by Graham Woods and Denise Oh, Cottle Bridge, Australia

Read the follow up report here!

For serious listening, my partner Denise and I power our primary system from an inverter fed by a Trojan J185G 12 volt battery, so the obvious 12 volt source for our Monica 2 was the same battery.

Fitted with a 2200mF cap and fed by the Trojan, our Monica sounds beguiling (see my Love Letter of 20.04.2007). There’s a drop in sound quality when Monica is on the battery and the rest of the system is on the mains, but that’s not Monica’s fault: blame relatively crappy mains power (which, of course, is why we prefer the inverter).

Monica 2 on our battery sounds great and, given our set-up, a battery is the most convenient power source and costs us nothing extra, so we’d never considered an alternative. Until recently.

A few weeks ago I read Clive Walker’s Love Letter [15.1.2007]. Clive had tried a battery with his Monica 2, but had decided that his own PSU sounded better (for details see his L.L).

I knew Clive’s experience wasn’t unique; other reviewers have praised battery power for some of its qualities but have also had some reservations. The main short-comings of a battery, compared with a PSU (I’m referring here to any active PS), seem to be diminished bass and treble extension and (as a consequence?) some loss of body and slam and of ‘PRAT’. Clive added another: some loss of low-level detail. I haven’t seen this reported by anyone else and it might be the result of Clive’s choice of battery; more on that later.

Despite its reported shortcomings, it seems to be almost universally agreed that battery power – for Monica 2 and for at least most other NOS dacs – offers blacker silences between notes and more transparency and ‘air’. When you’ve heard these qualities it’s hard to give them up: in fact they’re the qualities that make our ‘inverter power’ superior to our mains.

So, should we use a PSU or continue to use a battery? Is the choice inevitably a trade-off? These were the questions that prompted Denise and me to do a comparison. Before I talk about what we found though, I want to mention the results of an earlier test.

Big Battery vs Bigger Battery
A few months ago Denise and I had experimented with a standard car battery (90 RC, 460 CCA) in place of the 140 AH Trojan (both fully charged). For powering a Monica 2 most people would call the car battery big; we certainly thought it would be big enough to match the Trojan, and in fact our main interest was in the difference that might come from having a power supply for Monica that was separate from the –battery – power supply that fed the rest of the system.

We pitted the car battery against the Trojan in two configurations: the Trojan powering just the Monica (the rest of the system on mains power); and the Trojan powering Monica PLUS the rest of the system. (We didn’t use the car battery to power Monica plus the rest of the system. Compared with the Trojan it’s small, and it’s not a deep-cycle battery: it’s definitely not designed for powering an inverter.)

We’d expected that a separate, though smaller, battery for Monica would at least hold its own against a larger battery that she had to share with an inverter, but we were wrong. The bigger battery produced indistinguishable results in each configuration and in each case it outperformed the smaller one. It wasn’t a case of night versus day but the differences were quite obvious. Compared with the Trojan the car battery offered about the same (certainly not more) bass and treble extension and the same ‘battery qualities’ of black silences, transparency and air; however there was slightly less low-level detail and the presentation definitely lacked the body and slam produced by the bigger battery – qualities often associated with a good LP.

Big Battery vs PSU
Our battery for this comparison was the one I’ve mentioned: a Trojan J185G, conservatively rated at 140AH for 5 hours. Our PSU was the unit whose regular job is to charge the Trojan. It’s a laboratory PSU from ‘Powertech’, a Jaycar house brand (although I’ve seen the identical unit in other electronics shops, just with THEIR badge on it): reasonably large and heavy; variable 3-15V; analogue volt and amp meters; ripple and noise < 10mV (RMS). It was fairly easy to re-jig this so that it was fed from the inverter and could thus be used as an active power source for Monica.

We agreed to feed the PSU to Monica with her 2200mF reservoir cap still in the circuit. I wasn’t keen to cut the cap out of the circuit for the sake of a short-term trial and in any case Denise and I didn’t think it would affect the PSU’s performance. Others might disagree however, or, regardless, might want to experiment.

We warmed the system thoroughly, on mains power; switched to the inverter; played a disc for about another 20 minutes; then began the audition. It’s hard to hide the switch-over from one source to another so at all times both Denise and I knew which source was which.

