[Mauricio]

If you know something about signal theory you'll know that the reason for the square wave test has nothing to do with testing a component's response to a signal that does not exist in music, but rather to derive information about its frequency response characteristics.  Remember that a square wave is an infinite summation of sine waves, and that any real-world music signal can be represented as a summation of sine wave harmonics.  If a component reproduces a square wave imperfectly, that is an indirect indication that the component is not able to reproduce some sine wave harmonics, thereby suggesting frequency response anomalies (which may or may not be audible to humans).  The utility of the square wave test is not in the time domain, but rather in the frequency domain.

 

[Chris J]

infinitely SMALL rise time  

Ouch!
Yes, you're correct, thanks for pointing that out.

I will edit my post to read:
"You are more or less correct when you say that you need "unlimited power" to reproduce a steep waveform, but more accurately you need infinite power to reproduce a perfect square wave as a perfect square wave would have an infinitesimal (instantanteous) rise time. You would also need infinite bandwidth to reproduce the infinite harmonics of a perfect square wave."

 

[Audiophile1811]

Quote:

If you know something about signal theory you'll know that the reason for the square wave test has nothing to do with testing a component's response to a signal that does not exist in music, but rather to derive information about its frequency response characteristics.  Remember that a square wave is an infinite summation of sine waves, and that any real-world music signal can be represented as a summation of sine wave harmonics.  If a component reproduces a square wave imperfectly, that is an indirect indication that the component is not able to reproduce some sine wave harmonics, thereby suggesting frequency response anomalies (which may or may not be audible to humans).  The utility of the square wave test is not in the time domain, but rather in the frequency domain.

So how, when I read a Square Wave response graph, do I know that the component tested does not reproduce a square wave imperfectly? I have seen some SW response graphs but can never discern whether the headphone or speaker reproduces square waves badly or accurately. How would you describe them to someone trying to understand the technical side of audio reproduction?   

 

[Chris J]

Quote:

If you know something about signal theory you'll know that the reason for the square wave test has nothing to do with testing a component's response to a signal that does not exist in music, but rather to derive information about its frequency response characteristics.  Remember that a square wave is an infinite summation of sine waves, and that any real-world music signal can be represented as a summation of sine wave harmonics.  If a component reproduces a square wave imperfectly, that is an indirect indication that the component is not able to reproduce some sine wave harmonics, thereby suggesting frequency response anomalies (which may or may not be audible to humans).  The utility of the square wave test is not in the time domain, but rather in the frequency domain.

You can determine information WRT the systems amplitude, phase and response WRT time.

 

[188479]

Thanks very much for a great thread!  Here is a question I have not seen answered.  I'm pretty sure I will be buying a pair of active speakers at some point.  I will soon be running a turntable and a DAC through a Woo WA6SE.  So my question is if I had a pair of active speakers with RCA inputs, an I better off unhooking the RCA's from the WOO and going directly to the speakers or could I use the more convenient 1/4 headphone jack to RCA cable and then use the volume knob of the WOO to control volume to the speakers (and not have to disconnect any sources).  It seems the second way would be better, but I'm sure that I'm missing some sonic reason not to do it!

 

[Audiophile1811]

Since the Woo WA6SE is a headphone amplifier and you intend on using it for a pair of active monitors then it would probably be best to just feed the RCAs from your DAC into them, instead of having the Woo amplify the monitors. Anybody else?

 

[Chris J]

Quote:

Thanks very much for a great thread!  Here is a question I have not seen answered.  I'm pretty sure I will be buying a pair of active speakers at some point.  I will soon be running a turntable and a DAC through a Woo WA6SE.  So my question is if I had a pair of active speakers with RCA inputs, am I better off unhooking the RCAs from the WOO and going directly to the speakers or could I use the more convenient 1/4 headphone jack to RCA cable and then use the volume knob of the WOO to control volume to the speakers (and not have to disconnect any sources).  It seems the second way would be better, but I'm sure that I'm missing some sonic reason not to do it!

Try it both ways and see which one you prefer.
The Woo has a reputation for being a fairly colourless, transparent headphone amp, so using the Woo may be a great sounding, convenient way to do things.
I don't think that DAC has a volume control? 
How convenient and accessible is the volume control on the active speakers?

 

[Mauricio]

Active monitors should be fed line level signals directly from the source.  They should not be fed amplified/amplifier signals, and for optimal sound quality neither should they be fed a headphone signal.

 

[Chris J]

Quote:

Active monitors should be fed line level signals directly from the source.  They should not be fed amplified/amplifier signals, and for optimal sound quality neither should they be fed a headphone signal.

 
Why Not?
You have to give some reasonable explanation instead of presenting a statement like that as if it is a stone cold fact.

