Oddly enough, Frank, I have the same general feeling about capacitors. To wit, there I go doing everything with at least a 30% reserve, often more, yet I cannot escape the feeling that if I run my caps, the bigger the better, near to their voltage limits, somehow they seem to work better.
Take this flexibly, I'm not the industry, so I won't use a 56V cap with power raiols of 53V, but I will (and do) use a 63V cap with rails of 56V, even up to 58V. I am talking about caps I have lived and worked with for 20+ years (German made Fisher & Tausche, F&T), so I know them well inside out. I always do the whole rigamarole, you know, take a new one and charge it with 5V, empty with resistor, then with 15V, empty with resistor, and finally with 24V, I take pains to form it properly. The circuit is a simple triple regulated (with 7805,7815 and 7824) line output, each line using an MJE 15030 power devices as a current booster on a smaller local heat sink.
I honestly don't know whether it's because I'm running the caps relatively near to their declared limits, or perhaps because the technology to manufacture the same value 80V cap is different, and perhaps not so good. I am not overloking the possible placebo effect, either, maybe I'm just hearing things.
However, regarding power amplification, I beg to disagree. I find running an amp to somewhere near its limits to be very dangerous, as I don't know what transient may come along next, which may well drive the amp to beyond clipping. That I do not want.
The whole point of using a nominally 100W/8 ohms where I know a 50W/8 Ohms amp will do just fine is to have plenty of reserve for that transient, and of course, to have the actual power you need delivered as easily as possible with as little distortion as possible. Thus, I prefer to use more powerful amps than I know I actually need, which have been pushed more into pure class A operation.
This helps me avoid the distortion comeback effect. Many higher power amps will produce more distortion at 0.5W than at say 10W, or 50W, or even 100W. Early 1970 amps suffered from this effect, some horribly so, but then their bias currents were like 10 or maybe 25 mA only; mine are at or above 400 mA, drowning that first watt in pure class A, so in fact, what I get is a DROP of distortion at low power levels. For example, where I'll have THD of 0.03% (20-20,000 Hz into 8 Ohms) at full rated power, at 1 W that will be less than 0.003%, since the amp is working in pure class A.
So, do look at the distortion curves of your amps at 1W and at full rated power, and do not be surprised if you find that distorion is actually higher at low power. Anyway, it's an idea.
Tom, I also said that any self respecting amp should also have a decent overload margin above its nominal power rating. Impulse power, if you like, the ability to reproduce a fast transient at power levels higher than it's rated for.
That's a fancy way of saying that an amp should have a good margin before it starts to complain and serious distort. In this case, "seriously" means THD at over 0.1%. In most cases, it will soon collapse above that point anyway.
My sim says (and it's never lied to me yet) that my latest baby will produce 0.3% THD at 50 kHz into 2 Ohms, while still delivering just above 33 Vrms, or about 544 Watts, for impulses of 100 mS (just to remind you, IEC standards assume impulses of 20 mS). But then, not many people use 4 pairs of 200W devices for a nominally 100W/8 Ohms amp, do they?
Not that I have struck a mother lode here, of course, it's all simply about overload margins. If you stack it all up when designing, you are not likely to experience many problems. I use 500VA toroids per channel, 4 pairs of Motorola/ON Semi MJL 3281/1302 power devices, two parallel 10,000 uF per power line per side centrally and each of the power devices has an additional 2,200 uF cap right next to it. It all adds up to 28,800 uF per line, which is a grand total of 115,200 uF for a stereo amp. Since my power lines are nominally +/- 56.5V for the current stage (+/-61 V regulated for the input and VAS stages), and because of the large toroids there is almost no sagging until we get to 3 Ohm loads, it's capable of deliverng almost 180W/8 Ohms in impulses. Thus, I have full 2 dB impulse power reserve above my nominal output without any fancy circuitry, all 100% natural and healthy.
I regard this as the reserve's reserve. As Wayne mentioned a while ago, typical peak power levels inmy room don't go much over 14V (peak), so in effect, I am adding reserve and keeping the amp that bit more of a performer where I actually need it. And much less choosy about the load it needs to drive. For sheer prudence's sake, I have limited it at 2 Ohms (1.8 Ohms to be precise), at which point the fuses will be about to burn, but the overcurrent protection kicks in and limits the output. There's no faster acting protection than the transistor.
But, leaving the calc aside, in real life, it's hardly likely the protection will ever fire simply because by then, we are dealing with tremendous power levels, exceeding by a mile what is normally used in rooms. After all, you want to listen to the music, not be deafened by it.
