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paskinn Offline
#1 Posted : 01 October 2011 17:28:03(UTC)
paskinn


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Although I had been warned, I have been shocked by the differences when using different 12 volt, 5 amp, supplies to power my field-coil drivers. Battery supplies seem to win by a good margin, faster, smoother, richer, deeper..you know that classic low distortion sound. Worse, by far, a RS switched mode supply. Not good. In the middle, a decent linear supply.Still well below the big battery supply.
So, my question, can anyone recommend a truly outstanding supply : 12 volt, at least five amps per stereo channel. As the battery supply costs thousands, and involves two large boxes, I would be most grateful for something cheaper, smaller, but as good. Is there such a thing?

Edited by user 15 October 2011 10:14:14(UTC)  | Reason: Not specified

Pete_w Offline
#2 Posted : 01 October 2011 21:33:32(UTC)
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You've posted under "general", not DIY. As a man who's just bought his own field-coil drivers, are you up for a bit of DIY?

I know zilch about FC drivers, in terms of how they work with their power supplies? Do you have any feel that you can share with the rest of us about what they need? A steady 5A - implying a 1.5Ohm coil, or does their impedance get modulated by the music and cone movement and is different at different frequencies...?

ashleym Offline
#3 Posted : 01 October 2011 23:05:19(UTC)
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I know they recommend a bench power supply on the Squeezebox upgrade page. I use them to power my DIY synthesiser too. These are only about 100mA draw......but you can get meaty dual supplies.

It might be worth contacting
http://www.teddypardo.com/index.html

or a more commercial contact
http://www.benduncanresearch.com/

I am fairly ignorant too. Is there a chance of altering performance by adjusting the power supply, ie low frequency parameters to do you just move away from the optimum?

Edited by user 01 October 2011 23:06:38(UTC)  | Reason: Not specified

paskinn Offline
#4 Posted : 02 October 2011 10:38:53(UTC)
paskinn


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I am ignorant about such matters, not least because I have no electrical training....and am not looking for a DIY solution...rather a commercially available product.Perhaps the variables are too great, in which case I will end up buying the battery power supply from the supplier of the field coils (Voxativ.) What I can say, is that these field coils are incredibly sensitive to the quality of the supply. But surely there are first-rate commercially available supplies, perhaps my problem is that it needs to be unusually 'beefy'.
What does strike me is how much us hifi types obsess about such joys as tweaking Linn Sondeks and yet really basic stuff about electro-magnetic performance is well below the radar. Jonathon at Music First can produce transformers which appear identicial and yet sound quite different. I suppose these are all examples of how everything signifies.
Martin Colloms Offline
#5 Posted : 02 October 2011 19:00:13(UTC)
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Field coils , simples ...........

the audio input current from the amp is multiplied by the field coil magnetisation (current)

F , force on the cone is

Bli

B the magnetisation , l the length of coil wire in the gap and i the amplifier input current

So errors , noise ,hum , impedance, and RFI ( feeding back to the amp ) jump straight to the force equation, No wonder the field coil supply is critical.

Many argue more critical than the amp supply itself ...

Sure the field coil is something of a choke but this is not a full fix to the problems presented

Martin

Edited by user 03 October 2011 13:33:49(UTC)  | Reason: Not specified

Pete_w Offline
#6 Posted : 02 October 2011 19:25:34(UTC)
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paskinn wrote:
In the middle, a decent linear supply


Slightly off-topic, but I run the stators of my 'Logans, and my source components, from a sequential combination of Isol8 mains RF filter followed by PS Power Plant Premier to regenerate clean mains. Not suggesting that you buy on spec, but if you can borrow similar and try it with the mains linear supply, it might get you somewhere near where you want to go...

Presume you're not putting 12V/5A standing current into each speaker. When I was at school, that was 60W, which is going to make for a hot little driver...?

Cheers
Pete
Shuggie Offline
#7 Posted : 03 October 2011 09:13:51(UTC)
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I recommend having a chat with Paul Hynes ( www.paulhynesdesign.com ), whose power supplies and regulators I've used for many years to universally good effect on various projects including Squeezebox, valve amp HT circuits, turntables, media PC, USB-SPDIF converter.
paskinn Offline
#8 Posted : 04 October 2011 02:38:45(UTC)
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I have taken the advice of 'Shuggie' and had a chat with Paul Hynes. He is going to make me a couple of monobloc power supplies which should fit the bill. Thanks for the advice.
paskinn Offline
#9 Posted : 13 October 2011 05:37:35(UTC)
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For the sake of 'experimenting' I have put a new 12v power supply on 'hold' while I examine (ie..play with) the use of 12 volt car batteries. The sound with two standard car batteries is quite superb. All you need is a cheap trickle charger and you are in business. But you need a hifi room of your own....no partner will put up with such behaviour . Quite right too. Me, I'l try to retain the batteries, the sound is just so fine. A pure, uncontaminated power source.
My partner..I bought her some rather nice leather winter boots and have promised to keep my experiments confined to my 'listening room.' Seems a fair deal. No bits of hifi anywhere else in the house. I like that too.
ashleym Offline
#10 Posted : 13 October 2011 17:47:18(UTC)
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Have a look here, nothing too much and no field coils

http://www.hificritic.co...t.aspx?g=posts&t=528
Martin Colloms Offline
#11 Posted : 13 October 2011 18:47:35(UTC)
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there are smaller sealed lead acids , do you need such a monster?


