[oicdn]

Gain is not a 'compensation' mechanism for load impedance. The 'gain' at issue here more or less measures the factor by which the amplifier multiplies the amplitude of the signal at the input. With rare exception (i.e. those with charge pumps, such as some maxim chips and a few other parts), Op-amps don't swing past their rails, or even swing at their rails, so maximum amplitude will be some figure below the total supply. 2.828vpp is a 1vRMS sine wave. Peak amplitude may differ in actual music but suffice it to say at what is likely 3.7v supply, factoring in headroom, much above unity gain won't be particularly useful. On a smaller amplitude output, such as a PCM2704 (1.8vpp), gain can perhaps be a bit higher but unlikely even 2 when factoring in how close the amp will realistically approach its rails. Higher gain carries the side effects of higher distortion and noise floor, so it would seem reasonable policy to use not more than is practically required, especially if supply considerations bar effective use.

Now, whether distortion becomes perceptible is a different issue. Clipping at first introduces odd order harmonics, which change the character of the sound but may not obviously introduce what is considered audible 'clipping' such as crackling and the like. 2.8vpp of music on average is still pretty loud, to me at least, on the K701 for much of my music. Music that uses the full dynamic range of the output, however, may contain peaks that fall outside the supply range and thus introduce anywhere from audible 'clipping' to less tangible distortion, as it's likely the source can swing nearer to its rails than the amp as it sees a much lighter load. That is, if you have a source and an amp running off of the same or similar supply, and the source swings close to its rails, the amp will clip unless its supply is replaced with one of higher voltage.


------------------
That was the response of a friend I asked on this matter. I also asked for the math to be checked by several amp builders, if this math was infact correct, and it was. I didn't say what it was in reference to, but it was confirmed.

Whether or not I have "intentions to truely purchase this amp" or not is irrelevant (but if you read back a couple pages, you can see I was intrested). This is a question ON TOPIC, NOT SPECULATION, with numbers presented that I ask to be answered and how/if this is a problem that was corrected. There's no need to become defensive over it when IT POTENTIALLY IS A SQ issue, especially on an amp that's of this price. And it's not on "sound preference" basis, but on a hard numbers basis.

It's a completely valid question, and I think deserves a response from the Ray himself.

 

[fraseyboy]

Hmm I don't get this Amp/DAC thing.


For the price that most amp/dac combo's are going for, you could get a tc-7510 and a really nice portable (or home) amp. Wouldn't that do better than a DAC/Amp combo?

 

[oicdn]

Alot of people just like the all-in-one convenience...that, and it's REEEEEEEALLY small.

 

[fraseyboy]

Quote:

Originally Posted by oicdn /img/forum/go_quote.gif Alot of people just like the all-in-one convenience...that, and it's REEEEEEEALLY small.

But how portable does a DAC need to be? If it's gonna stay plugged into the computer, does it really need to be small? The only bit that really needs to be portable is the amp part...

 

[3x331m]

Quote:

Originally Posted by fraseyboy /img/forum/go_quote.gif But how portable does a DAC need to be? If it's gonna stay plugged into the computer, does it really need to be small? The only bit that really needs to be portable is the amp part...

In the corporate world, most of us have a laptop, and quite a few of us travel frequently. The laptop is used as a transport, hence, the DAC on a super portable is convenient, and you don't miss your favorite tunes and eargasm.

 

[dmk005]

Quote:

Originally Posted by 3x331m /img/forum/go_quote.gif In the corporate world, most of us have a laptop, and quite a few of us travel frequently. The laptop is used as a transport, hence, the DAC on a super portable is convenient, and you don't miss your favorite tunes and eargasm.

X2. I never check a bag, even on a 2 week trip so small, multi-use items are essential. The Predator or other portable dac/amp combos provide both the option of good sound from my laptop OR my ipod thus being a terrific device smaller than a hornet to include in my mobile set up.

 

[wakeride74]

Quote:

Originally Posted by 3x331m /img/forum/go_quote.gif In the corporate world, most of us have a laptop, and quite a few of us travel frequently. The laptop is used as a transport, hence, the DAC on a super portable is convenient, and you don't miss your favorite tunes and eargasm.

Plus if you want to use it as just an amp at certain times you have one that is slightly larger than the Tomahawk.

 

[voyage]

I really would like to know do this DAC with optical digital input?

 

[grawk]

The predator doesn't have optical in. I assume that's the question you're asking.

 

[NoiseGUI]

Quote:

Originally Posted by fraseyboy /img/forum/go_quote.gif But how portable does a DAC need to be? If it's gonna stay plugged into the computer, does it really need to be small? The only bit that really needs to be portable is the amp part...

So, I'll be using predator's DAC at work, where I don't want to take up room with a larger component and I don't want to leave anything overnight (cleaning crews, etc). For $200 (likely difference between Tomahawk and Predator) I'd much rather have a Predator than the Tomahawk + TC-7510 for the convenience of it being the same device and ultra-portable (use at home, work, or on the road with my laptop).

