Got a set of massdrop ESP95x today. The main purpose of the purchase was to get my hands on a E90.
some impressions:
the ESP95x phones:
-- Sound is brighter than the 950;
-- the velure pads are much more comfy than 950's pleather pads.
the E90 driver/energizer:
-- using the included wallward, voltage is 11.2v when the amp is on and idle (no music playing), Current draw 200mA. (wall AC outlet was at 121v)
********** caution, see the info at the end of this post.
-- thin plastic case; requires peeling off the aluminum face plate to fully open the unit, the face plate is rather thin and deforms easily (so don't do it unless you have to). If I end up modding this one I will put some details in the DIY section.
-- again do not open the case unless you have to. Very easy to get zapped by the high voltage from the top board (don't ask me how I know....)
sound impression of E90,
-- using the included wallward;
-- driving a pair of ESP950
-- signal source is a modded Fiio X3 classic (Mundorf SIO caps for line-out)
-- music (all FLAC from CDs): some Eva Cassidy songs, and Led Zeppelin concert live (the song remains the same).
compare to a modded SRM-Xh, a SRM-212, and a SRM-1 (not MK2):
* a lot less emotion from the E90 when listening to Eva Cassidy, everything (that I can hear) was clean and clear but there was not much of the emotional "feel" in the songs. Somehow it feels like the E90 might have some kind of background noise, not very obvious but is there, that might have prevented the emotions from coming out.
* live concert recording tracks: E90 was missing a lot of ambient details, just didn't have the "there" feel (not even "pretending" to be there). The live concert recording sounded more like a studio recording.
* bass from the E90 was not stronger than bass from the xh or the 212 (212 has slightly more solid bass than the xh)
I later changed the E90 power source to a AAx6 7.2v NimH battery pack (fully charged, provides 8v when running the E90 at medium volume), the background was somewhat cleaner but the emotion part was still lacking.
************ opened up the E90 a little more and took a closer look at the boards, and....
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power input reservoir cap C33 is 2200uf/10v (this cap is always connected to the power input jack, whether the amp switch is on or not).
So it is, at least in theory, NOT OK TO USE voltage higher than 10v. However the Koss stock wallward outputs 13.3v no load and 11.2v idle, and C33 will see these voltages as long as the wallward is plugged in.....not sure why C33 survives. Maybe it is super grade stuff.
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photos in the DIY section.