Martin C
paskinn Offline
#12 Posted : 14 October 2011 09:34:04(UTC)
paskinn


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Martin Colloms wrote:
there are smaller sealed lead acids , do you need such a monster?


Martin C

I am experimenting, and car batteries are cheap and easy to buy. It is indeed a bit over the top, but then Voigt horns are a bit over the top too. That's why I have a separate room for such silliness. To my ears it is sounding quite wonderful and I am beginning to ask myself if it would be possible to establish a system driven only by batteries. Others seem to have managed it and escaping from the mains becomes more and more tempting as electrical pollution increases.It has dragged sound down quite a lot.And despite valient efforts, I am not sure that anyone has found a truly effective solution, other than escaping from the mains altogether.
Pete_w Offline
#13 Posted : 14 October 2011 10:46:42(UTC)
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You probably know this already, but after the experimentation phase is over, remember that engine start batteries aren't really designed for long-term deep discharge. They don't take well to it. Boat and caravan "house" batteries are much better suited, but are more expensive. On the other hand, if your proposed mode of operation is to have the batteries on trickle charge while you sleep every night, it probably doesn't matter at all... :-)
paskinn Offline
#14 Posted : 15 October 2011 09:06:38(UTC)
paskinn


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Pete_w wrote:
You probably know this already, but after the experimentation phase is over, remember that engine start batteries aren't really designed for long-term deep discharge. They don't take well to it. Boat and caravan "house" batteries are much better suited, but are more expensive. On the other hand, if your proposed mode of operation is to have the batteries on trickle charge while you sleep every night, it probably doesn't matter at all... :-)


Yes, thanks for that. The garage warned me not to discharge car batteries, precisely for the reason you suggest. I do 'trickle charge' them. What I will do in the longer term I don't really know. I am just trying to establish a 'base' set of conditions in my own mind....if I can then find a mains powered supply which sounds as good as the batteries..problem solved! (what are the chances of that?).
Still, you have to experiment a bit to find out . I have always found that the only way with this hobby; advice is most useful, but in the end you have to find out what really works for you.
darkmatter Offline
#15 Posted : 15 October 2011 10:14:58(UTC)
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paskinn,
Hope you don't mind, I moved this thread to the DIY section and added to the title.
DM :)
kengale Offline
#16 Posted : 15 October 2011 19:45:48(UTC)
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paskinn wrote:
Pete_w wrote:
You probably know this already, but after the experimentation phase is over, remember that engine start batteries aren't really designed for long-term deep discharge. They don't take well to it. Boat and caravan "house" batteries are much better suited, but are more expensive. On the other hand, if your proposed mode of operation is to have the batteries on trickle charge while you sleep every night, it probably doesn't matter at all... :-)


Yes, thanks for that. The garage warned me not to discharge car batteries, precisely for the reason you suggest. I do 'trickle charge' them. What I will do in the longer term I don't really know. I am just trying to establish a 'base' set of conditions in my own mind....if I can then find a mains powered supply which sounds as good as the batteries..problem solved! (what are the chances of that?).
Still, you have to experiment a bit to find out . I have always found that the only way with this hobby; advice is most useful, but in the end you have to find out what really works for you.


You can also get sealed lead-acid "high-cyclic" batteries, intended for things like electric wheelchairs. Sonnenschein (yes, these German batteries do have a rising sun as a symbol!) and Yuasa do versions up to around 70Ah. Usually quote something like 600 cycles life when discharged to 40% (i.e. you can draw 60% of its design capacity) each time.

Edited by user 15 October 2011 22:35:23(UTC)  | Reason: Not specified

darkmatter Offline
#17 Posted : 16 October 2011 13:17:43(UTC)
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Found the link

Sonnenschein dryfit Gel Batteries

Wonder how they perform in Audio applications
Martin Colloms Offline
#18 Posted : 01 December 2011 15:47:32(UTC)
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Vol5 no 4 has coverage of field coil drivers

an interview with Voxative and a review of the Supravox.

the latter nearly did not happen as the reviewer suffered an unfortunate blow up of both review samples due to an amplifier fault , which may have been due to coupling via the field coil and its supply, something we will look into

Martin C
hifi addict Offline
#19 Posted : 13 December 2011 22:53:28(UTC)
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I listened to paskinns vocative field coils and I can confirm I liked them a lot. I think he should make some nice boxes to put the car batteries in though.

Martin Colloms Offline
#20 Posted : 21 December 2011 15:40:51(UTC)
Martin Colloms


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Martin Colloms wrote:
Vol5 no 4 has coverage of field coil drivers

an interview with Voxative and a review of the Supravox.

the latter nearly did not happen as the reviewer suffered an unfortunate blow up of both review samples due to an amplifier fault , which may have been due to coupling via the field coil and its supply, something we will look into

Martin C


Some more on this ..

a single 12v regulated supply was used ie shared by the two field coils

I do not have a good handle on the equivalent circuit but I presume there may be some mutual inductance coupling and some capacitance coupled across the live amplifier channels and this may have resulted in instability leading to blowing up the voice coils.

Can't be a good idea anyway if you think about it, separate batteries avoid this potential for mutual coupling and could well sound better, partly for this reason.

I would welcome some input on this topic , or related experiences

Martin C

Edited by user 21 December 2011 15:41:25(UTC)  | Reason: Not specified

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