[Sonic Defender]

Sorry if this post seems odd, but I'm trying to learn so I thought this situation might be a great opportunity so here goes. The mismatch in impedence comes from my HF2s with the Valhalla. I need to frame the background a little, so please bare with me a moment. The song where I noticed what I think is distortion related to the low vrs high impedence is Into the Fire by Sarah Mclachlan from her album Solace.
 
There are several places in the song where a pronounced bass swell is used. If anybody knows the song, or wishes to hear what I mean the possible distortion happens as the song enters the chorus and there is a large, deep bass swell that rumbles on into decay. With my DT 880 600 ohms, this bass swell is handled very well and sounds quite clean, however, with my HF2 it sounds quite distorted and edgey. I have two possible theories and I really hope a few of you can offer me your take on the situation.
 
a) I assume that the 880 has a deeper bass response due to the semi-closed design, and larger driver. Therefore it handles the bass signal from the swell better and reproduces it more accureatly than the HF2 which is distorting trying to not only reproduce a bass signal deeper than it goes, but doing so with the added disadvantage of the impedence mismatch.
 
b) The HF2 has a more revealing/forward mid and mid-bass presentation along with being more sensitive and the distortion actually accompanies the bass swell and is thus revealed. From what I can tell the 880 seems to smooth out the rough edges by being back in the mids and at the same time the louder and more plentiful bass also masks the distortion that the HF2 reveals.
 
I am really curious so ideally a few members out there have access to both the cans in question, the Valhalla and a lossless copy of the song. Regardless, I would love to hear what other members feel about this. I just find this situation so curious because other than that difference, both cans render the rest of the song quite well even if differently. I also know the HF2s are fine because I use them a great deal and have never heard them sound distorted before, only in this one song. Thanks in advance for your thoughts.

 

[Sonic Defender]

Bump, just hoping this topic might interest somebody. Cheers.

 

[kwkarth]

The HF-2 is a low impedance can, around 25 ohms, I think.  The Valhalla amp is designed and optimized to drive high impedance cans, with 32 ohms being the absolute minimum.

 

[Sonic Defender]

Hi kwkarth, thanks for the reply. The HF2 actually sounds fantastic with the Valhalla, it was literally just this one instance where I encountered any upleasantness so to speak. During the song it was only during the bass swell transition into the chorus where distortion occured, assuming it was distortion. I have listened to quite a few hours with the HF2/Valhalla combo and it is actually very nice, with some loss of bass control, but not so much so that the bass is flabby. Jason from Schiit told me he has some customers who are sound engineers who actually prefer the HF2 over high-impedence cans with the Valhalla.
 
 

 

[kwkarth]

Quote:

Hi kwkarth, thanks for the reply. The HF2 actually sounds fantastic with the Valhalla, it was literally just this one instance where I encountered any upleasantness so to speak. During the song it was only during the bass swell transition into the chorus where distortion occured, assuming it was distortion. I have listened to quite a few hours with the HF2/Valhalla combo and it is actually very nice, with some loss of bass control, but not so much so that the bass is flabby. Jason from Schiit told me he has some customers who are sound engineers who actually prefer the HF2 over high-impedence cans with the Valhalla.

I don't think you're going to hurt the Valhalla, but the effect of driving cans with too high an impedance is often an undesirable increase in the bass, and in extreme cases a lessening of the treble as well.  Just FYI, to help you undertand what's most likely going on.
 
 

 

[Sonic Defender]

Thanks again, and I do appreciate the information. I have been trying to learn as much about the science/sound marriage of impedence matching. I must say, that despite all of what I have read and expected to experience, the HF2/Valhalla combo hasn't yielded those type of results. Prior to my purchase of the Valhalla I had spent many hours with the HF2 and my solid state Creek integrated. I feel fairly confident that I was well acclimated to the HF2's sound. For what my experience is worth I can say that the treble did not lessen at all through the Valhalla, but the bass did increase slightly with less control as I alluded to before. Through the Valhalla the HF2's mids, already forward became even more so, but still remained quite enjoyable and seemed to benefit from some of the vaunted tube richness.
 
