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Why A Separate Headphone Amp cf "Normal" Amp?

post #1 of 7
Thread Starter 
My office moved to the basement of our house and the acoustics are terrible. While my system is pretty good, the weak links are the speakers (Thiel CS 1.5) and my high frequency hearing loss.

Recently I purchased a set of Sennheiser 600s and had Daniels Audio (see http://www.danielsaudio.com/) add a headphone jack. He determined that the jack would sound better in the amp (an old Bryston 2B that has been modified) as contrasted to the preamp. However, after the installation there is a substantial amount of noise transmitted through the headphones. It's not noticeable through the speakers but quite annoying through the headphones.

Butch Daniels says it's caused by the noisy amp. Before I start spending money trying to fix the amp (or removing the jack to a separate enclosure, interconnects, etc.) I would like to know if I'm pursuing the wrong course.

One would expect that participants in this forum would have experience with good sounding traditional amps (terminology?). Am I better off going with a separate headphone amp because they are quieter or better than going through the
amp? While anything is possible, is it simply too difficult (time consuming/expensive) to modify the amp to get it to the level of a separate headphone amp?

I thank you in advance for your input.

P.S. Is there a way to search all of this subset of the forum for a similar question? I paged through the 9 or so pages without much luck on this issue but I'm sure it's not a new question.
post #2 of 7
I don't see how well you can adapt a speaker amp to work well as a headphone amp. Speakers have much greater tolerance for noise and distortion that headphones don't have since quite simply you are putting transducers right up next to your ears. As such, noise tolerance for speaker amps aren't as good. I believe ASL tried making a high quality transformer as well so you could use speaker outputs and that this was showcased at a Headfize meeting, but according to feedback, the performance wasn't even as ideal as the cheapest DIY/DBSE amps (could depend on the speaker amp of course, but speaker amps were designed with speakers in mind).

Also if it is just the speaker amp with resistors in the path, it makes for little damping, possibly making the 600 sound muddy and uncontrolled. So a speaker amp with resistors is likely to be a noisy amp with poor damping for the HD600...so I don't see how that would be a good solution. An active preamp would closer be able to play the part of a headphone amp, and there are a couple that succeed in this.
post #3 of 7

Yes ! It depend on quality of your amps..

I had test our proto-type of Headphone adapter. Yes ! It sound quality is highly depend on your Speakers amplifiers quality. Due to Dedicate Headphone amps is very simple and have less signal loss. I'm not try to design a Adapter to replace Dedicate Headphone amps but only less a Normal Speakers amps can use
as a high qulity headphone amps. Also you can direct connect to
CD player. I test this connection in many low cost to high grade with good result. (You CD player should have a V.R control).

It also have a function can change high impedance OTL Headphone amps to drive Low impedance headphone amps like Grado.

Protype seen in Head-Fi is only a Prototype. It will change to better component - Gold Plate Input/Output Speakers Post , Better Headphone Jack. May be additional a Jack for Headphone amps in.
I also have test a circuit of Headphone amps - It is a OTL headphone use 6DJ8 as Driver and 6AS7/6080 (NOS Available very low cost in the world). 6AS7 connect in white cathode follower. It even can drive down to 16 Ohm. The drawback of this amps is need more power than normal headphone amps use small tube. It draw about 100ma/Channel at 135V DC. It retail price is so close to MG-Head.It is for some Head-fi did't like transformers.
post #4 of 7

AMPS

First, before I talk about headphone amps, I would like to talk about your stereo. You have high frequency hearing loss, and you think the Thiel CS 1.5s paired with a Bryston 2B amp is not right for you. For someone with high frequency hearing loss I couldn't think of a better system. Like you said, "The acoustics are terrible."
The HD600s can have a similar tonal character to Thiel when used with a transparent, detailed, and non-forgiving solid-state amp. What's your price range? How do you want to change the sound of the HD 600s? Maybe we can help you pick the right amp in your price range.
Good luck!
post #5 of 7
Thread Starter 
Tim -

Over the past 12 months I've upgraded my stereo system by replacing the CD player, preamp, phono stage and tweaking the amp. I've been able to play my system through a friend's high-end speakers (at his house) and compare them to my old equipment. The changes to the Bryston amp have been AMAZING! Much better sound all around.
In my opinion, the Thiel's bass is muddy, and the midrange and high frequencies slow. The cymbals don't sizzle; the acoustic bass sounds dead and the saxophone somewhat flat. Now add the move to the basement and I'm not happy with the sound.
I really like the sound of the Sennheiser 600s, however they may be a little bright when driven through the speaker amp. (The CD player's headphone jack has been disabled.) Make no mistake I like a bright sound. However, as I indicated in my initial post, the noise level is very high. When the music quiets on one or both channels, the noise is clearly audible.
Even with the noise, the 600s sound wonderful when compared to the Thiels in the basement. It's the noise level that I want to significantly reduce or eliminate.
I might be jumping ahead of myself now, but what's the story with Headroom's propriety signal manipulation to "blend" the sound through one's headphones?
Finally, you asked about a budget. I guess I would like to stay at or under $500 to start with. While I've never built any electronic device myself, I would give a DIY project careful consideration since one of my friends is very capable if I get in trouble.
Thanks.
post #6 of 7

Why I made the Headphone adapter ?

I understand What is your problem on your Speakers amps with Headphone. The Output Noise Level is very high comapre with Headphone amps. Due to high gain in Spks Amps. It want about 1,000 time more power than Headphone. So the Noise level also very high. Use a Resistor series only can limited the current but not low the noise when use high impdance Headphone.
I had build a Headphone Adapter by a step down transformers. It step it down to 1/6 Vout. So it noise lvel also reduce to 1/6. This turn ration may be still not good enough for high power amplifiers. I may be consider to add a switch to change the step down ration to more low level. I know our prototype had listen by some Head-Fi member and still have some noise connect with a Solid state Integrated amps. You made me know what happen on it ! Thanks for your post very much. It really helpful to me. It trigger me to know what happen on it. Why still have noise ? Our heaphone adapter is very simple . 100% passive , Fully enclose in aluminum box. Why still have noise. I know it now.
post #7 of 7
Hardhead:

I'm not sure if I understand exactly what you mean by "signal manipulation to 'blend'", but if you are refering to crossfeed, it means mixing the sound from one channel into the other with a delay. It is meant to improve the soundstage (sort of) by partly undoing the unrealistic sound of headphones. I hear it is quite effective and a worthwhile upgrade. You can build the signal processing unit for something like $20 (or a bit more if you want an adjustable one or use higher quality parts).

If you are willing to spend $500, I'd say you'd be best off getting a headphone amp. The HD-600s work particularly well with tube amps. The MG-Head DT plus HD-600 is thought to be an excellent combo. Plus, you can get this amp for under $250.

Building an amp yourself isn't that hard, and is cheaper than buying a retail one. I built an OTL tube amp based on Morgan Jones' design of a reverse engineered Earmax. I have absolutely no experience with building electronics, but still managed with the help of a friend who has quite a lot of experience, so you should have no trouble. You can find quite a few different DIY projects at headwize.com's library section. Kits are also available and make building a cinch since all the components are given to you and all you need to do is solder them together.

Oh, and regrading your concern with noise from your headphones, it may be due in part to the fact that headphones (particularly the HD-600s) bring out the detail in recordings. So using heaphones really emhasizes any inperfections in the source. Sounds otherwise unnoticed with speakers are very obvious and, particularly with older recordings, a loud hiss can be heard. Although if you still hear noise when the playback is completely stopped, the problem lies in the amp.
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