We listened first using the battery. Then we switched to the PSU, which was also taking its power from the inverter, not the mains. I made sure that the voltage from the PSU was the same as that currently being delivered by the battery, now under load from the rest of the entire system via the inverter. At intervals of a few minutes I switched back to the battery, then back to the PSU, then once more back to the battery. Denise and I took notes independently; the same tracks of a single CD comprised all listening samples.

Our Conclusions
In most respects our conclusions were very similar. The PSU sounds nice, perhaps you could say ‘slightly warm’, but compared with the battery it’s muddy, and yet, in Denise’s opinion, actually produces a ‘thinner’ sound. What I think she’s getting at is that it actually has less body and slam than the battery, but with the muddiness masquerading as ‘body’.

I didn’t notice the thinness that Denise reported. What I did notice was what a lot of commentators have already remarked on: the battery produced dramatically blacker spaces between the musical notes. The result is significantly more transparency and air, a spaciousness and lightness that the PSU just couldn’t match. Along with that, though, the battery produced at least as much treble and bass extension, a larger sound stage and more detail, and more slam and emotional involvement. In these areas Denise’s conclusions were the same as mine. Putting it all together, there was no parameter on which the PSU was superior.

Having Your Cake and Eating it too
Our experiments suggest that you CAN have the best of both worlds: i.e. the virtues of both a PSU and a battery. However, you can’t get them all unless you use a fairly big battery. Even a standard car battery isn’t really enough, although it does seem to deliver most of the goodies of its larger cousins. I’m reasonably sure, now, that as the size of the battery goes down, more and more of the virtues of battery power are lost; if you plan to use nicads, or lithium cells (as Clive did), or even a small SLA, you’ll definitely be in the compromise zone, where the merits and demerits of the two power sources will need to be carefully weighed up.

Passing the Baton (Passing the Buck?)
Our experiments comprise not much more than a couple of case-studies, so it would be premature to assume that our results are universally valid. I’d like to see the results of more experiments, using different amplification, different sized reservoir caps (and perhaps different brands), various types and qualities of PSU, perhaps a battery even larger than the one we use. On this last point: Denise and I are considering a 500AH 12 V battery bank. If we go ahead with that we’ll definitely want to see whether even 140AH is too small a battery to get the most out of Monica 2.

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by Graham Woods and Denise Oh, Cottle Bridge, Australia

A few months ago I reported on the results of some comparisons Denise and I had made between batteries of different sizes and between a large battery and a good quality PSU (see ‘Batteries and PSUs’). I mentioned then that we were considering buying a 500AH battery bank. We recently did, and we were keen to see how the new battery bank performed against our existing Trojan J185G. The fairly hefty Trojan had outperformed a standard car battery and we expected that an even heftier battery bank would either outperform the Trojan or produce no audible difference. However, read on!

The Trojan J185G is a deep cycle 12V battery rated at 140AH for 5 hours. Our new battery bank comprises six Century Yuasa VCI8C 2V cells linked by lengths of 30mm X 6.5mm thick copper bus bar. The cells are clustered (2 X 3) so as to keep the buses as short as possible. These cells are rated at around 600AH (5 hours).

We began our tests by running everything from the new battery bank: i.e. an inverter to provide 240V for our Rega Planet 2000, a VTL Super Deluxe preamp and a VTL 90/90 power amp; and a direct feed from the battery bank to our Monica. Our ‘test disk’ was our usual: Simon and Garfunkel’s ‘Old Friends: Live On Stage (2005)’. The presentation had the same slam as usual, but compared with our memory of how the system had sounded only two nights before – on the Trojan – it sounded hard and aggressive, though clean and detailed.

We get variations in sound quality that seem to depend on the weather, and at first we attributed the degradation in sound quality to that. However the same sound signature was apparent the next night, and two nights after that; this couldn’t be just the weather!

On the fourth listening evening we bit the bullet. During the day (a Sunday) I’d connected our Monica to the Trojan, leaving the rest of the system to be powered by the new battery bank – from now on I’ll call it ‘the Century’. Denise deliberately didn’t know whether Monica was connected to the Trojan or the Century, though she did know that the 240V supply would come from the new arrival.

We played the first two tracks of our test CD; then I switched Monica to the Century and we played the tracks again. Finally I switched Monica back to the Trojan and we listened to the same tracks. As usual we made separate notes and didn’t discuss our impressions during the auditions.

