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Asus Essence One Headphone Amp/DAC (CeBIT 2011)
May 25, 2015 at 1:37 PM Post #3,151 of 3,573
raoultrifan said:
  Hi Damir,
 
With default opamps I got the same hum. Like I said before, rearranging power transformer resolves the issue. I have reasons to believe that all E1s are like that because they all share the same trafo part no., so all you need is AKG K550 and a dead silent room (at 2AM in the morning) to do the testing. :) You will not hear hum with any kind of headphone, even not with all IEMs, so try it out with K550 please.
 
Feel free to check the screenshots here: http://www.homemedia.fr/tests/i/mesures/asus-essence-one-rmaa/ASUS%20Xonar%20Essence%20One%2096%20khz.htm and http://archimago.blogspot.ro/2013/02/measurement-asus-xonar-essence-one.html.You can see the hum I'm speaking about, especially 2'nd and 3'rd harmonic (around 200 Hz and 300 Hz). DACs having external PSU doesn't have this hum at all...just pure white noise maybe, but not hum.
 
Cheers, 
Raul.
Click to expand...


Hi Raul,
My Beyerdynamic DT770 PRO are among several HP's that are references for low frequency reproduction, down to infrasonic. Posted links show that there are no peaks above -100 db, and that is unhearable at low frequencies. Your situation must be much worse than that.
Here are two of my measurements taken two years ago during extensive swapping.


This is loopback measurement of my Terratec audio card in standard PC.
 
 

This is E1 measurement with LT1028+OPA627AU amps.
 
As you can see there is only slight contribution to Hum and Noise by E1.
E1 is obviously much better than my measuring audio card.
 
Now I use 6x Muses 01 opamps and that is the best setup (tried Muses 02 also).
 
Have you tried to move E1 away of the other possible sources of interference.
I have noticed that mobile phone can make noises in E1 if placed less than 1 meter close.
 
Best regards,
Damir
 
May 26, 2015 at 1:15 AM Post #3,152 of 3,573
Thanks Damir for your reply,
 
I will try to do a loop-back noise-check when I'll have the time; will probably use the U7 sound-card, as it has a quite decent ADC.
 
The tests I've done were outside the room, in the balcony, so there were no interferences.
 
My hum is almost gone now and I don't have the issue anymore, because, like you can see in my attached images from one of my previous posts, my trafo has been repositioned upside-down and a bit angled with about 30 degrees. This hum was only audible when case was closed, because the thick aluminium case was reflecting the electromagnetic interferences from transformer inside the PCB (most likely to LME49720 from headamp and to B10K pots).
 
Cheers,

Raul.
 
P.S.: AKG K550/32 have 114dB SPL/V, that means it only needs around 1Volt to get to 115dB. DT770/250 have an SPL of only 96dB/mW, so it needs about 4.5 times more voltage than K550 to get the same 115dB. :) This is the only reason I'm using K550 to test for noise background and hum. I also used them 1 year ago in finding the correct position for the trafo inside a DIY headamp with LME49720+BUF634 with quite good results.
 
May 27, 2015 at 12:44 AM Post #3,153 of 3,573
raoultrifan said:
  Hi guys, 
 
I just bought myself a piece of Essence One and I'm quite happy about it. :)
 
Of course, I'm already thinking of modding it:
- according to csarrow and mach3: replace KT with KA caps, increase PSU's caps
- add tantalums for+/-12V and +5V
- add 3 x 2.2uF in parallel with trafo's secondary coils;
- add EMI/RFI filter (capacitors and coils);
- replace BK10 with 4-gangs equivalent logarithmic from BOURNE (Mouser has something)
- according to MaestroSfai (https://audiofilifiorentini.files.wordpress.com/2014/04/modifiche-sonore-al-dac-asus-one-che-risorgerc3a0.pdf): replace output caps with dc-servo circuit with TL072, like is already implemented in E1's headphone amp with LME49720.
Well, I still love E1's warranty right now, so...I'll probably wait a couple of years till starting these quite intrusive/obvious mods. :)
 