And all the while, I am perfectly aware that I am not doing anything hitherto unseen before, I am simply doing it the right way (as I see it, of course). And cost be damned, in full knowledge that it's the cost that's holding back the industry, certainly not any lack of knowledge.
From a manufacturers point of view, running 63V caps at 58V with nominal AC supply voltage is getting into the marginal zone...58V + 10% is getting to rated cap voltage...maybe not a good thing if the product manufacturing quantity is high.
High output stage bias current is all well and good, but how much quiescent power are you consuming ????....have you measured it ?....those $20 plugin power meters are informative !.
I have run high high power amps that put up my power bill substantially/alarmingly
...if this wasted power is substituting for room heating then it is win/win , otherwise not 'cool' ime/imho.
My preferred way of operating my system(s) is to set the sensitivity such that max source level allows momentary clip....clipping indicators are quite useful.
Modern rock/pop recordings are usually normalised to maximum digital level, so using this gain structure allows confident 'turn it it up to the max' without serious clipping operation, when so desired.
Variable additional gain can be switched in to compensate for low level recordings, or those that do not achieve source full output level.
Not using a power amp to its full potential may be sonically pleasing, but intrinsically energy wasteful.
Dan.
High output stage bias current is all well and good, but how much quiescent power are you consuming ????....have you measured it ?....those $20 plugin power meters are informative !.
I have run high high power amps that put up my power bill substantially/alarmingly
...if this wasted power is substituting for room heating then it is win/win , otherwise not 'cool' ime/imho.My preferred way of operating my system(s) is to set the sensitivity such that max source level allows momentary clip....clipping indicators are quite useful.
Modern rock/pop recordings are usually normalised to maximum digital level, so using this gain structure allows confident 'turn it it up to the max' without serious clipping operation, when so desired.
Variable additional gain can be switched in to compensate for low level recordings, or those that do not achieve source full output level.
Not using a power amp to its full potential may be sonically pleasing, but intrinsically energy wasteful.
Dan.
How about using caps rated at 56V with nominal supply lines of 53V? Actually, manufacturers do this sort of thing quite a bit, for obvious commercial reasons - then they buy loads of these caps and get a better price. Plus they are inherentkly cheaper that their say 71V bretheren, and smaller too.
High output stage bias current is all well and good, but how much quiescent power are you consuming ????....have you measured it ?....those $20 plugin power meters are informative !.
I have run high high power amps that put up my power bill substantially/alarmingly
Quite frankly, Dan, I have never measured the quescent power consumption because I don't give a damn. In everything else, I pay much attention to power consumption, except in audio. Audio is my weak 100% blind spot.
Since everything I do is essentially class AB, there is a limit for the bias current. As a rough example, you can increase it to say 130 mA per trannie, and after that, there is no audible benefit - such is my experience. Hence, I am inherently limited to about that value. And that is far from turning an amp into a heater, although it does get reassuringly warm.
Otherwise, the only classic light bulb left in the house is the one in the pantry, and that one only until it blows. Its total daily working time is less than 3 minutes. All others are power savers fropm either Philips or GE. All my domestic electrical equipment is rated at European standards A++ the older units, or A+++ the newer ones.
Amen to that. I salute your your courage, if my clipping indicator blinked I'd probably faint.
[qure]Modern rock/pop recordings are usually normalised to maximum digital level, so using this gain structure allows confident 'turn it it up to the max' without serious clipping operation, when so desired.
Variable additional gain can be switched in to compensate for low level recordings, or those that do not achieve source full output level.[/quote]
Agreed on the recordings and thank the good Lord I buy only vintage music, recorded while that industry was still sane.
Well Dan, I'm in this hobby not to save and be energy frugal, but to enjoy it. While I will not ccarelessly waste energy, I will not bend backwards to save it either. I don't want my life centered around saving, I do want some pleasure in it as well.
That's what causes premature failure, way too common nowadays....it keeps Chinese factories busy however.
I used to run a tweaked 500W+500W PA amp....5 TO-3 output pairs per channel....the 5 1/4" cooling fan cycled in and out with the amp at idle.
It ate electricity but it sure was fun into 4 x 12" 3-way cabinets
.The rule around here is if not using it, turn it off at the wall socket
.The occasional clip (<1 per second) is quite inaudible, provided that it is shallow clip.
Repeated gross overload is of course badly audible.
Haha, get with the picture, some modern music can be impressive on a good system
.I have an energy meter supplying my lab/workshop room, and my audio systems.
I am not paranoid about this energy usage, but I do like to keep an eye/lid on it.
