There are two effects to be considered here:
- Magnetizing current inrush, depending on the moment of switching ON the Xformer, irrespective of connecting any circuit elements on the secondary side.
- High current due to first charging of the Capacitors.
I understand that, but I just finished a Leach with a 65-0-65VAC 800VA transformer and 44,000UF caps and it doesn't trip my 15A power strip with a couple other power amps running on the same strip. Surely the VSSA is not going to draw the kind of surge that will pop a breaker. I guess my point is using inrush current as an argument for SMPS on this unnecessary to me.
Indeed.
If we use to overkill the trasfo in linear PS, it is not to provide enough current to the amplifier, it is to provide enough current to the BIG primary CAPS. for they can be fully charged near the top of AC sin wave.
Why big caps values? Because they improve the dynamic behavior of the amp, providing a flatter voltage during high current demands of the amp.
This means a terrific inrush AC current at the power on, when caps are fully discharged.
On my 1000VA trasfo, it is enoughto fade down all the lights in my home. During a time too fast to fire the AC fuses or breaker, yes, but this huge current is not good for the CAPS long lasting, reason why i need soft start.
Unless the rating of the transformer is exceeded, a bigger transformer does not buy you much.
The point at which the diode starts to conduct is a function of the voltage difference between the caps and the secondary winding. The voltage at the cap bank will then increase as a function of the AC half wave. Rise time at the caps does not change much, the cap bank won't charge any faster from a bigger transformer.
The transformer will act mostly as an AC voltage source. The voltage remains the same, and the current varies depending on the demand. A cap bank of a given size will charge at the same point, and for the same period regardless of the size of the transformer, until the trafo rating is exceeded (or at startup).
Connecting a 1000 VA transformer to an amplifier capable of 100W per channel does not get you anything more than a 400VA transformer. It
uses a smaller percentage of the transformer capacity, but as long as the voltage rating of the secondary is the same, there is no way to use the excess power.
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Two smaller transformers will ensure some additional isolation between the channels, and in case of a poor grounding scheme, it may eliminate one potential ground loop. I think this was the point of AKN's post above.
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Indeed, and I am fully aware of that!
Anyway i don't intend to use the 1000VA transformer for VSSA single ended modules, but for the balanced ones. Expecting something close to 250W from each channel in balanced mode, I don't see 1000VA transformer as a waste of space or an overkill.
For the single ended modules I will use a 500VA transformer that has separate windings for each channel and it's in front of me right now
And even for this one I have a soft-start module ready to be installed. That was my point in the previous post: for linear PSU it's best to use a soft start module; I did not try to say that because of the inrush current you better use a SMPS. I just wanted to say that for SMPS you don't need a soft start (included in most) and that's why, if you compare all the costs, the SMPS is not THAT expensive as it seems.
Of course, for most of us it's not very likely that we'll find a SMPS matched to the specs in the drawer. Finding a quality transformer is more likely, almost everybody will find something close under the table
If that's the case, it's an important argument in the costs balance to follow linear PSU route for lots of us (including me) despite the benefits of a SMPS.
As LC said before, if you have to buy the transformer, better buy the SMPS. And I consider this a very good advice!
Cheers!
Up to now 190 VSSA modules were sent out and only a few GB members said to make it with SMPS. That is really sad because some members made their final opinion about VSSA sound based on classic PSU and I honestly think they missed their opportunity to gain best out of it. DIY-ers usually try to get good sound by shortcuts like simms and zillion times recycled VFA-s and still not learned their lesson. Correct and much easier way would be to follow the steps of proven recommendations and their exact execution, otherwise why bother at all.
As it can be understood from preceeded writting, my claim still would be that VSSA with SMPS in dual mono configuration would really be hard to beaten by any amp out there, including forthcoming First One.
It's simple, just copy/paste last post of the GB list and add your name to the bottom.
When summed number from the list will reach 110 VSSA sets than GB is encircled. After that I will give the instructions about the next step to be taken meaning order and personal info transfer to my e-mail, followed by proforma invoice.
Up to now 190 VSSA modules were sent out and only a few GB members said to make it with SMPS. That is really sad because some members made their final opinion about VSSA sound based on classic PSU and I honestly think they missed their opportunity to gain best out of it. DIY-ers usually try to get good sound by shortcuts like simms and zillion times recycled VFA-s and still not learned their lesson. Correct and much easier way would be to follow the steps of proven recommendations and their exact execution, otherwise why bother at all.
As it can be understood from preceeded writting, my claim still would be that VSSA with SMPS in dual mono configuration would really be hard to beaten by any amp out there, including forthcoming First One.
I think that's for me since i have (maybe should i not??) communicate on my listening impressions. For sure i can trust you on SMPS effect but first it's not for me a definitiv opinion (i could't try to sell the module but i keep it for later) and second i can simply not justify the 150-200€ extra spending as i have so many parts as trafo (up to 6 option for 2x25Vac, up to two for 2x29/30vac and up to 2x35vac) or screw cap (12x 22.000uf 40V and even many 15000uf 63V). What should i say to my son : boy i can you by your so desire latest toy/game...beacause i need to spend this on not vital SMPS. For me audio is a hobby and not a life style so i ever play at first with what i have on hand, not extra play for money windows throwing as we say in France. Vssa is a first class product, i recommand it to many other french DIY and will it at all but i must confess that i experiment less pleasure in building process than in other stuff (it's a major chapter for me in diyaudio as work stress derivativ). Right as i can have access to SMPS i will report on potential new listening impression with VSSA.
