[Taphil]

Ok, so I'm new here and read a lot about amps and have come across JMT amps.

What's a JMT amp? Is JMT someone who builds them? How big are they? What can they be used for? How much are they? How do I contact him?

The ipod has a 60mW amp. The Creative Nomad Jukebox 3 has a 100mW amp and 98db SNR. What do the amp ratings mean? What does signal-to-noise ratio mean? Is higher better or lower? And what is total harmonic distortion mean?

I have an iPod (and soon a Creative NJB3) and I mostly use Senn HD280's with them, but sometimes also Senn MX400 and HD497. Can a small JMT amp help the HD280 sound better? By small, I mean something the size of an Altoids box. (I read someone had one like that.) Also, in the future I may get some 580's or maybe Grado 125. I've read the Grado's can run fine off the ipod. But how well? Someone has said they use their 600's on the ipod but the volume is low. So I assume I'll need an amp to drive the 600's or 580's. How will a JMT amp do with the 580's, or should I be looking at the Airhead Headroom amp, which is still more than I want to spend on an amp? How big is the difference between the Airhead and Total Airhead amp? How important is it to match the amp with the headphone, since I would want to use the amp on both 64ohm 280's and 300ohm 580's?

Thanks. I learn so much from here.

 

[Driftwood]

a JMT amp is an amp that is built by the member JMT. It is actually a cmoy or CHA-47 design and he can build it to your specifications. It is about comparable to one of the headroom airhead variants.

Driftwood

 

[RVD]

From what I've read the JMT amps are excellent and are just as good as the airhead. You can get them in an altoids can. From what I've read the JMT amp should be able to power the hd600/580. If you plan to use an amp with the ipod it might not do so much for the sound because the ipod does not have a dedicated lineout, but you are getting a nomad 3 which does so that should not matter. Hope this helps.

 

[Gluegun]

I think the iPod exaggerates their mW ratings a bit... it isn't THAT loud....

 

[lextek]

I've used Grado's with the iPod with good results. I have also used the Sennheisser HD600's with an amp and the iPod. Myself the iPod (10gig) is the ultimate ultra-portable and I use Ety 4P's or a set of Grado's. I had an earlier version of the Nomad Jukebox, didn't care for it too much.

Lextek

 

[disturbed]

Usually it'll be a CHA (Three designers Chu Moy, Carl Hansen, Apheared) 47 with the gain adjusted to the phones of your preference. Unless you are looking for a particular type of sound...smooth...more bass etc.. But it could be a cmoy (Named after the designer Chu Moy) for you, it depends.

You can even ask him to make one which can be connected to an external power supply so in the end you save on battries at home and

when you go out portable bliss with batteries.

Generally speaking in many ways the CHA 47 sounds better than the airhead and vice versa but it really depends on ones preference.

You could also ask for a crossfeed circuit if you listen to a lot of music which has hard panning from the left to the right.

Size depends. If you opt for 9V then the size can be drastically reduced...but if you opt for AA then the size will be much larger...about the size of a RioVolt because you'll need at least 8 - 16 cells to power the baby.

AA's are cheaper and much easier to find anywhere. 9V are more expensive.

Alternatively you can check out:

http://www.thomasdistributing.com

They sell a wide rage of Rechargeable NimH cells in different sizes and they sell chargers too. A must buy if you are planning to use the amp portably a lot.

The price depens on the type of amp you are getting...and what variations you want like the ones mentioned above.

One thing is for sure...you will not be disappointed on the sound nor the price the good man JMT offers to his customers. He doesnt really look for profit as he personally told me and others here. What he wants, according to him, is to share good sound with everyone and help them get it with his hobby of building amps.

Hope you enjoy your soon to be amp

 

[The Quality Guru]

Taphil,

About Total Harmonic Distortion (THD) - I really don't have a great definition for you (go to Stereophile's website and they have a monstrous glossary that you can look it up) - it's something like the total distortion of the harmonics reproduced by the audio equipment . . . But I'm going to tell you something that you should truly remember. All specifications, which include petty details like THD (usually between 0.001% and 0.3%) are many times totally, completely, and so very meaningless!!

