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# Geek Pulse: Geek desktop DAC/AMP by Light Harmonics - Page 195

Quote:
Originally Posted by miceblue

Actually, while we're on this topic, for those who don't understand why current is needed:
Noting this, how does volume correlate to properly driving a headphone in this case? As in, what does the headphone sound like if it can't produce enough current to create the isodynamic field?

Simple.

Volume is related to power. Power is then related to current through the equation P=I²R.

Simply put, you would require a high enough current to drive the headphones at the volumes you need.

If the current is insufficient, the volumes you require cannot be achieved anyways.

Also, no current is necessary to create the isodynamic field.

It is produced by the permanent magnets in the headphone.

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Voltage can get you there too, current isn't the only factor unless you reconfigure P=IV into what you did.

Quote:
Originally Posted by Muinarc

Voltage can get you there too, current isn't the only factor unless you reconfigure P=IV into what you did.

Note that the 'P' used to calculate dB SPL is the power produced at the impedance of the headphones.

In this case, the 'V' in the equation P=IV refers to the potential difference over the impedance of the headphones.

Take the equation V=IR.

Taking the impedance R to be a constant, we have V proportional to I.

Now how do you suppose we increase V without increasing I?

Quote:
Originally Posted by LegendZenify

HE-500 requires 2.04mW to achieve 90dB SPL.

Let's take 300mW of power, that would be enough to achieve peaks of 111dB SPL

(Note that 110dB is the sound level of a jet flyover at 300m, really loud)

Geek Pulse is stated to have a headphone output with up to 3000mW of power, which should be able to drive the HE-500 fairly easily, as long as it manages to produce ~300mW at the 47Ohm impedance of the headphones.

TL;DR: The Geek Pulse should technically be able to drive the HE-500 comfortably at its stated spec of 3000mW, unless you like your music really loud

So does that mean that the geek pulse S with internal amp upgrade should be more than adequate?

Quote:
Originally Posted by LegendZenify

Note that the 'P' used to calculate dB SPL is the power produced at the impedance of the headphones.

In this case, the 'V' in the equation P=IV refers to the potential difference over the impedance of the headphones.

Take the equation V=IR.

Taking the impedance R to be a constant, we have V proportional to I.

Now how do you suppose we increase V without increasing I?

If you want to call R constant I guess. Though close in Planars, it's still not constant over all frequencies.

Quote:
Originally Posted by pauldgroot

This is just silly, why promote a 48h only deal when it reoccurs throughout time?! I thought I had to jump on board for this deal but now I feel like I could have just waited a bit to see if something else comes up.

I thought they would offer the deal, close it, contact HifiMAN about it and ship them out. The more they keep doing this deal, the longer backers will have to wait. I don't get it.

They probably had to make these deals with HiFiMan in advance and offer no more than what HiFiMan would commit to delivering.  The first round could be seen as a test case, and since it was successful, HiFiMan might have "found" more stock to do it again.

Also, a "limited time sale" is standard practice in the retail and marketing industries; used to generate buzz and create sense of urgency among potential buyers.

Yes but we are here to back their product. It's a community effort and they are abusing that power I think. Oh well, whatever. LHL is a weird business.

Quote:
Originally Posted by Muinarc

If you want to call R constant I guess. Though close in Planars, it's still not constant over all frequencies.

And how does that prove your point?

R (the impedance) is still independent of V & I, thus V (the p.d) is still directly proportional to the current (I).

Just because R varies over frequencies does not magically make them inversely proportional.

Anyway, let us derail this thread no further.

If you have a 56 page thesis disproving Ohm's Law, feel free to PM me.

I would love to give it a read.

I can't find the post now, but according to Larry:

- the Pulse is current constrained so that it will max at around 3 Watt total output (regardless of voltage), or otherwise, it will be voltage constrained to 1.8v, 3.5v or 7v in SE mode (or 3.6, 6 or 14v) depending on the gain setting.

- power will keep going up as the headphone impedance goes down until it hits the 3 Watt limit.

