Speaker amps for headphones
Feb 1, 2013 at 9:25 AM Thread Starter Post #1 of 3,871


100+ Head-Fier
Dec 9, 2012
I have a number of extremely high quality tube and solid state amps for speakers.  I am wondering about using them with Sennheiser HD800 headphones, which I do not have yet (backordered).  I know that my hundred watt transformer coupled tube amps will lost a lot of power at that impedance, and it's not an efficient use of gear and electricity, but are the results typically good when doing this? 
I also have 140 watt OTL (Atma-Sphere) amps I could  try.
Anything to watch out for when doing this?  Have folks had good results?
Thanks in advance.
Feb 5, 2013 at 8:39 PM Post #2 of 3,871
From what I've heard the HD800 tend to just not respond well to speaker amps. It works well with orthos though. 
Someone with more experience than I will contribute, but I'd be very careful.
Feb 5, 2013 at 9:02 PM Post #3 of 3,871
I tried this with my Hypex NCore NC400 amps that I built using a BAT VK-52SE pre-amp.  It sounded wonderful.  I have not done a lot of comparisons side by side but I would say it sounded AT LEAST as good as my WA-22.  Usable volume on the pre was maybe up to 15/140 steps.
I also have a hifiman speaker box thingy and will play around with that too as I get more time.  I am waiting on some speaker switches to get here (should be here tomorrow) so I can do some side by side comparisons. I may need to make another speaker tap, but will wait and see how it goes.
Feb 6, 2013 at 6:30 AM Post #4 of 3,871
Thaniks for the replies so far.
Senn-Fi, did you load the speaker amp down with series resistors between the headphones and amp?
I am also thinking of using a resistor between the + and - terminals of the amp so the amp is flowing a "normal" amount of current, as if it were driving 8 ohm speakers. 
I would love to hear from anyone trying the above.  It seems to me that only negative would be any sound of the resistors themselves.  But then I looked in my WA2 and it seems to have series resistors before the headphones to load the low impedance tube to the much higther impedance headphones. 
Again, thanks for reading and responding.  I will post my results when the resistors come in.     
Feb 7, 2013 at 9:46 PM Post #5 of 3,871
No on the resistors.  I just listened to it for a few minutes after I built my speaker tap cable for the HE-6 to see if it sounded good, bad, or mediocre.  I thought it sounded good.  I also listened to it with resisters in line ALA the HIFIMAN  speaker box thingy and it sounded the same, only a bit softer.
These Hypex amps are a bit unusual in their ability to drive both very low and very high impedence loads though.
Feb 22, 2013 at 7:21 PM Post #7 of 3,871
HD800s came in. Using 2 well respected, for the HD800s, headphone amps from 2 very well repsected headphone amp companies, they performed well. A bit coarse in the highs, and a bit prominent up there, and a little lean through lower mids and upper bass, but very clear, very transparent, and about what I would expect from reading hundreds of comments about the 800s. Problem is, not as easy to listen to as most of my speakers. Granted, speakers, amps, preamps, all that upstream stuff totals several hundred thousand dollars in my systems, so it hardly seems fair to compare when I'm substituting a few thousand dollars of headphone electronics for over $100k of preamp and amp.
So the itch remained to try my normal preamps (the headphone amps do not have an input avoiding the preamp, so I cannot avoid the headphone pre and use my great preamps) and my favorite speaker amp. Interestingly, many folks (the majority) said headphone amps are better, speaker amps have poor signal to noise ratios that headphones would uncover, not enough detail. I decided to try the idea I talked about earlier of loading the output of the amp at 10 ohms (could not find a high quality 8 ohm non-inductive wire wound resistor) and a dropping resistor after that and before the phones, starting with 100 ohms.
Well, the sound is phenomenal. A huge difference in width (not my most important thing), a major increase in refinement (really I'm saying major decrease in grain/distortion), beautiful sweet sweet, delicate highs with tremendous extension, deeper bass (the HD800s go amazingly low in the bass if the amp is stiff enough). The transparency is really amazing. I wondered if a bunch of parallelled tubes (8 per side) would be a bit crude or coarse at extremely low power levels, but it is the opposite. I will be trying several other speaker amps and will report. Certainly, information I received about speaker amps being too noisy, volume control will be at the bottom, headphone amps being much more detailed were simply not true. At least not universally true.
What amazes me is the sparse information about running headphones this way. To use dual mono amps I will need to make a "balanced" headphone cable as it would not be a good idea to have the speaker ground terminals of 2 different chassis tied togethere. Hope this information answers some questions for folks. I also would like to caution folks to not try this unless you understand exactly what you are doing, and have confirmed that the grounds of your left and right output lugs on the amp are connected. Further, no bridged amps, no dual mono amps. Dual mono amps should not be used unless the headpone wiring is balanced (different grounds on L and R channels, NO headpone plugs!)
