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# HE-500, LCD2, D5000, DT770, SR80, on a speaker amp (Emotiva mini-X A-100) Project - Page 177

Just looked at the he-adapter internals. If it is true that there is a 10 and 25 ohm resistor per channel, then judging from layout, it seems that the impedance seen by the speaker (using he-500) would be around 8.5 ohm. The output impedance from the headphones POV would be 25 ohm, I'd suppose. It would yield approx 2.2 dB decrease in volume (or a factor of 0.6). Anyway, the he-adaptor is definitely technically inferior to using robob's method, as it will alter output impedance.

### Gear mentioned in this thread:

This is the layout of the HiFiMAN resistor box:

Using the Headphone Resistor Network Calculator spreadsheet and HE-500 impedance of 38 ohms, if R1 = 10 ohms and R2 = 25 ohms then Effective Speaker Load = 8.6 ohms, Effective Headphone Output Impedance is 25.1 ohms and Amplifier Attenuation is -4.4 dB.

Using the much better performing "Preferred Resistor Network":

If R2 = 6 ohms and R3 = 2 ohms then Effective Speaker Load = 7.9 ohms (target is 8 ohms), Effective Headphone Output Impedance is 1.5 ohms (lower is better) and Amplifier Attenuation is -12.4 dB.

Edited by robrob - 12/12/13 at 7:17pm
Quote:
Originally Posted by robrob

This is the layout of the HiFiMAN resistor box:

Using the Headphone Resistor Network Calculator spreadsheet and HE-500 impedance of 38 ohms, if R1 = 10 ohms and R2 = 25 ohms then Effective Speaker Load = 8.6 ohms, Effective Headphone Output Impedance is 25.1 ohms and Amplifier Attenuation is -4.4 dB.

Using the much better performing "Preferred Resistor Network":

If R2 = 6 ohms and R3 = 2 ohms then Effective Speaker Load = 7.9 ohms (target is 8 ohms), Effective Headphone Output Impedance is 1.5 ohms (lower is better) and Amplifier Attenuation is -12.4 dB.

Thanks for this info. Yeah 33 ohms wouldn't make sense to be adapter to speaker amps. This also helps in my calculations for how much power my HE-500 is actually getting. The total resistance of the circuit is 8.63 ohms which is close enough to 8 so I'll assume the 50W from the Emotiva goes through the whole circuit. The R2 + HE-500 then gets 6.68W through parallel resistance calculations, and the HE-500 gets 2.65W after series resistance calculations. That number seems adequate, and it figures I don't hear the problems I heard when using only 1W or less with other amps. Now with the HE-6, the same calculation comes out to be 1.96W, which I don't think is enough seeing the HE-6 is even more power hungry than the HE-500. Need more powerful amp here.

Ultimately, I think had the HE-Adapter had a circuit like robrob's, it wouldn't fit the design goal of keeping the total impedance around 8 ohms. A higher resistance would be a problem when used with tube amps due to negative feedback loop damaging the transformers if I remember correctly, not an expert here. Still not sure why that 25 ohm resistor is in there. Not really needed for keeping around 8 ohms, as a headphone + 10 ohm parallel resistor is always around 8 ohms. Maybe it's to also provide a level of noise reduction and attenuation? I'm guessing robrob's design is better at attenuation though.

Edited by Sonido - 12/12/13 at 7:50pm

Order placed.  Looking to join the team.  I need an additional project this winter.  While I don't have a pair of headphones that need such power, It's still good to have when needed, or to use in a 2-channel audio system.

Mine should arrive tomorrow! :)

Quote:
Originally Posted by Nimzerz

Mine should arrive tomorrow! :)

Oh Schiit, Friday nite + Emotiva/He500 for Nimzerz = long long nite.

Quote:
Originally Posted by robrob

This is the layout of the HiFiMAN resistor box:

Using the Headphone Resistor Network Calculator spreadsheet and HE-500 impedance of 38 ohms, if R1 = 10 ohms and R2 = 25 ohms then Effective Speaker Load = 8.6 ohms, Effective Headphone Output Impedance is 25.1 ohms and Amplifier Attenuation is -4.4 dB.

