Question about amps

[Donald North]

Originally Posted by cerbie

Since I can only find that IEC doc for sale: is it equivalent to taking a near-0 Ohm source and adding an inline resistor? As in out->120 Ohms -> Driver -> Gnd per channel.

Yes

[odigg]

Originally Posted by Donald North

A zero output impedance is not necessarily the ideal for a headphone amp. It depends on how a particular headphone is designed. There is an international standard IEC 61938 which specifies 5V with 120 ohm output impedance for headphones of the range 8 - 600 ohm.

Yes but consumers have no idea which headphones are designed for what output impedance. I'm sure all headphone manufacturers are aware that consumers use everything from a sound card to a speaker amp. Wouldn't a headphone manufacturer say "optimized for a 120 ohm jack" on the headphone box if they were specifically designing a headphone to sound best with 120 ohms?

Plus, how many amps (headphone, speaker or pro audio) have a 120 ohm output? I can only think of one. I doubt headphone manufacturers expect people to build resistor networks to get the "ideal" sound of their headphones, meaning the FR the manufacturer designed the headphone to output.

[Donald North]

Originally Posted by odigg

Yes but consumers have no idea which headphones are designed for what output impedance. I'm sure all headphone manufacturers are aware that consumers use everything from a sound card to a speaker amp. Wouldn't a headphone manufacturer say "optimized for a 120 ohm jack" on the headphone box if they were specifically designing a headphone to sound best with 120 ohms?

Well, they don't specify but I do agree it would be a good idea if they included it in the product specifications.

Originally Posted by odigg

Plus, how many amps (headphone, speaker or pro audio) have a 120 ohm output? I can only think of one. I doubt headphone manufacturers expect people to build resistor networks to get the "ideal" sound of their headphones, meaning the FR the manufacturer designed the headphone to output.

I know of a few which provide the 120 ohm output. The beyerdynamic headphone amp has 100 ohm output impedance. Also many hi-fi stereo amps which include a headphone jack have series resistors. Although as shown in the recent post by Pio2001 these don't follow an exact standard either. Look at the difference in frequency response into the HD600 from the Marantz and Arcam amplifier. Do note the difference in SPL at 100Hz is 1dB between the two:
Headphone outputs : lots of measurments and one ABX

[IPodPJ]

120 ohm output: so does the Meier Audio Opera and Symphony.

[odigg]

The buffer section, however, sits there as a means to power the drivers. When signal goes up or down, and causes the driver to move, the driver then pulls current, and voltage drops (and exactly how much it does this is not the same for all frequencies!). If it's pulling more than your amp can provide (sink, usually) at any instant, or more total than your amp can provide over time, then you get distorted sound. If a big drum hit comes in, and the drivers go from ~2mA to ~50mA right then, and in no time flat go back to needing ~2mA, that can give a weak little amp some hell. With most typical consumer products being made with cost savings having priority over quality, things like this suffer.

Yes but the distortion you are talking would probably be audible (depending on how much distortion there is) and would be measurable. The definition of a weak amp would then be an amp that *measurably* fails such a current or voltage swing. But few people on Head-Fi perform measurements so all we've got is a bunch of subjective mumbo-jumbo, a lot of which could not be verified in a blind test.

If we are talking about pure slew rate, you don't need a very high slew rate for the voltages talked about with headphone amps.

Originally Posted by IPodPJ

120 ohm output: so does the Meier Audio Opera and Symphony.

So how many devices are there that adhere to this particular "international standard." Can I count them with my fingers? It's a stretch for me to believe that headphone manufacturers are designing to a standard when it seems few amp manufacturers actually follow it.

[cerbie]

Originally Posted by odigg

Yes but the distortion you are talking would probably be audible (depending on how much distortion there is) and would be measurable. The definition of a weak amp would then be an amp that *measurably* fails such a current or voltage swing. But few people on Head-Fi perform measurements so all we've got is a bunch of subjective mumbo-jumbo, a lot of which could not be verified in a blind test.

Better yet, objective equipment. Measure input, output at the jack, and rail voltage at the output chips' pins, at the least. AFAIK, the best we have for headphones are simulations by AMB showing what should happen in certain circuits, without real components getting in the way.

I don't have time to go hunting, right now, but some basic output testing has been done comparing DAPs and such with other models (such as when the iPod Shuffle got normal people noticing), and dedicated HP amps. Now, once things are given enough juice, then you have another can of worms open.

If we are talking about pure slew rate, you don't need a very high slew rate for the voltages talked about with headphone amps.

In fact, slew rate being high tends to be quite an enemy for audio.

So how many devices are there that adhere to this particular "international standard." Can I count them with my fingers? It's a stretch for me to believe that headphone manufacturers are designing to a standard when it seems few amp manufacturers actually follow it.

The best thing would clearly be to make it sound more accurate with the higher impedance out (divider), but not bad without it. How well it's done, who does it, and how, well...

