"quote:
A 1kW amplifier can easily use a 750VA rated power supply.
On this i dissagree, an amplifier cant produce power "
--
I would go one step further, taking losses in to account and that the power figure probably assumes a nominal 8 ohm load, a 750VA transformer is marginal at for a 750W amp!
Thats one channel. Two channels of 300W @ 8 ohms with little margin for 4 ohm loads would be OK with 750VA transformer. If you plan on driving 4 ohms cut it again.
A 1kW amplifier can easily use a 750VA rated power supply.
On this i dissagree, an amplifier cant produce power "
--
I would go one step further, taking losses in to account and that the power figure probably assumes a nominal 8 ohm load, a 750VA transformer is marginal at for a 750W amp!
Thats one channel. Two channels of 300W @ 8 ohms with little margin for 4 ohm loads would be OK with 750VA transformer. If you plan on driving 4 ohms cut it again.
But if you mange to take that 750W out continuously the trannie will be fried. Rule of the thump: For the amount of watts out of the amp you wil need a trannie with a VA rating of 2 to 3 times that amount of watts.
But let us don’t go too far. Class (A)B amps for music reproduction don’t need to be designed for spitting out continuous RMS power. Pure class-A and industrial amps for shaker tables are another matter.
It is basic commercial practise to use a transformer
with a VA rating ~ 70% of rated ouput power - fact,
and end of story.
Transformer continuous VA rating and
maximum VA output are not similar.
If you want to contradict this don't think you are arguing
with me, take it up with commercial amplifier manafactures.
sreten.
with a VA rating ~ 70% of rated ouput power - fact,
and end of story.
Transformer continuous VA rating and
maximum VA output are not similar.
If you want to contradict this don't think you are arguing
with me, take it up with commercial amplifier manafactures.
sreten.amp_man_1 said:
Hi to all of you,
As PSS AUDIO owner and designer I do understand that you can be sceptical about such way of manufacturing an amplifier.
First of all, to answer several other quotes, our amplifiers are double mono; each channel has his own transformer/bridge and capacitors.
To enhance the power of our transformers we use the twin bridge method that enables us to pull about 30% more out of a transformer than a single bridge, for quite good time (not continuous). This is true for an audio use only.
One must also know that a transformer can deliver more power for a small period of time but heat.
Our transformers made by TOROID, a Swedish company, are given at 60° (800VA at 60°).
The same transformer can deliver roughly 50% more if you allow an 80° temperature and even more if you accept a 100° temperature (more would be dangerous)!
We made the mistake not giving this information as our so-called 750 VA (800VA in fact) transformers can deliver about 1200 VA for 15 minutes if you allow an 80° temperature.
As our cooling system blows some “fresh” air directly on each transformer they can be considered as delivering 1200VA at 70° …
That is why we can use such transformers for a 1000W amplifier!
I hope this will help.
Ygutsatz@pssaudio.com
www.pssaudio.com
"The best and easiest way to acurately measure power is "thermally".
Sounds like a guy who has measured microwave gear for a living to me.
Becuase that is how it is done.
What is the point of this thread, anyway? Sounds like a ****ing contest between two amp companies most of us don't know.
Jocko
Sounds like a guy who has measured microwave gear for a living to me.
Becuase that is how it is done.
What is the point of this thread, anyway? Sounds like a ****ing contest between two amp companies most of us don't know.
Jocko
" 'A 1kW amplifier can easily use a 750VA rated power supply.'
On this i dissagree,. . ."
I sort od semi-agree / semi-disagree.
First parsing words: if the VA rating refers to the power supply as a whole and not just the transformer then losses are being taken in to account to an extent and the differences between the two values are not as great.
Next, the VA rating is made up of two variables. If one, voltage, is consistant with the 1kW rating, i.e., the rails support the required peak voltage not taking current into account then the remaining part of the question falls to how much current is available and for how long.
My understanding of a VA rating is that it is largely thermal. This suggests that you can exceed the current limit briefly. How briefly becomes the question. If the time the limit can be exceeded is long enough to allow for the peaks in typical (maybe even virtually all) music material, then in actual use there will be no percievable difference between the two amps in normal use.
For high-end fans or DIYers the ability to run sine waves at max power indefinately may well have utility but for the more mainstream customer that would simply be selling them something they don't need or care about. Per the Plitron price list a 1kVA transformer is only US$15 more than a 750VA transformer ($112 vs. $97). From a DIY point of view, why skimp? But if you are selling a product into them non-high-end market where buying decisions may come down to a price difference of less than $50-$25, that's a big deal.
