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Originally posted by bangraman Given the incredibly average components that go into a headphone jack typically, are you saying that sticking a couple of resistors on it are going to make it better than, say, a META42?
OK, so how many average parts need to be upgraded to clean this up? How much difference do you think it would make?
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Just one song to the next folks, don't look for anything else
Just as an experiment (two 10 ohm 1/2 watt metal oxide resistors were $0.99 at Radio Shack), I installed the two resistors on my Crown amp to drive the K501. I was hoping that it would brighten the K501s.
Unfortunately they did nothing but compress the sound and dampen dynamics (or there wasn't any discernable difference). Conclusion? This may not (and probably will not) work on vintage solid state equipment that has the speaker outputs directly tied to the headphone jack. So vintage Crown, Marantz 1060, Fischer 400 amps need not apply this mod. In the case of the Crown (and probably the Marantz and Fischer, too) the amp will see an eight ohm (actually a little over 9 ohms) load instead of a 120 ohm load. To the amp it won't make any difference. It was able to drive the 120 ohm load, just like it can drive the 8 ohm load. This is why Joe inserts his disclaimer that if it doesn't change the over-all sound, then chances are that you do not need it because you probably do not have op amps driving the headphone jack circuit.
So in my case, Jan's tweaks did not work. Chances are that they would have worked, had I been using op-amp amps.
Headphoneus Supremus: His PortaCorda walked the Green Mile.
I think this was a case of mistaken expectations rather than 'it didn't work'. I'd pointed out that 'effect of output impedance depends on impedance response of headphones' in the thread with the same title (or something like that).
As you can see, the K501's impedance response goes up in the treble. Thus the treble gets emphasized with high output impedance. Conversely, if you lower the output impedance, the treble would be *de-emphasized*. This result is the opposite of what you were looking for and you may have thus concluded that the impeder was not helping matters.
If you want more treble from the K501 you should leave out the impeder or even add a series resistance (or better yet, use tone controls; after all, more series resistance has a negative effect on damping factor). I must say though that yours is a strange preference indeed
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End of my head-fi journey (for this year): Creative Nomad Zen NX -> Etymotics ER-4P
It is good for Plate Load OTL design like MG-Head OTL in OTL mode. TwinHead ..... OTL32 already have a 100 Ohm Resistor parallel in Output.
What change ? It will change the output impedance to lower and it will have better damping factor.
Oh ! It will lower the Output Voltage but It is no need on
very high sensitive Low impedance Cans like grado. So I suggest use not less than 100 Ohm if use high impedance cans. a 24 to 33 Ohm is good for 32 Ohm Cans.
I had test it 0n twinHead also but I only use 100 Ohm resistor only not 10 Ohm. 10 Ohm may be too low and damping it too much. So I suggest try 100 Ohm not 10 Ohm.
It will don't have effect in white Cathode follower design like Morgan Jones. It will drop the output to very low.
I had use this method on MG-Head OTL32 with good result. This unit is on Gino hand. It had a Impedance switch to chnage output impedance. Low impedance = 32 Ohm resistor , high impedance is 100 Ohm. I never try 10 Ohm due to I had calculate it by computer. 33 Ohm is more reasonable value.
Yes ! I had received it ! I already use this technique in OTL32 which is on Gino hand. Had you seen a High/Low switch in OTL32 ? OTL32 don't have a Output transformers ! How can I change impedance ? Yes ! Parallel a Difference value resistors. I had already discusss in Hong Kong Head-Fi meeting but not open in Head-fi only.
Yes ! It really can change sound on Plate Load or SRPP
type headphone amps. Also It can lower the noise when using
low high impedance cans. It lower the Output impedance , lower the output level but also lower the gain also.
MG-Head OTL have 2 Output Jack - You can parallel a resistor in 1 output jack and use other for listen. I think it is good idea to change impedance. I'm not consider to add a impedance switch on MG-Head OTL due to I don't have profite margin on it ! can afford a little more cost.
New Proto type of MG-Head OTL is on my test bench now. It seem to be in very good condition. Will be more relaible. Hum and Noise free , V.R change to shunt mode. It attenuated the level to 1/3. So You will not listen on lower V.R setting position. It can solve the problem on unbalance V.R in low level.