Feb 22, 2013 at 8:06 PM Post #8 of 3,871
Thank you so much for the feedback. I myself am tired of the op amp wonders that are passed off for high end headphone amps and the tube offerings mostly seem like a take it or leave it, this is all your going to get proposition. What are the specs of your amp? Ive contacted Roger Modjeski to hopefully end this nonsense for me/us. This really isnt a niche anymore and the power of the home audio braintrust should be used. High end headphones arent $300 anymore, time to get serious
Feb 22, 2013 at 9:59 PM Post #9 of 3,871
Nice post Opera. I've been wondering about this for a while and got some good info in other places, but haven't gotten around to doing anything with it. Can you link me to, or tell me how to make the connections needed to get the impedances correct for use with a speaker amp?
Feb 23, 2013 at 9:41 AM Post #10 of 3,871
Last 2 posters, this is a work on progress as I think of where the best spot for attenuation is, try other amps, and make more progress.  For instance, I need more attenuation for my system, so I have been loading up on the series resistor before the phones.  This brings the amp to a higher power point, too, so I am changing 2 things: output of the amp, and impedence the headphones are seeing.  However, the amp is still seeing the same impedence load. Changes in sound could be from running the amp at a watt instead of 1/4 watt, for instance.  Or from running the phones from a current source, where the current will be constant in the face of changing impedance.  This is neither right nor wrong, depends on the headphone, how it was developed/tested, and the listener. 
In a way, part of the different sound of different amps into a particula phone would have to do with the output impedance, not quality of amp.  It could be an advantage in having enough power to try the amp both ways, as a voltage source and as a current source. 
Since this is not a finished work (though I love what I heard this morn, running the HD800 from a current source tames the high end and brings out the bottom, as well as richens the mids) I don't want to be misleading readers into thinking this is a finished work with definitive answers.  Many forum guys make one experiment and issue dogmatic statements.  It takes a long time and a lot of testing and measuring to really figure out what is going on and black and white answers are often not available.  For that reason, int might be best to pm me and I'll let you know what I'm trying and how it works.  I might be able to give you some direction based on the headphones you are using.  No promises.......!  
Feb 23, 2013 at 3:37 PM Post #11 of 3,871
There may or may not be differences in the resistors SQ. Whether you are willing to experiment with different resistors is up to you. It can easily get very expensive quickly.
Feb 23, 2013 at 5:53 PM Post #12 of 3,871
Yes, passive components can have their own flavor and one can tune (or truly improve things) but when starting with top shelf devices I have found over my 30 year career in audio that design considerations, matching impedances, etc. trump the smaller component differences (again, assuming we are starting with top shelf components).
For instance, today, after listening I decided to up the loading, but had to use a hodge podge of smaller resistor values, mixing 10 film and non-inductive wire wound resistors on each channel.
The resultant sound was absolutely fantastic, so low in perceived distortion yet so high in detail and dynamics, so realistic on my test albums, I just sat and smiled.  I might be able to gain that final 1 or 2% when I fix up the resistors to be all of one type and 2 pcs. per side max, but the big thing is certainly getting impedances in the right arena, and being able to use my superior speaker electronics. 
I go after primary and secondary effects before tertiary, it keeps the "gains per hour expended" ratio highest.
Feb 23, 2013 at 6:06 PM Post #13 of 3,871
Agree, impedance matching is more important and will have a higher affect on the SQ, higher than the quality of the resistors. With my HE-6 I'm using a 10 ohm resistor in parallel, however I would to change this value to slightly lower, 8.2 ohms instead using a Duelund Cast.
This is more like fine tuning.
Feb 23, 2013 at 7:32 PM Post #14 of 3,871
Very interesting........you are using a headphone amp, yet you are also loading the outputs with resistors across the + and -?  I did not know folks did this.  Is this to load the amp with a load it is more happy with?  
What headphone amp are you using?   Or are you using a speaker amp?  At the efficiency of those cans I'm thinking it must be a speaker amp.....
Feb 23, 2013 at 8:03 PM Post #15 of 3,871
Very interesting........you are using a headphone amp, yet you are also loading the outputs with resistors across the + and -?  I did not know folks did this.  Is this to load the amp with a load it is more happy with?  
What headphone amp are you using?   Or are you using a speaker amp?  At the efficiency of those cans I'm thinking it must be a speaker amp.....

I'm using a tube speaker amp, 50wpc P-P, two 6550 output tubes/channel.

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