[Xenophon]

Some speaker amps just have a loud background with headphones simply because as Kevin Gilmore stated...they're designed to work with speakers @8R or something, not with very sensitive headphones.  That's why simply throwing power at the HE-6 is not a sure way to make 'em sing.  They require an amp with enough but not too much power, a good power supply behind it and a silent background.  That's why some of the Pass amps work so well.  
 
@Justin_Time:  is the M2 noisy too with the HD-800?  Is it a hum at a certain frequency or just white noise hiss you're hearing?

 

[musicinmymind]

  I need help from the EEs out there on using speaker amps with the HE-6 and other headphones.
 
 
I have been experimenting a bit lately and got outstanding results from the HE-6 using several amps with a wide range of power rating and designs--some of the recent successful amps are the First Watt M2, Threshold S300, Nakamichi PA-5 II, Mark Levinson KAV 400xi, Conrad-Johnson MV75, BAT VK75SE and, unexpectedly, the Harman Kardon HK775, 770 and 870. 
 
With more efficient headphones such as the HD800, TH900 and PS1000, however, I typically get a constant background noise (low hum, buzz or hiss depending on the headphones and amps) when everything is connected even with zero volume from the direct source (Oppo 105 or PS Audio PerfectWave Mk II) or from the preamp when one is used (Krell KAV 400xi or Jeff Roland Consummate).  It sounded like the noise is from the amps themselves and is louder with more efficient headphones.  This happened with or without 8-ohm arrays used at the speaker outputs.
 
Is this normal and is there any way to reduce or eliminate that noise?
 
Sorry to be off topic but I thought that folks using this thread may be the most knowledgeable about this problem--and hopefully solutions. Help me, Obi-wan Kenobi... 

 
out all the amp you experimented, which one you like most with HE-6?

 

[Justin_Time]

out all the amp you experimented, which one you like most with HE-6?

I need to attenuate the gain and noise further with the tube amps first before making the final assessment of the sound.

Among the ss amps, there is a three-way tie and no clear winner:

The First Watt M2 wins in the midrange and treble, the Krell 400 xi wins in the bass, and surprisingly, the lowly HK870--I bought it for $170 shipping included--has the most pleasant sound to listen to.

I also need to replace the resistors in my homemade connector box with Vishay before doing an in depth assessment.

 

[Xenophon]

It's highly unlikely that changing resistors in that box will change anything audible (provided your solder joints are good), take a look here, it gives you an order of magnitude idea of thermal noise:


http://www.sengpielaudio.com/calculator-noise.htm

 

[musicinmymind]

 

out all the amp you experimented, which one you like most with HE-6?

I need to attenuate the gain and noise further with the tube amps first before making the final assessment of the sound.

Among the ss amps, there is a three-way tie and no clear winner:

The First Watt M2 wins in the midrange and treble, the Krell 400 xi wins in the bass, and surprisingly, the lowly HK870--I bought it for $170 shipping included--has the most pleasant sound to listen to.

I also need to replace the resistors in my homemade connector box with Vishay before doing an in depth assessment.

 
bass from 400 xi is awesome isint it, @ohhgourami found is still weak compared to big Krell he has, just make me wonder how good it is on his setup, it should be jaws dropping one for sure.
 
How good is HK700, I can pickup one for 130$ from local seller right now. it should be just fun to play from it and compare to 400xi

 

[wuwhere]

It's highly unlikely that changing resistors in that box will change anything audible (provided your solder joints are good), take a look here, it gives you an order of magnitude idea of thermal noise:


http://www.sengpielaudio.com/calculator-noise.htm

 
Not according to John Curl, http://www.parasound.com/pdfs/JCinterview.pdf.

 

[Happy Camper]

It is a common problem on speaker amps with more efficient headphones. The attenuation angle is the best you can do without a pre.

 

[Xenophon]

Iirc, he talks of resistors in the amps, potentially before the amplification stage or in the feedback loop. Not the same thing. If you amplify noise then of course it'll become worse but that's not what we're talking about here I believe

 

[wuwhere]

Iirc, he talks of resistors in the amps, potentially before the amplification stage or in the feedback loop. Not the same thing. If you amplify noise then of course it'll become worse but that's not what we're talking about here I believe

 
Its well documented that resistors affect SQ in a crossover network of a speaker which is not an active circuit.

 

[Justin_Time]

bass from 400 xi is awesome isint it, @ohhgourami
 found is still weak compared to big Krell he has, just make me wonder how good it is on his setup, it should be jaws dropping one for sure.

How good is HK700, I can pickup one for 130$ from local seller right now. it should be just fun to play from it and compare to 400xi

Sorry, I no longer want to lift anything heavier than 50 lbs. so the bigger Krell or Mark Levinson amps are now out of my life.

I am not familiar with the HK700. I tried the twin monoblocks (HK775), the dual stereo (HK 770) with the HE-6 and LCD. These amps have a sound similar to the later stereo model HK870, which seems to be just a tad better--it could just be that the later models are in slightly better shape.

Anyway, I am having two pairs of the monoblocks HK775 strapped into mono with new and bigger caps and the bias adjusted to run a little warmer. They should have more than 400 watts per channel into 8 ohms. I might melt the HE-6.

