ppav2??
dun simpan
share with us

i'm afraid i can be "kurus keding" if i buy this.

what's urs? come on.

thx for the input

may i know y must get a high current amp? because of the high impedence so the amp can drive the hp easily?

my 555 can be drove easily without amp, however, i do think that there is still room for improvement fot this hp..
do u mean that 555 suites better with an high current amp as well?



please, do share


This post has been edited by yeahs4.1: Sep 6 2006, 05:58 PM

It is commonly accepted that high impedance or hiZ phone need higher voltage to werk, ohms power law, P=VI, I=V/R, thus P=V^2/R and in current form P=R*I^2. For the same amount of power (as defined by system synergy of amp+headphone), hiZ would require more voltage than current. EG, two headphone, 1=200ohm, 2=50ohm. For an input power of 1W, headphone 1 would require 10V and 50mA while headphone 2 would require 5v and 100mA to produce the same output power, well, technically. So theres the reason for a high current amp. But this is a generalization and shoud not account any headphones, but a rough idea.

Extra useless info if u guys are more technical..


So, u are asking improvement with the HD555. It can be easily driven, no fuss there, 50ohm is not much (but SHP895 32ohm acts like a 500ohm megaphones, hard as hell to drive, so no generalization). I dun want to explain more than i should, so make a long long time ago past experience as a point, i had a HD555 before and tested them from my unamped emu 1212m output (this card was never designed to drive anything directly, thus the extremely low level of volume n clarity). Paired it with a CMOY and the volume gets ramped and all the details are there, visible since before, the small detail variations in the signal was not enough to move the transducers. There was major improvement, but maybe its because the original output is just weak. After a while, i procured sum ic discreet current buffer and paired it up. i laughed my heads off due to the VAST difference. The bass is very impactful and everything else has just gone three nothces up!



About my humiliation, not that i am a solid state guy, i love tubes, but honestly i have never tested them, but warnings were thrown at me not to waste my time on them..hehe! This i hope is no offence but to me, a pure solid state amplifier with a highly bias output stage is the BANG! for example the PPA-V2 and M3. Actually a PIMETA works quite well. A short circuited LDM+ or PA2v2 over HD555 can only give a 60mA current (if the battery can supply tat and thus as explained, these are only super low voltage opamp based amplifiers, thus wat u get are low voltage and lower current.

Aiyo..wat a long post..i blabber to much, sorry yea! Im sure sumone would come n flame me, but feel free to do so, i wont fight back

P/S, yeahs 4.1, hows ur first experience with the HD555? it aint comfortable but its tat musical for that price range

so far i am very satisfy with the hp.. love the sound although it is still in burn in process.. however, my ears do feel fatigue quite fast, about half an hour of listening.. i dunno y.. mayb my ears cant stand in closed place without sufficient air supply.. haha..

i took half an hour to digest ur post, do a little maths and ohm''s law, still got a little blurry.. nvm.. it takes time to digest..

i am planning to get LD2+, and the worst thing is i am not very good with the specs:

Frenquency response: 10HZ to 35KHZ (-3db)
Distortion: <=1% (50mW, 300ohm)
<=3% (92mW, 300 ohm)
Power handling capacity: 35W (under alternating current situation)
Output terminal: 6.5mm Mic Jack
Input terminal: RCA Jack
Can drive headphones with 30 ohm to 600 ohm

i dont see any statement that shows high or low current, mayb u can teach me how to do the maths a little there.. ( i dunno how i calculate, but looks like i got 31mA running for 50ohm, correct me pls.. )

will it be a wise choice then?

@ijan
thank for explaination
yeah i learn alot there

me oso intrested to knw that

This im not that knowledgeable, its related to audio engineering which is way different than electronics. But from an electronic POV, the frequency response of the LD2+ is respectable, power handling capacity is quite high, meaning the main purpose of the LD2+ aint only for headphones and seems to be focused more on HiFi setup either as a pre-amp or small power power amp.

HOWEVER, look at the THD, its quite bad with high impedance phone when higher current is needed (translates to higher volume, dynamics bla bla bla). Seeing it from a HD555 50ohm impedance, its impossible to say the THD the 555 is seeing deue to THD unlinearity, needs a plot of the THD in order to know, but in no way is it going to be less than 0.1%. 0.1% THD is still not that bad, audio opamps usually haf their THD in the 0.00001% or smaller region, this might give sum echo of unwanted signal in the output, but maybe thats how tubes are. If im no mistaken, tubes haf THD in the even number while ss has them in odds, and tubes are naturally more distorted (higher THD) than its SS brethren.

So in any other way, LD2+ seems to be good for a tube, cos i dun really know how tube response, u haf tow ait for TUBE guys to come in. For a SS to haf that specification, that SS amps would not be the better of anything. But in the end, its a mtter of preperences, sum high end amps distorts the signal n ppl like it more. the 1212m almost pure, no coloration and distortation, yet ppl find it bland and boring.

V=IR
P=I^2 * R or P= V^2 / R



I^2=P/R
I^2=0.05/300
I=sqrt(0.05/300) = 0.013A (13mA)

Vrms=0.013*300=3.9

The THD is <=1% when the amp is driving a 300ohm phone (say a sennheiser) at 3.9Vrms.


I^2=P/R
I^2=0.092/300
I=sqrt(0.092/300) = 0.018A (18mA)

Vrms=0.018*300=5.4

The THD is <=3% when the amp is driving a 300ohm phone at 5.4Vrms.

