I've been contributing to a discussion of the use of battery power supplies for preamps in another thread but I'd like to start a wider discussion here about the pros and cons of battery vs conventional capacitor smoothed & regulated active PSUs.
My understanding is that batteries are almost ideal low noise DC supplies when idle but are slower than active PSUs and produce higher levels of transient noise when supplying real life current because of the chemical reaction times and processes involved. Their output impedance may also be relatively high for some battery types compared to active PSUs.
It also seems to me that the major problem with conventional active power supplies is the wideband RFI generated by the sharp current pulses and diode switching noise of the capacitor smoothed diode bridge circuit which can be transmitted to sensitive preamp circuits via wiring and by radiating. Batteries do not suffer from this problem.
Is not the simple answer to combine the best of both types and regulate battery power supplies with high performance low noise regulators?
Gopher
My understanding is that batteries are almost ideal low noise DC supplies when idle but are slower than active PSUs and produce higher levels of transient noise when supplying real life current because of the chemical reaction times and processes involved. Their output impedance may also be relatively high for some battery types compared to active PSUs.
It also seems to me that the major problem with conventional active power supplies is the wideband RFI generated by the sharp current pulses and diode switching noise of the capacitor smoothed diode bridge circuit which can be transmitted to sensitive preamp circuits via wiring and by radiating. Batteries do not suffer from this problem.
Is not the simple answer to combine the best of both types and regulate battery power supplies with high performance low noise regulators?
Gopher
Hi Gopher,
glad to see someone trying to reason with the pros and cons.
That other guy seems to be blinkered (in all his threads).
I don't know where to find it, but there is a very full expose on regulated supply noise (and impedance?) and the site includes comparison with various battery types. A search might find it. It is referenced in this Forum.
glad to see someone trying to reason with the pros and cons.
That other guy seems to be blinkered (in all his threads).
I don't know where to find it, but there is a very full expose on regulated supply noise (and impedance?) and the site includes comparison with various battery types. A search might find it. It is referenced in this Forum.
Andrew
The link is
http://www.tnt-audio.com/clinica/regulators_noise1_e.html
and subsequent parts of the article.
My point with the regulated battery PSU is that the battery effectively replaces the mains, transformer and diodes with the advantage of almost zero RFI while the regulator supplies the stable, low noise, low impedance power that the battery can't on its own.
I don't think I've ever seen battery supplies regulated anywhere before. Has anyone else?
The link is
http://www.tnt-audio.com/clinica/regulators_noise1_e.html
and subsequent parts of the article.
My point with the regulated battery PSU is that the battery effectively replaces the mains, transformer and diodes with the advantage of almost zero RFI while the regulator supplies the stable, low noise, low impedance power that the battery can't on its own.
I don't think I've ever seen battery supplies regulated anywhere before. Has anyone else?
Please dont entertain the idea of regulating battery supplies - they limit the current available - and sound 'squashed' as a result.
Firstly, a battery supply needs to be designed in the same manner to a regular PSU. To inhibit chemical noise, I strongly recommend the use of a choke in each 'leg' of the supply (one for + and -, and a third on the Gnd leg - it doesnt need to be huge in value (0.5mH is more than enough), but it will work a treat.
Secondly, use a bank of small caps, as if you were using a normal AC supply. This will provide an initial reserve of current to 'cover' the slight lag in the chemistry.
Done properly, a battery supply is utterly silent. Sometimes they can sound 'slow' - in the main, but from experience, that is because there is no additional unwanted noise between each single note - the silences are more apparent, and so sound longer.
In terms of current delivery they have huge ability to deliver without the strangulation of regulators, from a very,very low source impedance at low frequency. This rises slightly because of the chemistry at higher frequencies, and that is why you need to design the PSU to improve current delivery in those circumstances, but current demand drops rapidly, so its influence is less anyway
However, this is the exact opposite of an AC supply, as the source impedance rises dramtically as you approach DC (to the resistance of the transformer windings) that you ameliorate using all sorts of band aids. This does however, mean that at high frequency, the impedance is low, and the coupling (how well a transformer works) is very very good - ideal circumstances for propagation of RF from the main supply itself.
