Hiow to replace wall wart on step up with battery

ALL audio equipment runs internally on DC. Most take the AC from the wall and convert it internally to DC, easily done. A scarce few don't have this AC to DC conversion and run solely off batteries. Some, like the Phonomena can run off either.

I didn't really modify the Naim. It has a plug on the back that accepts an external DC supply that Naim makes to the tune off about $4,500. It is not a battery supply but a much better AC-DC supply that bypasses the internal CDX2 supply. Using that plug it is easy to apply the same voltage that the expensive Naim supply has but use batteries.

That is similar to the Phonomena only the Phonomena external supply has batteries and a charger. The preamp has an internal AC to DC converter, or you can buy the external battery supply and the internal AC - DC is disabled.

In your case, the Benz AC to DC conversion is done in the external supply (there isn't one internally) and this DC is applied to the phono stage. This makes it easier for you since you can use the same plug to supply DC from batteries instead of the external supply.

Unfortunately the Phonomena battery supply doesn't have enough voltage for your Benz. It has 16 NimHi batteries so in series that is 16 x 1.25V = 20 volts at full charge and closer to 19V (16 x 1.2v) when it is being used, and your supply is 24V. I would use 20 batteries since they do drop a bit from the fully charged 1.25 V so 20 x 1.2V = 24 volts, perfect.

If the preamp draws 250 mA then an 1100mAh battery pack (about $100) will get you around 4 hours and a 3000 mAh pack (around $150) will give you 12 hours. Not Bad. Add a charger with supply for a few hundred with a few connectors and switches and you are in business.

Herman,
Once again, thanks for all the info.

But it does leave me a bit confused. The limits of my electrical understanding must have been reached, so if this seems too elementary, bear with me.

I don't understand how the AC to DC conversion is done externally to the Lukaschek if the output from the WW is marked "24V 250mA, AC," rather than "24V 250mA,DC." The Lukaschek case, itself, is marked "24V, 3 VA" above the input connector -- a further confusing item for me.

Many of the WW's I have for, admittedly less complex, devices are marked DC on the output description. That makes it clear to me that these devices operate internally on DC.

I also e-m'd the distributor of the Phonomena and Benz about the output of the Phonomena, and their reply was that the Benz is AC while the Phonomena was DC.

So how does this all fit together? I understand what you have written about battery choice, etc. It also makes sense to me that the conversion from AC to DC for the Lukaschek would take place outside of the unit itself because of its small size. The output info on the WW and what's printed on the case of the Lukaschek, though.... The case of the Lukaschek is metal, and I assume that it is supposed to operate, at least partially, as a heat sink. It stays warm to the touch

I guess it's clear that the background issue is that I am concerned about frying this in some way, and this leads me to proceed with caution in what I might actually be a rather straightforward process.

So, what am I missing?

Thanks.

You are missing nothing, I was wrong. Sorry. I looked at some websites for info on the Benz and for some reason gathered that the supply to it was DC. I now look and see that it says right on the front of the unit that it is AC 24V 3VA.

The only way you are going to run this off batteries is to go inside the unit, figure out where DC regulators are, and feed DC from the batteries directly to the regulators. I doubt you want to do that.

Herman,
At least, I did manage to learn a good bit from this dialogue. You are right that feeding DC from the batteries directly to the regulators is something tht I don't want to attempt. Seemed like such a good idea, though....