[vkvedam]

Very interesting thread. Even when I auditioned Graham Slee Novo I felt it didn't bring any audible improvement over when compared to iPod's line out feeding my headphones using an in-line volume attenuator. I spent about a week and tried to appreciate the improvements an amp brings but failed. Many people said my source wasn't great. But the same people when auditioned iPod as their source posted different thoughts. I even tried the same with my vintage Sony PCDP and I couldn't hear any difference.

[odigg]

Originally Posted by vkvedam

Very interesting thread. Even when I auditioned Graham Slee Novo I felt it didn't bring any audible improvement over when compared to iPod's line out feeding my headphones using an in-line volume attenuator. I spent about a week and tried to appreciate the improvements an amp brings but failed. Many people said my source wasn't great. But the same people when auditioned iPod as their source posted different thoughts. I even tried the same with my vintage Sony PCDP and I couldn't hear any difference.

If people were doing blind tests of the IPOD versus "audiophile" CD players you'd probably find many people unable to tell the difference. The IPOD, along with many portable audio players, actually has a good sound output.

As for lossy music VS lossless in blind tests, a lot of people can't pass those tests either. However, there are people who have ABXed high bitrate lossy files versus lossless.

That being said, I'm not an advocate of totally ditching lossless music. There are reasons to keep lossless around even if you use lossy on a daily basis.

[Bullseye]

Originally Posted by royalcrown

Good point odigg, I neglected to note that his headphones are low-impedance Grados. Bullseye, if you search pro audio sites such as sweetwater or zzounds you can find a huge selection of pro headphone amps. Try the SM Pro Audio HP4 available at zzounds (SM Pro Audio HP4 Headphone Amp from zZounds.com!), it will perform identically to the other amplifiers but it has a 22 ohm output impedance - not the lowest, but it should be low enough for 32 ohm headphones. From my personal experience and observations, so long as the damping factor is a bit above 1.0 (that is, the headphone impedance is at least a bit higher than the amp's output impedance), you should be fine with headphones. Speakers need much more, but (likely due to the small size and power requirements of headphones) this doesn't seem to be the case for headphones.

The downside is that there's no pass-through for a pair of speakers. I bought the HP4 based on that, and I could've probably had the same performance for 20 bucks, but the convenience of having a quick button to switch between headphones and speakers was worth the extra cash. You can find various pro amps at many price ranges, and they all perform the same (given a proper match in terms of impedance), but they have different features.

Hi again,

Well I had to revive this thread because searching for more low cost headphone amps I found one which can't compete with the price of the S·Amp, but has some interesting specs. In the end maybe (most likely) it sounds the same as the S·Amp, but it has different specs and that is where I am going.

The amp I am talking about is the Musical Fidelity V-Can.

Its has this specs:

Power: 0.25W /channel into 32 Ohms
Output devices: 2 per channel
Output impedance: 5Ω
Total harmonic distortion: <0.005% typical 20Hz-20 kHz
Signal/noise ratio: >109dB ‘A’ weighted
Input impedance: 25KΩ
Frequency response: +0,-1dB 20Hz to 80 kHz
Power requirement: 12V DC 500mA

Link: http://www.musicalfidelity.com/manua...n_manual_1.pdf

The interesting part of this is the output impedance of 5Ω
The total harmonic distortion is low, but even if it were <0.05 or more it would be ok. What do you think about the S/N?

The MSRP price is $199. Almost 4x the price of the S·Amp. However it can be found for $160 (shipping included to my place) (still around 3x the price of the S·Amp)

Another amp I have found is the Pro-Ject Headbox II:
These are the specs:

Power output 330mW/30ohms, 60mW/300ohms
Headphone connection > 30ohms
Signal to noise 78dB (100dB - A weighted) at full output
Frequency response 30Hz – 20kHz/-0,05dB
THD (IMD) ,005%/30ohms, 0,007/300ohms
Gain 11dB
Headphone jack 3-pole ¼" (6,3mm Ø) phono socket
Outboard power supply 16V/500mA AC, suitable for your country's mains supply
Power consumption 16V/120mA AC
Dimension W x H x D 103 x 38 x 127mm
Weight 600g without power supply

Link: http://www.project-audio.com/inhalt/...al_headbox.pdf

This amp seems to allow headphones with impedances higher than 30 Ohm

Price is a bit more than the V-CAN: ~$170 (Much more than the S·Amp)

Finally the Creek OBH-11

Specs:

Output Power > 10 mW into 30 ohm / 300 ohm loads
Headphone Impedance 30 ohm to 300 ohm
Total Harmonic Distortion < 0.01% at 1 kHz
Signal To Noise Ratio > 70 dB
Power Consumption < 4 VA
Power Supply Requirement 24V DC 150mA (Uni-OBH)
Weight 3Kg
Size W/H/D 130 x 100 x 65mm

Link: http://www.creekaudio.com/products/leaflets/obh11.pdf

Price: ~$220 The priciest. This one also has a variable headphone output impedance.