Using a battery supply, a humble LF353 opamp, and 6 or so other parts, I built a preamp that slaughtered a numbver of very, very expensive comercial pre-amps (my Meridian included). It had imaging to die for, huge dynamics (and I mean HUGE), and a lovely relaxed 'listen to me' manner.
I liked it so much, I will be building another when time permits.
Owen
Firstly, a battery supply needs to be designed in the same manner to a regular PSU. To inhibit chemical noise, I strongly recommend the use of a choke in each 'leg' of the supply (one for + and -, and a third on the Gnd leg - it doesnt need to be huge in value (0.5mH is more than enough), but it will work a treat.
Secondly, use a bank of small caps, as if you were using a normal AC supply. This will provide an initial reserve of current to 'cover' the slight lag in the chemistry.
Done properly, a battery supply is utterly silent. Sometimes they can sound 'slow' - in the main, but from experience, that is because there is no additional unwanted noise between each single note - the silences are more apparent, and so sound longer.
In terms of current delivery they have huge ability to deliver without the strangulation of regulators, from a very,very low source impedance at low frequency. This rises slightly because of the chemistry at higher frequencies, and that is why you need to design the PSU to improve current delivery in those circumstances, but current demand drops rapidly, so its influence is less anyway
However, this is the exact opposite of an AC supply, as the source impedance rises dramtically as you approach DC (to the resistance of the transformer windings) that you ameliorate using all sorts of band aids. This does however, mean that at high frequency, the impedance is low, and the coupling (how well a transformer works) is very very good - ideal circumstances for propagation of RF from the main supply itself.
Using a battery supply, a humble LF353 opamp, and 6 or so other parts, I built a preamp that slaughtered a numbver of very, very expensive comercial pre-amps (my Meridian included). It had imaging to die for, huge dynamics (and I mean HUGE), and a lovely relaxed 'listen to me' manner.
I liked it so much, I will be building another when time permits.
Owen
Owen
I was going to suggest filtering the battery output with C-R-C network using large electrolytics in the same way as a conventional PSU. The more chemical noise can be removed the better.
As I see it, the overriding reason for using a battery to replace the mains, transformer and diode bridges is that they won't have the broadband RFI out to several MHz that conventional active supplies have.
Others have reported opposite results to your experience with the sonics of battery PSUs, namely they sound good initially but ultimately lack the dynamics of active supplies.
Whether regulators following a filtered battery will give the best of both worlds is surely something worth trying.
Gopher
I was going to suggest filtering the battery output with C-R-C network using large electrolytics in the same way as a conventional PSU. The more chemical noise can be removed the better.
As I see it, the overriding reason for using a battery to replace the mains, transformer and diode bridges is that they won't have the broadband RFI out to several MHz that conventional active supplies have.
Others have reported opposite results to your experience with the sonics of battery PSUs, namely they sound good initially but ultimately lack the dynamics of active supplies.
Whether regulators following a filtered battery will give the best of both worlds is surely something worth trying.
Gopher
Ordinary supplies can sound more dynamic - and I think thats an artifice created by the crud floating on the supply, and poor implementation.
Nail an ordinary supply (without regs) to kill the RF, and have a battery supply (properly designed) to compare to, and they sound very, very alike.
All I have are rules of thumb - upto 0.5mH choke (speaker supply house, air core, high current, must have a low DCR) is fine, and I use between 5 and 10k uF of capacitance - either as banks of 100uF caps or bypassed 1000uF caps.
If you were going to be bold, a large supply could be realistically built with polypropylene caps (and audiofool grade if you so wish). The Battery needs to be a cyclic duty type - as you'll be using it, and then recharging, not topping it up as you go along. These however are relatively easy to find.
One of the best bypassing tips I was given by Nelson Pass - put a bypass cap between the + and -rail, as well as betwen each rail and ground.
Definitely a case of 'try it and see', but in my view, you will be astounded by the results, even with low budget parts.