Meantime, after swapping some opams (NE5532, LM4562, OPA2604, OPA1602) in different positions I realized that best sound I could get is having OPA2604 in I/V and OPA1602 in LPF. Best soundstage indeed, but too bad I can't keep the OPA2604 in IV anymore, because of overheating: around 65C with case open and most likely 75C or even more with case closed. :frowning2: Will not try adding heatsinks on OPA2604 because I really think they are oscillating, so I'll try finding an oscilloscope first or I'll just try OPA1642 in IV soon.
 
Speaking of opening and closing E1's case, while keeping my AKG 550's on my head with volume pot at max. (E1's mute button = ON) I realized that I have an audible hum around 100-200Hz when case is closed or even partially-closed, but not hum at all while case is fully open. Same hum, but a little bit less disturbing, was heard with my Grado SR60i L-cush, so looks like thick aluminium case is reflecting trafo's hum/noise back inside the DAC's circuit.
Then, I realized there are tests proving the existence of this noise: http://www.homemedia.fr/tests/i/mesures/asus-essence-one-rmaa/ASUS%20Xonar%20Essence%20One%2096%20khz.htm and http://archimago.blogspot.ro/2013/02/measurement-asus-xonar-essence-one.html.
So, I found out that trafo needs to be repositioned and least hum-noise I could get is placing it vice-versa (yes, with bottom on top) and angled with about 30 degrees, like in pictures attached. This decreased the hum-noise with more than half. I've used 1 x clothes-pin and 1 x rubber-band to do this "trafo rearrangement", but I'm sure this can be done way much better looking. :)
 
Just to be sure noise will decrease further, I've also added a ferrite-core around the power cord and a small DIY RC filter between chassis ground and mains power ground (5K/4Watts resistor || 330nF cap), somehow similar with what Meier Corda does in his amps.
 
Is anyone else able to hear that hum I'm speaking about or just my E1 has this issue?
 
Thanks, 
Raul.
Click to expand...

 
Hi Raul,
 
That's really odd with the hum you mentioned. I have tested for the so call hum on both my Essence One and I do not hear it at all.
Sounds like you could benefit from a power conditioner.
 
Anyway, it's been a while since I posted any update on my modding adventure with both my E1.
For a starter, I'm glad to announce. It's possible to create the high gain and low gain feature on the standard E1.
That means if you do the mod below, change the B10K pot (You don't need to change the pot if you don't have imbalance issue) and Muses 01 opamps you got yourself a Muses Editio
I've also upgraded both unit to DSD and now it showing up as MKII in the taskbar icon.
 

 
May 27, 2015 at 2:44 AM Post #3,154 of 3,573
Sounds like you could benefit from a power conditioner.
Click to expand...

 
Hi Mach3, glad to read about the gain mod on regular E1. Thank you!
 
The hum I'm hearing is from transformer's electro-magnetic waves (50Hz, 50Hz x 2, 50Hz x 3...) and can't be filtered with a power conditioner (I already have a small power conditioner). I need to create a EMI shield to return EMI waves inside transformer (like a Faraday cage): http://www.digikey.com/Web%20Export/Supplier%20Content/SignalTransformer_595/PDF/signal-transformer-pi-caging-transformer.pdf?redirected=1.
 
Anyway, by repositioning the trafo inside E1 I'm pretty fine right now.
 
Raul.
 
May 28, 2015 at 2:56 PM Post #3,155 of 3,573
Hi guys,
 
I fixed the hum noise for good today by wrapping twice a band of "grain-oriented silicon steel" (G.O.S.S. band) around the toroidal transformer. Now there's absolutely no hum at all (AKG K550, quiet night, mute=ON, pot. to the max.).
 
The G.O.S.S. band I got it from a friend who works as engineer for Petra-toroid (I got it for free, they don't sell this). Also Talema is implementing this as well in Hi-Fi equipment: http://www.nuvotem.com/en/products/gossband_large.shtml.
 