Why am I putting all of these amps here? Well my intention was mainly to mention the V-can due to its specs and its very low output impedance. The others just for reference, and due to their multi purpose with different headphone impedances.

So far I still feel the S·Amp will be the best buy. For the price you just can't go wrong. But for people who use low impedance HPs, the V-Can, even if pricier than the S·Amp might be a good amp.

What do you guys think? (Mainly directed to Royalcrown?

Edit: Forgot about one last thing. It is still unbelievable how much the price sky rockets as soon as "Hi-Fi" is mentioned... Luckily we also have the word Pro that sometimes it is well used

[royalcrown]

Bullseye:

I just found out from a friend that SM Pro also makes this headphone amplifier:

SM Pro Audio XPH4 4 Channel Headphone Amp

I haven't listened to it personally, but my friend has and found it transparent - he uses it for music production more so than reproduction.

As for the amps you picked, you can't really go wrong with any of them - most amplifiers work just as well as the next, they just overcharge after espousing "detail," "transparency," "soundstage," and other words that have no fixed meaning. If I were to pick, I'd choose the V-Can just because it's the cheapest one available, though you can find pro offerings with low output impedances (like the one I just linked, 10 ohms is low enough for just about anything) for far cheaper that will give you the same performance.

[odigg]

Pio2001 recently posted a (don't know which one) test of a Pro-Ject headphone amp.

I'll quote his comments on the amp"We also noted the level for each channel. The Pro-ject is quite unbalanced with 0.7 dB of difference between the left channel and the right channel at the listening level for hifi headphones, and 1.5 dB of difference at the level for earphones (11 db lower). And it doesn't feature a balance setting. Too bad for a dedicated headphone amplifier."

At least to me, such an imbalance is unacceptable in a $100+ piece of gear. Even my motherboard's onboard sound has less channel imbalance and my motherboard probably cost less than the amp.

[Bullseye]

Originally Posted by royalcrown

Bullseye:

I just found out from a friend that SM Pro also makes this headphone amplifier:

SM Pro Audio XPH4 4 Channel Headphone Amp

I haven't listened to it personally, but my friend has and found it transparent - he uses it for music production more so than reproduction.

As for the amps you picked, you can't really go wrong with any of them - most amplifiers work just as well as the next, they just overcharge after espousing "detail," "transparency," "soundstage," and other words that have no fixed meaning. If I were to pick, I'd choose the V-Can just because it's the cheapest one available, though you can find pro offerings with low output impedances (like the one I just linked, 10 ohms is low enough for just about anything) for far cheaper that will give you the same performance.

Thanks for that royalcrown, the problem is that they don't sell it to Europe anymore -I could see that in their homepage-. And the site you have given me the link does sell over seas, but maybe it becomes more expensive than the amp itself, and it becomes more of a hassle, and maybe I just go with the V-Can.

Then about using different terms it is really the perfect excuse for them to increase the price so that people who don't understand can repeat after they have bought it and they are showing it to other friends... "Yeah, you can hear the soundstage expanding, ..."

Anyways it is good to have alternatives now. When the time to buy an SS amp comes, I will check the market and the headphones impedance I will be using it with and will decide whether, for the money, I shall go with the Samson, or SM Pro, or V-Can.

[cerbie]

Originally Posted by odigg

Pio2001 recently posted a (don't know which one) test of a Pro-Ject headphone amp.

I'll quote his comments on the amp"We also noted the level for each channel. The Pro-ject is quite unbalanced with 0.7 dB of difference between the left channel and the right channel at the listening level for hifi headphones, and 1.5 dB of difference at the level for earphones (11 db lower). And it doesn't feature a balance setting. Too bad for a dedicated headphone amplifier."

At least to me, such an imbalance is unacceptable in a $100+ piece of gear. Even my motherboard's onboard sound has less channel imbalance and my motherboard probably cost less than the amp.

If carbon resistors weren't used, chances are that you can blame the volume knob. That kind of imbalance is why folks spend so much, when DIYing, on pots (or stepped attenuators).

I was surprised at the FR differences. I'd have liked to have seen full circuits, to see what was going on (IE, from amplifier input to headphones, measurement bits included). A good test, nonetheless (I just wish there were more easily available than pushing sine waves through). It does show what I and others have found, in terms of integrated amps having some coloration.

[royalcrown]

Ah, sorry about that bullseye, I forgot that you don't live in the US. Try sweetwater.com, they have a number you can call about international orders. If nothing works out, by all means grab the X-can if it turns out to be the cheapest.

[Bullseye]

^Well, the cheapest is (shipping included) the Samson S·Amp, but the V-Can is a great contender due to its specs for low impedance cans, like the ones I have/will be getting.
Unless the SM Pro goes shipped for <$55 (Well, actually because I have a shop that sells me the amp and I have bought from it before, it is ~$77 shipped. Bare in mind prices in europe (and with the €/$ rate), turns to be higher...

I am basically looking for the cheapest amp that has good specs for low impedance HPs. From HPs with impedances from 25 Ohm to 50-60 Ohm.