Battery-powered transports

Thanks Dave. I'm not handy but I know those who are. When you say 12V, are suggesting using a 12V car battey?

I'm trying to come up with a list of criteria that account for one transport sounding better than another. I know there is much more to it than reading 1s and 0s.
Why, for instance, does the Zanden tranport at $25,000 sound so much better than an Accustic Arts tranport at $5,000 when both of them are built around the same Philips mechanism?

Many of the top transports use the same Philips mechanism at heart. The manufacturers then put some thought and expense into vibration control. They then put effort into designing a good power supply.
Am I correct in assuming that an inexpensive transport (with a good Philips mechanism and good vibration control) could be made to sound as good as a very expensive transport simply by replacing its poor power supply with a 12 V battery?

I can try to answer this question from the perspective of my Sony project, where I took cues from pro modders like Reference Audio Mods, VSEI, and Richard Kern, and added my own tweaks. In selecting a mule platform, the analog section of a CDP doesn't matter much, as it is typically replaced. I believe pro modders select their mule platforms based on the quality of the transport section circuitry (not so much the the opto/mechanical elements, which as you point out are typically unmodified Philips; custom opto/mechanicals such found in the SCD-1 or the new Esoterics may be better yet.) There is fairly wide divergence between original manufacturers in the design/execution of transport circuitry. This becomes a gating factor, as these circuits are difficult to modify given the complexity of the VSLI chips & the high density of surface-mount components. So in order to obviate the problem of redesign, modders select transport sections with well-designed circuits and concentrate on mods to power & perhaps replacement of the master clock & parts-bin quality surface-mount components in the critical paths. I bet Zanden and the other hi-end transport manufacturers take a similar approach based on OEM circuit boards.

Modifications to power make a huge difference in the performance of the DSPs. I learned that even the best AC/DC discrete DC regulation I could find in the aftermarket could not match the sound of batteries, together with increased capacitance at the application and discrete DC regulation in place of stock cascaded 3-pin regulators. The best sounding batteries have low internal resistance in the 2 milliohm range-- which cannot be obtained with compact batteries such as alkaline, NiMH, or lithium. To get to this level you need high amp-hour, sealed lead-acid batteries with thin-plate technology, such as Odyssey PC2150 or Optima Yellow Top. Their size and weight would limit their appeal to commercial manufacturers. Also, it's critical to attend to DC trunk wiring of adequate thickness & quality and to use fast filtering capacitors at the application. I can't imagine that hi-end manufacturers with more portable battery-powered components can achieve this level of performance. I LOL at photos of the bank of D-sized alkalines inside a Sutherland phono stage.

Finally, the ability of the tranport/DAC combo to work together at a high level will be limited by the interface (I2S, PDIF, clock-link, etc.) One reason why I decided to mod a CDP rather than a combo.

Dave

Thanks very much.
The DAC was designed using an Optima Red Top but it can be used with any 12V battery. Is the Yellow Top superior to the Red Top?

If I'm reading the spec sheets correctly, the Yellow Top has the edge over the Red Top associated with slightly lower internal resistance and deep cycle capability (meaning it can be discharged to a lower voltage without incurring damage; the low limit is about 10.5V). The Odyssey PC2150 is also deep cycle and has the lowest internal resistance of the three. I am currently using both the Odyssey and the Yellow Top. The Odyssey sounds faster, more dynamic, more resolved-- a clear step up. It is about twice the cost tho ($250 at batterymart.com)

Hope this helps.

Red Top:

http://www.optimabatteries.com/publish/optima/americas0/en/config/product_info/automotive/starter/technical_specs.html

Yellow Top:

http://www.optimabatteries.com/publish/optima/americas0/en/config/product_info/automotive/deep_cycle/spec_sheets.RowPar.0001.ContentPar.0001.ColumnPar.0004.File.tmp/D34_082104.pdf

Odyssey

http://www.odysseyfactory.com/specs.htm

Great; I'll go with the Odyssey PC2150.