Before these tests I was hoping to hear, at worst, no difference between the two power sources. I certainly didn’t want the Trojan to outperform the new battery bank: the whole idea was to obtain a longer-lasting power supply and, as a bonus, to sell the Trojan to offset some of the cost of the changeover. Just before we began this phase of our tests Denise confided that she, too, was hoping to hear no difference.

However there was no way we could avoid the facts. Though our words were sometimes different, our opinion was the same. Fed by the Trojan our Monica returned to what we were used to; the hardness, the clinical ‘dryness’, the ‘CD’ edge of the music disappeared.

For the sake of completeness Denise and I then compared the Trojan with the Century as a source for our inverter-generated 240V supply, with Monica taking her power consistently from the Trojan. Here the differences were more subtle, and there was no clear winner. The Trojan offered a more mellow sound, with a slightly rolled off top end; the Century offered a sound that was more detailed and had a little more air and transparency, and which, probably as a result of that, conveyed the ambience of the performance a little more convincingly. Denise and I agreed that the Trojan would be kinder to hard, ‘edgy’ CDs, whereas the Century would be the winner with top quality sources. On balance, on the night of our tests, I preferred the Century; for Denise it was a dead heat. The bottom line, however, is that, even going through an inverter, these batteries didn’t produce the same sound.

Putting it all together, I believe we have to revise our earlier conclusion (in ‘Batteries and PSUs’). When it comes to powering Monica 2, it’s possible that the SIZE of the battery is not very important at all; it could well be that it’s the BRAND of battery that’s most important. Although we haven’t put them head-to-head, our recollection of the sound of the car battery (not a Century Yuasa and not a Trojan) is that, as a power source for Monica, it was actually superior to the sound produced by the 600AH Century, despite being only about half the size of the Trojan and an eighth the size of the newcomer.

There’s probably only one way to decide the issue: to do a series of tests using batteries of, say, three different sizes and, say, five different brands. That could be expensive, and would certainly be time-consuming (and it won’t be us who’ll be doing it!). In the meantime, however, Denise and I would put brand ahead of size, and, when our Trojan finally dies, we’ll be buying a – smaller – TROJAN replacement to power our Monica.

[yeo’s comments : yes, battery makes to me is more important than capacity. i have been very happy with a yokohama rechargeable sealed lead acid until i tried a hitachi one day at an insistence of a customer. oh my! never going back to the yokohama now. call it their secret sauce if you which but the chemical composition of the battery definitely affects its performance.]

FURTHER THOUGHTS
It might be speculated that the new battery bank needs to be run in: after all, its six cells are linked by copper buses that might be likened to interconnect cables, and these, at least, might need to be broken in. I doubt that this is an important factor though, because the Trojan also outperformed a well run-in standard car battery (see ‘Batteries and PSUs’). Nevertheless, Denise and I will do some more tests after the Century has racked up a couple of hundred hours. Long before that we’ll clean all contacts between cells and apply a contact enhancer, to see if that makes a difference.

Perhaps the copper buses that link the cells are acting like small antennae for RFI or other grunge, but, having done extensive tests in this respect on other aspects of our system, I believe that can be ruled out.

Is the superior performance of the Trojan with Monica the result of its being a SEPARATE power supply for her? I would say no: in our earlier comparison of the Trojan and a car battery the Trojan outperformed the smaller battery even though it (the Trojan) was also powering the rest of the system.

CONCLUSION
Before our tests I would have smirked if someone had suggested that the SORT of 12V battery you use could make a difference to how Monica sounds. I recall now that Yeo has reported just this possibility, as a result of the experience of a few DIYers, and I remember that I was sceptical when I read that. After all, the battery just supplies 12V DC, ultimately to be massaged by Monica’s circuitry anyway, and above a possible minimum why should even size make a difference, let alone brand? I’m not willing to speculate as to why, but our tests suggest that brand certainly DOES make a difference. Our most recent tests and the earlier ones, taken together, also suggest that size related differences – if they exist at all – might be so subtle that they can be disregarded.

In addition to brand, perhaps battery TYPE makes a difference: nicad (or nickel hydride or lithium) versus lead acid; or even SLA versus the more traditional flooded lead acid battery. It’s quite possible that a certain sort of active PSU, in a particular system, will sound better than ANY battery. And does a particular battery type, or brand, sound equally good in all systems? Possibly not. A rich playing field awaits the dedicated experimenter and tweaker …

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