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Hi everybody!

I got my CLP785 in October and I gotta say I'm very happy with it so far.
There's just one thing baffling me, so I'm wondering if others are dealing with the same issue.

I tested the headphone jack with multiple different headphones now:

1. Austrian Audio Hi-X55 (Studio headphones, 25 Ohms)
2. Shure SE215 (in ear) (17 Ohms)
3. Beyerdynamic DP770 PRO (32 Ohms)
4. Beyerdynamic DP770 PRO (80 Ohms)

The problem is that only number 1 and 2 are able to produce output I actually consider to be "loud" (still far from hurting my ears though at 100% volume piano-wise).

32 Ohms and even more so 80 Ohms seem to be too much, the volume at 100% doesn't even reach a "sweet spot" if played softly -
and I just can't understand why that should be intended for an instrument being priced like that.

Do you experience the same issue?
Is there any internal tweak to be made to fix this?

To me this really is a problem, since there are quite few headphones on the market which are below 32 Ohms, but produce decent sound.

32 Ohms are considered to be industry standard even for mobile devices, so I was astonished to learn that the instrument isn't able to deliver sound loud enough.

I was able to test this on a CLP635 a while ago - it was much louder using headphones 1 and 2 of above list, so there doesn't seem to be a technical barrier or anything wrong with the headphones itself.

Best regards from Vienna,

Lukas

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Yeah I ran into this as well. I have a 50-70 Ohms high-end headphone, but it's just not loud enough on the 785. I manage, but it's not great. There is only one solution if you want to use higher impedance headphones: use a headphone amplifier. Are you sure the 32 Ohms isn't loud enough though?

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Ok, that's quite disappointing..

Yeah.. It's "loud enough" - I can hear everything I play.
The thing is, if I want to have my brain washed away while playing lower impact pieces, it actually isn't loud enough and nowhere near to the volume level you would get from an actual acoustic piano.

At least I know it's not just my model, maybe I really need to buy low-impedance headphones then..
What I didn't try so far is to use headphones with a higher sensitivity while still using 32 Ohms, maybe that's worth a shot (Beyerdynamic with about 96 db is on the lower end here as far as I know).

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WARNING: School lesson follows. smile

"Impedance" = "resistance to electrical current flow". The higher the current flow the higher the power (also known as "watts").

For direct current, such as that supplied by a battery, the resistance to electrical current flow is a constant. 32 ohms is 32 ohms is 32 ohms.

For alternating current, whether it's coming out of the outlet on the wall of your home or whether it's sound coming out of the headset jack or speaker jack, the "impedance" increases as the frequency increases when coils are involved.

A speaker's impedance is usually measured at 400 hertz (Hz) while headsets usually are measured at 1,000 Hz. That 32 ohms measured at 1,000 Hz will be higher at 2,000 Hz and higher yet at 3,000 Hz etc.

For maximum efficient power transmission from the amplifier to the headset (or speaker) the impedances should match. A 32 ohm amplifier should have a 32 ohm headset plugged into it.

If the amplifier is designed correctly, it also will deliver power on an increasing curve. The designer knows that the higher the frequency the more power the amplifier must deliver because the resistance to electrical current flow increases and thus the power delivered to the headset coils decreases. Otherwise, the higher the sound frequency the lower the volume coming out of the headset.

If you use a lower impedance headset than the amplifier is designed for, the current (power) pulled from the amplifier increases so the volume increases at the same volume control setting. But the lower impedance can appear as closer to a short circuit to the amplifier circuitry. That can either damage the amplifier or more likely, damage the coils in the headsets if pushed too far.

If you use a higher impedance headset than the amplifier is designed for, the current (power) pulled from the amplifier decreases because the amplifier is expecting a lower impedance. That results in a lower volume at the same volume control setting.

Modern electronics usually can handle a limited range of impedances without damage as long as it's not pushed too far power-wise. But if you have an amplifier designed to match a 250 ohm headset and you plug in a 25 ohm headset, the amplifier is seeing a device that is a whole lot closer to a short circuit because the headset presents only 1/10th of the electrical resistance that the amplifier was designed for. That can result in a current flow of 10 times more at the same volume setting.

In the (not so) good, old days, it was not uncommon to blow up an amplifier designed for 16 ohm speakers by installing 3.2 ohm speakers. Or installing multiple 3.2 ohm speakers in parallel.

