[penmarker]

So the previous owner/technician decided its better to drill holes and run wires through, than to change the pinch posts.
Well... if it works, it works.

 

[i luvmusic 2]

It does work however it is not safe because if you're not careful it is easy to short those speaker wires they are exposed it does work for the previous owner but not for me not comfortable with those flying leads.

 

[AWP3888]

Oh man, I can't believe its been over 2 years since I started using that Pioneer SX-580 for a headphone amp. Full disclosure: my last post on this was way back in 2015!
Still going strong, I use it 5 days out of the week to listen to while working at my desk. so that's going on about 500+ days (5 days/week) at anywhere from 4 to 8 hours listening. I get tired of my headphones before I ever get tired of the amp output. As to the questions above (that I never answered in a timely fashion) I plug into the Receiver at the Headphone Jack on the front face using the larger headphone-jack adapter that downsizes for a 3.5 stereo "mini" jack, which then has the extension plugged in which winds its way around my desk to the jack for the headphones themselves. Overall I am very pleased with this setup, especially since it obviously have power to spare, but more importantly the Bass and Treble control knobs allow me to adjust the output reduce or increase as needed (yes they work very well). And I have not had to replace that headphone-out stage resistor yet ( thank you Pioneer Japan Corp.).

I have been contemplating adding a DAC, because the output form my desktop workstation is ... well frankly its just crap. My android phone is better, but only just so. I've been following Schiit-Audio for a while and I believe I am close to pulling the trigger on a Modi-2. The other half of that equation is the headphones, which I began with a cheap pair of skullcandy over-ear closed backs, and then I went to the HiFi-man Waterline 400 ear-buds (which now reside in my back-pack so I don't forget them when I go to the gym).
Now I find myself looking into on-ear or over-ear closed back headphones to use. Recently I have been looking at the Beyerdyamnic 1350 and the Sennheiser 25 HD. Don't get me wrong, I enjoy my 400's, but there is only so long my ear holes will tolerate those (my ears hate ear-plugs in general so...). Then sometimes I wander over to the beautiful things like the Meze 99s. Oh curse you Budgets, Curse you! All the money in the world ...

My biggest consideration is both comfort and lightweight. Yes I care about sound quality, that's why we're all here. But for 4-to-8 hours of non-stop music I do not need to induce neck problems and a headache at the end of the day. So if any one has a good suggestion for a good pair in the $200-$300 budget range (or less), let me know your thoughts.

So I have the beefy Amp/Reciever and I'm sure a DAC will do wonders for that. Now comes the math questions: Will a Pioneer SX-580 with a 680-R1w resistor on the headphone output handle headphones with High Impedance. SX-580 is spec'd at 20-watts into 8-Ohms per channel (reduced at the headphone jack of course). But will it survive running the 25-HDs which have an impedance of 70-ohms (granted that's at like 200 Milli-watts) or the 1350's at 80 ohms. I'm sure in shear output an SX-580 could do the job from the actual speaker outputs (and blowup the drives doing it), it's getting that from the Headphone out on the front face that is the goal.

But I digress, the Pioneer SX-580 works and works very well for a headphone amp. AND considering what one of those, or even the older brother SX-550 or SX-450 receivers, cost on the the ol' craiglist and ebay it might be a better deal than buying that very dedicated brand-new headphone amp the rest of you may have been eyeball'n. Sure all the controls are analog, but that's part of the fun right?!!! Old vintage late-1970's receiver for a headphone amp, with built-in AM/FM too, is good stuff in my book.
Oh, did I mention I have a built-in PHONO stage on that SX-580 also? No? Shame on me. :-D

... Wonder if my wife will let me get another one, hmmmmmm ...

