[CEE TEE]

@OP:  Late morning or late afternoon, you might...
 

• take the amp outside (in the shade but where it is bright enough to shoot well)
• place on ground (not on dirt of course, concrete is better)
• use exposure compensation of about +1 stop (or don't if you are unfamiliar with this control)
• stand over amp and photograph downward (adjust zoom depending upon lens)
• try to shoot in-focus (zoom-in to max on your camera's display to see if you are sharp)
• don't worry about color balance (bluish-tinge look)
• sharpen
• adjust exposure globally (should be pretty evenly lit, probably "brighten")
• OR: if pics are looking a bit "off" in any way- send pics to me in PM to correct and return.

 
Just an offer...so we may SEE the amp too!

 

[Willakan]

 
Quote:

I think Willakan has a sensible point about discrete vs opamp.  The more components in a design, the more variance that can occur between assemblies of the same design.  With discrete there are collections of transistors, caps, resistors, etc from different vendors. Of course, they are spec'd within a tolerance but there is variance.  So it is probable that each amp rolling off the assembly line has a unique signature. On the other hand, opamps are manufactured from monolithic blocks, as far as I know, so I expect they will be self-consistent.
 
Opamps and buffers from National and others claim incredible low distortion. They provide reference boards (too expensive for DIY) which others vendors can test for quality.
 
IMO, discrete designs without blocking capacitors are too difficult and risky for DIY. One mistake, and poof goes the expensive headphones.  Stick with opamps.
 
 

It's not just being fully discrete. Avoiding negative feedback like the plague and going single ended are certainly not done for "sound quality." Either the designer believes they do in fact boost sound quality, or he knows exactly what affects sound quality and is more interested in meeting various arbitrary "audiophile" criteria. Neither makes me want to hand over my CC.
 
Anyways, back on topic: pics? 
 

 

[Shike]

 
This seems to be about the best PCB pic I can get.  Not sure how helpful it will be, but might give people an idea of the attention to layout of the design.  It's going to go back in the enclosure and stay there now, I don't want to risk any ESD.
 
@Willakan
 
I actually believe opamps can perform well even in speaker amplifiers.  See the gaincard and various clones for example - as long as nothing nasty is popping up on the measurements and it's providing sufficient power all is good IMO.  Discrete should only really be considered in very high power designs IMO - we're talking greater than 100W into 4 ohms territory though.

 

[Deep Funk]

Interested...

 

[Willakan]

By all means, opamps can perform well in power amps, it's just not as clear cut as I understand it vs headphone amps or other low power applications (DAC internals). It's rather harder to say definitively to the designer "There is no audio-related reason for doing that."
 
PCB looks like a nice job.

 

[everlong]

Looking forward to test this all-for-one amp
 
But i can't see anywhere what kind of inputs this got? And has there been any mention on a recommended dac?
And any status on the desktop edition with AC-adpter power?

 

[LizardKing1]

Guys I by no means want to start a flamewar. Understand that this is a question since I am not sure about these things. But I read a quite convincing argument about how all good DACs would/should sound exactly the same. I mean, obviously an amp can have minute differences, since that deals with an analogic sound signal. But a DAC deals with 1s and 0s, with digital content. Basically the point I read was that even though a DAC could be flawed and transmit the music badly, the differences wouldn't be "slightly veiled mids" or "a bad extension on the treble", it would be more like "choppy music" and audible artifacts. Jitter would be a problem, but it would result in a certain part of the music playing or not, not in playing with a slightly worse quality. Not so much bad perception of music, but more like a corrupted file. So, if two DACs are well-designed and don't have these artifacts audibly, the music they play is exactly the same right?

 

[castlevania32]

"If two DACS sounds different, it means at least one of them is a flawed design"

 

[Willakan]

@everlong:
Inputs: Either board mounted 3.5mm jack or case-mounted RCA jacks.
Recommended DAC: NwAvGuy is evaluating various cheap DACs at some point, but any competently designed DAC will be fine. I'm pairing mine with a Cambridge Audio DACmagic; it is considerable overkill from an objective perspective but the input switching and digital passthrough made it just about justify a not insignificant cost.
Desktop Version: The current version has a jack to plug in a recommended AC adapter. NwAvGuy's summary article on his blog details the particular advantages a desktop version might hold - mainly dealing with weird, high voltage sources and the ability to boardmount everything.

