Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › AMB M3 at gain 8 for Beyer T1?
New Posts  All Forums:Forum Nav:

AMB M3 at gain 8 for Beyer T1? - Page 2

post #16 of 25
6/26/10 at 6:21am

So you have the gain set so high you cant even use the amp with some headphones. Having the volume at 9 o clock means you are throwing away nearly all of the audio signal only have have it made back up later on. I'm not surprised there is a lot of hissing.

 

Aim for normal listening volume to be at the 3 o clock position. A gain of 1 is probably fine. I have no problem with volume with Senn HD650 and no amp! So a gain of 1 would be fine. You definitely need some sort of amp or buffer for SQ reasons. But it seems that more gain = reduced performance so what's the point?

Reply
post #17 of 25
6/27/10 at 10:03am
Thread Starter 

Thanks Mr. Duck. I cant DIY so cant change the gain myself plus I am getting the 600 ohm Beyer T1 anyway (AD2K is gone).

 

Could you please elaborate why "Aim for normal listening volume to be at the 3 o clock position. A gain of 1 is probably fine."? Some calculation will help here. I have a PhD and had basic EE course before.....so feel free to get technical here.

 

Will gain 1 work for the 600 ohm T1? What sort of amp or buffer will be needed? I will like to get some action plan here, thank you.

 

 

 

 

Reply
post #18 of 25
6/27/10 at 10:43am

Hi, the volume control is known as a potential divider. Fully counter clockwise puts the wiper down to ground where there is no audio signal left. Fully clockwise is the maximum audio signal - where the signal is strongest with no attenuation.

 

The amplifier gain remains constant and amplifies whatever noise is present as well as the audio signal. You want to keep the audio signal as strong as possible so that you can have as big a difference as possible between the audio signal and the noise floor of the system.

 

I said aim for the 3 o clock position because it leaves some headroom if you need more volume. But the ideal would be normal listening volume when turned up to maximum (assuming you never need more gain). Because this would mean you don't have to throw away any of the audio signal. Commercial and mainstream "hi-fi" likes to use a gain too high because it gives the impression that the equipment is very high quality and powerful if it's loud when the volume is only at 9 o clock position. I think that can carry over into the DIY world as well.

 

There is a good article written by nelson pass. The car analogy on the 1st page is a good one. Download here (PDF)... http://www.google.co.uk/url?sa=t&source=web&cd=1&ved=0CBUQFjAA&url=http%3A%2F%2Fpassdiy.com%2Fpdf%2FB1%2520Buffer%2520Preamp.pdf&rct=j&q=pass+B1+pdf&ei=04onTKO2NMyTjAeBmqR3&usg=AFQjCNEKTfobsW09G6_jUIAQrD8841MW1Q

 

I suspect a gain of 1 to 3 will give enough volume for any headphone you would own. But others will have to confirm this as I only have not played around with this much.


Edited by Mr.Duck - 6/27/10 at 10:45am
Reply
post #19 of 25
6/27/10 at 1:32pm
Thread Starter 

I also like to add the information I gethered online pertaining to M3 and 600 ohm headphones.

 

First, some “take home message” based on my research:

1, For low-mid impedance phones, a gain of 2-4 should be plenty. So I will extrapolate by saying that: for 300 ohms above, you may want to use gain 5 above. If you will NEVER use phones of 300 ohms above, you don’t need gain 5 above. Everything depends on the specific setting of your audio system of course.

 

2, As for the Beyer T1 (600 ohm, 102 db/mw), to get 120 db TRANSIENT peak, you need 63 mw / 6.15 v  / 10 mA at peak level. Judging from AMB’s M3 spec: http://www.amb.org/audio/mmm/   M3 with 27v PSU can output enough for T1 to get 120 db transiently (Sigma 11 provideS 36v). M3’s output result with 330 ohm load looks good there.

 

Explanation for the above statement:

 

1, Quote from Morsel :

“Jason is right about lower noise and greater useful volume control range. Don't use more gain than you need. If your headphones are low impedance high efficiency types and you never use high impedance phones, a gain of 2-4 should be plenty.”

 

2, Quote from Tangent :

“The only reason you see a gain of 11 so often is because the resistor values are easy to come up with, and it'll work with just about any combination of headphones and sources.”

 

3, Quote from Morsel :

η = Sensitivity in dB SPL/mW

SPL = η + 10Log(1000P)

P = V²/R

 

4, Specifications page from AMB’s web site regarding M3 (thanks to Ti Kan).


Edited by zzffnn - 9/20/10 at 10:35pm
Reply
post #20 of 25
6/27/10 at 1:36pm
Thread Starter 

I like to add the information I gethered online pertaining to M3 and 600 ohm headphones.

 

First, some “take home message” based on my research:

1, For low-mid impedance phones, a gain of 2-4 should be plenty. So I will extrapolate by saying that: for 300 ohms above, you may want to use gain 5 above. If you will NEVER use phones of 300 ohms above, you don’t need gain 5 above. Everything depends on the specific setting of your audio system of course.

