instrument to measure it in few minutes 🙂.
hose4 is there a chance dual cabinets make a solution 
. I mean smaller footprint mono cabinet with PSU and amp, one for left and one for right.
. I mean smaller footprint mono cabinet with PSU and amp, one for left and one for right.
hose4,
With the two separate power supplies vs the single power supply was the single twice the size transformer as the two single units? Could that account for the more solid bass, just a lower amount of total amperage available to drive two units rather than one?
With the two separate power supplies vs the single power supply was the single twice the size transformer as the two single units? Could that account for the more solid bass, just a lower amount of total amperage available to drive two units rather than one?
Comparison was done with 2 Hypex SMPS1200 vs 1 Hypex SMPS1200.
Audible frequency response of single vs dual is similar, almost the same. There is all the deep and tuneful bass you would need.
What is lacking is definition. Single PS does not give enough spatial information. When big drum kicks in you can hear it, feel it, but the ears have hard time locating it. The best way to describe it is that scattered pieces (all over the "imaginary" space) of drum on FOSP are gathered and combined to the single drum on FODP (making it more palpable). Energy comes from the instrument. It is easier to distinguish the instrument from the background.
When comparing single supply FirstOne to dual supply VSSA. VSSA wins with correct instrument placement in mind.
To answer your question: Single power supply is powerful enough for 2 channels, maybe even more. there are sound tradeoffs in this config. I would say that single power supply is like having pink glasses in front of your eyes. It can be little more romantic. Some people like that. I could live with single PS if I had not heard dual PS.
hose4,
I would say then if you did not double the power supply size the test is worthless really. It only goes to the fact that one of these smps supplies is not enough to drive two channels. There are other reasons that the two channels will be affected by a single supply though and this is something different than what is being described. And as far as hearing the separation and directionality of the bass that is another red herring. You can not identify directionality of low bass, mid bass yes, low bass no. So I don't believe the test is valid except for the fact that one of those power supplies was insufficient.
I would say then if you did not double the power supply size the test is worthless really. It only goes to the fact that one of these smps supplies is not enough to drive two channels. There are other reasons that the two channels will be affected by a single supply though and this is something different than what is being described. And as far as hearing the separation and directionality of the bass that is another red herring. You can not identify directionality of low bass, mid bass yes, low bass no. So I don't believe the test is valid except for the fact that one of those power supplies was insufficient.
One Hypex SMPS1200 gave same amount of bass as 2. One Connex 2000 Watt power supply was not able to deliver.
I understand the directionability of low bass only is questionable, but bear in mind that a musical instrument is not a single frequency signal source, but a complex signal of base frequency and a bunch of higher harmonics. The higher harmonics are the ones that bring ability to position an instrument.
Maybe I have to put a disclaimer. This is my impression and my explanation of what I heard. I welcome anyone to test for themselves.
Thanks hose4,
I would expect the higher harmonics to be the directionality clues also. As far as the other issues I really would like to hear what someone says if they used a higher output power supply as a single source and compared that to the dual power supply setup. At least as far as the ground loops the single supply in a single chassis seems it should have less ground loop potential. As far as the interaction of audio signal and a common power supply that is another issue entirely and this may be what you are actually describing in your listening tests.
I would expect the higher harmonics to be the directionality clues also. As far as the other issues I really would like to hear what someone says if they used a higher output power supply as a single source and compared that to the dual power supply setup. At least as far as the ground loops the single supply in a single chassis seems it should have less ground loop potential. As far as the interaction of audio signal and a common power supply that is another issue entirely and this may be what you are actually describing in your listening tests.
The description I gave was for dual power supply without any ground loops. Only then the dual config became better than single config. All listening after that was done in this config.
We listened at the same level and same tracks. Also compared with lower power level to see if there are issues with delivered amperes. We tried to observe if we can regain focus. The difference stayed similar also with lower power.
Smps3k power supply from Hypex has multiple connectors to supply power for more modules. The price is similar to 2x smps1200.
Hi hose4
Thanks for the input taking your time to explain our findings regarding single vs. dual SMPS and grounding solutions, appreciate it alot.
Single power supply offers cheaper, easier to realize solution, recommended for less demanding applications, like smaller low frequency reduced speakers drive, PA or similar. Dual SMPS offers better channel's separation, independent full power reserved for each channel only, better grounding solution, at the end all resulting in better overall sound quality.
The fact is, however one may turn, dual SMPS is an ultimate way to go powering a stereo power amplifier. Of course that takes some effort to lay-out proper in chassis grounding wiring avoiding interference currents. Bottom line is that an ultimate solution is just that, no compromise design that can be reproduced at any given time.
Hearing is believing.
Regards L.C.
I'm not fully convinced, while i trust fully your listening impressions.
Because it contradict a lot of experiments done in the past on my side.
This is an interesting point, on my point of view, and need to be clarified by more experiments in order to reach to some kind of 'LAW' for the future.
(You know, the things you know they work and save time and money)
First, the comparison has to be fear: 1X2000 W. SMPS vs 2X1000 W. same CAPS, double value.
Second, great care about ground wiring, preferably in a symmetrical configuration (trafos ?) or bridged amps to minimize leakage evils for this experimentation.
