[kwkarth]

Who cares what the O2 sounds like anyway as long as it measures well in the listed parameters.  I guess the other measurements left out or neglected don't matter in that case either.
 

 

[Anonanimal]

Quote:

Who cares what the O2 sounds like anyway as long as it measures well in the listed parameters.  I guess the other measurements left out or neglected don't matter in that case either.
 

Huh?

 

[amb]

Sorry I have to break my promise to post any more, but Anonanimal, what you said is not the same thing.
 
A DIYer could indeed make mistakes installing parts on a PCB, this is not just trimpots, nor is it restricted to the β22.  But one could only go so far to prevent something like that from happening.
 
Now about the gain structure of the O2 amp and its low input overload margin, is a problem that cannot worked around in many circumstances, even if the builder/user has full knowledge of the limitations.  For example, I find that with a γ1 or γ2 DAC feeding an amp with a gain of 5x just about perfect for my Sennheiser PX100 headphones (which are portable).  If you were to build an O2 with a gain of 5x and use it with these DACs, it will clip badly (on battery power or AC power) regardless of where you turn the volume knob.  If I was to use the O2 amp for my Sennheiser HD600 or HD800, I would prefer a bit more gain, which would make matters worse.

 

[purrin]

      Quote:

Now about the gain structure of the O2 amp and its low input overload margin, is a problem that cannot worked around in many circumstances, even if the builder/user has full knowledge of the limitations.

And I was just assuming a gain of 2, forgetting that a higher gain may be necessary.
 

      Quote:

If I was to use the O2 amp for my Sennheiser HD600 or HD800, I would prefer a bit more gain, which would make matters worse.

 
Didn't you hear? Users of the Objective2 are not expected to be using these types of headphones. 

 Now I'm just being plain nasty...
​

 

[kiteki]

I do not understand this thread.
 
Just give me a link to where to order this thing, for once I'm going to do an impulse buy without any researching ^^

 

[odigg]

Quote:

 For example, I find that with a γ1 or γ2 DAC feeding an amp with a gain of 5x just about perfect for my Sennheiser PX100 headphones (which are portable).  If you were to build an O2 with a gain of 5x and use it with these DACs, it will clip badly (on battery power or AC power) regardless of where you turn the volume knob.  If I was to use the O2 amp for my Sennheiser HD600 or HD800, I would prefer a bit more gain, which would make matters worse.

 
I have a question.  Please note that I'm asking this question honestly - I'm not an engineer and don't know the answer.
 
What is the difference between the O2 and some other amp (e.g. the Mini3) in the regard?  In a previous post you stated that the "γ1 DAC puts out 1.6Vrms @0dBFS"  I have a MisterX Mini3 with a gain of 5 (the recommended gain).  I know the specified on battery output voltage is "9Vp-p (3.2Vrms)" according to the Mini3 spec page.  I have changed the battery - if I remember correctly its a 8.3V, so the output is even lower than 9Vp-p.
 
Wouldn't the Mini3 with a gain of 5, or even 2, also clip with the y1 at 0dbfs?
 

 

[purrin]

Quote:

I have a question.  Please note that I'm asking this question honestly - I'm not an engineer and don't know the answer.
 
What is the difference between the O2 and some other amp (e.g. the Mini3) in the regard?  In a previous post you stated that the "γ1 DAC puts out 1.6Vrms @0dBFS"  I have a MisterX Mini3 with a gain of 5 (the recommended gain).  I know the specified on battery output voltage is "9Vp-p (3.2Vrms)" according to the Mini3 spec page.  I have changed the battery - if I remember correctly its a 8.3V, so the output is even lower than 9Vp-p.
 
Wouldn't the Mini3 with a gain of 5, or even 2, also clip with the y1 at 0dbfs?
 

No, because you have a pot (volume control) in front of the voltage gain stage on the Mini3. The OBJ2 has the pot after the voltage gain stage. That means the output of the DAC is running full juice into that first op-amp.
 

 

[SpaceTimeMorph]

Quote:

Sorry I have to break my promise to post any more, but Anonanimal, what you said is not the same thing.
 
A DIYer could indeed make mistakes installing parts on a PCB, this is not just trimpots, nor is it restricted to the β22.  But one could only go so far to prevent something like that from happening.
 
Now about the gain structure of the O2 amp and its low input overload margin, is a problem that cannot worked around in many circumstances, even if the builder/user has full knowledge of the limitations.  For example, I find that with a γ1 or γ2 DAC feeding an amp with a gain of 5x just about perfect for my Sennheiser PX100 headphones (which are portable).  If you were to build an O2 with a gain of 5x and use it with these DACs, it will clip badly (on battery power or AC power) regardless of where you turn the volume knob.  If I was to use the O2 amp for my Sennheiser HD600 or HD800, I would prefer a bit more gain, which would make matters worse.