Do you care to know why specifications, in general, are meaningless?

It is simply because (a) many of the specs are put in the literature simply for the sake of advertising purposes, to make people think that a variance of 0.03 in THD is going to make that product better, also (b) they are many times not very accurate, and (c) most importantly, many of the specification of certain audio products DO NOT AFFECT the sound to a noticeable degree. A variance of THD in small amounts really makes no difference whatsoever! What makes products sound better is not the specs (though in some cases, specs are useful ONLY for informative purposes) but what makes the sound what it is are the other factors, the more subjective, non-measurable factors; this whole forum is here because sound is not 'measurable' scientifically, but rather, only to be discovered through listening.

And to answer some of your other questions:

About the Total Airhead versus the JMT CHA-47 (it is built into an altoid/ penguin mint encasing), just go with the JMT amp; almost everyone says that the JMT beats the Total Airhead and the Porta Corda (another portable amp you'll eventually come across).

Yes, the JMT CHA-47 will drive the 580's effectively, but the Grado SR-125 will be driven more effectively with the JMT amp. Also, you must decide on which headphone you will buy and use with the JMT amp, because you need to tell JMT, the builder of these amps, so he can adjust the amp to match the impedence of the 'phones and adjust the volume gain. Also note that because the Senn 580's have a higher impedence these are not ideal portable 'phones and will in most cases sound less loud when compared to Grados; the Grados are lower impedence 'phones
and do not require an amp, while the Senn 580's are very close to requiring an amp.

Do a search on the JMT CHA-47 amp if you need more info on it. Send a private message to JMT if you wish to commision him to build one for you. He has along waiting list though; for he does, after all, build them himself by hand.

Regards, Luke

 

[The Quality Guru]

Bah humbug, disturbed! You beat me to it; posting your long response before me!! Pooey!

 

[archosman]

Quote:

One thing is for sure...you will not be disappointed on the sound nor the price the good man JMT offers to his customers. He doesnt really look for profit as he personally told me and others here. What he wants, according to him, is to share good sound with everyone and help them get it with his hobby of building amps. Hope you enjoy your soon to be amp [/B]

I second that fully! I really, really enjoy mine! When I took it apart to put in the batteries I was blown away by the construction. It looked like any of the electronic devices I've taken apart at work... sturdy and professional. No bulls__t...

 

[Taphil]

Thanks everyone. I have a few more questions.

I walked by a Tweeter today and tried the HD600 and HD590. Wow. I didn't really get to test them much though. They was plugged into some Sennheiser display and playing some jazzy blues (I don't know exactly what it was, I don't know about that kind of music). I like the 600's, and the 590's were noticably bright in comparison. Some of it was so bright that it hurt my ears, although the volume was a bit high. But if I upgrade my HD280's, I'll go with the HD580. I think I'll get ask for a JMT amp after I get them when I have the money. So here are my questions:

1) Is getting the HD580 worth it, considering I'll be listening exclusively to mp3's with them? I'm a pre-med college student, so it will be forever or never before I can afford to use them on anything but an iPod or Nomad Jukebox 3.

2) Is the HD580 good with rock, alternative, and metal, especially in terms of the bass? Is the bass heavier than the 497 and 280? I'm looking for something in between the 280's and Koss Porta Pros. I've never tried Grado's, but I don't want to risk buying them and finding them uncomfortable or fatiguing. And I like the Sennheiser's laid-back and relaxing sound anyway.

3) Is the HD580 "bright" bright? I know the HD590 is a bit bright and I don't like it. With some albums (as mp3's), the HD280 are scratchy at the high end so that I can't use them, and have to use the HD497 (which I don't like anymore because they can no longer satisfy me=endless upgrading desires). So would the 580's give me the same problem?

IMPORTANT: When I say bright, I'm only referring to vocals. I don't mind if the music/instruments are just a bit bright, but it's the vocals that get bright and scratchy on the stuff I listen to. I don't think it has to do with MP3 encoding though. If I play a song such as Travis "Side" on my old Sony CD player (D-T405) or as a 320kbps MP3 off the iPod, some of the vocals are scratchy (or sound like cymbals), like when he says "circle," "side," "stay," or "the". It's the t and s syllables that are scratchy. I don't have this problem with the 497, though they are have less clarity and are muddy. Or maybe it's the 280's that's causing this.