 

2, As for the Beyer T1 (600 ohm, 102 db/mw), to get 120 db TRANSIENT peak, you need 63 mw / 6.15 v  / 10 mA at peak level. Judging from AMB’s M3 spec: http://www.amb.org/audio/mmm/   M3 with 27v PSU can output enough for T1 to get 120 db transiently (Sigma 11 provideS 36v). M3’s output result with 330 ohm load looks good there.

 

Explanation for the above statement:

 

1, Quote from Morsel :

“Jason is right about lower noise and greater useful volume control range. Don't use more gain than you need. If your headphones are low impedance high efficiency types and you never use high impedance phones, a gain of 2-4 should be plenty.”

 

2, Quote from Tangent :

“The only reason you see a gain of 11 so often is because the resistor values are easy to come up with, and it'll work with just about any combination of headphones and sources.”

 

3, Quote from Morsel :

η = Sensitivity in dB SPL/mW

SPL = η + 10Log(1000P)

P = V²/R

 

4, Specifications page from AMB’s web site regarding M3 (thanks to Ti Kan).


Edited by zzffnn - 9/20/10 at 10:36pm
Reply
post #21 of 25
6/30/10 at 7:46pm
Thread Starter 

I want to cry now......my Beyer T1 (600 ohm, 102 db/mw) hisses badly with the M3 (with AD843, gain 11 with Sigma 11), a lot more than the ATH-AD2000 (40 ohm, 102 db/mw).

 

Does it make sense? Why..................

Reply
post #22 of 25
6/30/10 at 9:52pm
Quote:
Originally Posted by zzffnn View Post

I want to cry now......my Beyer T1 (600 ohm, 102 db/mw) hisses badly with the M3 (with AD843, gain 11 with Sigma 11), a lot more than the ATH-AD2000 (40 ohm, 102 db/mw).

 

Does it make sense? Why..................

 

It certainly doesn't make sense that there is more hiss with your T1.  If both of them are rated at 102dB at 1mW, and one of them is 40 ohms while the other is 600 ohms, then the output voltage needed to develop 102dB is 0.2V for the AD2000 and 0.77V for the T1.  So, for a particular gain and noise floor, there should be 11.7dB less audible noise with your T1 compared to the AD2000.  That is, unless the sensitivity specifications are not comparable.

 

At any rate, I don't have a T1 to verify this, but you could also do a different experiment.  At the same volume knob position, play the same music from the same source and compare the perceived volume level between the two headphones.  Is the AD2000 about 11.7dB louder than the T1?  It should be, unless the sensitivity specifications of one or both or them are not to be believed.

Reply
post #23 of 25
6/30/10 at 11:38pm

Does the amp have output resistors? Its a reachy guess. 

 

As another guess. Is it possible that the T1 have better low level detail? What SPL do the ATH and T1 run with 0.001mw of power? 

 

I should note: the second point is something I have been curious about. Do speakers stop having a predictable relationship of power VS SPL at some point and simply stop working (assume fixed frequency and ignore Fletcher-Munson curves) before the calculator would suggest? Put another way: are there speakers that cant produce SPL's below some given level? It makes intuitive sense to me that there are: Eventually there is not enough power on tap to overcome losses somewhere... Are there any articles or papers on the subject? Please forgive me if this is commonly known in speakervile. I dont think I have seen it come up here before and dont travel speaker sites.



HTML Hit Counter
HTML Hit Counter


Edited by nikongod - 6/30/10 at 11:40pm
Reply
post #24 of 25
7/1/10 at 5:53am
Thread Starter 

Thank you all for replying.

 

@ AMB: I traded the AD2000 for the T1, so I dont have them side by side to compare. 102dB/mW [JEITA] is AD2000's sensitivity according to audiocube.com. I heard T1's sensitivity level from FallenAngel at page 1 (he said 102dB/1mW) and also somewhere else online.

 

You are right, to get the same sound level, T1 is at 9:30 to 10 o'clock, while AD2000 is at 9 o'clock; however, based on my memory, T1's hiss is still louder than AD2000's, so much so that I notice that (as I said, T1 hisses at volume zero).

 

I did notice a few things that significantly increased hiss: 1) when my finger touched the 1/4'' plug of T1 (on shielded part); less so when my finger touched the wire of T1 (still audible); 2) when my laptop is on. Note that laptop is on one outlet, while my source (Archos 605 coaxial out) and dac (Buffalo 24), the M3 amp are on a power strip from the other outlet....although the two outlet are 2 cm apart (from same jack). I can probably try another outlet/jack far away from the laptop power. 

 

Another thought, could it be the strong 1 tesla magnet of T1 that "picks up" all the interference?

 

@  nikongod : I dont know if the M3 amp has output resistors; I do know that to lower the gain, resistors have to been soldered into M3. T1 DOES have more lower level details compared to ATH-AD2000, no doubt about it. Both T1 and AD2000 produce 102 db with 1mw of power. What you said about SPL seems to make sense.

 


Edited by zzffnn - 7/1/10 at 5:56am
Reply
post #25 of 25
7/9/10 at 4:56pm
Thread Starter 

Finally found out: the hiss should be caused by ground loop of my M3 amp. FallenAngel helped me to trouble shoot and solved problem. Thanks a lot, FallenAngel!

Reply
New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › AMB M3 at gain 8 for Beyer T1?