Whether it's measurable or not isn't relevant to my question. I'm wondering if there would be a noticeable subjective difference but more importantly if so, would it be detrimental further up in the spectrum. PRaT is all about perceived speed and reference to realism. The difference between up front immediacy and laid back dark and distant. Extremes at both ends of that yard stick are probably undesirable. Somewhere up past center is where life is. The Brits are the first to focus on it as a first requisite, enter NAIM, Meridian, Quad, Sugden.
The only way to quantify it is with your foot. You'd have a good chance of picking it out in an ABX if it was my Boothroyd Stuart Meridian 105. 🙂
Second result on Google seems fitting...
PRaT: "Pace Rhythm and Timing" or "PRetentious audiophile Trash"? | What's Best Audio and Video Forum. The Best High End Audio Forum on the planet!
PRaT: "Pace Rhythm and Timing" or "PRetentious audiophile Trash"? | What's Best Audio and Video Forum. The Best High End Audio Forum on the planet!
If you say so... I read it, and it sounded like horsesh*t. Subjective horsesh*ti, but horsesh*t none the less...
Pace, rhythm, and timing applies to playing drums, not amplification - unless the amplifier is truly trash to begin with.
Just my opinion, I could be mistaken.
Pace, rhythm, and timing applies to playing drums, not amplification - unless the amplifier is truly trash to begin with.
Just my opinion, I could be mistaken.
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Hi ginetto61,
There's something from much earlier in the thread that I can't resist mentioning -- but scanning back through, I couldn't find the number to quote. Sorry. 😱
You were observing differences in secondary impedance, for two transformers with the same VA rating. The problem with that is that you're ignoring the voltage and current ratings. If you measure a transformer designed to provide a high voltage, say for a valve amp main B+, it could easily be a few hundred ohms. Awful, you groan! 😉 The very same VA-rating transformer designed to light filaments might be a few tenths of an ohm. It doesn't make sense to compare secondary impedances/DCRs unless the output voltages are reasonably similar.
Cheers
There's something from much earlier in the thread that I can't resist mentioning -- but scanning back through, I couldn't find the number to quote. Sorry. 😱
You were observing differences in secondary impedance, for two transformers with the same VA rating. The problem with that is that you're ignoring the voltage and current ratings. If you measure a transformer designed to provide a high voltage, say for a valve amp main B+, it could easily be a few hundred ohms. Awful, you groan! 😉 The very same VA-rating transformer designed to light filaments might be a few tenths of an ohm. It doesn't make sense to compare secondary impedances/DCRs unless the output voltages are reasonably similar.
Cheers
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Hi ! thanks a lot for the kind and valuable advice. You are right.
I should have said that for power amp i have settled on solid state. With ss is very possible to have good power in a smaller package. I am fighting always with space ... so i am not much on tube power amps.
The situation is very different for line preamps ( i listen only from dacs)
I have listened many very good sounding hybrid solution with tubes at the input. And i liked them a lot.
Going back to amp my ideal amp is a low wattage class A amp but with reduced bias. I am sure of this now.
The class A amp will have a very robust and oversized psu ... it will be designed for high idle currents. If i lower that current i am sure the sound penalization will be minimal but in change i will get higher reliability.
Or a class AB design with a class A psu. Even better maybe.
And with big caps able to cope with peak power demands.
Thanks a lot again.
Hi Learned People,
I am a novice and read this thread several times and it confused me. Please do not hate me for asking. I have a humanities background, but good with numbers and spread sheets.
Is there a formula? I can put this into excel and then insert the numbers.
I am building a:
LM3886 x 3 Gain clone Mono amp (150W) - https://www.yuan-jing.com/mono/lm3886-x-3-gainclone-mono-power-amplifer-150w
Sigma 22 Clone PSU - set for +/- 35V - https://www.ebay.com/itm/115630831821
Speaker protector needs about 15VAC
So, I need a transformer (I am in Australia - same voltage as EU) with (please correct my mistakes):
Primary (input) 220VAC
Secondary (output) 32-33VAC (according to the Chinese seller) I think 35 is a common number
Other (Output) 15VAC for the speaker protector
How is the size, I think it is called VA calculated? Is there a formula? I am not sure what VA is, is it the same as watts or amps?
If you want to email me direct this is OK – foxint@foxint.com.au.
I am a novice and read this thread several times and it confused me. Please do not hate me for asking. I have a humanities background, but good with numbers and spread sheets.
Is there a formula? I can put this into excel and then insert the numbers.
I am building a:
LM3886 x 3 Gain clone Mono amp (150W) - https://www.yuan-jing.com/mono/lm3886-x-3-gainclone-mono-power-amplifer-150w
Sigma 22 Clone PSU - set for +/- 35V - https://www.ebay.com/itm/115630831821
Speaker protector needs about 15VAC
So, I need a transformer (I am in Australia - same voltage as EU) with (please correct my mistakes):
Primary (input) 220VAC
Secondary (output) 32-33VAC (according to the Chinese seller) I think 35 is a common number
Other (Output) 15VAC for the speaker protector
How is the size, I think it is called VA calculated? Is there a formula? I am not sure what VA is, is it the same as watts or amps?
If you want to email me direct this is OK – foxint@foxint.com.au.
VA is Volt Amps, which is close enough to to a Watt that you can think of it as the same basic thing.
Nigel’s recommendation of choosing VA 2x the output watts is a good suggestion.