 

[Mauricio]

At the risk of stating the obvious, you should not feed an amplifier an amplified signal because--to use a technical term--you will blow da thing, cause it to pop a fuse or at least drive it to some serious distortion.
 
Would you drive a 600Ohm headphone from the headphone jack of an Ipod?  Sure, you can, but are you gonna get any appreciable volume and SQ?  Crank up the volume, and you're gonna tax its tiny amplifier into distortion and noise.  Now imagine driving a monitor that typically has input impedance of 47,000 Ohms (unbalanced RCA) from a headphone jack.  But don't take it from me.  Try comparing feeding a monitor a line signal and headphone signal.  The difference and the inferior SQ of the latter will be immediately obvious, particularly in revealing speakers like monitors.   Avoid hacks and work-arounds.  Do it right.  Presumably you are seeking to improve SQ, right?
 
Search the forum.  I started a thread dedicated to DACs with variable line output (aka "preamp" function) several months ago.  You can find a USB DAC with a volume knob controlling the RCA output to monitors for as low as $99.

 

[pyramid6]

Quote:

Thanks very much for a great thread!  Here is a question I have not seen answered.  I'm pretty sure I will be buying a pair of active speakers at some point.  I will soon be running a turntable and a DAC through a Woo WA6SE.  So my question is if I had a pair of active speakers with RCA inputs, an I better off unhooking the RCA's from the WOO and going directly to the speakers or could I use the more convenient 1/4 headphone jack to RCA cable and then use the volume knob of the WOO to control volume to the speakers (and not have to disconnect any sources).  It seems the second way would be better, but I'm sure that I'm missing some sonic reason not to do it!

Unless you have a specific need or desire for a certain sound, you are probably going to be better off bypassing the WA6SE.  You will just wind up amplifying noise and distortion.  If your speakers do not have a volume control, then you will need some sort of pre-amp (if your DAC doesn't have volume control).  The WA6 could do it. That is the only reason I would put it in the chain.

 

[Chris J]

Quote:

At the risk of stating the obvious, you should not feed an amplifier an amplified signal because--to use a technical term--you will blow da thing, cause it to pop a fuse or at least drive it to some serious distortion.
 
Would you drive a 600Ohm headphone from the headphone jack of an Ipod?  Sure, you can, but are you gonna get any appreciable volume and SQ?  Crank up the volume, and you're gonna tax its tiny amplifier into distortion and noise.  Now imagine driving a monitor that typically has input impedance of 47,000 Ohms (unbalanced RCA) from a headphone jack.  But don't take it from me.  Try comparing feeding a monitor a line signal and headphone signal.  The difference and the inferior SQ of the latter will be immediately obvious, particularly in revealing speakers like monitors.   Avoid hacks and work-arounds.  Do it right.  Presumably you are seeking to improve SQ, right?
 
Search the forum.  I started a thread dedicated to DACs with variable line output (aka "preamp" function) several months ago.  You can find a USB DAC with a volume knob controlling the RCA output to monitors for as low as $99.
 

 
Sure, no problem.
The question really wasn't for me, it was really for Kev.
 
There was a review of a headphone amplifier used as a Pre-Amp in HI FI + magazine a few months back.
This was a very high quality head phone amp (I think it was Musical Fidelity M1HPA).
The reviewer raved about what a great sounding pre amp the M1 made. 
 
The only point that I was trying to make was to try it and see.
A high quality headphone amp should not have any difficulty driving a 47,000 ohm load.
The output voltage is basically same as a line level voltage.
 
But you do raise a good point, since the Woo WA6 and WA6SE have output transformers, they would not be my first choice as a headphone amp re-purposed as a pre amp.
So you have a good point.
Sounds like he has a problem, unless he gets a DAC with a volume control and at least ONE analog input, like the Benchmark DAC1 HDR.
An OTL Woo like the WA2 won't get along with his Grado 225s.

 

[188479]

Quote:

Sounds like he has a problem, unless he gets a DAC with a volume control and at least ONE analog input, like the Benchmark DAC1 HDR.
An OTL Woo like the WA2 won't get along with his Grado 225s.

Well not really...I will just use the volume control on the speakers and feed directly from the source.  Not a huge problem, as I use speakers only about 10% of the time...I was pretty sure I would have to do it that way, but wanted to ask.  Now I just have to make sure I buy a pair of speakers with volume control!  Thanks everybody for your help.

 

[burgunder]

I bought a pair of audioengine A5+ for my daughter but they are a bit bigger than I imagined, so I guees she will need to wall mount them, is it possible to find some wallmounts that will make use of the 1/4 threded insert in the buttom of the speakers? I have been searching a bit, but it seems difficult.

 

[Mauricio]

Just a point of clarification for the thread.  The Audioengine range of speakers are not active.