3 images attached; not very eye-caching, but now with case closed the hum is completely gone and I'm happy again. :)
 

 
 

 

 
Cheers,
Raul.
 
May 28, 2015 at 9:01 PM Post #3,156 of 3,573
raoultrifan said:
  Hi guys,
 
I fixed the hum noise for good today by wrapping twice a band of "grain-oriented silicon steel" (G.O.S.S. band) around the toroidal transformer. Now there's absolutely no hum at all (AKG K550, quiet night, mute=ON, pot. to the max.).
 
The G.O.S.S. band I got it from a friend who works as engineer for Petra-toroid (I got it for free, they don't sell this). Also Talema is implementing this as well in Hi-Fi equipment: http://www.nuvotem.com/en/products/gossband_large.shtml.
 
3 images attached; not very eye-caching, but now with case closed the hum is completely gone and I'm happy again. :)
 
Cheers,
Raul.
Click to expand...

 
I don't need this, but I want some of that G.O.S.S. to do both my E1 :) Modding bug is addictive.
 
May 29, 2015 at 1:16 AM Post #3,157 of 3,573
:)
 
Now really Mach3, get out the capacitors from RCA/XLR output and remove DC-offset with opamps like TL082 or anything else. I need to wait for the warranty to expire to start modding my E1...:frowning2:
 
BTW, I found GOSS on Aliababa; they're selling in small pieces of 5 tons. :D
 
P.S.: Mach3, I realize that you have 2 E1s; did you happen to have an A/B testing device (for phones/RCA/XLR)? If yes, then from where did you bought it, please?
 
May 29, 2015 at 2:30 AM Post #3,158 of 3,573
raoultrifan said:
  Hi guys,
 
I fixed the hum noise for good today by wrapping twice a band of "grain-oriented silicon steel" (G.O.S.S. band) around the toroidal transformer. Now there's absolutely no hum at all (AKG K550, quiet night, mute=ON, pot. to the max.).
 
Cheers, Raul.
Click to expand...

Well done
gs1000.gif
. Is the shield grounded or not?
 
Best regards,
Damir
 
May 29, 2015 at 1:40 PM Post #3,160 of 3,573
raoultrifan said:
:)


 


Now really Mach3, get out the capacitors from RCA/XLR output and remove DC-offset with opamps like TL082 or anything else. I need to wait for the warranty to expire to start modding my E1...:frowning2:


 


BTW, I found GOSS on Aliababa; they're selling in small pieces of 5 tons. :D


 


P.S.: Mach3, I realize that you have 2 E1s; did you happen to have an A/B testing device (for phones/RCA/XLR)? If yes, then from where did you bought it, please?
Click to expand...

 


Hi Raul,

I'm not sure what you asking me to do exactly between my two E1. Can you clarify thanks
 
May 30, 2015 at 1:24 AM Post #3,161 of 3,573
Mach3, could you please check http://www.head-fi.org/t/542563/asus-essence-one-headphone-amp-dac-cebit-2011/3135#post_11630160? There are 6 mods I'd like to try out when my E1 will be out of warranty. Eliminating (shorting) the output capacitors is the last mod from this list.

My E1 right now has an output DC of +/-7mV measured before output capacitors, but this may very, depending on OPAMPs used. Basically, anyone can measure the output DC before capacitors and if it's lower than 10-20mV can easily bypass output capacitors, but it's not a safe thing to do without implementing a DC-servo circuit, because in case of fail-over (PSU damage, OPAMP damage etc.) there will be a lot of DC voltage present on output and this might completely damage the input stage of devices connected to XLR/RCA outputs of E1.

So, you might try the circuit presented by MastroSfai from the link above or you can modify the circuit presented by TI, the same circuit from E1's headphone amplifier; see the datasheet of LME49600 for this. TI is using half of OPAMP for audio and the other half for DC-servo. You can adapt this circuit by only using 1 x OPAMP for DC-servo.