So if I were building amps (in volume) as a business I would try to use the smallest transformer I could get away with without impacting my warranty return rate.
On this i dissagree,. . ."
I sort od semi-agree / semi-disagree.
First parsing words: if the VA rating refers to the power supply as a whole and not just the transformer then losses are being taken in to account to an extent and the differences between the two values are not as great.
Next, the VA rating is made up of two variables. If one, voltage, is consistant with the 1kW rating, i.e., the rails support the required peak voltage not taking current into account then the remaining part of the question falls to how much current is available and for how long.
My understanding of a VA rating is that it is largely thermal. This suggests that you can exceed the current limit briefly. How briefly becomes the question. If the time the limit can be exceeded is long enough to allow for the peaks in typical (maybe even virtually all) music material, then in actual use there will be no percievable difference between the two amps in normal use.
For high-end fans or DIYers the ability to run sine waves at max power indefinately may well have utility but for the more mainstream customer that would simply be selling them something they don't need or care about. Per the Plitron price list a 1kVA transformer is only US$15 more than a 750VA transformer ($112 vs. $97). From a DIY point of view, why skimp? But if you are selling a product into them non-high-end market where buying decisions may come down to a price difference of less than $50-$25, that's a big deal.
So if I were building amps (in volume) as a business I would try to use the smallest transformer I could get away with without impacting my warranty return rate.
My Peavey CS-400 power amp has a power supply rated for 800VA and the output power is described in the manual as follows:
Could I then assume that this is an “honest” 120 watts per channel, or is there some deception in that statement, or would a time figure be needed to make it really honest?
Could I then assume that this is an “honest” 120 watts per channel, or is there some deception in that statement, or would a time figure be needed to make it really honest?
Attachments
hi
well its nice to hear that you admit that you need 1200 va to rate your amps at 1000 W RMS sine continuous
yet i feel its far too low as even with mosfets the efficiency factor put in ull need a more than 1200 VA
for the benefit of doubt suppose your amp doesnt
then you admit as a cost saving measure you used a 750 va to a 1200 va tranny and yet quoted your amp at 1000 W RMS
you should have put in the conditions apply (star mark atleat)
as for dual bridges its been in audio for ages ,
and the heat factor the fans ets my friend Amp Man in his original post - mentioned testing amps , if he says ure pwoer supply is rated at 750 VA i take it as so
as the way with us is we power up an amp , monitor the voltage drop and clipping simultaeneously (dummy load fitted)
with constantly monitoring the input current to the out put boards ,
if the voltage drops before clipping the power supply is weak
then measure the input current at this point - and work out the va of the tranny
if the amp clips without woltage drop the thats the power rating possible with that set of out - put , and the power supply is strong
plus given 750 va at 60 deg centigrate and going by a linear increase of temp - when the toroids are suppling over current how a 80 deg figure was calculated
for a jump in 450 va over current supply the temp will be much more - ive toasted eggs on tranny s before (figure of speech only)
or are PSS audio amps made for 15 mins use only - like in the Beatles Era where they commercials in between a concert !
Suranjan
Transducer Deasign Engineer
well its nice to hear that you admit that you need 1200 va to rate your amps at 1000 W RMS sine continuous
yet i feel its far too low as even with mosfets the efficiency factor put in ull need a more than 1200 VA
for the benefit of doubt suppose your amp doesnt
then you admit as a cost saving measure you used a 750 va to a 1200 va tranny and yet quoted your amp at 1000 W RMS
you should have put in the conditions apply (star mark atleat)
as for dual bridges its been in audio for ages ,
and the heat factor the fans ets my friend Amp Man in his original post - mentioned testing amps , if he says ure pwoer supply is rated at 750 VA i take it as so
as the way with us is we power up an amp , monitor the voltage drop and clipping simultaeneously (dummy load fitted)
with constantly monitoring the input current to the out put boards ,
if the voltage drops before clipping the power supply is weak
then measure the input current at this point - and work out the va of the tranny
if the amp clips without woltage drop the thats the power rating possible with that set of out - put , and the power supply is strong
plus given 750 va at 60 deg centigrate and going by a linear increase of temp - when the toroids are suppling over current how a 80 deg figure was calculated
for a jump in 450 va over current supply the temp will be much more - ive toasted eggs on tranny s before (figure of speech only)
or are PSS audio amps made for 15 mins use only - like in the Beatles Era where they commercials in between a concert !
Suranjan
Transducer Deasign Engineer
hunter audio said:
Sunranjan sab,
Please read and do not distort what I wrote.
The power of a transformer is rated at a certain temperature.
Our transformers, made by TOROID, are delivering 800VA at 60° and 1200 VA at 80°.