 

[K1030]

Oh man, I can't believe its been over 2 years since I started using that Pioneer SX-580 for a headphone amp. Full disclosure: my last post on this was way back in 2015!
Still going strong, I use it 5 days out of the week to listen to while working at my desk. so that's going on about 500+ days (5 days/week) at anywhere from 4 to 8 hours listening. I get tired of my headphones before I ever get tired of the amp output. As to the questions above (that I never answered in a timely fashion) I plug into the Receiver at the Headphone Jack on the front face using the larger headphone-jack adapter that downsizes for a 3.5 stereo "mini" jack, which then has the extension plugged in which winds its way around my desk to the jack for the headphones themselves. Overall I am very pleased with this setup, especially since it obviously have power to spare, but more importantly the Bass and Treble control knobs allow me to adjust the output reduce or increase as needed (yes they work very well). And I have not had to replace that headphone-out stage resistor yet ( thank you Pioneer Japan Corp.).

I have been contemplating adding a DAC, because the output form my desktop workstation is ... well frankly its just crap. My android phone is better, but only just so. I've been following Schiit-Audio for a while and I believe I am close to pulling the trigger on a Modi-2. The other half of that equation is the headphones, which I began with a cheap pair of skullcandy over-ear closed backs, and then I went to the HiFi-man Waterline 400 ear-buds (which now reside in my back-pack so I don't forget them when I go to the gym).
Now I find myself looking into on-ear or over-ear closed back headphones to use. Recently I have been looking at the Beyerdyamnic 1350 and the Sennheiser 25 HD. Don't get me wrong, I enjoy my 400's, but there is only so long my ear holes will tolerate those (my ears hate ear-plugs in general so...). Then sometimes I wander over to the beautiful things like the Meze 99s. Oh curse you Budgets, Curse you! All the money in the world ...

My biggest consideration is both comfort and lightweight. Yes I care about sound quality, that's why we're all here. But for 4-to-8 hours of non-stop music I do not need to induce neck problems and a headache at the end of the day. So if any one has a good suggestion for a good pair in the $200-$300 budget range (or less), let me know your thoughts.

So I have the beefy Amp/Reciever and I'm sure a DAC will do wonders for that. Now comes the math questions: Will a Pioneer SX-580 with a 680-R1w resistor on the headphone output handle headphones with High Impedance. SX-580 is spec'd at 20-watts into 8-Ohms per channel (reduced at the headphone jack of course). But will it survive running the 25-HDs which have an impedance of 70-ohms (granted that's at like 200 Milli-watts) or the 1350's at 80 ohms. I'm sure in shear output an SX-580 could do the job from the actual speaker outputs (and blowup the drives doing it), it's getting that from the Headphone out on the front face that is the goal.

But I digress, the Pioneer SX-580 works and works very well for a headphone amp. AND considering what one of those, or even the older brother SX-550 or SX-450 receivers, cost on the the ol' craiglist and ebay it might be a better deal than buying that very dedicated brand-new headphone amp the rest of you may have been eyeball'n. Sure all the controls are analog, but that's part of the fun right?!!! Old vintage late-1970's receiver for a headphone amp, with built-in AM/FM too, is good stuff in my book.
Oh, did I mention I have a built-in PHONO stage on that SX-580 also? No? Shame on me. :-D

... Wonder if my wife will let me get another one, hmmmmmm ...

A Dac is a great add-on for a vintage amp. I found the Cirrus logic or sabre dacs worked best with my Technics SA-828 because of the clarity and transparency they put out. Some dacs like schitts AK4490 implementation I found added warmth to the sound that the amp was already providing so the end result was just a lil too dark for my taste. And as for headphones that amp will provide all the power you need. I use 250ohm BeyerDynamic DT770s and 50ohm planar Mayflower T50RPs and nothing comes close to what my amp does for my setup. Japanese steel baby.

 

[AWP3888]

Oh good g*d, I am such a duffus ...

