Direct Path on Test

[jtfoo 0]

The sound directly from the source (or its proprietary line-out amp, resp.) without the detour through an additional amplification stage represents the sonic truth - in the ideal case.

I've never tried direct path, but nevertheless here's what I think,

 

IMHO, what direct path need is an invention of a headphone transducer that has ultra high impedance while sensitivity almost must increase accordingly. Ideally its inertia should be almost nil so that very little current is needed to move it to it's max length, without distortion..

 

 

[JaZZ 0]

Maybe you can try taking the opamps and/ or buffers off your CDP. Then drive your speakers/ phones out of the DAC chip directly. =)

As I said: I'm not the one to do some soldering inside a CD player or DAC, so removing op-amps is not my cup of tea; and unfortunately amps are indispensable when it comes to drive sound transducers... I just don't like the idea of having a strong signal from an output stage amp, boosting it up with a second amp in series to a level way too high to be useful with any *headphone* so that it has to be attenuated by a volume pot again, notably to a level clearly below the maximum of the original line-out signal (spoken in volts).

 

I seriously think there is more than just a 500ohm pot to achieve this direct path thingy.. Perhaps a custom wound tranny from extremely pure silver/ copper wires + dual-gang log pot. or attenuator.

 

Here's an example for a quite cheap transformer-based attenuator specially designed for headphone direct-path operation. Unfortunately it's not loud enough for normal sources and headphones, at least it requires low output impedances, high-sensitivity headphones (preferably the HD 600) and loud recordings... But the sound is excellent, slightly different from resistor-based attenuators, but on an almost comparable quality level as to the signal accuracy.

 

Even then, you'd need some form of buffering.

Explain! No, you don't need one. It wouldn't hurt the signal accuracy that much as an amplification stage though, but the unbuffered direct signal path provides the greater sonic accuracy. In the case of the transformer, this one is itself the buffer; and in the case of the resistor (= voltage divider) solution, the 500-ohm pot doesn't corrupt the signal that much. You shouldn't see headphones as speakers; they don't necessarily need a really high damping factor to work properly. Some of them are even designed to work best with serial resistors (some Beyer models, Etymotic ER-4 series), and some (OTL) tube amps have a similar output impedance as the effective serial resistance of the 500-ohm pot in this case. So what's your point? Do you think amps alter the signal less than an unbuffered 500-ohm pot or a dedicated transformer? In contrast to you I have some experience with the direct path, and I have systematically tested the impact of serial resistances and low-impedance loads. With an appropriate source, you get unbeatable accuracy and neutrality.

 

It's a well-kept secret that amps aren't really neutral - none is, not in the least. Actually that's quite logical, because every one sounds different than the other. So if you can renounce an amplification stage, do it! And be it just out of curiosity, to experience the true nature of your amp's sound. You may like the more colorful presentation through the amp better though, but don't mix this up with accuracy. Also analog discs often sound better than CDs, even when the same digital master has been used.

 

 

Rameish...

 

...«sonic truth» explicitly referring to the path «source line-out --> headphone». Not absolutely (of course not!) . Sometimes it's hard not to be misunderstood... BTW: the pot is on the way.

 

[JaZZ 0]

IMHO, what direct path need is an invention of a headphone transducer that has ultra high impedance while sensitivity almost must increase accordingly. Ideally its inertia should be almost nil so that very little current is needed to move it to it's max length, without distortion..

In fact line-out amps are of a similar design and not so much weaker than headphone amps - 2 volt is really enough to drive headphones, and some are even stronger than that; the only caveat is their ability to supply enough current with low impedances. I have already mentioned that some are even explicitly used as headphone amps (Sostenuto-1 portable DAC + headphone amp).

Edited September 4, 2003 by JaZZ

[matbon0013 0]

So, from what I would understand so far is to get as pure as possible any signals from the media??

Than why have recorded music to begin with? Just my logic setting in, please do go on.........

[JaZZ 0]

matbon...

 

...sorry, I don't understand your question.

[matbon0013 0]

Thats ok JaZZ! I'm just wierd like that.......

[Rameish 0]

Jazz,

 

Thanks for the pot. Will try it out again. In the mean time...we're on this journey to enjoy the music, so lets try somthing different and give it a chance to work. If it's limited to a couple of CDPs and would depend on several factors like op-amp choice, that's okay. Anyway, lets try at least. I'm gonna to so...lets wait a litlle ok?

