Just meant w/ a sound card 1Vrms out tells a lot. No biggy just curiousity.
Lateral mosfet headamp is a bit of an innovation I think.
Well, I have access to a few different spectrum analyzers at work so I should be able to do better than a soundcard FFT.
I don't know if it is an innovation as such, but from googling there doesn't seem to be any similar designs with Lateral FET's.
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I have sold a few PCB's so far but now that I'm done with designing all the PCB's and everything works as it should I have a bunch of PCB's left from V1 of my amp.
They are all fully functional.
Only issues are :
Amp board : Have to bend the legs of the 2 compensation caps if you are using Silver Mica caps or any other cap that wont fit otherwise.
No Thump Board : Have to rotate T1 180 degrees compared to silkscreen.
Supply Board : Have to use the other secondary for AC detection. Connector was added to the wrong secondary.
For this reason they are sold for a fair price.
2 x Amp Boards + 1 x No Thump Board + 1 x Supply Board is included in a set of boards
What I have left of V1 is :
2 pairs of Amp Boards left(maybe 3 if one can live with the soldermask being a little lumpy in some places)
9(or 11) No Thump Boards
10 Supply Boards
Price will be $30 USD for a set of V1 PCB's of which I'll be donating $3 USD to Diyaudio.com.
All boards are almost done being upgraded to V2(MKII) and I have fixed the few issues mentioned earlier as well as rearranging a few components, of which the Amp Boards will see the biggest change. One can see my Amp Board MKII in an earlier post. I'll be posting the final versions when they are done and I have the time for it.
Boards will be upgraded to MKII as needed. Once all boards are upgraded to MKII the price will increase to $40 USD for a set, of which I will be donating $5 USD to Diyaudio.com
As I mentioned in an older post, I'll be supplying schematics as well as a rudimentary BOM for all boards. So people will have to source their own components.
They are all fully functional.
Only issues are :
Amp board : Have to bend the legs of the 2 compensation caps if you are using Silver Mica caps or any other cap that wont fit otherwise.
No Thump Board : Have to rotate T1 180 degrees compared to silkscreen.
Supply Board : Have to use the other secondary for AC detection. Connector was added to the wrong secondary.
For this reason they are sold for a fair price.
2 x Amp Boards + 1 x No Thump Board + 1 x Supply Board is included in a set of boards
What I have left of V1 is :
2 pairs of Amp Boards left(maybe 3 if one can live with the soldermask being a little lumpy in some places)
9(or 11) No Thump Boards
10 Supply Boards
Price will be $30 USD for a set of V1 PCB's of which I'll be donating $3 USD to Diyaudio.com.
All boards are almost done being upgraded to V2(MKII) and I have fixed the few issues mentioned earlier as well as rearranging a few components, of which the Amp Boards will see the biggest change. One can see my Amp Board MKII in an earlier post. I'll be posting the final versions when they are done and I have the time for it.
Boards will be upgraded to MKII as needed. Once all boards are upgraded to MKII the price will increase to $40 USD for a set, of which I will be donating $5 USD to Diyaudio.com
As I mentioned in an older post, I'll be supplying schematics as well as a rudimentary BOM for all boards. So people will have to source their own components.
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I'm using a Stanford Research Systems SR780 2-channel network analyzer for the measurements.
The built in generator is worse than I expected, but the measurements should still give an idea of what the amp can do. Dynamic range of the SR780 FFT is limted to about 80-90 dB and the max frequency is 100 kHz, good enough for 1kHz but not ideal for 20kHz but it will have to do.
First 3 attached pictures are 1kHz generator output at 0.7Vpk, 1.4vpk, 2.8Vpk.
Last 3 attached pictures are 1kHz amp output at 1Vrms, 2Vrms, 4Vrms into a 33 Ohm dummy load.
Amplifier gain is X2
Generator distortion is 0.7Vpk/0.021% THD, 1.4Vpk/0.011% THD, 2.8Vpk/0.007% THD.
Amp distortion is 1Vrms/0.015% THD, 2Vrms/0.033% THD, 4Vrms/0.072% THD.
The somewhat high distortion of the generator as well as the limited dynamic range of the SR780 FFT puts a limited on how good I can get the measurements.
I do have access to an audio analyzer from Rohde & Schwarz and I might try using that some day, it might have better specifications.