"So I have the beefy Amp/Reciever and I'm sure a DAC will do wonders for that. Now comes the math questions: Will a Pioneer SX-580 with a 680-R1w resistor on the headphone output handle headphones with High Impedance. SX-580 is spec'd at 20-watts into 8-Ohms per channel (reduced at the headphone jack of course). But will it survive running the 25-HDs which have an impedance of 70-ohms (granted that's at like 200 Milli-watts) or the 1350's at 80 ohms. I'm sure in shear output an SX-580 could do the job from the actual speaker outputs (and blowup the drives doing it), it's getting that from the Headphone out on the front face that is the goal."

So did anyone catch my mistake? Hmmmm. So far No, so lucky me. Impedance, which is listed in units of Ohms (#ohms or #-symbol for ohms), has a somewhat non-conventional way of being notated. Where normal units of measure increase with increase in measured subject, Impedance (when noted in ohms) Decreases with increase in measured subject and decreases in measured subject and Increases with a decrease in the measured subject. "Electrical impedance is the measure of the opposition that a circuit presents to a current when a voltage is applied"~ Wikipedia. Also note "admittance is a measure of how easily a circuit or device will allow a current to flow."~ Wikipedia.

Exp.: 2-ohms has LESS impedance than 4-ohms but more current, 4-ohms has LESS impedance than 8-ohms but more current, 8-ohms has LESS impedance than 16-Ohms but more current, so on and so forth.
> This is why my SX-580 will run basically any loudspeaker (pair) at not less than 10Watts/4ohms, but any load at/over 5watts/2ohms risks damaging it quite badly.

As far as Big Stereo Receivers go (and this is a generalization) The higher the # listed as -Ohms, the better the Amp will preform. The lower the # listed as -Ohms the more work the Amp has to do. This is why matching impedance matters more than wattage. Impedance mis-match has the potential to destroy your Amp (Low #-Ohms Speakers) or blow your speakers (High #-Ohms Speakers). Confused yet? Electrical Theory has a tendency to melt brains ( see Indiana Jones Raiders of the Lost Ark).

In my case (SX-580), I cant use speakers below 4-ohms impedance and I will *likely* destroy any speakers above 16-ohms. Note that this would be from the main speaker output stage on the back of the receiver, the headphone stage is restricted with a resistor to prevent making me go deaf.

So in short a 70-ohm or 80-ohm load, especially at less than 5-watts is nothing for this receiver, even out of the Headphone output stage on the front face.
Really what I should be looking at are Headphone with impedance between 40-ohms and 20-ohms, 'cause yea the SX-580 can take it.
Still though I also should consider that my budget should probably also be between $250 and $350. Has anyone seen a high impedance headphone for less than that?

In any case, there I have now corrected myself (yet again) .... Wow, I had a long day and a late night when I made that last post. Holy Cow batman, way to fail.

Anyone out there that is an Electrical Engineer please feel free to jump in here and correct me.

*** Also remember to cite your sources ....

https://en.wikipedia.org/wiki/Electrical_impedance
https://en.wikipedia.org/wiki/Ohm
https://en.wikipedia.org/wiki/Admittance
https://en.wikipedia.org/wiki/Ohm's_law
https://en.wikipedia.org/wiki/High_impedance

(edited ... yet again)
http://www.audiogurus.com/learn/speakers/speaker-impedance-rating/1092
http://www.prestonelectronics.com/audio/Impedance.htm
http://www.toa.jp/soundoh_wiki/index.php?Difference between low and high impedance speakers?

 

[AWP3888]

Yea, I'm replying to my own post ....

Reading through the forums on Head-Fi I've noticed that questions about impedance, what that means for Amps & Headphones, and how we can use it come up frequently.
I have also seen in many of those same forums users posting that Impedance is not important.
I'm going to kindly agree to disagree with them on that point.
Impedance does not change sound, but does affect whether your AMP will power those Headphones (well or even at all).

However, sometimes it is difficult to get an explanation about Impedance that can make it easier to use as an application for the situation to develop a working configuration for AMP-to-Headphone relationship.
That in mind, some quick Google-ing has led me to find some decent articles that do a better job of explaining Impedance than I can give (links below).