Nigel’s recommendation of choosing VA 2x the output watts is a good suggestion.
Efficiency of any amp-size transformer is so close to 95% that we don't care.
VA is NOT an absolute limit. Take your "100VA" transformer and adjust the load to suck 200VA. It will sag but it WILL do it. For a while. For our hundred-Watt amps the PTs will supply twice rated VA for many minutes. Longer than any musical crescendo. Longer than it takes to read a power meter. It is getting hot but in any Real-Life speech/music work it will not burn-up.
Maximum LOUD stage amps are a bit tougher.
Older US FTC ratings were quite tough. But only 1 hour total? A PT that can deliver 100VA for 1,000 hours can do 200VA for an hour easy (but may die in the 2nd hour of abuse).
STEADY LOADs can be much tougher. I got some Bogens which had been driving the motors in projectors with 59.9Hz power for long film-to-video transfer sessions. 5 of 6 channels did it fine. (The 6th channel had a bad solder joint and caught fire. On the 12th floor of a NYC high-rise...) Powerful synchro motors another, Shaker-tables (military shake-tests) were another high-duty application.
Wow – thank you both. We will go for 300VA (watts).
Watts = Amps x Volts = VA. So why can they not call them Watts??? Do not need an answer.
I just spent the last 45 minutes trying to find the formula for amps. Is/are amps current? (As in V = IR)
I hope you do not hate me…. but if 35volts (needed to run the amp) x 8 (8 Ohms speaker resistance) just happens to equal 280…. is a coincidence???
But I am not understanding in terms of V =IR. I messed around with the formula and got I (current) of 35/8 is 4.375 amps, but I am not sure if this helps at all.
Or should I just forget it?
Sort of makes sense. A/B amplifier about 50% efficient, needs twice the power. I read a similar thing, but it confused me as they said 50 watts @ 50% efficient = 75 VA…. that even to a student of humanities did not add up.
I tried to mess around with the formula, but I do not know the value for I (current)
I am good…. thank you.
I am just going to wing it with the Speaker protector that need 15VAC and just buy what is cheap at about AUD25.00 for a 15VA.
I am feeling a lot better. As I said I am doing with for my mental health while we finalise the property settlement in my messy divorce from a cheating narcissistic wife.
As I have read…the enclosure is the most expensive part of the puzzle.
Thanks again.
Dan
Watts = Amps x Volts = VA. So why can they not call them Watts??? Do not need an answer.
I just spent the last 45 minutes trying to find the formula for amps. Is/are amps current? (As in V = IR)
I hope you do not hate me…. but if 35volts (needed to run the amp) x 8 (8 Ohms speaker resistance) just happens to equal 280…. is a coincidence???
But I am not understanding in terms of V =IR. I messed around with the formula and got I (current) of 35/8 is 4.375 amps, but I am not sure if this helps at all.
Or should I just forget it?
Sort of makes sense. A/B amplifier about 50% efficient, needs twice the power. I read a similar thing, but it confused me as they said 50 watts @ 50% efficient = 75 VA…. that even to a student of humanities did not add up.
I tried to mess around with the formula, but I do not know the value for I (current)
I am good…. thank you.
I am just going to wing it with the Speaker protector that need 15VAC and just buy what is cheap at about AUD25.00 for a 15VA.
I am feeling a lot better. As I said I am doing with for my mental health while we finalise the property settlement in my messy divorce from a cheating narcissistic wife.
As I have read…the enclosure is the most expensive part of the puzzle.
Thanks again.
Dan
Volts X amps AC is not the same as DC. For AC you have to worry about the phase between voltage and current and the harmonic content - both of which reduce the number of real watts you get for a given volts X amps. To really understand it requires college level math, in practical use they just use a term called “power factor”, which is less than 1. Works well enough for electricians and the HVAC business - and usually they've never seen a differential equation. For this type of amplifier power supply the number is 0.65, give or take. An exact number takes a lot of math (Computer simulation is just doing math.) It’s one of the reasons for the rule of thumb to double the size of the trafo to 2X when you feed an X watt amp.
300 VA trafo is about right. Store-bought units will go smaller (as low as 100), due to the fact that the average load is not very high. But it will work better with the bigger trafo, since LM3886’s aren’t very tolerant of power supply sag compared to comparable discrete designs. The price of using a simple cheap chip is less efficient use of the available power supply voltage (you can’t afford the sag). 300 VA are still quite inexpensive from places like Antek (and direct from China even cheaper).
300 VA trafo is about right. Store-bought units will go smaller (as low as 100), due to the fact that the average load is not very high. But it will work better with the bigger trafo, since LM3886’s aren’t very tolerant of power supply sag compared to comparable discrete designs. The price of using a simple cheap chip is less efficient use of the available power supply voltage (you can’t afford the sag). 300 VA are still quite inexpensive from places like Antek (and direct from China even cheaper).
A capacitor-input rectifier is not a simple reactance.
For class AB audio amplifiers and supplies in the 10VA to 1000VA range we often object to the sag before any strain on the iron. Cap-input supplies take energy in very short jolts so voltage losses may seem high.
Past 5,000VA the losses on our side look less but the heavy jolts may annoy our neighbors ("Why do my lights blink 'Iron Man'?") and the power utility. Broadcast radio transmitters traditionally go to 3-phase power and choke-input supplies to spread the spikes... I have not been allowed inside a transmitter in a while so I dunno what is the fashion today.