- When you guys says good headphones are very revealing of bad recordings, what do you mean? What are characteristics of bad recordings?

- Are scratchy highs caused by bad recordings or headphones?

- Do I just have abnormal hearing if I find lots of vocals to be scratchy? If so, is my hearing bad or good, as in is my hearing ability poor and unable to distinguish high frequencies, or is is my hearing too good that I can hear higher than 20,000kHz so that poorly recorded vocals hurt my ears?


Ok, that's it for now

. Thanks.

 

[Driftwood]

if you are going to be using the headphones from an ipod or some equally low-hi source, and without an amp to boot, I think the HD-580 or HD-600 would be overkill. It would sound good, yes, but it might be overly revealing of the flaws of the source, and in addition, you could probably get something else that would provide you with as good of sound for a lot less.

Why are you upgrading from the 280? Seems like those would fit your requirements pretty well to me.

Driftwood

 

[violeta88]

Taphil, what you are referring to as "scratchy highs" is more commonly termed as "grain". Grain is abundant in low quality sources like MP3's, but I bet you didn't even notice it until you heard the HD600's compared with your HD280's. That's the other cause of the sensation of grain. When a headphone that has a almost non-existant amount of grain is compared with a headphone with a much higher sound quality, or at least less grain, you magically start to hear the grain. It goes away almost completely after a few minutes if you don't listen to the better headphone any longer, but the longer you listen to the better headphone, the more agony you suffer when you listen to the headphone that exhibits the grain. That doesn't mean that the HD600 doesn't have grain, it's been said to have some grain when compared to the Audio-Technica ATH-W2002 and ATH-W100. So, basically, almost any good headphone has a little grain. It's nothing to worry about. Just let your ears adjust back, and you won't even notice the grain, unless you compare it to a headphone with less grain. You just happen to be "blessed" with the type of ears that have a "grain detector" in them. But, the 280 is a wonderful headphone, and is probably all you need for what you are listening to. An HD600 would probably be overkill. It would be like getting an Orpheus to listen to your cassettes. Yeah, they would sound great, but you probably wouldn't be able to stand all that high-fidelity hiss.

 

[delenda est Sony]

hey Taphil---

JMY CHA 47 drives my HD600s fine even though the gain (volume range) was originally set for Grados (much lower resistance). Also, anyone thinking of buying 580s, consider ordering the 600s from Hand der Baer on eBay (new for $210 shipped) or Jan Meier (new for $220 shipped). The cans are indeed new and come with full Senn warranty. These prices are generally only a few bucks more than what you can get the 580 for, so why not splurge?

 

[Taphil]

I figured 580/600 would be overkill for mp3's, but I'm still looking for something better than the 280's, mostly in terms of bass and less grain. (Thanks Violeta888 for explaining that.) I know that mp3 is lossy, but when comparing 320kbps mp3's to original CD's, I really can't tell the difference. My only concern is if the 580/600 will reveal grain and kill my ears. And I hear the grain on both mp3's and CD's anyway, so I'm hoping that the mp3 players will provide good enough quality for me, and the headphones will in turn provide great (or decent for those who really care about quality) sound. Is that possible?

I guess if can spend $80 more to get the 600 over the 580. So once more before I splurge, I'm asking: should I?

 

[archosman]

Quote:

My only concern is if the 580/600 will reveal grain and kill my ears. And I hear the grain on both mp3's and CD's anyway, so I'm hoping that the mp3 players will provide good enough quality for me, and the headphones will in turn provide great (or decent for those who really care about quality) sound. Is that possible? I guess if can spend $80 more to get the 600 over the 580. So once more before I splurge, I'm asking: should I? [/B]

By all means... splurge! I have a pair of Grado 325s and a pair of Etys4Ps. I also have an Archos Jukebox that I rip alot of cds at 256kbps. I also use both headphones with my stereo. Do it!