I know this might not be the best place to put this, but I would rather give good information out than just "mansplain" my way into being a Jacka**.

Short Answer is:
Where Source is the Amp, Destination is the Driver (Speaker, Headphone)
> that the higher the Impedance at the destination the less current will be demanded by the destination and/or supplied by the Source
> that the lower the Impedance at the destination the more current will be demanded by the destination and/or supplied by the Source (This is how you "Cook" an Amp)
* It is more taxing on an AMP to deliver higher current than it is to push-through increased resistance.

But don't just take my word for it, please please take the time to research impedance, the links below should be helpful to anyone who wants to better understand Impedance.
- Because YES it DOES Matter.
---

Site: http://www.hometoys.com/content.php?url=/htinews/feb04/articles/polk/impedence.htm

Speaker Impedance, Your Amplifier And You.
Understanding Impedance Will Help You Achieve Better System Performance.
by Paul DiComo, Ken Swauger & Scott Orth
Polk Audio, Inc.

Ref: http://www.hometoys.com/content.php?url=/htinews/feb04/articles/polk/impedence.htm

---

Site: https://www.lifewire.com/speaker-impedance-3134705

What Speaker Impedance Means and Why It Matters
by Brent Butterworth
Updated July 07, 2017

Ref: https://www.lifewire.com/speaker-impedance-3134705

---

* Also, remember to site the sources if anyone re-posts this elsewhere

 

[PhoenixG]

Hey man, electrical engineer here. Resistance is the ability of a device to oppose DC current. Impedance is the complex resistive ability of a device to oppose AC current (i.e. all sound) and is frequency dependent. That's why impedance curves have such a massive impact on sound. A non-flat impedance curve is also known as a filter in the frequency domain. For many purposes, the two terms can be used interchangeably more or less.

Both are related to current by ohm's law, which states that current (i) = voltage (v) divided by resistance (ohms). Most amplifier designs effectively act as a 'constant voltage source', so lower impedance sources results in higher current.

Bottom line, your amp is designed to work in a range of 4-16 ohms. less than four ohms will look like a short circuit to your amp and cause excess current draw at lower volume knob positions, potentially allowing you to put out some expensive smoke from the amp. You will see clipping at lower volume knob positions, which could also damage your tweeters by shunting high frequency high power through them.

More than 16 ohms will look more kinda like an open circuit to your amplifier. You won't damage anything, especially not your speakers, but it also won't be very loud, as you will lose your ability to deliver peak current to your speakers. Most head phones are around 32 ohms, but can only handle a fraction of a watt before they are damaged, that's why you have a dropping resistor, to allow you to use the full volume knob swing (or at least more of it) before you smoke your headphones. It isn't uncommon to have high impedance phones with impedance greater than 600 ohms. They are often effectively driven by vintage 'high power' amps since those amps have the capability to achieve the voltage swings necessary to fully power those phones, despite their overall lower power consumption.

Don't confuse the volume knob with a power knob. Max volume typicaly relates to max voltage, not necessarily max power - that depends on what you have hooked up.

Regarding 'impedance matching', there's almost no difference between 20 ohms and 40 ohms or even 80 ohms. They may sound different, but that'll be because they are different headphones. You've got a 680 ohm dropping resistor, you've got to break through the margin of error before impedance will start having an appreciable effect on volume/sound.

To use some numbers as an example - you have a 20W @ 8ohm machine. Using ohm's law, I find the peak voltage output to be 12.6 volts rms. Since your machine uses that same output for the headphones, but also has a dropping resistor, your peak voltage and power across your phones becomes complicated by what is known as a voltage divider, but effectively your max power from the HP out is 58 mW @ 680 ohms resistance and less at any other value (which is still a fair amount).

As far as headphones go, I love the HD6xx from massdrop (also known as HD650's). I own them and they are the best headphones period for $200.
https://www.massdrop.com/buy/massdrop-sennheiser-hd6xx

Oh good g*d, I am such a duffus ...