 

 

[Firefox 0]

Unfortunately it's not loud enough for normal sources and headphones, at least it requires low output impedances, high-sensitivity headphones (preferably the HD 600) and loud recordings...

Answers:

 

Explain! No, you don't need one. It wouldn't hurt the signal accuracy that much as an amplification stage though, but the unbuffered direct signal path provides the greater sonic accuracy.

[JaZZ 0]

Rameish...

 

...it should arrive at you in four days or so. In the meantime... well, enjoy your life! And so do afterwards...

 

 

Firefox...

 

...I don't get your post. Is it that you want to insinuate that the transformer needs a sort of «buffer» to sound loud enough? That's certainly not the case. It's designed to provide a high input and a low output impedance, so to create «normal» circumstances for both line-out stage and headphone - thus it's a buffer itself; that's its actual raison d'être. The crux is the Reference Tool's low efficiency, which logically is a matter of (the extremely low) price.

 

John Chapman from Bent Audio, with whom I had an extensive exchange of ideas, has said to be able to build a transformer-based attenuator for headphones + line outs with the same 1:1 efficiency as a resistor-based attenuator. But let's not talk about the price...

[Firefox 0]

Firefox...

 

...I don't get your post. Is it that you want to insinuate that the transformer needs a sort of «buffer» to sound loud enough? That's certainly not the case. It's designed to provide a high input and a low output impedance, so to create «normal» circumstances for both line-out stage and headphone - thus it's a buffer itself; that's its actual raison d'être. The crux is the Reference Tool's low efficiency, which logically is a matter of (the extremely low) price.

 

John Chapman from Bent Audio, with whom I had an extensive exchange of ideas, has said to be able to build a transformer-based attenuator for headphones + line outs with the same 1:1 efficiency as a resistor-based attenuator. But let's not talk about the price...

Well... I believe that even a transformer changes the sound. The wires + core used and winding definitely "distort" the original sound from the line-out.

 

DAC's that can directly drive headphones are more often than not, powered with a higher than specified voltage to output an even higher output voltage. Most of them are not capable of a 2v. RMS output.

[Rameish 0]

Okay all this is beginning to zoom right past my head. I beleive in the 2-ears approach :-).

So I just wait the the pot arrives...I will reserve comment till then. Am negotiating with a fellow sgheadphones member for some op-amp replacements that hofully would work better with lower impedence. Till then I'm gonna sit in a corner and enjoy music.

[JaZZ 0]

Well...  I believe that even a transformer changes the sound.  The wires + core used and winding definitely "distort" the original sound from the line-out.

Although I have no info about transformer distortion, this sounds very plausible (thinking of magnetic saturation of the iron core). And it corresponds exactly to my listening experience with the Reference Tools: Although close to the typical (resistor-based) passive attenuator, the sonic signature was leaning somewhat towards headphone amps: warmer than the pot-based attenuator, like «filling the gaps between the notes» - creating a greater coherency, which is what's missing a bit with the pot type, which in turn seems to sound downright too clean at times. Given that the amps' distinct sonic characters are based on their harmonic-distortion spectra, it's a small step to postulate an equal behavior for transformers, just in a clearly milder occurence - which is deserving from a puristic point of view.

 

DAC's that can directly drive headphones are more often than not, powered with a higher than specified voltage to output an even higher output voltage.  Most of them are not capable of a 2v. RMS output.

The output voltage isn't the problem, but the output impedance. My former DAC, the Theta Pro basic II, offered 6 volt (and 5 ohm), whereas my now Bel Canto DAC2 contents itself with modest 2 volt (and 20 ohm). (BTW, 2 volt are a common value; few DACs offer less than that, but some even more.) Although it has less volume headroom than the Theta, it works equally well with driving headphones directly, and I never reach the upper limit of the volume control. 2 volt is enough.

Edited September 6, 2003 by JaZZ

[JaZZ 0]

Rameish...

 

...I really hope you can wait. But till then take care to have a low-impedance source at your disposal!

[Firefox 0]

The output voltage isn't the problem, but the output impedance. My former DAC, the Theta Pro basic II, offered 6 volt (and 5 ohm), whereas my now Bel Canto DAC2 contents itself with modest 2 volt (and 20 ohm). (BTW, 2 volt are a common value; few DACs offer less than that, but some even more.) Although it has less volume headroom than the Theta, it works equally well with driving headphones directly, and I never reach the upper limit of the volume control. 2 volt is enough.

Actually, by DAC, I meant the actual DAC chip. It's more likely than not, buffered with JFETs and / or opamps on the output. =)