As they are cooled by our unique cooling system they deliver 1200VA at 70° only.
If you fried a transformer getting it heating at 85° or so it is a low quality transformer as a well-built transformer can accept an internal temperature of 100° or so, but it would be dangerous for a long time use.
Do not jump that fast into conclusions.
Numbers given without any specification means quite nothing.
As our amplifiers are running 24hours out of 24 hours it means that their power supply are well designed (several test reports measured the modulation thru the power supply at 4 and 8 ohms with a difference of less than 0,15% at full power; it means that our power supplies are excellent and that their drop voltage is quite inexistent).
We are working on a studio amplifier witch will deliver 2x150W under 8 ohms and to drive it we will use 2x1600VA (60°) transformers and 200 000MF capacitors (those numbers are for commercial use).
Out of the entire audio test we made, no one heard any difference with the use of either a 1600VA transformer, or a 250 VA one … and 80 000MF or 200 000MF!
All is in your head as you are convinced that more there will be something somewhere better it will work. This is not always true. Once you reached the minimum, all extra is quite useless.
Just think about it but, as a dyer, you must have something more than others to keep on arguing that more there will be better it is.
I will not go into it.
Ygutsatz@pssaudio.com
www.pssaudio.com
hi
i have mentioned about tests , as audible sound is percieved .
and now i would like to refer you back to my intial post on Companys misleading - customers in their flashy catalogues
and one should read the fine print prior purchase
i am not distorting i am debating and now i have a manufacturer :- that is you - who has admitted that
your amps are rated at 1000 W RMS - provided certain conditions are met
those conditions may be easily achievable conditions , or may not be possiblle at all (thats another issue)
but the core topic is , printing matter of - 750 VA and 1000 W RMS output its misleading
thats why in my first post on this thread i advised people to go through the fine print
and by your own admission of the over current capacitie of your transformer taken into account (which is a matter of scrutinity)
and your cooling system taken into account (which again is a matter of scrutinity)
its quite clear - where the fine print lies - and who is distorting what
and another qs - while the fans are cooling the tranny - who or what is cooling the out - put as clearly you are in this predicament due to cost cutting procedures - to increase your share of profits
and going by that - heat sinks (after the capacitors) are the next most expensive thing in a amplifier
i may be wrong but what i have been taught is that
a transformer wire guage calculation is based on the amount of current the transformer is to deliver
and the winding ratios - to the voltage
the voltage X current will then be the VA rating where did the temp come in
either your reference is from more advanced study material
where the temperature is a deciding factor in transformer calculations
if it is please send me the name of the book
ofcourse where transformer effciency is plotted to make way for new age materials and devolopment - temperature will be plotted and - new radical designs are possible
but then such a tranny will be expensive - will you go for it , when a 1200 va normal toroid tranny would have suffice (then profits will be a bit less)
suranjan
i have mentioned about tests , as audible sound is percieved .
and now i would like to refer you back to my intial post on Companys misleading - customers in their flashy catalogues
and one should read the fine print prior purchase
i am not distorting i am debating and now i have a manufacturer :- that is you - who has admitted that
your amps are rated at 1000 W RMS - provided certain conditions are met
those conditions may be easily achievable conditions , or may not be possiblle at all (thats another issue)
but the core topic is , printing matter of - 750 VA and 1000 W RMS output its misleading
thats why in my first post on this thread i advised people to go through the fine print
and by your own admission of the over current capacitie of your transformer taken into account (which is a matter of scrutinity)
and your cooling system taken into account (which again is a matter of scrutinity)
its quite clear - where the fine print lies - and who is distorting what
and another qs - while the fans are cooling the tranny - who or what is cooling the out - put as clearly you are in this predicament due to cost cutting procedures - to increase your share of profits
and going by that - heat sinks (after the capacitors) are the next most expensive thing in a amplifier
i may be wrong but what i have been taught is that
a transformer wire guage calculation is based on the amount of current the transformer is to deliver
and the winding ratios - to the voltage
the voltage X current will then be the VA rating where did the temp come in
either your reference is from more advanced study material
where the temperature is a deciding factor in transformer calculations
if it is please send me the name of the book
ofcourse where transformer effciency is plotted to make way for new age materials and devolopment - temperature will be plotted and - new radical designs are possible
but then such a tranny will be expensive - will you go for it , when a 1200 va normal toroid tranny would have suffice (then profits will be a bit less)
suranjan
The temperature is valid when quoting transformer VA. I totally understand what PSS is talking about. It's not just a cost saving, there can be size and weight saving as well.