"So I have the beefy Amp/Reciever and I'm sure a DAC will do wonders for that. Now comes the math questions: Will a Pioneer SX-580 with a 680-R1w resistor on the headphone output handle headphones with High Impedance. SX-580 is spec'd at 20-watts into 8-Ohms per channel (reduced at the headphone jack of course). But will it survive running the 25-HDs which have an impedance of 70-ohms (granted that's at like 200 Milli-watts) or the 1350's at 80 ohms. I'm sure in shear output an SX-580 could do the job from the actual speaker outputs (and blowup the drives doing it), it's getting that from the Headphone out on the front face that is the goal."

So did anyone catch my mistake? Hmmmm. So far No, so lucky me. Impedance, which is listed in units of Ohms (#ohms or #-symbol for ohms), has a somewhat non-conventional way of being notated. Where normal units of measure increase with increase in measured subject, Impedance (when noted in ohms) Decreases with increase in measured subject and decreases in measured subject and Increases with a decrease in the measured subject. "Electrical impedance is the measure of the opposition that a circuit presents to a current when a voltage is applied"~ Wikipedia. Also note "admittance is a measure of how easily a circuit or device will allow a current to flow."~ Wikipedia.

Exp.: 2-ohms has LESS impedance than 4-ohms but more current, 4-ohms has LESS impedance than 8-ohms but more current, 8-ohms has LESS impedance than 16-Ohms but more current, so on and so forth.
> This is why my SX-580 will run basically any loudspeaker (pair) at not less than 10Watts/4ohms, but any load at/over 5watts/2ohms risks damaging it quite badly.

As far as Big Stereo Receivers go (and this is a generalization) The higher the # listed as -Ohms, the better the Amp will preform. The lower the # listed as -Ohms the more work the Amp has to do. This is why matching impedance matters more than wattage. Impedance mis-match has the potential to destroy your Amp (Low #-Ohms Speakers) or blow your speakers (High #-Ohms Speakers). Confused yet? Electrical Theory has a tendency to melt brains ( see Indiana Jones Raiders of the Lost Ark).

In my case (SX-580), I cant use speakers below 4-ohms impedance and I will *likely* destroy any speakers above 16-ohms. Note that this would be from the main speaker output stage on the back of the receiver, the headphone stage is restricted with a resistor to prevent making me go deaf.

So in short a 70-ohm or 80-ohm load, especially at less than 5-watts is nothing for this receiver, even out of the Headphone output stage on the front face.
Really what I should be looking at are Headphone with impedance between 40-ohms and 20-ohms, 'cause yea the SX-580 can take it.
Still though I also should consider that my budget should probably also be between $250 and $350. Has anyone seen a high impedance headphone for less than that?

In any case, there I have now corrected myself (yet again) .... Wow, I had a long day and a late night when I made that last post. Holy Cow batman, way to fail.

Anyone out there that is an Electrical Engineer please feel free to jump in here and correct me.

*** Also remember to cite your sources ....

https://en.wikipedia.org/wiki/Electrical_impedance
https://en.wikipedia.org/wiki/Ohm
https://en.wikipedia.org/wiki/Admittance
https://en.wikipedia.org/wiki/Ohm's_law
https://en.wikipedia.org/wiki/High_impedance

(edited ... yet again)
http://www.audiogurus.com/learn/speakers/speaker-impedance-rating/1092
http://www.prestonelectronics.com/audio/Impedance.htm
http://www.toa.jp/soundoh_wiki/index.php?Difference between low and high impedance speakers?

 

[AWP3888]

Hey man, electrical engineer here. Resistance is the ability of a device to oppose DC current. Impedance is the complex resistive ability of a device to oppose AC current (i.e. all sound) and is frequency dependent. That's why impedance curves have such a massive impact on sound. A non-flat impedance curve is also known as a filter in the frequency domain. For many purposes, the two terms can be used interchangeably more or less.