Mg_Head OTL can PS2 or PS3 to suppplier power.
PS2 - It have 6.3V FIlament supplier , a 9V Supply for HB1 low voltage supply. (a New Hybird Buffer amps with 6BQ5 x 2 , IRF150 x 2). It will be in a Metal Case. It can supply New MG-Head OTL , HB1 and may be some module comming later. e.g a Phono amplifier , Simple Line amp , OTL headphone simulair as Morgan Jones or your DIY amps ..... I also will open the design in my web and welcome any manufacturer supply module to support this power supply. I will start to design more power module later if this idea is accept by the user. Oh ! I forget ! You can buy its seperately. You can buy power supply , Gain Module only or anything you like.
PS3 - It is simulair as PS2 but no 9V DC supply for MoSFEt and it is in a Plastic case. So It can keep in cheap price. It is standard supply for New MG-Head OTL. PS2 can order in option.
Actually, Joe, the tips and tweaks section states:
"The headphone jackets on power amplifiers and receivers very often are directly connected to the loudspeaker outputs. To prevent damage to the headphones, resistors are placed in between. These resistors generally have values between 200 and 600 Ohm. On the other hand, radio's and CD-players have headphone jackets that are driven by an opamp with limited power and have much smaller impedance values (< 50 Ohm) between opamp and jacket.
"The resulting output resistance Ro of a headphone jacket has a major impact on the sound. Not only does it reduce the voltage seen by the headphone, it also changes the frequency characteristics of the sound.
"With most headphones, increasing the output impedance makes the headphone sound darker and more muddy (the amplifier loosens his grip/control on the movement of the driver). <damping>
"If your headphone sounds sharp and aggressive, you might consider increasing the effective output impedance of your headphone jacket.
"If your headphone sounds dark and muddy and is driven by an amplifier or receiver, you might try to decrease the effective output impedance.
" The value of the resistor should be 0.1 <to? or remove next "1"?> 1 times the impedance of the headphone drivers to have a noticable effect. However, be aware that with very low values of Ra your amplifier has to deliver a much higher signal to obtain the same sound pressure. This might have some adverse effects on sound quality by itself. Also be aware that the resistors should be able to dissipate enough heat!"
________________________________________________ BOLD and < > = emphasis mine
Yes, you are right about solid stae amps having a low output source impedance, and Jan did state that "you might try to decrease the effective output impedance." In my case it didn't have a dramatic improvement. So now I am looking to purchase the AKG K401 which is supposed to sound better with rock music. Barring that, I am trying to find out if the K401 drivers can be installed inside the K501 enclosures.
Headphoneus Supremus: His PortaCorda walked the Green Mile.
With most headphones, increasing the output impedance makes the headphone sound darker and more muddy
Note that he said *most* headphones. I believe the K501 is an exception because of its impedance response characteristics (see above).
The headphone and the series resistors divide the supply voltage by the following relationship:
Vp = V * Zp / (Zp + Zo)
Where
V = total voltage supplied by amplifier
Zp = Headphone impedance
Zo = Output impedance (from series resistor)
Vp = voltage across headphone transducer
The output impedance from the series resistor is constant across all frequencies while the headphone impedance varies across frequencies--the plot in my last post showed the variation of impedance with frequency for the K501.
Here's a typical impedance response graph:
Most headphones have an impedance bump in the bass. Something to do with chamber resonance frequency...
These phones would have their bass response bumped up when connected to a high impedance output.
Your K501 on the other hand has a high frequency bump, so has its treble response bumped up when connected to a high impedance output, simply because it grabs a bigger share of the voltage swing in the higher frequencies because of its higher impedance in that region.
Damping factor is also affected of course but this may or may not have an effect on overall frequency response It depends on what extra frequencies the phones tend to emit when underdamped, right?
I witnessed this myself--I don't have the k501 but I do have the etys, which when connected to the high output impedance of the MG Head sounded thin rather than dark. The HD580 do sound darker when connected directly to the OTL output than when connected in parallel with the impeder, but the etys actually warmed up instead.
So, it all depends on the phone...
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End of my head-fi journey (for this year): Creative Nomad Zen NX -> Etymotics ER-4P
Linear Mode
