[Lvivske]

On my Pioneer 7500, which I use as a headphone amp, I was wondering if anyone knew what impact, if any, changing the resistors before the headphone jack would do? Either upgrading to an 'audiophile' part (versus whatever they used on the assembly line back then) or messing with the values

The stock ones in my unit are 'metal oxide' 2W 150ohm

 

[tomb]

Yes, you would most likely perceive a difference if you used something besides metal oxide, especially at 150 ohms. I recommend a pair of Kiwame in the same rating. They are wonderful "audiophile" resistors - sweet, with great detail. You can look them up at Partsconnexion.com, but don't buy them there. They are actually KOA resistors that can be purchased at Mouser. I sell them, too, btw.

 

[Lvivske]

Yes, you would most likely perceive a difference if you used something besides metal oxide, especially at 150 ohms. I recommend a pair of Kiwame in the same rating. They are wonderful "audiophile" resistors - sweet, with great detail. You can look them up at Partsconnexion.com, but don't buy them there. They are actually KOA resistors that can be purchased at Mouser. I sell them, too, btw.

They're only $1 on partsconnection, what are your margins like?

 

[tomb]

They're only $1 on partsconnection, what are your margins like?

I guess they lowered their price over the years, given the knowledge about what they really were (KOA).* I have sold them at that price for over 10 years. As it happens, I'm out of stock on the 150 ohm anyway.

You're in Canada, so you should go ahead and order them from PartsConnexion. You won't suffer the extra shipping costs those of us in mainland USA experience from PartsConnexion. My opinion still stands about the Kiwame/KOA resistors - they are worth the money, at least at $1 each.

* Pete Millett, one of the original pioneers of headphone amplifiers (he is Apex Audio), discovered this about the "Kiwame" resistors after ordering the KOA from Mouser, taking them both apart and reporting here on Head-Fi, that they were identical.

 

[Lvivske]

I guess they lowered their price over the years, given the knowledge about what they really were (KOA).* I have sold them at that price for over 10 years. As it happens, I'm out of stock on the 150 ohm anyway.

You're in Canada, so you should go ahead and order them from PartsConnexion. You won't suffer the extra shipping costs those of us in mainland USA experience from PartsConnexion. My opinion still stands about the Kiwame/KOA resistors - they are worth the money, at least at $1 each.

* Pete Millett, one of the original pioneers of headphone amplifiers (he is Apex Audio), discovered this about the "Kiwame" resistors after ordering the KOA from Mouser, taking them both apart and reporting here on Head-Fi, that they were identical.

haha well they're a short drive away so I go to them for other normal parts (though I was looking at the gold plated amtrans ones because I have issues...)

but as far as ratings go, dont mess with stock? a tech who worked on it (and never actually did the fix he suggested) once told me

headphone noise is due to the design of the circuit leading to the headphone jack not sending enough signal to ground, and getting rid of it would most likely require replacing the resistors in that circuit with different valued ones

He was wrong about the noise but it's had me thinking ever since what different values would achieve

 

[tomb]

He was wrong about the noise but it's had me thinking ever since what different values would achieve

You have to be very careful about that. Those resistors are there to cut the voltage and power down from a receiver that's primarily designed to power speakers.

It's true that the lower the resistor value, the more "transparent" will be the signal. However, 150ohms is also there to block the current and power buildup. Using ohm's law, 10V at 150ohms will result in 67ma. More importantly, the resistor only has to withstand 0.67W. Lower that resistor to 75 ohms, it'll have to withstand 1.3W. In electronics, you never, ever, ever, want a resistor to burn up, so you always specify at least 2X rating, which means you'd need at least 3W resistor. I'm not sure those are widely available. After 2W, resistors typically go up to 5W ratings and you'll never find them in an audio quality. (Not to mention that they are about 2 inches long and as thick as a pencil.)

Lower the resistor to something even more reasonable for headphones, like 32 or 10, and your headphones will burn up from the voltage, regardless of how long it takes for the resistor to burn up.

Your service rep could be talking about a voltage divider circuit, but that involves even more resistors and high-powered ones to ground. You'd still be playing with fire (literally?) to plug your headphones into it.

This is the downside to using vintage receiver equipment with modern headphones. They were never designed with separate amplifier circuits for the headphone connection. Heck, go back far enough and headphones were in thousands of ohms impedance (crystal sets). They had no issue because the super-high impedance prevented damaging current and therefore, power buildup.

Sorry, but a good receiver for headphone use is one that has a separate amplification circuit for the headphone connection. This is typically some sort of opamp with associated capacitors and resistors ahead of the headphone jack. It's not competitive with a true separate headphone amp, but it's better than just current blocking resistors.