Both are related to current by ohm's law, which states that current (i) = voltage (v) divided by resistance (ohms). Most amplifier designs effectively act as a 'constant voltage source', so lower impedance sources results in higher current.

Bottom line, your amp is designed to work in a range of 4-16 ohms. less than four ohms will look like a short circuit to your amp and cause excess current draw at lower volume knob positions, potentially allowing you to put out some expensive smoke from the amp. You will see clipping at lower volume knob positions, which could also damage your tweeters by shunting high frequency high power through them.

More than 16 ohms will look more kinda like an open circuit to your amplifier. You won't damage anything, especially not your speakers, but it also won't be very loud, as you will lose your ability to deliver peak current to your speakers. Most head phones are around 32 ohms, but can only handle a fraction of a watt before they are damaged, that's why you have a dropping resistor, to allow you to use the full volume knob swing (or at least more of it) before you smoke your headphones. It isn't uncommon to have high impedance phones with impedance greater than 600 ohms. They are often effectively driven by vintage 'high power' amps since those amps have the capability to achieve the voltage swings necessary to fully power those phones, despite their overall lower power consumption.

Don't confuse the volume knob with a power knob. Max volume typicaly relates to max voltage, not necessarily max power - that depends on what you have hooked up.

Regarding 'impedance matching', there's almost no difference between 20 ohms and 40 ohms or even 80 ohms. They may sound different, but that'll be because they are different headphones. You've got a 680 ohm dropping resistor, you've got to break through the margin of error before impedance will start having an appreciable effect on volume/sound.

To use some numbers as an example - you have a 20W @ 8ohm machine. Using ohm's law, I find the peak voltage output to be 12.6 volts rms. Since your machine uses that same output for the headphones, but also has a dropping resistor, your peak voltage and power across your phones becomes complicated by what is known as a voltage divider, but effectively your max power from the HP out is 58 mW @ 680 ohms resistance and less at any other value (which is still a fair amount).

As far as headphones go, I love the HD6xx from massdrop (also known as HD650's). I own them and they are the best headphones period for $200.
https://www.massdrop.com/buy/massdrop-sennheiser-hd6xx

AWESOME, Thank you PhoenixG!

So now I have some *more* questions ....
If I were to create a spreadsheet using both the Ohms-Law (V=I*R) & Power-Law (P=I*V), Do I use the Current ( value for I ) as a constant value (not-changing)?

When I plug the numbers into an online Calculator ( http://www.rapidtables.com/calc/electric/ohms-law-calculator.htm ) I get the following:

Where Loudspeaker Power=20watts and Impedance=8ohms
Loudspeaker Voltage = 12.64911060 volts

Where Headphone Power=0.0580watts and Impedance=680ohms
Headphone Voltage = 6.32455530 volts
(Voltage Divided = 12.64911060 / 2)

So for example if I have a headphone(s) that has an listed impedance of 150ohms, 200ohms, and 250ohms (respectively) I would get the following result from the calculator (assuming Voltage is constant at 6.32455530 volts) from the Pioneer SX-580 Headphone jack:
Impedance (Ohms) Current (Amps) Voltage (Volts) Power (Milli-Watts)
150.0 0.0421637020 6.32455530 266.667
200.0 0.0316227765 6.32455530 200.000
250.0 0.0252982212 6.32455530 160.000

This would show that as Impedance (Ohms) increases the Amplifier will supply lower Power (Watts) as well as Lower Current (Amps), and the opposite relationship would be true also.
> I found an interesting result when running numbers through that calculator ...