Then if you used those DACs you could up the voltage of the power supply (the 2068 will handle 30Vpp) and substitute 30Vgs FETs for the ones listed to handle the clipping issues.  The point is, for normal sources, the clipping won't be an issue.  And for the 1% or so that fall outside of this, there are options to upgrade the power supply/adjust the gain structure at the build stage to accommodate the sources.  If you have source(s) with nominal output voltages, all it would take is a careful selection of the proper gains to prevent clipping at the user stage.  Again, he talks about this in his articles.  If you have better suggestions for how to handle the outlier situations, I for one, would love to hear them.
 
I will say, one point of disagreement we are having here is based on what NwAvGuy measured for the maximum voltage swing out of a 2068 versus what you are claiming.  He measured something much closer to the power supply rails than what even the spec sheet I found listed.
Lastly, to maybe try to steer this thread towards some measure of amiability... good call Amb on the two Schottky's vs one... I wasn't thinking there.  See, we can get along after all. 

 

[purrin]

Quote:

 The point is, for normal sources, the clipping won't be an issue...
 

It also depends upon what one considers is a normal source. Also higher gain levels needed to power the more demanding headphones will throw a wrench in the works. Here's one way to fix it:
 
http://www.amazon.com/DEWALT-DC9360-36-Volt-Lithium-Ion-Battery/dp/B000FNQYM0
 
Quote:

I will say, one point of disagreement we are having here is based on what NwAvGuy measured for the maximum voltage swing out of a 2068 versus what you are claiming.  He measured something much closer to the power supply rails than what even the spec sheet I found listed.

Spec sheets are always conservative - they are for a reason - to allow margin for worst case scenarios, manufacturing variances, bad power, etc. These debates just come down to matter of philosophy regarding safety margin. Fortunately, it's concerning the design of an amp, not a car.

 

[upstateguy]

 
Quote:

I think your post is pretty good.  I was thinking something similar myself.  Rather than reading about other's opinion about reading about reading about the amp design, I would like to start reading about how the amp sounds...
 

 
Quote:

Who cares what the O2 sounds like anyway as long as it measures well in the listed parameters.  I guess the other measurements left out or neglected don't matter in that case either.
 

Kevin ! 

 
 

 

[SpaceTimeMorph]

Quote:

Originally Posted by purrin /img/forum/go_quote.gif

http://www.amazon.com/DEWALT-DC9360-36-Volt-Lithium-Ion-Battery/dp/B000FNQYM0
 
lol... yea that was along the lines of what I meant by "upping the power supply voltage."  There is actually considerable talk about lion battery power on the diyaudio forum, including grabbing cells from a drill battery; good stuff if you want to check it out.
 
Spec sheets are always conservative - they are for a reason - to allow margin for worst case scenarios, manufacturing variances, bad power, etc. These debates just come down to matter of philosophy regarding safety margin. Fortunately, it's concerning the design of an amp, not a car.
 
True, but on his clipping tests the clipped portions were clearly set at 20Vpp without oscillation or output slam into the opposite power supply rail, which lends more credence to NwAvGuy's claim on his site that it can safely pass closer to the rail voltage than others have claimed.

 

[odigg]

Quote:

No, because you have a pot (volume control) in front of the voltage gain stage on the Mini3. The OBJ2 has the pot after the voltage gain stage. That means the output of the DAC is running full juice into that first op-amp.
 

That makes sense.  Thanks.  I think most every portable device I use outputs less than 1Vrms, so I guess I don't have to worry too much.

 

[jude]

I'm cleaning up some of this thread.
 
If you want to discuss the moderating, send me (and/or other moderators) a PM.  I can't promise you'll receive an answer (and, if you do, it may or may not be one you'll like).
 
If you want to discuss the amp, okay.

 

[Shike]

Quote:

No, I am not interested in discussing this directly with the designer.  If he is the brilliant engineer that he makes himself out to be, then he must know these limitations.  Must use a weak source, must use low gain, must use AC power... too many ifs, ands and buts.  None of the amps that he lists as "competition" have these problems.

I'm pretty sure I posted that he was clearly aware.  Here's a question for you though: how is the Mini^3 immune to clipping with a gain of 5, or even 3 with the same examples?  Math please.

 

[JamesMcProgger]

I was asking of anyone have a link to a case that would fit and if the board will come in that design only? its kind alike square, not very pocket friendly-