My argue is better stereo image stabilty to be expected from a single configuration, a lot more important than crosstalk issues we don't care of.
The second point is regulated VS unregulated.
I am not satisfied by the results i read near everywhere: "Non regulated sound better".
Let's make the things clear. I reached the same conclusions long time ago and still stay on this position.
But it goes against logic and theory.
So what are the evils at work with regulated PS ? Regulation not fast enough ? Did some of you tried some active cap multiplier between a regulated SMPS and amplifier (it always gave me better results than simple unregulated ones, in fact the best of all the combinations i tried with linear PSUS, never had time to try-it with SMPS) ?
At the level of quality both VSSA and FO (and some other CFA amps) can reach, i believe all the efforts has to be addressed power supply side, now.
Each time i tried experimental batteries PS, the improvement was so amazing, even with midfi amps !!!!
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Hi Christophe
Yes, but batteries are unregulated low Z power source.
Dual mono unregulated SMPS sounds better of them all, excluding batteries.
I would not be convinced to say it so firmly if there would not be an extra pairs of ears to confirm the obvious.
That's the case, anyone can check it anytime.
It is not system setup related because it was consistent in all cases.
Regards, L.C.
I believe the improvement is due to:
- Perfect isolation between ground of preamp, and ground of amp, because you can have good result, powering your amp with AC, and your sources with batteries,
- No RMI RFI because, it is yet better when both are powered with separated batteries.
WHat i said is your experiments with FO Power supplies were too short to can reach such a definitive and general conclusion.
Your dual VS mono was unfair (half of the power when mono). And what about isolated ground during those tests, as well as various AC sens ?
For the moment, i just believe "Dual mono unregulated SMPS sounds better of all the combinations we tried". See what i mean ?
And, anyway, we need to fully understand why.
While I had a hard time finding a good combination of grounding in the dual supply, Single ended VSSA, and even had to suppress the ground-lift 10OHM resistors on board to make it hum-free and good sounding, it was a total relief to work with X-VSSA's and a big surprise to get them work perfectly the same with and without the connection to the GND. No matter how many stupid mistakes I intentionally have done in creating ground loops inside the case of XVSSA, I had absolutely no issues. of course, I left XLR pin1 tied to the case and only two wires connected to the inputs of the modified VSSAs. It seems very important to get the speaker out of the ground and you're a big step forward.
My XVSSA's are playing happily since their first day, powered from single (not dual + and - vs gnd, just plus and minus) supply for each channel and resistor divider for virtual GND. Not any issue with this setup.
I will be doing the First one's still single ended, to keep the price and the power down to what I am allowed. But I guess i will do a First one balanced in the future (hoping the offer from LC will still be there).
Not sure if Andrej will have an out-of-the-box balanced solution in the future. (wondering)
Cheers!
My XVSSA's are playing happily since their first day, powered from single (not dual + and - vs gnd, just plus and minus) supply for each channel and resistor divider for virtual GND. Not any issue with this setup.
I will be doing the First one's still single ended, to keep the price and the power down to what I am allowed. But I guess i will do a First one balanced in the future (hoping the offer from LC will still be there).
Not sure if Andrej will have an out-of-the-box balanced solution in the future. (wondering)
Cheers!
Hi.Can not we use 2sa1380 and 2sc3502 ? It seems they have lower Cre 1,2pF npn and 1,7pf pnp. Or can we use 2sc3503 and 2sa1380 together.They will have almost same Cre then.
After one year or so, I finally managed to built two VSSA channels.Calibration was a demanding procedure , but at the end I got 120mV between TP1 and TP2 and <2mV DC offset at the output.Next time I switched the amplifier on, DC offset was around 50-60 mV,both channels.I trimmed it with much difficulty down to 2-3 mV.After that,when the amp was turned on again ,the DCoffset climbed to 160 mV in one channel and to 330 mV in the other.Rotating TR1 and TR2 had no effect.I have to say that, by mistake,I tried to measure voltage during the initial calibrating procedure with the DMM set on diode check mode!Could this have made some damage to the transistors?Or have I destroyed the trimmers?Anyway,apart of DCoffset,the amp shows no sign of audible distortion and is completely silent with no input signal.Right now I am listening to it through a pair of Q 1010i speakers, source is a PAL Tivoli radio and the sound is really pleasant.
yep its demanding, smt is not diy friendly IMO.
LC, I now have 4 channels of this amp that don't work, any chance you can send me a real schematic with some test points and voltages?
From what I can tell, I read some instructions to modify the board, I cant find it now, but what I did was short both bases with a jumper to ground. Now all I get from the second pair of modules is heavily distorted sound.
LC, I now have 4 channels of this amp that don't work, any chance you can send me a real schematic with some test points and voltages?
From what I can tell, I read some instructions to modify the board, I cant find it now, but what I did was short both bases with a jumper to ground. Now all I get from the second pair of modules is heavily distorted sound.
It looks the trimmers has gone, meaning slider lost connection to resistance material.
TR1, TR2 serves to set VAS bias current and output DC offset at the same time. Easiest way is to observe both values and see how rotating changes values. Once recognized it is trivial.
TR3 serves to set output bias current after TR1, TR2 has been properly set.