Marc
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OT
Dimming lights combine them with another big powerconsumer (oven?) and mainsfuse/circuitbreaker may go or...
I know of a situation where if garden lights switched on the power dipped and the preamp at 192V started trying to start-up again, preamp switched power to 2 poweramps so the 3 of them were trying to start-up at 50hz interval till preamp relais burnt, only then power was able to recover to 230v lolol I can only laugh because only relais and part of PCB burnt and that was easily repaired and modified once I understood what was happening. Had the house burnt down it wouldn't have been funny and I probably would have been sued, since I installed and sold the audiosystem jeje.
Dimming lights
combine them with another big powerconsumer (oven?) and mainsfuse/circuitbreaker may go or...I know of a situation where if garden lights switched on the power dipped and the preamp at 192V started trying to start-up again, preamp switched power to 2 poweramps so the 3 of them were trying to start-up at 50hz interval
till preamp relais burnt, only then power was able to recover to 230v lolol I can only laugh because only relais and part of PCB burnt and that was easily repaired and modified once I understood what was happening. Had the house burnt down it wouldn't have been funny and I probably would have been sued, since I installed and sold the audiosystem jeje.Schematic is provided in post #300 of this thread. As it is, it might deliver 100W into 4OHms according to LC. Two modules bridged might go up to 250W into 8Ohms. I intend to test that in the future, but as far as I've read, nobody did it yet; so it was just me, wishful thinking
Exactly this happened to me in one evening while testing the 1kW toroid without anything connected to the secondary. Add to this picture my scared wife, telling me I will burn the house one day... So better safe than sorry!OT
Dimming lights
I have built a variac/light bulb based testing environment since then, but that proved me that not only the caps charging can create a surge in the AC line. I will use a soft-start circuit on anything using toroids over 300VA. Of course, your opinions/experiences may vary.
Cheers!
BYRTT 8 PCB set
CaféNoir 6 PCB set
ColinAlex 8 PCB set
DavorXXL 6 PCB set
DuffyDawg 4 PCB set + 4 SMPS400
electromf 4 PCB set
badrisuper 2 PCB set
volavola 2 PCB set
JethroTull 2 PCB set
kp93300 2 PCB set
momomo67890 4 pcb set
ua3grn 6pcb set
mj777 2pcb set
mkusan 2pcb set
Odysseas 4pcb (2 pairs)
hcbonfim 2pcb set
Albrerta 2pcb set
dw1narso 2 pcb set (1 stereo) + extra output device pairs & isolators (for stereo if possible)
supernet 2 pcb set
milandks 4pcb set
tjencks 2pcb set
quanghao: 2pcb set
audionootje: 4pcb set (2x stereo)
tritosine 4pcb (2 pairs)
Bobo le Chat 2 pcb set
AP2 2pcb set+2pcb empity (i need this also)
Meganinja 2 set ( stereo )
coolewater 2 pcp set
mikvous 2 pcb set
still4given 2 PCB set
Rick G 2 PCB set
CaféNoir 6 PCB set
ColinAlex 8 PCB set
DavorXXL 6 PCB set
DuffyDawg 4 PCB set + 4 SMPS400
electromf 4 PCB set
badrisuper 2 PCB set
volavola 2 PCB set
JethroTull 2 PCB set
kp93300 2 PCB set
momomo67890 4 pcb set
ua3grn 6pcb set
mj777 2pcb set
mkusan 2pcb set
Odysseas 4pcb (2 pairs)
hcbonfim 2pcb set
Albrerta 2pcb set
dw1narso 2 pcb set (1 stereo) + extra output device pairs & isolators (for stereo if possible)
supernet 2 pcb set
milandks 4pcb set
tjencks 2pcb set
quanghao: 2pcb set
audionootje: 4pcb set (2x stereo)
tritosine 4pcb (2 pairs)
Bobo le Chat 2 pcb set
AP2 2pcb set+2pcb empity (i need this also)
Meganinja 2 set ( stereo )
coolewater 2 pcp set
mikvous 2 pcb set
still4given 2 PCB set
Rick G 2 PCB set
I suspect it is not so much an issue of trust, but in my opinion, of understanding, at least for the rest of us.
Aside from the obvious costs, it might help to explain why the SMPS approach is better, or at least, what are the issues with VSSA and conventional linear supplies that the SMPS will address.
To put it another way, early on it was stated that the PSRR was relatively high, so to me this would suggest that VSSA should work well with the same linear power supply as a similar class A-B amp. If not, why?
Besides, switching power supplies are not always trouble free. Note the recent discussion in the Honey Badger thread about noise evident following changes in power demand (starting around Post #967). I am only citing that, because it happens to be a recent example, not because I think it is related to VSSA.
SMPS, noise on output & gnd