Perhaps the reason I do not find much of a change between the HF2 and either amp is due to the fact that the output impedence from my integrated's headphone jack is 220ohm. I'm not even sure what impedence the Valhalla is? I welcome any other feedback. Thanks in advance.

 

[kwkarth]

Quote:

Thanks again, and I do appreciate the information. I have been trying to learn as much about the science/sound marriage of impedence matching. I must say, that despite all of what I have read and expected to experience, the HF2/Valhalla combo hasn't yielded those type of results. Prior to my purchase of the Valhalla I had spent many hours with the HF2 and my solid state Creek integrated. I feel fairly confident that I was well acclimated to the HF2's sound. For what my experience is worth I can say that the treble did not lessen at all through the Valhalla, but the bass did increase slightly with less control as I alluded to before. Through the Valhalla the HF2's mids, already forward became even more so, but still remained quite enjoyable and seemed to benefit from some of the vaunted tube richness.
 
Perhaps the reason I do not find much of a change between the HF2 and either amp is due to the fact that the output impedence from my integrated's headphone jack is 220ohm. I'm not even sure what impedence the Valhalla is? I welcome any other feedback. Thanks in advance.

Dr. Jan Meier published a brief one pager on the effects of raising the output resistance of the headphone amp on the sound from a typical headphone.  I'll see if it's still published...
BRB.
Try this:
http://www.meier-audio.homepage.t-online.de/tipstricks.htm
 

 

[Sonic Defender]

Thanks for the link, here is a good read on the subject. I would appreciate your assessment of the information provided, i.e. sound reliable, well supported by science. Cheers.
 
 

 

[kwkarth]

A lot of his ideas are good, but his integrity has proven to be very questionable.  Sorry about having to delete your link.  I hope you'll understand.

 

[Maverickmonk]

This is probably a dumb question...but has anyone tried making an output transformer box to lower the output impedance to their low impedance headphones? what effect would this have on sound quality?

 

[kwkarth]

Quote:

This is probably a dumb question...but has anyone tried making an output transformer box to lower the output impedance to their low impedance headphones? what effect would this have on sound quality?

That would depend on a lot of variables, and a good transformer designed for wide bandwidth and that would handle a little power would not come cheap.  RKV did that with their "impedancer" if I recall correctly.

---

 
8. Use of the IMPEDANZER 
In case headphones with impedances below 100 Ohm are to be connected, it is recommended to use 
the so-called Impedanzer for a better match between amplifier and load impedance. This device 
allows to connect headphones with impedances between 8 – 64 Ohm. 
Also high efficiency loudspeakers can be connected through the two pairs of connectors at both 
sides of the front. The rotary switch selects the right amount of impedance matching. In case of 
doubt optimal matching can be established by ear. 
At the middle of the front plate two headphone jacks can be found. Again, optimal matching can be 
selectec by the switch. 
The backside of the Impedanzer has a cable connector that is to be connected to one of the 
headphone jacks of the RKV. 
If you like to use two headphones of the same load impedance please select a matching impedance 
at the Impedanzer that equals half the impedance of each headphone. Example: Both headphones 
have a 32 Ohm load impedance and both are connected. Please select the 16 Ohm setting for a 
proper matching. 
The two pictures show the frontplate and a photograph of the Impedanzer and visualize the various 
control elements. 
(Upgrading Febr. 2004) 
The Impedanzer is equipped with a bypass switch that completely removes the built-in transformer from the 
circuit, a so-called true bypass.  This feature allows the RKV owner to hook up headphones such as the AKG 
K-1000 directly to the speaker binding posts of the Impedanzer using the headphone's standard cables and 
without any need for custom terminations.   At the same time the RKV's output impedance remains 
unchanged, resulting in a perfect impedance match between RKV and headphone.
  
When the bypass switch is facing upwards, the Impedanzer's impedance selector is activated and may be 
adjusted to loads of 8, 16, 32 and 64 Ohms.  When the bypass switch is facing downwards, the impedance 
selector is bypassed, and the RKV will work best into loads of approximately 100 Ohms or higher.
  
A word of warning:  The volume control of the RKV should always be turned all the way down before 
operating the bypass switch.  Bypassing the Impedanzer will otherwise result in a considerable jump in 
volume, which may damage your hearing or your equipment. 

---