I have a variable AC supply regenerator...variable output frequency and low thd is sonically great...the downside is that it uses more power than it delivers
.Dan.
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Amen Brother , Waste not want not .....
Speaking of wanting , recording the output VA while playing Film and the BB's tricycle cd , the recording starts out at 1.5VA and hits 15 VA on peaks , increase the start to 3VA and you can see where this is going . If playing only compressed rock music then i guess some clipping distortion adds to the flavor ...
Dan, the quickest way I am aware of to shorten the life of your equipment is to introduce lots of switch offs and ons.
Consider. In the instant you flick the power on switch, there is a surge, which in case of powerful power supplies needs to controlled or fuses will start blowing, so we have a time delay built in. Still, in that instat, EVERYTHING is in effectively short circuit and gets blasted by a part of a second of uncontrolled surges.
Because of this, I try to have as few power off/on cycles as possible. On a normal day, that's exactly one cycle, power on at 8 AM, power off at 10-12 PM. Obviously, if I have to leave for several hours, I will switch the lot off, but if I'm to be out for 2 hours or less, I will leave it on. I prefer the monetary loss to burnout before its time. Which is very possibly the reason why I have had any PSU and/or device go sour on me, except a few times when the problem was traced to faulty capacitors and once to a leaking transistor.
Uses more power than it delivers? Thrifty, aren't we? I have solved my problems with an AC line filter (a.k.a. "conditioner") which rids me of AC line muck before it even gets to the transformers.
Anyone wondering what the hell am I talking about, please connect your 'scope to an AC outlet and take a peek at what your 50 or 60 Hz line signal looks like up to 900V and across the frequency spectrum. If you think that filtering it out after the transformer is enough, no matter what sexy components you use, you are wrong, because by then that muck has already reduced the efficiency of your transformer by God knows how many percent.
Consider. In the instant you flick the power on switch, there is a surge, which in case of powerful power supplies needs to controlled or fuses will start blowing, so we have a time delay built in. Still, in that instat, EVERYTHING is in effectively short circuit and gets blasted by a part of a second of uncontrolled surges.
Because of this, I try to have as few power off/on cycles as possible. On a normal day, that's exactly one cycle, power on at 8 AM, power off at 10-12 PM. Obviously, if I have to leave for several hours, I will switch the lot off, but if I'm to be out for 2 hours or less, I will leave it on. I prefer the monetary loss to burnout before its time. Which is very possibly the reason why I have had any PSU and/or device go sour on me, except a few times when the problem was traced to faulty capacitors and once to a leaking transistor.
Uses more power than it delivers? Thrifty, aren't we? I have solved my problems with an AC line filter (a.k.a. "conditioner") which rids me of AC line muck before it even gets to the transformers.
Anyone wondering what the hell am I talking about, please connect your 'scope to an AC outlet and take a peek at what your 50 or 60 Hz line signal looks like up to 900V and across the frequency spectrum. If you think that filtering it out after the transformer is enough, no matter what sexy components you use, you are wrong, because by then that muck has already reduced the efficiency of your transformer by God knows how many percent.
Amen Brother , Waste not want not .....
Speaking of wanting , recording the output VA while playing Film and the BB's tricycle cd , the recording starts out at 1.5VA and hits 15 VA on peaks , increase the start to 3VA and you can see where this is going . If playing only compressed rock music then i guess some clipping distortion adds to the flavor ...
Yeah, that's like using Tabasco instead of the real deal chilli sauce you guys have and told me about.
But seriously, fresh green or red chilli paprika is by far the best deal, that's a live performance man, no compression.
I just got through two big 'uns and I am still under the impression. They go down well with Wiener schnitzel (part of my heritage from my father's side, Wienese for 7 centuries back).On another subject, most of modern music leaves me stone cold. Not my kind of sound, most of it, although of course, there are pieces here and there I'd love to have.
Wayne, ol' buddy, do take a look at "The Boys Are back In Town" (Universal, 5339039) and "Best Of British" (EMI/Universal, 5333322), excellent compilations purchased on Amazon.com.
I assume that you mean switchable primaries according to AC supply voltage ?.
Your 240V (USA) is balanced power is it not ?.
Dan.
As I understand the USA power system, two 180* opposite phases of 120V are available for GPO distribution, and 240V across these two phases is used for higher power appliances such as clothes dryers, hot water systems, kitchen stoves etc.
Three phase is another case altogether.
Please educate me if I am misinformed.
Dan.
Three phase is another case altogether.
Please educate me if I am misinformed.
Dan.
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