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iBasso PB-2 Pelican fully balanced portable, DB-2 Dac . . HiFlight recommended op amps page 16. . - Page 59

post #871 of 1123
Quote:
Originally Posted by spurxiii View Post

Nigel, do you reckon I will get much of an improvement in SQ from my PB2 with a TP60 on my HE500s since you've used them with the HE6s it might give me some insight into what to sort of expect.

 

Definately.... I still use my TP60 when I fancy a change from my HP-8 with my HE-6. For the price it is an astounding amp. It can't compete with the HP-8 in true terms but it does make me smile when listening via the TP60 because it's not a million miles away but costs five times less. There's something nice about knowing you have a quality piece of kit punching above it's price point.

 

I've used the HE-6 balanced with the PB2 to good effect but the TP60 just makes them sing. Expect a bigger, fuller sound with improved dynamics and extension. It needs a decent input, rubbish in = rubbish out.

post #872 of 1123

Thanks Nigel. Its a good feeling to know the TP60s won't sound like rubbish. I almost regretted buying it until I plugged them into my speakers and my speakers have never sounded better. It seems I hear so much more detail from the speakers with the TP60 over my Home Theatre AVR. Am I right in saying that the TP60 will also present lots of detail to my head phones via the speaker taps? I found the sound from the speaker to be very very neutral and linear and somewhat cold and dry.    

post #873 of 1123
No worries....

The TP60 will offer lots of detail for your HE-500's, I very much doubt you will be disappointed. Have you taken into account the resistors required across + and - ? I added a 10ohm (7 watt) across mine for the HE-6.

Hey we are all family here! What do we call you?

Cheers - Nigel
post #874 of 1123
Quote:
Originally Posted by SpudHarris View Post

No worries....

The TP60 will offer lots of detail for your HE-500's, I very much doubt you will be disappointed. Have you taken into account the resistors required across + and - ? I added a 10ohm (7 watt) across mine for the HE-6.

Hey we are all family here! What do we call you?

Cheers - Nigel

Hi, just realised I've never advertised my name before on this forum. You guys can call me Tom, my Vietnamese name is a bit difficult to pronounce so Tom's easier.

 

I'm going to try it out without any resistors in place and take some care with the volume. Do the resistors give you improved SQ or is it to allow better adjustment of the volume?

 

Tom

post #875 of 1123

You might want to look into the reasoning behind the resisters shorting + & - on the TP60 Tom. I'm no expert but it's something to do with reducing the load to 8 ohms (I think?). I would hate for you to fry your HE-500's for the sake of a little research.

 

This is a pic that was sent to me.... 

 

 

700

post #876 of 1123
Quote:
Originally Posted by SpudHarris View Post

You might want to look into the reasoning behind the resisters shorting + & - on the TP60 Tom. I'm no expert but it's something to do with reducing the load to 8 ohms (I think?). I would hate for you to fry your HE-500's for the sake of a little research.

 

This is a pic that was sent to me.... 

 

 

700

Thanks Nigel, I'll look into it. Glad I asked.

post #877 of 1123

Nigel, after reading the first few pages of the speaker amps for headphones thread I think I'll go get a couple of 10ohm 10w resistors and perhaps 10ohm 7w like yours to try out. Thanks for the heads up.

 

Tom

post #878 of 1123

No worries pal. I only went with 7w because they didn't have 10w at the time. If you go lower than 10w you just need to check the heat and ensure they are not changing colour.

post #879 of 1123

Tom and Nigel,

 

I barely have a grasp of this stuff myself, but I've been studying this subject quite a bit lately and can say with some certainty that the following statements are true.  (How's that for a disclaimer?) redface.gif

 

1)  Amps don't mind seeing a greater load (running uphill), but can be damaged by seeing a load that's less than that for which they are designed (running downhill).  So... you don't have to add resistance in parallel (across the + and - of each channel), for the sake of protecting an amp that's designed for the 4- or 8-Ohm load of speakers from the greater impedance (i.e. 38-Ohms) of a headphone.   For the amp's sake, it's perfectly OK to run without adding parallel resistors to a load that has a higher impedance than that which the amp expects.

 

2) Headphones, like speakers, can tolerate only so many watts peak from any given amp.  If the amp can produce more power than the headphone can handle, it's a good idea to add parallel resistors - for the sake of the headphones, not to protect the amp.  I've just read that the HE-500 has an impedance of 38 Ohms, but I can't find a specification for the number of Watts it can handle.  The Audeze LCD-2, can handle up to 13-Watts rms (where rms is typically about 70% of peak) into its 50-Ohm load.  You need to find out how many watts your HE-500 can handle into its 38-Ohm impedance.  If the amp does not exceed this rating into 38-Ohms, you don't need to add parallel resistors for the sake of protecting the headphones.

 

3) How do you translate a power rating into 4- or 8-Ohms into that for a higher impedance (i.e. 38-Ohms)?  For most amps, the relationship between power out and impedance of the load is not linear, but we can get in the ballpark by using an inverse proportion.  The TP60 is rated at 80 Watts (rms) into 4-Ohms, but the HE-500 presents a 38-Ohm load.

 

Power Rating of Amp * Expected Impedance / Actual Impedance = Watts into Actual Impedance (approximate)

 

80 Watts *  4-Ohms / 38-Ohms =  8.42 Watts (into 38-Ohms)

 

So, if the HE-500 can handle 8.5 Watts into 38-Ohms, there's no need to add parallel resistors for the sake of protecting the headphones, but you may want to do so for the sake of tailoring the sound, because the amp might actually sound better, or at least different, by adding parallel resistors (or for that matter, by adding series resistors). More on that in the next points...