 

[upstateguy]

Quote:

"If two DACS sounds different, it means at least one of them is a flawed design"

I was under the impression that although digital 1s and 0s go into one end of a DAC, good old fashioned analog music comes out of the other.   It is in the analog sections that the differences in sound occur.

 

[mikeaj]

Quote:

I was under the impression that although digital 1s and 0s go into one end of a DAC, good old fashioned analog music comes out of the other.   It is in the analog sections that the differences in sound occur.

Yes, but the DAC itself is one of the analog sections you're referring to, since the output of the DAC is an analog waveform after all.  It's something like copying bits of a music file off of the hard drive or optical drive to the USB interface that is pretty much irrelevant, so long as the bits all get there.  There are plenty of ways for DACs to muck up the signal such that you don't get what was intended (but getting it "right" or good enough for music playback, really shouldn't be too hard or require exotic implementations and super-duper expensive-o components).

 

[upstateguy]

 
Quote:

Yes, but the DAC itself is one of the analog sections you're referring to, since the output of the DAC is an analog waveform after all.  It's something like copying bits of a music file off of the hard drive or optical drive to the USB interface that is pretty much irrelevant, so long as the bits all get there.  There are plenty of ways for DACs to muck up the signal such that you don't get what was intended (but getting it "right" or good enough for music playback, really shouldn't be too hard or require exotic implementations and super-duper expensive-o components).

I wish it was so simple.  I have 2 USB transports, (Blue Circle Thingee/ HiFace) that don't sound the same......  and if you really want to make yourself crazy, the BCT uses the same PMC2707 chip that is built into my Stello DA100 DAC, and the two of those don't sound the same.

 

[judmarc]

Quote:

Guys I by no means want to start a flamewar. Understand that this is a question since I am not sure about these things. But I read a quite convincing argument about how all good DACs would/should sound exactly the same. I mean, obviously an amp can have minute differences, since that deals with an analogic sound signal. But a DAC deals with 1s and 0s, with digital content. Basically the point I read was that even though a DAC could be flawed and transmit the music badly, the differences wouldn't be "slightly veiled mids" or "a bad extension on the treble", it would be more like "choppy music" and audible artifacts. Jitter would be a problem, but it would result in a certain part of the music playing or not, not in playing with a slightly worse quality. Not so much bad perception of music, but more like a corrupted file. So, if two DACs are well-designed and don't have these artifacts audibly, the music they play is exactly the same right?

Read some online academic papers or other available information written by audio engineers regarding jitter.  The result is not just dropouts, which are vanishingly rare in the absence of something badly wrong.  It also, in well-known non-voodoo ways, causes at least the following two problems: (1) raising the noise floor, resulting in less dynamic range; and (2) high frequency intermodulation distortion.
 

 

[Willakan]

True, but you need obscene amounts of jitter to be audible. Ironically, the gear with the most jitter is likely some dodgy, half-baked "audiophile" design. Stereophile have measured some insanely pricey equipment with very high jitter levels. For example, when used as a USB DAC the HifiMan HM601 had so much jitter that it was difficult to reliably measure it.

 

[judmarc]

 
Quote:

True, but you need obscene amounts of jitter to be audible. Ironically, the gear with the most jitter is likely some dodgy, half-baked "audiophile" design. Stereophile have measured some insanely pricey equipment with very high jitter levels. For example, when used as a USB DAC the HifiMan HM601 had so much jitter that it was difficult to reliably measure it.

I'm sure there's gear of which that's true.  The audiophile gear I'm familiar with does a lot better on these sorts of things - e.g., the Wavelength stuff, whose Cosecant was measured by Stereophile as having the best jitter numbers they'd ever seen in a USB DAC; or the Theta I've got, 20 years old but designed by folks who knew jitter was bad and how to minimize it.
 
Regarding how much jitter is audible, I've seen statements all over the lot.  There are some extremely well respected people in the industry (Keith O. Johnson of Spectral is one who comes to mind) who claim differences in the tens of picoseconds are audible.  I don't know about that, but then there's a hell of a lot I don't know about audio compared to Keith O. Johnson.