Next up is 20kHz measurements.
The built in generator is worse than I expected, but the measurements should still give an idea of what the amp can do. Dynamic range of the SR780 FFT is limted to about 80-90 dB and the max frequency is 100 kHz, good enough for 1kHz but not ideal for 20kHz but it will have to do.
First 3 attached pictures are 1kHz generator output at 0.7Vpk, 1.4vpk, 2.8Vpk.
Last 3 attached pictures are 1kHz amp output at 1Vrms, 2Vrms, 4Vrms into a 33 Ohm dummy load.
Amplifier gain is X2
Generator distortion is 0.7Vpk/0.021% THD, 1.4Vpk/0.011% THD, 2.8Vpk/0.007% THD.
Amp distortion is 1Vrms/0.015% THD, 2Vrms/0.033% THD, 4Vrms/0.072% THD.
The somewhat high distortion of the generator as well as the limited dynamic range of the SR780 FFT puts a limited on how good I can get the measurements.
I do have access to an audio analyzer from Rohde & Schwarz and I might try using that some day, it might have better specifications.
Next up is 20kHz measurements.
Attachments
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First 3 attached pictures are 20kHz generator output at 0.7Vpk, 1.4vpk, 2.8Vpk.
Last 3 attached pictures are 20kHz amp output at 1Vrms, 2Vrms, 4Vrms into a 33 Ohm dummy load.
Generator distortion is 0.7Vpk/0.035% THD, 1.4Vpk/0.0135% THD, 2.8Vpk/0.007% THD.
Amp distortion is 1Vrms/0.019% THD, 2Vrms/0.045% THD, 4Vrms/0.09% THD.
Last 3 attached pictures are 20kHz amp output at 1Vrms, 2Vrms, 4Vrms into a 33 Ohm dummy load.
Generator distortion is 0.7Vpk/0.035% THD, 1.4Vpk/0.0135% THD, 2.8Vpk/0.007% THD.
Amp distortion is 1Vrms/0.019% THD, 2Vrms/0.045% THD, 4Vrms/0.09% THD.
Attachments
Yesterday I finally finished my amp and took it home.
It sounded great at work, no hum or buzz.
So I hooked it up to the lineout out from the crappy integrated sound on my motherboard, turned the volume knob and there was silence. Then I reached about 10-11 o'clock on the volume knob and the hum started, increasing in intensity and then falling slightly towards the end of the volume knob, turning into a small background hissing type of sound. Great, sounds like I got a ground loop going.
Found my 6 year old crappy MP3 player and hooked it up and the hum or buzz was gone.
Today I hooked it up to a work laptop, same issue, hum and buzz. However, touching the case of my amp with one hand and the small metal hinges used on the laptop screen with my other hand cured it, once again there was silence. The hum and buzz was 100% gone, only thing left was a slight hiss from about 15 o'clock on the volume knob to max volume, most likely just the laptop putting out some noise.
Annoying as hell, but I'm just glad that it isn't my amp that is at fault.
Edit : Removing the laptop from the charger reduces the hum and buzz significantly, but it is still there. One hand on amp and one on laptop still works 100%. Annoying.
Edit#2 : If the latop is removed from the charger, it shouldn't be possible to get a ground loop. Hmm...
Edit#3 : Maybe I should just go ahead and buy that Cambridge Audio Dacmagic 100 DAC that I have been wanting for a few weeks now. It has a ground lift switch, problem solved. Or?
It sounded great at work, no hum or buzz.
So I hooked it up to the lineout out from the crappy integrated sound on my motherboard, turned the volume knob and there was silence. Then I reached about 10-11 o'clock on the volume knob and the hum started, increasing in intensity and then falling slightly towards the end of the volume knob, turning into a small background hissing type of sound. Great, sounds like I got a ground loop going.
Found my 6 year old crappy MP3 player and hooked it up and the hum or buzz was gone.
Today I hooked it up to a work laptop, same issue, hum and buzz. However, touching the case of my amp with one hand and the small metal hinges used on the laptop screen with my other hand cured it, once again there was silence. The hum and buzz was 100% gone, only thing left was a slight hiss from about 15 o'clock on the volume knob to max volume, most likely just the laptop putting out some noise.