Also, a RLC filter and a ferrite bead over the power cord will decrease further the noise of E1. Most noise in an audio device comes from PSU, unshielded or bad/cheap cables and bad PCB design, but not from OPAMPs. Cheap RFI/EMI power line suppressor filters could be found on Mouser, Digikey, TME, Farnell, Arrow etc. Right now I'm using a small power stripper which already has such a suppressing filter inside; a ferrite bead I installed myself over the power cord.
https://electrosome.com/x-and-y-rated-capacitors/
http://www.digikey.com/Web%20Export/Supplier%20Content/Lambda_285/PDF/TDKLambda_all_about_emi_epmag.pdf?redirected=1

Also, if you have a noisy electrical ground (home electrical appliances generate a lot of noise on mains ground which is connected with E1 circuit's ground and case) you can anytime create a ground-loop breaker circuit like the one implemented by Meier Corda: http://2.bp.blogspot.com/-ZKbJDWQf0Bg/Uyl8vfXe8RI/AAAAAAAAEs4/2vP3e0WS4Xs/s1600/powersupply1mk2.gif. You will not be able to fully separate the circuit ground from the main chassis, but at least you will be able to separate the main chassis from the mains electrical ground (https://cdn.head-fi.org/a/7391574.jpg).

Thanks,
Raul
 
Last edited:
Jun 1, 2015 at 1:40 AM Post #3,162 of 3,573
I was trying to investigate why 4 x OPA2604 in I/V are so hot; even the PSU's regulators are hotter than usual. So, without a proper scope to investigate for oscillations, I was measuring the power drawn by 4 x NE5532 and then with 4 x OPA2604:
- 4 x NE5532 in I/V: 54-55mA/230V, 12.65 Watts
- 4 x OPA2604 in I/V: 70-71 mA/230V, 16.1 Watts (almost 30% more power drawn from the main outlet!)
Looks like the OPA2604 drains with 3.45 Watts more than NE5532 and that means an additional 0.8625 Watts more per each OPA2604, that means the OPAMP is really oscillating and based on TI datasheet this is the max. power possible for this OPAMP at around 75-85C. :frowning2:
Strange thing, these OPA2604 does not oscillate when used in LPF.
 
I did some tracing a little bit around I/V and LPF stages and looks like the circuit is quite similar with the original presented by TI here http://www.ti.com/product/PCM1795/datasheet/application_and_implementation (fig. 53).
I was able to identify:
R1, R2 = 820ohms
R3, R4 = 220ohms
R5, R6 = 200ohms
R7, R8 = 180ohms
C1 = 2200pF
C3 = 8200pF
Pins 3 & 5 for all 4 x OPAMPs from I/V stage are directly connected to GND.
 
Decoupling is correctly done with SMD capacitors (electrolytic parallel with ceramic/MLCC) very close to +/-V pins, so my only explanation for OPA2604 oscillating is that PCB power traces are too close to Input- or Output pins of the OPAMPs or ground or power planes are not perfectly for use with OPA2604. :frowning2:
Too bad, because I really liked the sound from these OPAMPs, maybe because they were oscillating. :) I'll probably try OPA1642 soon, just to give it a try.
 
Regards!
 
Jun 4, 2015 at 11:57 PM Post #3,163 of 3,573
I'm not really technically minded but when I first had my E1 I also had a hum, it was because of a grounding loop. I fixed this by plugging in power using 2 different circuits, E1 on its own circuit, source on the other.
 
Another way of doing this if you don't have access to 2 separate circuits is to modify the USB cable by breaking off or covering the ground pin
 
Jun 25, 2015 at 12:56 PM Post #3,164 of 3,573
Say, I'm not all that advanced in the Tech part of this whole audio world. and so I will be getting passive speakers. and a temp amp which is very basic and I need to use a dac. I assume the E1 RCA will do the trick for E1 to be used as dac and volume control for speaker amp? Should work right? :D
 
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