Impedance (Ohms) Current (Amperes) Voltage (Volts) Power (Milli-Watts)
160.0 0.0395284706 6.32455530 250.000
250.0 0.0252982212 6.32455530 160.000

... Sooo, does Voltage stay constant?
( for some reason I cant seem to format the number values in this post to not look like a string value)

 

[PhoenixG]

Whew! Let's me break out my calculator here haha.
FIrst thing first, you need to use max voltage as a constant. The voltage comes from your amp. That max voltage is a design feature you can't really change without unreasonable modifications. The change in voltage over time is also known (sometimes) as music when played through a speaker. For this purpose, we can pretend it is DC and nothing really changes in this case. Current isn't able to be assumed constant in this case as you have already established your amp as a constant voltage source (which is effectively true for 99% of the amps out there).
Your amplifier is capable of putting out 12.6-ish volts max. That's the number we go from. When you have a "simple" load of 8 ohms, it's easy to figure out power, current, etc.

When you have two resistors in series you make what is known as a voltage divider. In that case, the voltage across each resistor is equal to total voltage X value of that resistance / sum of all resistance. The input voltage can still be pretended to be constant, but the voltage across an element will be different. This is the situation at your hp jack.
I used the HP value of 680 ohms earlier as I already knew it would be your highest possible power output at 58miliwatts due to the properties of a voltage divider. Using a different value will give you a different solution.
SOoooooo volts across 150 ohm HP's = 12.6v X 150 /(150+680) = 2.27v
Where p=v^2/r, power = 2.27^2/150 = 34miliwatts. (15 miliamps)
Power across an element r1 of a voltage divider is ((v X r1/(r1+r2))^2)/r1
Now try saying that 5 times fast

"This would show that as Impedance (Ohms) increases the Amplifier will supply lower Power (Watts) as well as Lower Current (Amps), and the opposite relationship would be true also."

Not really, since it is a square relationship, you have a peak power from your HP jack when the HP resistance is 680 ohms (i.e. equal to your dropping resistor!!!).
150 ohms gives 34miliwatts, 15 miliamps
200 ohms gives 41miliwatts, 14 miliamps
250 ohms gives 45 miliwatts, 13 miliamps
680 ohms gives 58 miliwatts, 9 miliamps
820 ohms gives 57 miliwatts, 8 miliamps
9320 ohms gives 14 miliwatts, 1 miliamp
Your current is actually decreasing with the increased total resistance, but power also increases to a point.

Not a linear thing eh?

At the end of the day, you're just really not taxing your amp with literally any headphones ever. Furthermore, when you have enough power, it doesn't really matter what the impedance of the headphones is, but you can get some pretty cool behavior when your HP impedance is 'small' compared to your dropping resistor (which is why many amps 'sound different' from the HP jack vs the speaker taps and is kinda what keeps the vintage amp/modern HP hobby exciting). Final thing, your instinct is right to look for an electrical engineer, as it is a lot more nuanced than casual googling will turn up.

AWESOME, Thank you PhoenixG!

So now I have some *more* questions ....
If I were to create a spreadsheet using both the Ohms-Law (V=I*R) & Power-Law (P=I*V), Do I use the Current ( value for I ) as a constant value (not-changing)?

When I plug the numbers into an online Calculator ( http://www.rapidtables.com/calc/electric/ohms-law-calculator.htm ) I get the following:

Where Loudspeaker Power=20watts and Impedance=8ohms
Loudspeaker Voltage = 12.64911060 volts

Where Headphone Power=0.0580watts and Impedance=680ohms
Headphone Voltage = 6.32455530 volts
(Voltage Divided = 12.64911060 / 2)

So for example if I have a headphone(s) that has an listed impedance of 150ohms, 200ohms, and 250ohms (respectively) I would get the following result from the calculator (assuming Voltage is constant at 6.32455530 volts) from the Pioneer SX-580 Headphone jack:
Impedance (Ohms) Current (Amps) Voltage (Volts) Power (Milli-Watts)
150.0 0.0421637020 6.32455530 266.667
200.0 0.0316227765 6.32455530 200.000
250.0 0.0252982212 6.32455530 160.000

This would show that as Impedance (Ohms) increases the Amplifier will supply lower Power (Watts) as well as Lower Current (Amps), and the opposite relationship would be true also.
> I found an interesting result when running numbers through that calculator ...