P.S. I'm making a lot of assumptions without looking at the entire schematic of your receiver. If it has a separate opamp amplification circuit for the headphone jack and is still using 150 ohm resistors, then yes, you may very well get superior sound with lower resistors ... and without having to worry about burning something up. I'm assuming that's highly unlikely with resistors as high as 150 ohms, however.

 

[Lvivske]

After 2W, resistors typically go up to 5W ratings and you'll never find them in an audio quality. (Not to mention that they are about 2 inches long and as thick as a pencil.)

There's actually a few small 5W's on partsconnection, Kiwame no less

Sorry, but a good receiver for headphone use is one that has a separate amplification circuit for the headphone connection. This is typically some sort of opamp with associated capacitors and resistors ahead of the headphone jack. It's not competitive with a true separate headphone amp, but it's better than just current blocking resistors.

Funny enough that's usually why people knock integrated amps: "They have opamps and other resistors in the signal that ruin the sound", and why some people recommend speaker taps

I'm assuming that's highly unlikely with resistors as high as 150 ohms, however.

Correct, this is an older model without an op-amp and just the resistors

 

[tomb]

There's actually a few small 5W's on partsconnection, Kiwame no less



Funny enough that's usually why people knock integrated amps: "They have opamps and other resistors in the signal that ruin the sound", and why some people recommend speaker taps



Correct, this is an older model without an op-amp and just the resistors

Yep - I was definitely "assuming" a receiver, not an integrated amp, but the same comments apply.

I suppose if someone is "stuck" on vintage receivers or integrated amps (not speaking about you personally), going from the speaker taps would yield a purer signal. However, it's still a speaker amplifier, not a headphone amplifier. This may shock some, but I'd bet dollars to donuts that an opamp-based amplifier optimized for headphones is going to sound 100% better with most headphones than a non-opamp-based amplifier optimized for speakers.

 

[Lvivske]

Yep - I was definitely "assuming" a receiver, not an integrated amp, but the same comments apply.

I suppose if someone is "stuck" on vintage receivers or integrated amps (not speaking about you personally), going from the speaker taps would yield a purer signal. However, it's still a speaker amplifier, not a headphone amplifier. This may shock some, but I'd bet dollars to donuts that an opamp-based amplifier optimized for headphones is going to sound 100% better with most headphones than a non-opamp-based amplifier optimized for speakers.

The argument against vintage or consumer grade op-amp headphone sections is usually "they are an afterthought on a speaker amp and generally suck" (just going by what people have ripped me for time and time again)

but I have other amps for different things, the headphone section on this is wonderful since restoring and I'm just trying to mod/tweak what I can if its possible to make it better

as far as resistors go...better off going 47R 5W or trying stock 150R 2W but flashy?

 

[SilverEars]

Those resistors are the reason why receiver headphone output sucks, and there are dedicated headphone amps. That's output impedance for your headphones that would skew the headphone response or tonality of what was originally intended. You are still going to get tonal skews from the resistor no matter the type. The resistance is still there that effects the overal circuit response with the headphone attached.

Those resistors are basically protecting your headphone from being fried especially if they are sensitive headphones. HE-6 on the other hand is a different story.

There you have it. Headphone amps exists for a reason.

 

[Lvivske]

Those resistors are the reason why receiver headphone output sucks, and there are dedicated headphone amps.

There's always gotta be a troll

 

[SilverEars]

What a hobby with people of all kinds. lol Enjoy your amp with the changed resister.

 

[pravous]

Sorry to necro the thread but I am in a similar situation. Just recently purchased a vintage Sanui amp which sounds amazing with my ZMF Atriums. Currently recapping it and figured I might change the headphone jack resistors. What resistor did you end up going with and was it noticeable?

 

[tomb]

Sorry to necro the thread but I am in a similar situation. Just recently purchased a vintage Sanui amp which sounds amazing with my ZMF Atriums. Currently recapping it and figured I might change the headphone jack resistors. What resistor did you end up going with and was it noticeable?

If you read the entire thread, you will note that the resistor values are there specifically to protect headphones from the voltage available in a speaker amp. You risk blowing your headphones if you change the values - the previous post explaining that was in no way a "troll."

As for brands, I would still recommend the Kiwames as the best for biggest bang for the buck. There are many more that you could try, just take a look at the offerings on PartsConnexion or similar shops. Stick with the same ratings you have, however, or your headphones could be at risk.

 

[pravous]

Was planning on staying with the same values. Ordered some 5w Kiwame 220r to replace the cement 3w 220r.