Think of it like this. A power resistor is rated at 10W in free air. It has a wire thickness that can carry a certain amount of current, but the body dissipation is the limiting factor. If the resistor is now force cooled, it can take a bit more power, up to the limit of the wire capacity perhaps.
But you completely forget about the core
Think of it like this. A power resistor is rated at 10W in free air. It has a wire thickness that can carry a certain amount of current, but the body dissipation is the limiting factor. If the resistor is now force cooled, it can take a bit more power, up to the limit of the wire capacity perhaps.
But you completely forget about the core
hunter audio said:
Suranjan sab,
Canna manta?
Panni manta?
You are wrong and please read again and browse our website carefully.
We are not cutting down quality components to make larger profits, we are kicking away craps component to manufacture high quality AUDIO amplifiers, not boxes making some noise.
Depends of the output power of an amplifier, the box can be the most expensive thing in an amplifier.
In our case, the most expensive parts are for a PSS2400 amplifier delivering 2x1200 Watts under 4 ohms loads:
2 x 1600 VA transformers rated at 60° (25% of the cost of the amplifier)
mains capacitors (15% of the cost of the amplifier)
Power transistors (15% of the cost of the amplifier)
Full case (15% of the cost of the amplifier)
Heat sink and fan (7% of the cost of the amplifier)
About what can be pulled out of a transformer:
A transformer is given to a rated power AND at a rated rise of temperature.
In our case, TOROID, rates the power at 60° and 80°.
We made the mistake printing the rated power at 60°, not at 80°!
At 80° their transformers are delivering 50% more, in means that an 800VA (and not 750VA) rated at 60° delivers 1200 VA at 80°.
As we use a very specific cooling system (blowing directly fresh air on top of the metallic case of the output devices and not cooling the heat sink witch is cooling the output devices, the air that flows out of the heat sinks cools also the transformers).
It means that either we will consider our transformer delivering its 1200VA at 70° and not at 80° or it delivers 1400VA at a virtual 80° (in fact 90° if not cooled).
On a second hand we also use a twin bridge witch improves what can be pulled out of a transformer in an audio use!
If you do not understand this elementary physic calculation methods, then I cannot go further explaining you how an amplifier is built and calculated (sound quality is an other debate as it is not because you use high quality components with great numbers that the box will make nice music)!
Are Krishna,
Are Ramah …
Yuri D. GUTSTAZ
Ygutsatz@pssaudio.com
www.pssaudio.com
sam9 said:
Hi,
I stated that we are cooling our amplifiers with ha fan since the first post!
In a regular use the CFM is important, with my method (the fan is placed at less than 2 inches from the output devices) the CFM is less significant, but still important as the air flow has no loss compared to other system loosing its efficiency with 10 to 15 inches long heat sinks!
I was aknowledging that and that it changes the whole nature of the discussion that came before. I didn't mean to sound as if I had not read your post.
We are about 9 hours apart and there may be a delay between when you post and when I wake up and read. Much may have ocurred in between.
Anyway, it would be desirable to find a means to "normalize" the VA figures. Heatsink manufactures sometimes do that by specifying W/degC in ambient aie and also at a choosen CFM. I've not seen transformer manufacturers doing that.
We are about 9 hours apart and there may be a delay between when you post and when I wake up and read. Much may have ocurred in between.
Anyway, it would be desirable to find a means to "normalize" the VA figures. Heatsink manufactures sometimes do that by specifying W/degC in ambient aie and also at a choosen CFM. I've not seen transformer manufacturers doing that.
Why can't you keep it simple ?
The thermal time constant of a transformer is far slower than
the dynamic envelope of music waveforms, so a transformer
only has to deliver the average power of a clipping 1KW
waveform at rated temperature.
The actual transformer continuous VA needed for 1KW music
on the point of clipping is quite low, 700VA is commonly accepted
as a rating that does not unduly limit short term RMS output,
which is typically 1.5KW.
Given a 1KVA transformer would you set voltage for 1 KW
rms continuous or set voltage for 2KW rms short term ?
Given a choice of only the two options, I know what I'd do.
sreten.
The thermal time constant of a transformer is far slower than
the dynamic envelope of music waveforms, so a transformer
only has to deliver the average power of a clipping 1KW
waveform at rated temperature.
The actual transformer continuous VA needed for 1KW music
on the point of clipping is quite low, 700VA is commonly accepted
as a rating that does not unduly limit short term RMS output,
which is typically 1.5KW.
Given a 1KVA transformer would you set voltage for 1 KW
rms continuous or set voltage for 2KW rms short term ?
Given a choice of only the two options, I know what I'd do.
sreten.- Status
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