How loud is 3.9Vrms or 5.4Vrms? take a test tone generator and play a 1khz freq @ 0db. Take your multimeter and take the measuremet at that volume then plug in ur headphone and give it a try.


let's say you are listening to a volume of 6Vrms with your 555, your headphone is sucking up:
V/R=I
6/50=0.12A (120mA)
P=0.12^2 * 50 =0.72W (720mW)

50mW, THD <=1%
92mW, THD <=3%
120mW, THD <=

gotta love tube amps.

So, you can see from the above example that low impedance phone suck up ALOT more current than high impedance phone. Whereas high impedance phone requires alot more voltage swing than low impedance phones. That's why you need an amp capable of delivering lot's of current for low imp phone. Cmoy works better with high imp phones than low imp phones

ps: you prolly wont listen to it at 6Vrms i was just exaggerating

This post has been edited by AlamakLor: Sep 7 2006, 01:24 PM

Found Corda Headfive in Headfi forum.

Measures: 10,5 x 18 x 6 cm

Weight: 0.7 kg

Power supply: 110/115 or 220/230 Volts switchable

Power uptake: 3 Watts

Maximal amplification (1 kHz): 10 dB

Maximum output: 12 Volts

Input impedance: 12 kOhm

Output impedance: < 1 Ohm

How can I compare like the above one?

how does it compare? you can barely tell how an audio equipment sounds from spec, they usually just let u know what it can do and how well the amp does it.

the amp has a gain of 3:
20 log 3 = 9.5db(10)

the amp can do 12Vrms, and has a maximum power handling of 3W.

WOW! 3W vs LD2+ 35W....wtf mate? no worries...the head-five is a headamp, the LD2+ works as a speaker amp. You'd barely need more than 1W(1000mW) of power for a headphone.

EDIT: Sometimes when you read the spec (and if you understand it) you will find some of them very funny. Here's one:


LMAO......basically, they are implying that you can take the v700dj, plug it into the head-five and blast it at 90% (dun go 100%) of the volume I think all you could hear would be distortion. The k701 on the other hand can only handle 200mW of power...

This post has been edited by AlamakLor: Sep 7 2006, 09:25 PM

if the amp is driving 50ohm senn,
it sucks up 31mA ( 3 times the 300ohm does )
and Vrms = 1.55 Vrms

so, the THD is <= 1% when the amp is driving a 50ohm at 1.55 Vrms?
in other words, the THD for driving 50 ohm phone is quite high although it's in low volume, right?


y u still like tubes le?

you get different distortion with different loads but u can just take it as it is (<=1%)...so yeah, around 1% THD. Compared to solid state...yes...it is very high, that's the "beauty" of tubes. BUT having higher THD doesnt mean that it will sound worse than those amps with less THD...it just means that the sound you are hearing is less original - more coloration. If you want something that sounds as close to linear as possible, you should avoid tubes.

why i still like tubes? I dont really like them....I was just being cynical, as usual . Tubes have their pros n cons...but at the end of the day, whatever sounds best is all that matters...it;s not the numbers that you are hearing anyway, it's the sound the amp puts out.

Solid state can be modified to sound like tube(with tube buffers), but tube can't really be made to sound like solid state. I'm a solid state guy myself.


btw, amps are rated by their power handling capabilities. Current and voltage are components of power. You should already understand by now how much current/voltage a headphone would need by now, and whether the amp could "drive" them.

There are other things people should know. Having more Gain(signal amplification) doesnt bring any benefits...but they definitely bring disadvantages. If you are designing your own amp, particularly for personal use, you should only allocate just enough gain to drive your phone to max volume you'd ever hear. Another funny thing is that many ppl think that when amp A needs only 40% volume to drive a phone/speaker to a particular volume, while amp B needs 70% volume...they's start to assume that amp A can drive the phone and amp B can't. Truth is, as long as you can get the volume you want, that means the amp can drive it..end of story. Amp A simply has more gain, more noise, and if not coupled, should have even higher dc offset.

This post has been edited by AlamakLor: Sep 7 2006, 06:24 PM

gonna give ld2+ a try after this, else, gonna look for other choice..
thx a lot..

dun wanna support my portable amp? it's designed with a topology not used in any headphone amp yet and made particularly for low imp phones

this 1??
where can find the info and spec?

soon but not so soon, I need to order parts for the amp first just to verify that the component layout is correct. then prototype boards take a week to get to me..if everything goes right...should have them in production by end of the month.

spec wise...
-output impedance 1ohm
-three channel configuration
-trickle charger circuit
-battery life should be 20+ hours or more
-gain of 2
-powered by one 9V batt
-integrated battery charger, can be wall powered
-secret topology ()
-it will take in all low power opamps...will require four of them. (duh )
-power handling depends on the opamp used, will be using 227 as std version, max current output would be 180mA with them.

this sucker is made for performance...not for the looks...so they will be priced fairly.

This post has been edited by AlamakLor: Sep 7 2006, 07:00 PM

so lame

looks very nice. It's going to be in a mint tin?

Btw, about something you said about gain. Some opamps needs a certain level of gain then only they will be stable right? If so then gain isnt something that we should go as low as possible eventhough the user prefers low volumes right? (Example: 627BP and 637BP) Please fill me with knowledge, my ignorance begs for your education

EDIT: Quote went haywire.

This post has been edited by LittleGhost: Sep 7 2006, 08:44 PM