Annoying as hell, but I'm just glad that it isn't my amp that is at fault.
Edit : Removing the laptop from the charger reduces the hum and buzz significantly, but it is still there. One hand on amp and one on laptop still works 100%. Annoying.
Edit#2 : If the latop is removed from the charger, it shouldn't be possible to get a ground loop. Hmm...
Edit#3 : Maybe I should just go ahead and buy that Cambridge Audio Dacmagic 100 DAC that I have been wanting for a few weeks now. It has a ground lift switch, problem solved. Or?
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Found the issue.
The cabinet of my Headamp is grounded, the AC plug for the laptop charger does not have a ground pin. Pulled out the power plug from the wall socket with the cable and charger still attached to the laptop. Put one hand on my headamp cabinet and a finger on where the round pin should have been on the power plug and the hum was gone. There is still a hole there for a ground pin, just no pin.
This is great news as it not only explains why I have hum when using the work laptop I'm typing this on, but also why I have hum using the Headamp at home.
At work, my stationary work PC was grounded as well as my Headamp = No hum.
At home, my private stationay PC is not grounded and my Headamp wasn't either = Hum.
At school, my work laptop was not grounded but my Headamp was = Hum.
First thing I do when getting home is buying a decent power strip WITH ground.
The cabinet of my Headamp is grounded, the AC plug for the laptop charger does not have a ground pin. Pulled out the power plug from the wall socket with the cable and charger still attached to the laptop. Put one hand on my headamp cabinet and a finger on where the round pin should have been on the power plug and the hum was gone. There is still a hole there for a ground pin, just no pin.
This is great news as it not only explains why I have hum when using the work laptop I'm typing this on, but also why I have hum using the Headamp at home.
At work, my stationary work PC was grounded as well as my Headamp = No hum.
At home, my private stationay PC is not grounded and my Headamp wasn't either = Hum.
At school, my work laptop was not grounded but my Headamp was = Hum.
First thing I do when getting home is buying a decent power strip WITH ground.
With that issue out of the way, lets talk about sound.
I'm limited by my low-end Sennheiser HD415 but I can still hear a clear improvement compared to driving them from my PC onboard soundcard.
It is a clear improvement in clarity and detail with the biggest change being the bass. The HD415 are known to have a bass that is a little loose or boomy. They are still tending to sound a little loose and boomy with the Thor headamp, but they subjectively sound like they go an octave lower than before and there is a lot more detail and slam in the bass now. Suddenly I hear a lot of little details in the bass that wasn't audible before.
What it is eaxctly that gives the improvement is not something I can 100% put a finger on, but it is probably a combination of the high 180mA bias setting+ability to deliver more current, as well as the almost 0-Ohm output impedance. It just gives a great deal of control over your headphones.
My next headphone(probably Beyerdynamic DT880/250) will be in a whole other league than the HD415 and I'm sure the Thor headamp will have no trouble living up to it.
I'm limited by my low-end Sennheiser HD415 but I can still hear a clear improvement compared to driving them from my PC onboard soundcard.
It is a clear improvement in clarity and detail with the biggest change being the bass. The HD415 are known to have a bass that is a little loose or boomy. They are still tending to sound a little loose and boomy with the Thor headamp, but they subjectively sound like they go an octave lower than before and there is a lot more detail and slam in the bass now. Suddenly I hear a lot of little details in the bass that wasn't audible before.
What it is eaxctly that gives the improvement is not something I can 100% put a finger on, but it is probably a combination of the high 180mA bias setting+ability to deliver more current, as well as the almost 0-Ohm output impedance. It just gives a great deal of control over your headphones.
My next headphone(probably Beyerdynamic DT880/250) will be in a whole other league than the HD415 and I'm sure the Thor headamp will have no trouble living up to it.
I have to find somewhere to listen to it first.
Or maybe I'll buy it unheard , but it might still be several months off, gotta save up some money for it. I'm not so sure I would want something that sit tight on the head. I'm not only after good sound but also good comfort and from what I have heard the hifi version of DT 880 are among the most comfotable headphones on the market.
I'll probably end up buying it from Germany, there is around EUR 60 to be saved compared to buying it here in Denmark.
I think the Pro is only available in 250 Ohm while the hifi edition comes in 32, 250 or 600 Ohm versions.
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