Have fun, and report back
Owen
Nail an ordinary supply (without regs) to kill the RF, and have a battery supply (properly designed) to compare to, and they sound very, very alike.
All I have are rules of thumb - upto 0.5mH choke (speaker supply house, air core, high current, must have a low DCR) is fine, and I use between 5 and 10k uF of capacitance - either as banks of 100uF caps or bypassed 1000uF caps.
If you were going to be bold, a large supply could be realistically built with polypropylene caps (and audiofool grade if you so wish). The Battery needs to be a cyclic duty type - as you'll be using it, and then recharging, not topping it up as you go along. These however are relatively easy to find.
One of the best bypassing tips I was given by Nelson Pass - put a bypass cap between the + and -rail, as well as betwen each rail and ground.
Definitely a case of 'try it and see', but in my view, you will be astounded by the results, even with low budget parts.
Have fun, and report back
Owen
It is simply not worth regulating a battery, as the main shortcoming of the battery supply - that of high impedance and thus poor burst current delivery, is only worsened by placing a regulator after it.
Also, to cope with the other shortcoming and reject the noise, a regulator would have to be extremely fast.
I think the way forward would be to simply tag a conventional regulated supply for AC onto a battery - bridge and smoothing caps and all - and let the caps do the work for low impedance drive and also some noise reduction as well.
Also, to cope with the other shortcoming and reject the noise, a regulator would have to be extremely fast.
I think the way forward would be to simply tag a conventional regulated supply for AC onto a battery - bridge and smoothing caps and all - and let the caps do the work for low impedance drive and also some noise reduction as well.
Rechargable Batteries (unless they are *disposable* carbon types) do not have a high output impedance - infact it is the other way around, by usually an order of magnitude or more.
A rechargable battery can deliver a burst current that is huge (a 1.3V NiMH 1300 mAH can deliver > 3 amps as a burst), and once again, it is the other way around. The impedance of a standard transformer limits the current deliverable, as a product of the magnetic flux capability of the core.
Both of these facts are grounded in simple physics - the burst current capability of a large SLA battery is high enough that a spanner isnt a big enough fuse (yes, the spanner will explode apart!). Not to be recommended, as the battery usually bursts too due to shock. .. electrolyte everywhere!!!!!
Hybrid supplies can work, but there is something quite magical about a good pure battery supply implementation.
Owen
A rechargable battery can deliver a burst current that is huge (a 1.3V NiMH 1300 mAH can deliver > 3 amps as a burst), and once again, it is the other way around. The impedance of a standard transformer limits the current deliverable, as a product of the magnetic flux capability of the core.
Both of these facts are grounded in simple physics - the burst current capability of a large SLA battery is high enough that a spanner isnt a big enough fuse (yes, the spanner will explode apart!). Not to be recommended, as the battery usually bursts too due to shock. .. electrolyte everywhere!!!!!
Hybrid supplies can work, but there is something quite magical about a good pure battery supply implementation.
Owen
"glad to see someone trying to reason with the pros and cons.
That other guy seems to be blinkered (in all his threads)."
Dear AndrewT
You suggest that this type is me? Because i have obvious reasons to suspect such something, i ask an answer from you immediately. If you do not answer, i will consider in absentia your answer affirmative.
Honor
Fotios Anagnostou
That other guy seems to be blinkered (in all his threads)."
Dear AndrewT
You suggest that this type is me? Because i have obvious reasons to suspect such something, i ask an answer from you immediately. If you do not answer, i will consider in absentia your answer affirmative.
Honor
Fotios Anagnostou
Dear AndrewTAndrewT said:
Say did me that my own opinion is the one that measures only in anyone from my threads? You believe that what i write it is unproved? After 30 years of continuous occupation with electronics, i have my own opinions which i do not try to impose in no one. Simply i report my observations, not only through reading, but also through practical applications. I know very well certain things that I am never him to write because afterwards it needs I answer in a pile of remarks, and no queries. Moreover you saw what caused my report in the batteries, even if she is fool? Two entire threads in continuous development that they have make with a very important subject and no with advices for repairs of amplifiers. If you were careful, never I answered in such thread.