I think this means it will drive the HE-500 more than comfortably as this implies that at 50 Ohms (somewhere around the HE-500's nominal impedance), it will be able to generate around 1 Watt of power in SE mode and the full 3 Watts in balanced mode. Assuming the HE-500 can survive it, that implies SPLs that is louder than any reasonable listening levels.

That's all theoretical of course, but on paper there is nothing to say the amp stage is not more than capable of driving the HE-500 to any level you want, maybe up to 10 times over.

I think LHL tests the Pulse with HE-560s so I am sure the same is true of the HE-560 (although anecdotal evidence is that the HE-560 is much harder to drive than the HE-500 even if on paper it doesn't seem to be the case).

What is MUCH more of a worry to me is sensitive IEMs, as the GO 720 and 450 I have are quite hissy with sensitive IEMs and the concern is even 1.8v is too much for things like the Shure 535s, Jerry Harveys and less than 16 ohm impedance headphones of the world

Edited by nudd - 11/22/14 at 11:33pm
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Edited by snip3r77 - 11/23/14 at 12:10am
Quote:
Originally Posted by nudd

I can't find the post now, but according to Larry:

- the Pulse is current constrained so that it will max at around 3 Watt total output (regardless of voltage), or otherwise, it will be voltage constrained to 1.8v, 3.5v or 7v in SE mode (or 3.6, 6 or 14v) depending on the gain setting.

- power will keep going up as the headphone impedance goes down until it hits the 3 Watt limit.

I think this means it will drive the HE-500 more than comfortably as this implies that at 50 Ohms (somewhere around the HE-500's nominal impedance), it will be able to generate around 1 Watt of power in SE mode and the full 3 Watts in balanced mode. Assuming the HE-500 can survive it, that implies SPLs that is louder than any reasonable listening levels.

That's all theoretical of course, but on paper there is nothing to say the amp stage is not more than capable of driving the HE-500 to any level you want, maybe up to 10 times over.

I think LHL tests the Pulse with HE-560s so I am sure the same is true of the HE-560 (although anecdotal evidence is that the HE-560 is much harder to drive than the HE-500 even if on paper it doesn't seem to be the case).

What is MUCH more of a worry to me is sensitive IEMs, as the GO 720 and 450 I have are quite hissy with sensitive IEMs and the concern is even 1.8v is too much for things like the Shure 535s, Jerry Harveys and less than 16 ohm impedance headphones of the world

Shouldn't be an issue as Larry actually uses the HE560.

But what about Audezes @ 15ohm. Anyone has a calculation on this?
Quote:
Originally Posted by snip3r77

Shouldn't be an issue as Larry actually uses the HE560.

But what about Audezes @ 15ohm. Anyone has a calculation on this?

Which Audeze are you talking about?

Audeze headphones are generally less power hungry than the Hifiman-560 tho.

To demonstrate, from measurements taken from innerfidelity, the power required to achieve 90dB SPL are as follows:

LCD-2 - 0.75mW

LCD-3 - 0.66mW

LCD-X - 0.22mW

HE-560 - 2.53mW

Quote:
Originally Posted by LegendZenify

Which Audeze are you talking about?
Audeze headphones are generally less power hungry than the Hifiman-560 tho.

To demonstrate, from measurements taken from innerfidelity, the power required to achieve 90dB SPL are as follows:
LCD-2 - 0.75mW
LCD-3 - 0.66mW
LCD-X - 0.22mW
HE-560 - 2.53mW

OMG HE560 is insane. The LCD-X is so much easier to drive.
And the best of the HiFiMan breed, HE-6, only take 19.69mW for 90dB SPL.
Quote:
Originally Posted by snip3r77

OMG HE560 is insane. The LCD-X is so much easier to drive.

In practice it is not.

Are those measurement taken at 1kHz? If yes, some headphones might require to play louder to achieve the same overall volume across the bandwidth. Audeze are dark, if you want the same treble quantity as the HE-560, you need to push it way past the 1kHz rating.

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