 

[NoiseGUI]

Quote:

Originally Posted by voyage /img/forum/go_quote.gif I really would like to know do this DAC with optical digital input?

and not possible per the first post on page 8... DAC's input and power both come solely from USB.

Maybe Santa Ray can come up with one for next XMas. Optical in to DAC/Amp combo. No USB, just power all off the battery.

 

[immtbiker]

Quote:

Originally Posted by NoiseGUI /img/forum/go_quote.gif So, I'll be using predator's DAC at work, where I don't want to take up room with a larger component and I don't want to leave anything overnight (cleaning crews, etc).

Kepp it uncased (naked), and you probably won't have to worry about anyone stealing it at work.

 

[NoiseGUI]

Quote:

Originally Posted by immtbiker /img/forum/go_quote.gif Kepp it uncased (naked), and you probably won't have to worry about anyone stealing it at work.

Hehe... that's probably true!

There are benefits to keeping it naked... I'm sure it would get more attention too...

 

[dmk005]

Quote:

Originally Posted by immtbiker /img/forum/go_quote.gif Kepp it uncased (naked), and you probably won't have to worry about anyone stealing it at work.

Yeah! I doubt Ray will glue it together like some others

.

 

[holland]

Quote:

Originally Posted by oicdn /img/forum/go_quote.gif Gain is not a 'compensation' mechanism for load impedance. The 'gain' at issue here more or less measures the factor by which the amplifier multiplies the amplitude of the signal at the input. With rare exception (i.e. those with charge pumps, such as some maxim chips and a few other parts), Op-amps don't swing past their rails, or even swing at their rails, so maximum amplitude will be some figure below the total supply. 2.828vpp is a 1vRMS sine wave. Peak amplitude may differ in actual music but suffice it to say at what is likely 3.7v supply, factoring in headroom, much above unity gain won't be particularly useful. On a smaller amplitude output, such as a PCM2704 (1.8vpp), gain can perhaps be a bit higher but unlikely even 2 when factoring in how close the amp will realistically approach its rails. Higher gain carries the side effects of higher distortion and noise floor, so it would seem reasonable policy to use not more than is practically required, especially if supply considerations bar effective use. Now, whether distortion becomes perceptible is a different issue. Clipping at first introduces odd order harmonics, which change the character of the sound but may not obviously introduce what is considered audible 'clipping' such as crackling and the like. 2.8vpp of music on average is still pretty loud, to me at least, on the K701 for much of my music. Music that uses the full dynamic range of the output, however, may contain peaks that fall outside the supply range and thus introduce anywhere from audible 'clipping' to less tangible distortion, as it's likely the source can swing nearer to its rails than the amp as it sees a much lighter load. That is, if you have a source and an amp running off of the same or similar supply, and the source swings close to its rails, the amp will clip unless its supply is replaced with one of higher voltage. ------------------ That was the response of a friend I asked on this matter. I also asked for the math to be checked by several amp builders, if this math was infact correct, and it was. I didn't say what it was in reference to, but it was confirmed. Whether or not I have "intentions to truely purchase this amp" or not is irrelevant (but if you read back a couple pages, you can see I was intrested). This is a question ON TOPIC, NOT SPECULATION, with numbers presented that I ask to be answered and how/if this is a problem that was corrected. There's no need to become defensive over it when IT POTENTIALLY IS A SQ issue, especially on an amp that's of this price. And it's not on "sound preference" basis, but on a hard numbers basis. It's a completely valid question, and I think deserves a response from the Ray himself.

Your logic is sound...or rather your friend's explanation is solid.

Don't forget the pot, which attenuates the source signal. So even though you may have a source which hits the full peaks of 2Vrms (assuming perfect line out into the gain stage), it gets attenuated down so what is presented for amplification is considerably less. I didn't read this thread with care, and I'm not sure what DAC chip is utilized, but if there's I/V, it could be that the resistor chosen is low enough to not even have 1Vp-p....I'm not sure why one would do that, but it's possible. Also, as stated I don't know what this circuit is, or where the attenuator lies, so that's speculation on my part. It's normally at the source, and not output, for obvious reasons.

Still, 11 is high and noises get amplified as well. It's there, probably, to allow more volume knob resolution at the cost of having potential distortion and to make people comfortable that they don't have to go to 75% volume on a less efficient headphone....which is

. It's a marketing perception thing. On a portable device, I would tend to run around 4, 6 at most due to the limitations noted....which is mid-gain on this device. If it truly is only on a 3.7V battery, I'd just stick with unity gain. Hopefully, it's doubled up to 7.4V.

Still, many people think the HD580, HD600, HD650, AKG K701, etc. are "hard to drive". It's not. It's easy to get the swing to make those headphones insanely loud and amplified properly from an opamp like an AD8397. I doubt the more esoteric headphones would work well, though.

Getting the "color" that you want, that's a different issue.