For what it's worth, the manual for the CLP-635 and the CLP-785 both list the same optional headsets:

HPH-50 = 35 ohms
HPH-100 = 46 ohms
HPPH-150 = 48 ohms

I also would not be surprised to learn that the manufacturers are artificially limiting the overall power delivered to the headsets due to lawsuits about hearing damage. The 635 was launched in mid 2017.

I hope this helps explain what you're experiencing rather than adding to the confusion.

Ray

Last edited by NXR; 11/26/21 12:29 PM.

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Originally Posted by NXR
. . .
I hope this helps explain what you're experiencing rather than adding to the confusion.

It's almost right. Two issues:

1. It (implicitly) assumes that all headphones have the same efficiency (or "sensitivity") -- that a milliwatt of electrical power sounds as loud in headphone A, as in headphone B.

My Senn "HD280 pro" is stamped "64 ohms". My AKG K240 Studio is stamped "55 ohms" -- not significantly different.

. . . But the HD280 is significantly louder than the K240.

2.
Quote
. . .
If the amplifier is designed correctly, it also will deliver power on an increasing curve. The designer knows that the higher the frequency the more power the amplifier must deliver because the resistance to electrical current flow increases and thus the power delivered to the headset coils decreases. Otherwise, the higher the sound frequency the lower the volume coming out of the headset. . .

I don't know how much the inductance of the headphone-coil winding contributes to the headphone's impedance. And I'm reasonably sure that normal amplifiers (including headphone amps) are not built with frequency compensation that increases their gain, as the signal frequency increases:

. . . the good ones measure flat (voltage gain vs frequency), into a resistive load.


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I've noticed a similar difference between the CLP 575 I've had previously and the 785.

I have the AKG K702 (62 Ohms) and the Beyerdynamic DT 131 (40 Ohms).

The Beyerdynamic is clearly louder via headphones. Luckily the AKG is still loud enough for me.
I remember having tested the Casio GP510 which was unusable with the AKG.

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Blame it on the iPhone. In the old days home amplifier equipment mostly required 80 Ohms or higher for headphones for optimal response - now iPhones work best at around 32 Ohms so its not hard to guess why digital pianos have had to "comply".

Last edited by Jonky Ponky; 11/28/21 01:11 AM.
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Thanks for your replies.

I think it's an interesting decision to design the headphone jack like that if you consider the price you pay and by that the quality you'd expect.

I wrote to Yamaha Support about this - I don't expect them to be able to do anything about the impedance story, but who knows what kind of volume reducing software might be in place.

If they provide any fix, I'll let you know, but I guess I'll just have to get to know all the <25 Ohms headphones out there to find something suitable sound-wise.

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I use Beyerdynamics DT-770 PRo 250Ohm and Sennheiser HD580 without issues, although I need to keep the volume at about 95 or 85% respectively for these headphones.

The issue is helped by changing the voice volume from 100 to 127 by going to menu Voice > Voice Edit > Volume.

The is enough headroom for one instrument to be at 127 volume without any clipping (this volume change is in the digital domain - 127 is normal volume. 100 is reduced volume. Yamaha does did this even on my MU100R rompler from late 90s). It would only be an issue if you stack multiple instruments and run out of headroom.

If you are not stacking multiple instruments, this will not cause any clipping. If it did, it would be a very obvious awful digital clipping sound.

Last edited by bumblebee; 11/28/21 04:03 PM.
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Originally Posted by bumblebee
The issue is helped by changing the voice volume from 100 to 127 by going to menu Voice > Voice Edit > Volume.
Thank you so much! This is a big improvement for me. It's still not an ear-shattering volume, but the sound has a lot more body and is a lot more fun to play.

Last edited by Ostinato; 11/28/21 04:40 PM.
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Another thing I should mention, since the thread focuses on impedance... my understanding is that efficiency is going to determine how loud different headphones get, and many low-impedance headphones are very inefficient. This article may help.

https://www.headphonesty.com/2019/04/headphone-impedance-demystified/

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Solid State power amplifiers, whether for speakers, or included in the digital piano for headphones, are extremely low impedance devices (typically a few hundredths of an ohm). Their purpose is to provide current (not voltage, which is electromotive force) to create a magnetic field in the voice coil, moving it so that it moves a mass of air. Doubling the impedance of a voice coil halves the output power, which is why amplifiers often specify power output at both 4 and 8 ohms. All this is moot however, if the power supply cannot provide enough current to the amplifier to adequately drive the voice coil, or the amplifier has a built-in current limiter to prevent overheating.