You are right. I forgot it was 20*log and not 10*log...

Quote:
Ultimately, I think had the HE-Adapter had a circuit like robrob's, it wouldn't fit the design goal of keeping the total impedance around 8 ohms.

The "Preferred Resistor Network" shown gives 7.9 ohms of Effective Speaker Load. This value changes 0.1 ohm when going from 32 ohm impedance headphones to 600 ohm headphones. That's why it's the "preferred" network.

Quote:
Originally Posted by robrob

The "Preferred Resistor Network" shown gives 7.9 ohms of Effective Speaker Load. This value changes 0.1 ohm when going from 32 ohm impedance headphones to 600 ohm headphones. That's why it's the "preferred" network.
My bad. I see you got different resistor values. Still, one caveat is the power the HE-500 ends up getting is 1.9W vs 2.65W. Probably still more than enough.
Edited by Sonido - 12/13/13 at 8:19am
Got mine last night, finished my exams an hour ago. This is gonna be a sweet night :-D lol. Instead of studying last night I compared it to my lyr. So far I really like it. Slightly better stage. Feels more natural. I also find some of the little background noises/quieter parts in a song tend to pop out more. Seems like the presentation is more balanced. Maybe due to the huge amount of extra power. Suffice it to say I will probably be getting rid of my lyr. Although it wont be as "pretty" as a schiit stack :-(.

Hey guys? So even with my Denon receiver the right channel of my headphones were cut out until the volume was turned up. Now that I got my Mini-x I am trying it and the same problem shows up, except its the left channel that's quieter. The right channel is louder than the left depending on what volume is put out by the amp. This wasn't the problem straight out of my computer, so I'm guessing it might have to do with the cable? I'm quite confused, any help would be appreciated.

Quote:
Originally Posted by Nimzerz

Hey guys? So even with my Denon receiver the right channel of my headphones were cut out until the volume was turned up. Now that I got my Mini-x I am trying it and the same problem shows up, except its the left channel that's quieter. The right channel is louder than the left depending on what volume is put out by the amp. This wasn't the problem straight out of my computer, so I'm guessing it might have to do with the cable? I'm quite confused, any help would be appreciated.

It's mostly likely a cheap attenuator that doesn't track well at low volumes. If it was the same channel on both units, then it could possibly be the cable.

Quote:
Originally Posted by brunk

It's mostly likely a cheap attenuator that doesn't track well at low volumes. If it was the same channel on both units, then it could possibly be the cable.
Hmm, attenuator where? In the amp itself? Cause I thought both units were very solid and well built.

Ah I see. According to my cousin what you said makes sense. That the attenuator doesn't work well at low volume (7-8 o'clock) and causes channel imbalance.
Edited by Nimzerz - 12/13/13 at 11:47am
Quote:
Originally Posted by Nimzerz

Hmm, attenuator where? In the amp itself? Cause I thought both units were very solid and well built.

You're using an adapter for speaker taps right?  That could possibly be it since it's the one component that isn't being used on your computer/ipod.  If I still had one around I'd forward it to you to try but I gave it to a friend.

Edit - try switching left and right taps to see if the cutting out switches sides.

Quote:
Originally Posted by modulor

You're using an adapter for speaker taps right?  That could possibly be it since it's the one component that isn't being used on your computer/ipod.  If I still had one around I'd forward it to you to try but I gave it to a friend.

Edit - try switching left and right taps to see if the cutting out switches sides.
My cousin has an adapter for his Macintosh that he uses for his headphones too. He said he will bring it next time he comes. It seems the problem is not as obvious after the amp has been running for a while. It's still there, just not to the extent as before. I can definitely say that the emotiva seems to have better detail than the denon but the FR seems more toward the treble region than the warm sounding denon.
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