No, actually these amps are so good I will use them to drive my Magnepans 3.7 which have low impedance (5 ohms) and are very power hungry, just like the HE-6. What I have learned is that 25 watts into 8 ohms is more than enough for the HE-6 when that is pure class A power supported by a huge power supply.

A word of caution: the bias on these amps tend to drift badly. To need to get the amp checked out first befor hooking it up to your HE-6. Or use a pair of cheap speaker first.

 

[musicinmymind]

 

bass from 400 xi is awesome isint it, @ohhgourami
 found is still weak compared to big Krell he has, just make me wonder how good it is on his setup, it should be jaws dropping one for sure.

How good is HK700, I can pickup one for 130$ from local seller right now. it should be just fun to play from it and compare to 400xi

Sorry, I no longer want to lift anything heavier than 50 lbs. so the bigger Krell or Mark Levinson amps are now out of my life.

I am not familiar with the HK770. I tried the twin monoblocks (HK775), the dual stereo (HK 770) with the HE-6 and LCD. These amps have a sound similar to the later stereo model HK870, which seems to be just a tad better--it could just be that the later models are in slightly better shape.

Anyway, I am having two pairs of the monoblocks HK775 strapped into mono with new and bigger caps and the bias adjusted to run a little warmer. They should have more than 400 watts per channel into 8 ohms. I might melt the HE-6.

No, actually these amps are so good I will use them to drive my Magnepans 3.7 which have low impedance (5 ohms) and are very power hungry, just like the HE-6. What I have learned is that 25 watts into 8 ohms is more than enough for the HE-6 when that is pure class A power supported by a huge power supply.

A word of caution: the bias on these amps tend to drift badly. To need to get the amp checked out first befor hooking it up to your HE-6. Or use a pair of cheap speaker first.

 
I was referring to this amp http://www.thevintageknob.org/harman_kardon-hk770.html
 
if I get them will test with old yamaha speakers before trying on HE-6.

 

[Xenophon]

   
Its well documented that resistors affect SQ in a crossover network of a speaker which is not an active circuit.

OT but out of curiosity:  do you have a verifiable technical source for that statement that demonstrates audible (as opposed to theoretical) differences?  If you want to mention inductance:  for the resistor values typically used there the inductance is so small that it can't have any impact in the audible spectrum.

 

[Justin_Time]

I was referring to this amp http://www.thevintageknob.org/harman_kardon-hk770.html

if I get them will test with old yamaha speakers before trying on HE-6.

We both misspoke while talking about the same amp!

You called it the HK700, which does not exist. I responded by calling your amp the HK 770, which of course does exist. What a mess. Let's start over.

The HK 870 (later and slightly larger stereo model) and the dual monoblocks HK 775 may be a little better than the HK 770 but they all have similar sound.

These amps normally run fairly warm. If your unit does not, it's likely that the bias has drifted downward which may have helped the amp last this long. The amp would work OK but would not sound its best and should be checked. You should at least replace the electrolytic caps and check the bias circuit and fix poor solder joints. A full restoration should cost no more than $200-$300--you may need a good tech--and would give you an excellent amp for the HE-6 that will last another 15 years.

 

[SilverEars]

   
Its well documented that resistors affect SQ in a crossover network of a speaker which is not an active circuit.

In a passive cross-over network, it's the interaction with the resistor and a reactive component(capacitor or inductor) which passes certain bands like a high pass, band pass, and low pass filter if for a 3 way cross-over.  Adding a resistor in network could affect the cross-over points depending on the value of the resistor, and I take it that is what you mean by SQ, since a basic filter is combination of a reactive component such as an capacitor and a resistor(high-pass).  This would change the impedance response and therefore the FR.
 
Also dynamic driver based transducer is inductive in it's impedance response so there is some consequence to it's sound output based on the added resistor.  HE-6 we all know is a planar which has a flat impedance response like a resistive load, which it's impedance response should not be affected by the output resistor.   
 
An amp typically has input attenuation for volume control before gain stage, and the source noise should be attenuated according to the volume level set which would be attenuated proportionally to the input attenuation with the signal.  Likely the noise heard for reasons of headphone being more sensitive is the amp's internal noise.  That internal noise should be at fixed level based on how significant the gain is, and likely for high power amps that expects much less sensitive load would typically have much higher gain then for headphones.  For this reason, the internal noise can be heard when the input is fully attenuated at 0 volume.  I noticed this for my sensitive iems on my Beta22 which has too much gain, and can hear the power supply humm which I cannot hear with HE-6.  
 
I'm reading that noise is attenuated with output resistor, and I understand this as the amp's internal noise is fixed output which cannot be adjusted with the volume control.  By adding a resistor at the output, it drops partially, the noise's voltage like in a voltage divider.  The signal is unaffected since the volume control decreases the attenuation of the input source signal which the amplitude increases while the noise is dropped from the output resistor.  This is how I understand what the output attenuation used for dropping noise.

 

[Xenophon]

^ No argument at all with the above, it's correct as I understand it.  But what wuwhere was trying to say according to his post was that there is an audible difference in sound quality between cheap and expensive resistor brands (Vishay) in the connector box plugged in to the amp.  And there I disagree, or at least, I don't see how they could audibly differ and have never read a technical article saying they do.