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68.53.150.47
My question concerns a bank of capacitors-let's say 250 1500mf/16 volt vs 500 680mf/16 volt.Other than size,would the smaller bank of caps function better for quicker discharge and speed than the 1500mf bank?I will be using as part of batter ps.
Mike
Follow Ups:
Since no body has really answered your question I will take a stab at it...
I would say (total capacitance being equal) the smaller number of larger value caps would perform better because the larger plate area would have a lower ESR. A single very large capacitor would be best.
I still do not understand what people here mean when they talk about caps making amps "slower". Power supply filter capacitors are like an "energy bucket". Besides smoothing rectified DC. They provide a local storage of bulk energy for the amp to use during fast transients. (like a loud orchestra burst) If the capacitors in your power supplies are too small your amp would be power starved and clip during loud music bursts, even worse at loud listening levels.
I tried an 80,000mf Mallory large cap and it was not good at all.The small bank killed it in every way.I think they are talking about the ability of the bank to discharge its voltage at a faster rate than the one large cap.This is what I'm hearing:tighter,deeper bass,cleaner treble with blacker background,more natural midrange.Major upgrade.The sound was quite good before I increased capacitance from 115,500mf to 378,000mf.It did take about a week before it really started to sound good.Still tweaking.I will get back with everyone when I get the other boards etched and stuffed.
Mike
Photo of cap bank and battery
Mike
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For super clock 4 oscillator and will also be going to buf634's when I get them finished.Major improvement.
Mike
Hallo Mike. Multiple capacitors, in B+ smoothing, in parallel, makes for a lower series inductance and series resistance. This means "noise" finds it easier to follow path to ground. Instead of proceeding to whatever electronics you're powering up.
As always, depends on your intent, but one of the main benefits of a battery supply, in my opinion and experience, is to banish all of those irritating electrolytic capacitors to the parts bin. If you can, try the battery with just a good sounding film capacitor(s) at the circuit connection point to minimize connection impedance affects. Provided the rest of the circuit is free of bad sounding capacitors, you may be surprised. "Fast" power supplies are really only needed for unstable audio circuits using lots of feedback. Look at the schematic of a good sounding tube preamp sometime. The big electrolytics of common solid state gear are replaced by the copper windings and magnetic circuit of a choke, along with a small amount of quality film caps. And the sound is much better for it.
Hi.
Battery NEEDs, repeat needs an audio signal bypass if used to power audio amps. A cap, being an AC passing component, is commonly used as audio signal bypass for any power supply, be it a conventional AC-DC, or simply a battery.
A battery is not a pure DC low ohm (down to milliohms) circuit at all as commonly mistaken.
Like a cap & in fact worse, a battery is a very complex AC network comprising serie & parallel resistance DCR, inductance L & capacitance C plus Warburg impedance (W) which does not exist in a cap.
This is not a smooth highway at all for audio signals. So a bypass by a cap is a must. The battery will take back the used DC return currents while the bypass cap is to provide a smoother bypass for the signal return instead of going thru the impedance of the battery.
The choice of type of caps depends on the audio amp power requirement.
For battery powered phonostages & linestages where the current load from teh battery is not that big. Caps with smaller capacitance will do the job. Here the battery, besides acting as an audio signal bypass, also acts as a small reservoir to store up the electrical energy required by the amps. So small film caps may do the job.
Like the SLA cell (6V5AH) I used to power the heaters of the tubes in my tube phonostage is bypassed with a AC fan cap (7uf250V) parallel with a 0.333uF PP film cap.
Also in my SS phonostage which is also 18V battery powered, I chose a
2uF PE film cap to bypass the battery for each channel (dual mono design).
In fact, I was given advice I should use much larger 'lytic caps for the bypass. I was told by some battery amp experts larger the bypass caps more fluid would be the sound. I don't argue as huge 'lytic caps are being used in those hi-end brandname amps, like the one I posted below.
Filter chokes with smaller caps used in conventional HV tube amp PS is totally another story.
c-J
I just don't think a bank of electrolytic caps sounds as good as a battery with a quality film bypass, applied at the point in the circuit where it is most effective. But we all have different experiences, and there is no right or wrong for everybody :-)
Hi.
Did I say you're wrong? As you already said, it depends on "where is most effective".
But for SLA cells & car batteries, which the orginal poster asked, film capacitors, being too small in value, can't fill the huge shoes of 'lytic caps as a large current load reservoir which a car battery needs.
FYI, I installed PE film caps to replace all the 'lytic caps in my dual-monoral SS phonostage with PE film caps for I/P & O/P coupling. But it was a real pain to squeeze them all in as I have to parallel 5x 2uF PE film caps to give the required 10uF for O/P coupling! Surely film caps sound better than 'lytic caps in signal paths.
For SLA cells & car batteries, we got to use huge size 'lytic caps as a reservoir for large current loads consumed by say, a class B SS power amp, and add film caps as audio signal bypass only.
Film caps can't take the function of a 'lytic caps in this issue.
c-J
The capacitors are there to lower the impedance. I run my whole system without electrolytics, so it can certainly be done. Just a matter of what you want. Most amplifiers don't have a huge bank of capacitors, so they obviously aren't necessary for operation. But if you like the sound better with a bank of electrolytics to further lower the bus impedance, that's completely understandable. I was just mentioning to the OP that there is more than one path, and for some of us that other path with the electrolytics designed out of the audio circuits is the more fulfilling one. The power supply is all in the signal path.
What size film would you recommend?