The sensitivity of the headphones, usually measured in dBm (0dBm = 1 milliwatt), is the best measure to include along with the rated impedance of the headphones. Choosing headphones with a rating of 104dBm vs. a rating 101dBm will sound equally loud when only half as much power is delivered to the 104dBm phones.

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Originally Posted by prout
S . . .
The sensitivity of the headphones, usually measured in dBm (0dBm = 1 milliwatt), is the best measure to include along with the rated impedance of the headphones. Choosing headphones with a rating of 104dBm vs. a rating 101dBm will sound equally loud when only half as much power is delivered to the 104dBm phones.

That's true. But impedance comes into the discussion in a fundamental way:

. . . A high-impedance headphone may be very efficient (lots of dB per milliwatt),

. . . . . but delivering those milliwatts is difficult for an amp that's "voltage-limited" -- for example,
. . . . . . a battery-powered amp in a portable device.

_Both_ the current- and voltage-limits of the amp (or its output impedance and maximum power) come into play. And neither one is usually supplied by the DP manufacturer.

My Shure SE215 "in-ear monitors" are rated at 17 ohms. They work well with battery-powered phones and laptop computers. The sensitivity is given as
Quote
General results Shure SE 215
. . . Sensitivity by voltage: 125.34 dB/V SPL
. . . Sensitivity by power: 107.44 dB/mW SPL
which is pretty loud, even with a smartphone.

Of course, being in-ear devices, the diaphragm only has to move a tiny bit of air, to generate lots of dB's of SPL.


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Yes, this is correct, regarding voltage-limited devices. The problem here is the same as I discussed above. The power supply (a battery, which has internal resistance which lowers its voltage when heavily current loaded, and thus not able to deliver as much current as required), or an AC power supply, must be rated to deliver sufficient current. Most amplifier power supplies have large capacitors to provide short-lived (a few milli-seconds) large values of current above the continuous current rating.

Just a quick point. dBm is the ratio of Watts to 1 milliwatt, dBV is the ratio of Volts to 1 Volt, dB SPL is the ratio of Sound Pressure Level at a given point (very very different from dBm) to 20 microPascals. Normal atmospheric pressure is about 101,300 Pascals.

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In spite of what the internet says about amplifiers, they do not deliver volts. That would like saying that a battery delivers volts. They don't. They deliver current. A 12 volt battery, or a 120,000 volt power line deliver only one thing - current, and they do that only when there is a load (resistance or impedance), otherwise the voltage (pressure) just sits there doing nothing. Voltage is force.

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I should correct a misstatement I made above. Power amplifiers do not deliver volts.

I design and use daily voltage amplifiers. They are used in practically every pre-amp, microphone amp, and instrumentation amplifier. For all practical purposes they provide electrical potential, whose electrostatic field provides for controlling the current flow in a power amplifier, and do so without consuming power (not much at any rate) themselves.

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Originally Posted by prout
Yes, this is correct, regarding voltage-limited devices.

Might one ask what devices are not voltage-limited ? wink

I think the plate voltage on a 25KW lowband TV transmitter where I worked in the 80s was 17 KV... which is still "limited" (although highly lethal). crazy

In the vacuum tube era, where amplifiers generally had a couple of hundred Volts B+, headphones were often in the range of 2,000 Ohms. (At the opposite end of the voltage scale, crystal receivers also required 2K or higher headphones so as not to load down their circuitry).

As everyone in this thread has pointed out, a higher impedance load requires higher voltage to generate power (similar to E-squared over R in a DC circuit).
Interfaces such as the Focusrite that are driven from a 5 Volt USB connector are limited as to their voltage swings since they don't include circuitry to boost that voltage. An AC-powered instrument is not inherently limited, but is probably designed based on what the majority of consumers purchase.

As to the OP's original question... assuming that you own all those headphones you've tested, it would seem a lot more economical to buy an AC-powered headphone amplifier to give you enough drive to run them properly.


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Originally Posted by bumblebee
I use Beyerdynamics DT-770 PRo 250Ohm and Sennheiser HD580 without issues, although I need to keep the volume at about 95 or 85% respectively for these headphones.

The issue is helped by changing the voice volume from 100 to 127 by going to menu Voice > Voice Edit > Volume.