Impedance (Ohms) Current (Amperes) Voltage (Volts) Power (Milli-Watts)
160.0 0.0395284706 6.32455530 250.000
250.0 0.0252982212 6.32455530 160.000

... Sooo, does Voltage stay constant?
( for some reason I cant seem to format the number values in this post to not look like a string value)

 

[r2muchstuff]

Concerning this impedance stuff and the Battle of the Amps (see post #675):

Based on the specifications the amps are similar (however look at the Headphone out resistors)

The Pioneer SA 8500 has been serviced by the same shop that did the AU 7700.
Sanusi AU 7700 - 54 watts/channel @ 8 Ohms, < .1% THD, < .15% IM for Pre and Main Amps combined, < .1% IM Main Amp only - Headphone out uses 220 Ohm 1 Watt resistors
1974 -1976
Pioneer SA 8500 - 60 watts/channel @ 8 Ohms, < .1% THD, < .1% IM for Pre and Main Amps combined, - Headphone out uses 150 Ohm 2 Watt resistors
1975-1977

I am finding that at least some of the sound difference is most likely caused by the impedances that are presented to the headphones.

With the Beyerdynamic DT 880/600ohm -
The Sansui presents a warmer sound with less top end air.
If I use an "impedance adapter" (lowering the impedance the headphone "sees") with the Sansui the sound is less warm and closer to the Pioneer's sound.

I am currently trying the comparison using a set of Oppo PM-3 which are not as affected by the impedances.

In the end the impedances are part of the specific amps sound, unless they are changed to match each other or the speaker taps are used, the headphone outs will sound "like they sound".

With the Beyerdynamic DT 880, the Sansui is warmer with less air (words always over describe subtle differences). I can listen to either presentation for time on end if I do not A/B them. They both sound great.
However, now that I have done this and cannot undo it, at least with the DT 880/600 ohm, I prefer the Pioneer's presentation.

More listening with other headphones to come.

YMMV,
r2

 

[anbinhv]

Hi all, just got my HE-400, I have 1 question:
A mini amplifier like this: Kenwood R-SA7 could drive HE-400 well?
Thank you!

 

[Oscar-HiFi]

Hi all, just got my HE-400, I have 1 question:
A mini amplifier like this: Kenwood R-SA7 could drive HE-400 well?
Thank you!

Should power them fine, I would even suggest getting a balanced cable for the HE-400 and then a 4-pin XLR to bare speaker wire and run the HE-400 from the speaker outputs instead of the headphone output.

 

[anbinhv]

Should power them fine, I would even suggest getting a balanced cable for the HE-400 and then a 4-pin XLR to bare speaker wire and run the HE-400 from the speaker outputs instead of the headphone output.

Thanks you! I going to get this just to drive He-400 (because they are cheap here), so I dont have speakers.

 

[northendjazz]

I think I'm about done taming my Sansui G-401, the power of the headphone out was eaten up by the ZMF Vibro's but I wanted to try some beyerdynamic T90's.
I found the G-401 needed taming if I was to use the T90's , it was plain noisy with a heavy hum when nothing was playing and through quite passages of tunes,
I added a grounding box to the ground terminal and that halved the noise. The final piece was an iFi iematch and with that I can enjoy the T90's and the upgraded
dac a Metrum Acoustics Octave.

I also added some speakers for the first time they are Epos M5 bookshelf and I'll be giving them a proper listen tonight but impressed with a few familiar tracks so far.

 

[r2muchstuff]

...
I found the G-401 needed taming if I was to use the T90's , it was plain noisy with a heavy hum when nothing was playing and through quite passages of tunes,

"Heavy Hum" that sounds like the G-401 needs a trip to the Dr.
Older amps may show some background noise however, a hum is not normal and may either be a ground loop or an amp issue.

JMTC & YMMV,
r2