Shoot-out, AC / DC
while the blackgates and Sonic caps are still being bombarded/tortured by friendly musical electrons, lets talk about power.... Obviously the best power source is large capacity pure DC ( ie battery banks), but AC adaptors are (or can be) still great for desktop use, since they just keep on going 24/7. The most commonly found/used AC adaptors are the Sony and Panasonic 4.5V discman wallwarts. Here is a review on the sonic difference between these wallwarts. We will also take a look at higher power options, ie. regulated power supply.
(Left to right: Sony 4.5V/500mA; Panasonic 4.5v/800mA; modified 5V/1A, originally for external zip drives)
Everything in the SRM-001 is done like what will be in a FatCat class mod, except the input electrolytics are still 22uf tantalum (since the blackgates NX's are still being burnt in). C17/18 are using 220uf/16v miniature aluminum electrolytics, C26/27 are 47uf BlackGates PK miniature (you can also use the same 220uf/16 as in C17/18 position, I installed PK because I am out of 220uf miniatures). The results below will be what happen with these power sources driving a FatCat SRM-001 (SRM-001-FC?).
Now the shoot-out:
--in previous posts I have mentioned this wallwart gave a hum.... that was during minimun cap size testing, and with the AD825 installed. In the FatCat/SuperFatCat mod we use 220uf +/- caps and 8599, with this configuration there is basically no hum from any of the wallwarts.
--The sound: a little layback and distant; has a emphasis in mids therefore showes vocal charactoristic very well, especially if the voice is "raspy and gritty". Some minute details don't stand out very well, possibly due to the mids emphasis, this gives a false sense of "cleaner" sound when playing vocal tracks. Strong bass, good texture. The sound stage is the narrowest of the group.
-- measures 4.61V under load.
-- the first thing you will notice is the sound is Soft. Showes details better than the Panasonic, larger sound stage. Bass is a little drier, and not showing bass texture very well. Kind of strange, all the details are there, but I sense a layer of haze.....
-- measures 4.67V under load.
*Modified 5v/1A regulated zip wallwart.
-- the zip wallwart requires quite some modification, first of all you will have to change the plug to fit the SRM's jack. In my previous posts I have mentioned when the zip wallwart (before mod) was plugged in, the sound was good for the first 2 seconds then got very bad. I first thought the slightly higher voltage (5V vs. 4.6v) caused the SRM's inverter to act up, but latter thought it could be the inverter's pulse spikes going back into the wallwart and confused the regulator chip. Now it seems that the pulse spike is indeed the cause. After adding a CLC filtering circuit (regulator -> 2200uf cap -> small coil -> 4400uf cap ->output), the wallwart now works very well. The purpose of the filter stage is mainly to prevent the high frequency inverter pulse from reaching regulator. The 4400uf cap also acts as a power reservoir, it might not have to be that big, I put it in simply because I had one laying around and it would fit into the case.
-- The sound is analytical, well, kind of. Showes lots of details clearly, great bass thump(relatively speaking) and texture. It manage to show the sounds a lot better than the above two without letting you enjoy a lot more.....
Strangly wide sound stage, almost speaker like (again, relatively speaking), the sound field is diffused and doesn't allow easy instrument pin-pointing.
-- voltage is 5.04V, regulated, same voltage loaded or not.
* DC! Lithium batteries, 2000mAH capacity.
-- I used two 14650 in parallel, they are older cell phone pack batteries so the capacity is only 2AH total. If you use the newest ultrafire 14500 (AA size, 900mAH each) you will get 1800mAH with two in parallel, the result should be the same as my test setup.
-- The batteries are about 3/4 full when tested, at 3.85V.
-- The cleanest sound so far, crispy and clear; intimate vocal, even better than the panasonic. It has the best bass thump, though the texture is slightly less "visible" than the modified zip wallwart. Sound stage wise is slightly larger than the Sony.
It really surprised me that the power source actually made this much difference, I used to think since there is a step-up inverter inside the SRM-001 (all the actual amp power come from the inverter), the wallwarts should work the same as long as they provide enough current.... how wrong I was.
Here is a summary of this power source comparison:
(in the order of best -> not so great)
*Bass thump: Lithium -> modified zip wallwart -> Panasonic -> Sony
*Bass texture: Modified zip wallwart -> lithium -> Panasonic -> Sony
*Vocal/mids: Lithium -> Panasonic -> Modified zip -> Sony
*Details (high/mids fineness): Lithium & modified zip -> Sony -> Panasonic
*Sound stage(wide -> narrow): Modified zip -> Lithium -> Sony -> Panasonic
*sound locating: Lithium -> Panasonic -> Sony -> modified zip
As we can see, the DC power is indeed the best overall, and the regulated high output power source doesn't necesary do that well. I have no idea why the Sony and Panasonic sound so different, they are just transformer/diodes/capacitor, unregulated output, both at 4.6V level...
-- Pure DC is the best, get a bunch of 14500 lithium rechargable batteries and call it good
-- If you already have a wallwart of some kind and want to "upgrade" to a big-axx bench-top supply, well the expensive and super-stiff bench-tops might not give the best results with the SRM-001. Meanwhile, the smaller/lesser/more-cheaply-made regulated supplies might not work(or not as well as it could be) due to the inverter spike situation, some modification might be needed.... well, might as well inverst the benchtop PSU money for lithium rechargables and keep the wallwart for warm up purpose.
-- or, if you have tax return $$ burning holes in your pocket/wallet/purse, get a bunch of different 4.5v-5v power supplies and do the experiment yourself, one will work best for a certain type of music while the other one best for another genre. Panasonic will be good for vocal (only), while a regulate supply, with that much details and good bass and super wide diffused sound stage will be the best for trence..... kind of like keeping different headphones you see
(I can't believe I put down this much BS just on power sources, it was supposed to be a short review....