The is enough headroom for one instrument to be at 127 volume without any clipping (this volume change is in the digital domain - 127 is normal volume. 100 is reduced volume. Yamaha does did this even on my MU100R rompler from late 90s). It would only be an issue if you stack multiple instruments and run out of headroom.

If you are not stacking multiple instruments, this will not cause any clipping. If it did, it would be a very obvious awful digital clipping sound.

Wow, this does indeed make a huge difference - I never saw this setting, thanks a lot for pointing it out!


Originally Posted by JaneF
Originally Posted by prout
Yes, this is correct, regarding voltage-limited devices.

Might one ask what devices are not voltage-limited ? wink

I think the plate voltage on a 25KW lowband TV transmitter where I worked in the 80s was 17 KV... which is still "limited" (although highly lethal). crazy

In the vacuum tube era, where amplifiers generally had a couple of hundred Volts B+, headphones were often in the range of 2,000 Ohms. (At the opposite end of the voltage scale, crystal receivers also required 2K or higher headphones so as not to load down their circuitry).

As everyone in this thread has pointed out, a higher impedance load requires higher voltage to generate power (similar to E-squared over R in a DC circuit).
Interfaces such as the Focusrite that are driven from a 5 Volt USB connector are limited as to their voltage swings since they don't include circuitry to boost that voltage. An AC-powered instrument is not inherently limited, but is probably designed based on what the majority of consumers purchase.

As to the OP's original question... assuming that you own all those headphones you've tested, it would seem a lot more economical to buy an AC-powered headphone amplifier to give you enough drive to run them properly.

I don't own them, these are just the ones I could borrow for testing / "buy" and return.

I tested the above (127 volume) with DT770 32 Ohms and it isn't even necessary to go to either 127 or max volume on the instrument.

This opens a lot more possibilities, impedance about (I guess) at least 80 Ohms should now be "loud enough" for most of the people.

Thanks a lot to everybody for your contribution, also for adding details about the technical background - this thread should be of great help for anyone dealing with similar "issues".

Have a nice day and enjoy your DPs as much as you can!

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Originally Posted by JaneF
Originally Posted by prout
Yes, this is correct, regarding voltage-limited devices.

Might one ask what devices are not voltage-limited ? wink

I think the plate voltage on a 25KW lowband TV transmitter where I worked in the 80s was 17 KV... which is still "limited" (although highly lethal). crazy

In the vacuum tube era, where amplifiers generally had a couple of hundred Volts B+, headphones were often in the range of 2,000 Ohms. (At the opposite end of the voltage scale, crystal receivers also required 2K or higher headphones so as not to load down their circuitry).

As everyone in this thread has pointed out, a higher impedance load requires higher voltage to generate power (similar to E-squared over R in a DC circuit).
Interfaces such as the Focusrite that are driven from a 5 Volt USB connector are limited as to their voltage swings since they don't include circuitry to boost that voltage. An AC-powered instrument is not inherently limited, but is probably designed based on what the majority of consumers purchase.

As to the OP's original question... assuming that you own all those headphones you've tested, it would seem a lot more economical to buy an AC-powered headphone amplifier to give you enough drive to run them properly.

We could have a whole new thread here. Thanks for responding and revealing my limitation of language use.

Perhaps I should have said: 'All devices are voltage-limited, some are just more limited than others.'

I am in the midst of designing a Class B RF push-pull power amplifier using an 829B output tube for SSB and CW use. Choosing the anode load impedance is limited by the power supply transformers I have on hand and how to design the power supply to deliver the required current at a voltage that is held constant to within 20% or so.

Incidentally, I use 2000-4000 ohm headphones for a number of tube radios I have built that use the headphones as the direct (transformerless) anode load.

Cheers.

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Originally Posted by prout
We could have a whole new thread here. Thanks for responding and revealing my limitation of language use.

Perhaps I should have said: 'All devices are voltage-limited, some are just more limited than others.'

I am in the midst of designing a Class B RF push-pull power amplifier using an 829B output tube for SSB and CW use. Choosing the anode load impedance is limited by the power supply transformers I have on hand and how to design the power supply to deliver the required current at a voltage that is held constant to within 20% or so.

Incidentally, I use 2000-4000 ohm headphones for a number of tube radios I have built that use the headphones as the direct (transformerless) anode load.

Cheers.

LOL. And "all animals are equal but some are more equal than others." cool

For headphones as an anode load, a good blocking capacitor may save more than just your hearing...LOL...

Cheers!


Jane - expert on nothing with opinions on everything
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