Fotios
Gopher said:
I'm not saying any different to that above. What I'm saying is that to put a series regulator after a battery to try and make 'the best of both worlds' is wrong as the impedance of the series regulators output can never be lower than that of the supply feeding it. And if you are feeding it with a non-rechargeable battery then it will only ever be as good as that in terms of impedance.
As Owen points out , if you use a rechargeable battery it's another story. But rechargeable batteries self-discharge amongst other problems.
Ok you have a microsecond transient that demands more than 200 mA - where does your regulator go then? It clips. The output is a flattened at that point.
The battery wouldnt flinch if you asked for 20 A in that timescale (assuming it was a reasonable sized SLA).
The input impedance of the poweramp plays an important role in this 'equation', as that is the load to be driven by the preamp, and that is comprised of three polar componants - inductance, capacitance and pure resistance. More current delivery ensures that you maximise the linearity of the output stage of the preamp into that load.
I personally find that a straight comparison between a regulated powersupply and an unregulated one is very interesting. The unregulated (assuming the PSU is executed to excess as usual) tends to sound more organic, less forced, and loses the slightly 'sat-on' feel that you can get with a regulated supply (the best description I can give is that it is like comparing a tape recording made with no noise reduction to a recording made using Dolby C noise reduction - the latter sounding clanky and mechanical).
The Jung regulator is a great design that is very musical, but I still have reservations about a device or series of devices that have complex polar interactions (phase shifts, noise characteristics, and variations in distortion) used, when a predictable series of passive componants can be used instead, and that is ignoring the self noise of the active componants (and the supporting passive componants) - although some have very low published figures within a given bandwidth, I have no doubt that those figures will rise sharply outside of that bandwidth...
Just my observations.
Regulators do a great job at making everything uniform, and allowing folks to get away with less than optimal designs...
Just my thoughts
Owen
The battery wouldnt flinch if you asked for 20 A in that timescale (assuming it was a reasonable sized SLA).
The input impedance of the poweramp plays an important role in this 'equation', as that is the load to be driven by the preamp, and that is comprised of three polar componants - inductance, capacitance and pure resistance. More current delivery ensures that you maximise the linearity of the output stage of the preamp into that load.
I personally find that a straight comparison between a regulated powersupply and an unregulated one is very interesting. The unregulated (assuming the PSU is executed to excess as usual) tends to sound more organic, less forced, and loses the slightly 'sat-on' feel that you can get with a regulated supply (the best description I can give is that it is like comparing a tape recording made with no noise reduction to a recording made using Dolby C noise reduction - the latter sounding clanky and mechanical).
The Jung regulator is a great design that is very musical, but I still have reservations about a device or series of devices that have complex polar interactions (phase shifts, noise characteristics, and variations in distortion) used, when a predictable series of passive componants can be used instead, and that is ignoring the self noise of the active componants (and the supporting passive componants) - although some have very low published figures within a given bandwidth, I have no doubt that those figures will rise sharply outside of that bandwidth...
Just my observations.
Regulators do a great job at making everything uniform, and allowing folks to get away with less than optimal designs...
Just my thoughts
Owen
Gopher said:
Better for what? Not for music reproduction IME. Jung, great as it is still doesn't do anything about the hi-freq noise from the ac line, diodes, etc. In short, if you can hear the PC before using the regulator you'll be hearing it just as clearly afterwards.
I've been using batteries to power MC step-ups and phono preamps for many years. They produce a dramatically different sound to any mains-derived ps but they are not without problems.
For one i find them sounding as diverse as capacitors. Slow and fluid if they are acid based or fast (and still fluid) if they are NiCd or NiMHi. And size matters a lot for the tonal balance. Bass is often nimble but with little "substance" and kick.
I even get the suspicion that most records are balanced to sound "normal" on mains supplies.
At this stage i won't seriously consider batteries again. I simply lack the dedication
Now, if someone offers a simple recipe for a "never connected" ps...
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