 

4)  Keeping all of the above in mind, even if you don't need parallel resistors to protect the headphone from excessive power, you can use parallel resistors to tailor the sound.  Adding parallel resistors will make the amp sound more aggressive or sharp, less muddy or fuzzy, generally speaking. The parallel resistance should be 1/10th to 1 times the impedance of the headphones - to decrease the effective output impedance. The lower the value of the parallel resistors, the harder the amp has to work to deliver the same SPL at the headphones.  So when you add parallel resistors, SPL at the headphones will increase.  It may seem counter-intuitive, but you're allowing the amp to see less total impedance, not more (just as when switching in two pairs of 8-Ohm speakers instead of one pair, on an amp that offers the ability to drive two pairs simultaneously, presents a 4-Ohm load to the amp, not a 16-Ohm load.)  A lower value of parallel resistance gets closer to being as if there's no parallel resistor. (Duh!)  Increasing the value of the parallel resistor decreases the effective output impedance, but don't bother going any higher than the impedance of the headphones.

 

5) And now let's talk about series resistance...  If you want your amp to sound less aggressive or sharp, more relaxed, you can add series resistors to the + side of each channel - to increase the effective output impedance. The series resistance should be 1 to 3 times the impedance of the headphones. Once a series resistor hits a value that's 3 times the headphone driver impedance, you've done all the good you're going to do in terms of reducing an aggressive sound by increasing output impedance.  Increasing the series resistance to values higher than three times the headphone impedance will only make things worse, with insufficient damping factor making things muddy.  But there's more...

 

6) Understand that with dynamic headphones, when adding series resistors, you will also be changing the frequency response, because impedance is not flat across the frequency spectrum with dynamic headphones.  With planars, which have a purely resistive impedance, their impedance is flat across the frequency spectrum, and thus, you will not get a shift in frequency response by adding series resistors.

 

Wow... I wrote a book - a  book that's completely off-topic for this thread. Sorry!

 

biggrin.gif

 

Mike


Edited by zilch0md - 8/20/13 at 8:38am
post #880 of 1123
Mike, for someone who has barely got a grip you certainly seem to know ten times more than me biggrin.gif

Don't ask me to explain but I tried the LCD2 with the TP60 and they sounded weird and not in a good way. The HE-6 on the other hand was the best I'd heard them sound (until getting the HP8).

I don't mind going off topic a bit so we shouldn't get too bent out of shape. However, due to activity back on this thread I decided to get the PB2 out again and see what it was that made me keep it over the SR-71B. I took my son for his life guarding lesson and relaxed poolside for 45 mins.... This is a truly brilliant amp, I am sticking with my chipset even though runtime is sacrificed. 4 x AD743 + 8 x BUF634 is my choice.

Since I've become satisfied (for now) with my home listening I have given less time to portables. I think I could be happy with just the PB2 now as the form factor and SQ is well suited to my iPod Classic. I think I will shed some portable stuff as the cash would come in handy for my new house move. I just need to pull together a transportable rig for vacations etc.... I think the iCan + CLAS would work for this.

I am quite content at the moment biggrin.gif
post #881 of 1123

Thanks Nigel,

 

I'm a teacher at heart (not for a living), but teachers will tell you that explaining stuff to others is the best way to learn the material yourself.  I swear I couldn't have told you all of that standing face-to-face.  I had to pull it from several sources to make sure it was correct, and even now, I invite anyone who can find fault with it to set me straight, because I don't want to lead anyone astray.  In other words, that dissertation, above, is really at the limits of my understanding - not at the forefront.  redface.gif

 

I hear you regarding the PB2 - I tried replacing dummy buffers with another row of LME49990, but didn't like how "rich" it sounded, nor the slight loss of transparency.  We all have our unique tastes, of course, so I'm back to digging on 4x LME49990 in L/R + dummy buffers sounding great with my PCM-M10 as source and LCD-2 rev.1.  

 

Like you, however, I'm sometimes amazed at just how satisfying this little portable amp can be - holding its own very well against my Emotiva a-100 Mini-X + Decware ZSTAGE tube buffer - lacking some of the dynamics that come with 8 Watts per channel, but not suffering any of the negative traits I'm hearing with the desktop rig (bright and harsh treble without the tube buffer -or- a loss of resolution and low level detail with the tube buffer).  If only I could find an op-amp as powerful as the HA5002, that's more transparent, I think my PB2 would be "perfect."

 

Mike


Edited by zilch0md - 8/20/13 at 11:57am
post #882 of 1123
You are a bad man! You know I now have to try your chipset rolleyes.gif

Tonight is the night I may fall off the Rolling wagon. My name is Nigel and I'm a recovering rollerholic biggrin.gif
post #883 of 1123
Wow Mike you could write a thesis on this. I'll take my time to read this later as I just quickly skim read this. I kind of had a feeling this might have worked without resistors but now I feel better in giving thus a go. Mind you my cables don't come for another week so I'm pretty stoked. Malveaux on the other thread connected the HE500s to the Emotiva which is rated at a similar 50w into 8ohms so I believe I should be ok. Gotta go to work

Tom
post #884 of 1123

Hi guys, just had quick listen to the TP60s via the speaker taps I received today and I think they're awesome. Night and day for me. Everything sounds so much more open, cleaner and clearer. I get so much detail now. I'm running it with no resistors and had the volume at 10 o'clock so I don't believe I will fry these. It sounds like it can take more than my ears can. I'm so happy.

 

Tom

post #885 of 1123

That's awesome, Tom!  

 

I love seeing a content audiophile!   Rarer than hen's teeth.  biggrin.gif

 

Enjoy!

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