Mike
Also depends on what you are after, specs or sound quality. Small, tightly wound film caps sound better than bigger ones. Caps with more massive electrodes sound better, ie film and foil. I personally prefer the sound of epoxy impregnated paper caps like the WIMA MP3-X2, but there are many other designer types that sound great. Experiment. But the size and type you ultimately need for your circuit depends on its requirements, as far as stability and other source impedance issues.
that's too much electrolytic capacitance to be in parallel with batteries.
If you leave them connected to the batteries, the leakage current will drain and damage the batteries over time, unless you leave the charger on at all times. The trouble is, you can't really be sure the charger will be on at all times 24/7 can you?
If you switch them in as and when, the large in-rush current over many duty cycles will stress and damage the switch contacts and the batteries over time, unless you implement some form of soft-start (initial charging through a resistor).
What size resistor should I use and would it be in series on positive leg for soft start?What would be the maximum capacitance you would recommend?Presently using SLA 12/18aH and will be switching to Optima yellow top or Odyssey PC2150 or PC1500.All are deep cycle low impedance car batteries.
Mike
a few ohms I guess. It's simple Ohm's law. For a 12V supply, a 12ohm resistor will limit the charging current to 1A. Use a high power resistor 15W, 20W or more. The resistor gets switched out of the circuit (shorted across with a manually-thrown switch or timer-based relay) after a couple of seconds. Note again this is necessary only for "huge" capacitor banks.
I don't see a problem with increasing capacitance, as long as you hard-wire the cap array between the terminals and just switch the battery back and forth between the charger and the application.
Like I said, if you can be sure the charger is always on 24/7 (no prolonged power outages, and no unplugging of the equipment to put aside even just for a few days), then it's fine to hardwire a huge electrolytics bank to the batteries.
Hi.
Up to 1F huge cap, size like a 2-litre bottle, are commonly used by car-amp lovers to top up the amp performance.
Let me quote an unbelievable enormous 'lytic cap consuming Hi-end intergrated SS amp: the Germany Hi-End Award winner: Emitter II Exclusive Battery model, made by ASR Audiosysteme, Germany. Probably the most expensive intergrated amp in the world now!
This SS amp used many many 'lytic caps in parallel, totally: 1,140,000uF
housed in a see-thru acrylic housing !! Weighting 32Kgs !!
Thess caps are for the different stages, powered by an outboard battery-bank/charger with 400,000uF filter cap bank to supply up to 200VA DC power to the integrated amp.
To answer the question: would too many 'lytic caps parallel slow down the amp? Here is the anwer: the rise time of this very very expensive
German made SS integrated amp is only 0.8uS.
c-J
I use a 100AH SLA battery with low 2 milliohm internal resistance to power a CDP that draws less than 1A. There was audible improvement after adding a large electrolytic cap array between the battery terminals, futher improvement after adding a second smaller electrolytic array inside the CDP, and improvement once more after placing .1uf teflon and .47uf film bypass caps at the chipsets. Film bypass caps by themselves are not enough with batteries. There seems to be no diminishing return on capacitance, even with a large battery powering a light load.
Hi.
Now you've tempted to try some large 'lytic caps with my SLA cells for my phonostage tube heaters as well as the batteries for my SS phonostage, as I have got already AC oil cap & film caps bypass.
c-J
I think you will be pleasantly suprised in the improvement.It took these about a week to sound their best but right off the bat-improvement is evident.
Mike
1. Car audio "stiffening" capacitors are designed with low leakage current in mind, usually based on carbon aerogel technology. They are not electrolytics.
2. You'll find that "big" amps that have huge capacitor banks implement some form of soft-start. Either timer-relay based switching-out of series resistor, or simply an NTC (negative temp coefficient) in-rush limiter for class-A amps, or tube rectifiers (the heating up of the filament provides the slow ramp-up) for tube amps.
Hi.
I hate to put any current limiter or even a serie resistor upstream of the tube heater circuit, maybe for sonic reason.
So instead of putting a resistive current limiter downstream of the SLA cell powering the tube heaters of my phonostage, I do it the tedious way.
I add a basic 6V AC-DC adapter, which I found sleeping for ever in my dump bin, & hook it up outboard to the phonostage so that I can pre-heat the tube heaters first with the 6V adapter, before the SLA cell kicks in. So the damaging surge to the cold heaters is eliminated, and the tubes will last longer (IMO, long enough already - these are the original 50-year vintage tubes came as stock with the phonostage.)
c-J
c-J
Therefore-would the smaller 680uf bank be quicker than the 1500mf bank-looks like it may-even if I double up on the 680mf(possibly not)in theory?
Mike
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Rubycon ZL series.
HI.
Rubycon makes excellent 'lytic caps, including Black Gates which are considered by many tube/SS builders king of caps.
In fact, I've & am using wideband fastspeed 'lytic caps made by Rubycon for my tube HV filters: 80uF-160uF 330V. They all sound very fast & transparent.
Who said 'ltyic caps sound crappy ????
c-J
680mf bank 293760mf and 1500mf bank 378000mf!!WOW!!
Mike
Hi.
Since you already got both banks built. Just try them both & see if you could hear the difference. IMO, I doubt yu could.
c-J
I only have one 1500mf bank built for now.That's why I posted to get opinions on the matter.That's a lot of caps Granpa!!
Mike
Hi.
A cap in theory would be pure capacitive. But any realworld cap is a very complex AC network comprising series & parallel resistance DCR, inductance L & capacitance C. So by parallel multi caps, the resultant impedance of the cap bank would be reduced due to reduced internal DCRs & inductances vs a single cap of same size.
If an amp with 1.4 million uF 'lytic caps in parallel can give 0.8uS rise time as I posted above, why you worry?
c-J
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