It will depend more on your rail voltages and bias current.
If you have 500mA and +/- 20V then you will need something like a 100VA transformer for stereo.
However I am always thinking of possibe future projects so I generally go bigger when it comes to transformers. I generally buy 300VA as a bare minimum, even if it is not required in the project I'm working on, because I know at some point in time in the future I might need a more powerful transformer for a future project.
If you have 500mA and +/- 20V then you will need something like a 100VA transformer for stereo.
However I am always thinking of possibe future projects so I generally go bigger when it comes to transformers. I generally buy 300VA as a bare minimum, even if it is not required in the project I'm working on, because I know at some point in time in the future I might need a more powerful transformer for a future project.
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Ureka
I completed the amp as described By Grey in the first post. I am using HD600 cans. The impedance of the headphones is 300 ohms. The amp sounds very nice,very detailed. The " veil" effect of the Sens seems to be greatly diminished. I used IRF630'S for the outputs. Thank you grey for posting the schematic and all youre advice.
I completed the amp as described By Grey in the first post. I am using HD600 cans. The impedance of the headphones is 300 ohms. The amp sounds very nice,very detailed. The " veil" effect of the Sens seems to be greatly diminished. I used IRF630'S for the outputs. Thank you grey for posting the schematic and all youre advice.
It's an outdated standard.I am "sort of" sure.
Take a look at this: Death of Zen Class-A - Use it as a headphone amplifier
It says that a headphone should want to see 120r, regardless of its own impedance. Its easy enough to test though, so its not a big deal. Just thought I would mention it
If someone knows, please tune in.
Steen
Modern headphones of the major brands (Grado, Sennheiser, Audio-Technica, AKG) are designed for low output impedance. Those brands also demonstrate their cans in audio events out of such amplifiers (and some as Grado sell amplifiers with 0 ohm output impedance).
Iirc, only Beyerdynamic still adheres to the 120ohms "standard".
Of course, having 120ohms in serie saves the amplifier of seeing a short circuit, should the output be shorted. Sadly, with the way headphones jacks and plugs are designed, this can be a common occurrence.
With all respect to Grey for a very simple, great sounding circuit, I would only encourage you to try this next :
http://www.diyaudio.com/forums/pass...r-configurations-post1603771.html#post1603771
It gets rid of the output coupling cap for one, and works with a power JFET in triode mode for another.
Patrick
http://www.diyaudio.com/forums/pass...r-configurations-post1603771.html#post1603771
It gets rid of the output coupling cap for one, and works with a power JFET in triode mode for another.
Patrick
output circuit question
The original print posted has for the output a 1 uf cap across a 1000uf cap which goes to a 1K ohm resistor to ground. Is the 1000uf cap the actual coupling cap, it has much less reactance in the audio bandwidth than 1 uf. And why use both caps?. I assume the resistor just discharges the large cap.
J
The original print posted has for the output a 1 uf cap across a 1000uf cap which goes to a 1K ohm resistor to ground. Is the 1000uf cap the actual coupling cap, it has much less reactance in the audio bandwidth than 1 uf. And why use both caps?. I assume the resistor just discharges the large cap.
J
The 1000 uF cap is indeed the coupling cap. The 1 uF cap is just ignorant "audiophile" pampering nonsense. It shows a fundamental lack of understanding of where and when bypassing should be used, so delete it.
I don't use designs with coupling caps, so I cannot possibly comment from experience.
But if I remember correctly, Nelson Pass also use 1x 15000uF electrolytic, 1x 220uF electrolytic, and 1x 1uF MKP in parallel for output decoupling for his First Watt F3 power amplifier.
http://www.firstwatt.com/downloads/F3-service-manual-sm.pdf
Could one then conclude from your argument that Nelson also lacks understanding of the use of bypass and is thus also guilty of spreading "ignorant audiophile pampering nonsense" ?
Looking very much to your expert advice,
Patrick
But if I remember correctly, Nelson Pass also use 1x 15000uF electrolytic, 1x 220uF electrolytic, and 1x 1uF MKP in parallel for output decoupling for his First Watt F3 power amplifier.
http://www.firstwatt.com/downloads/F3-service-manual-sm.pdf
Could one then conclude from your argument that Nelson also lacks understanding of the use of bypass and is thus also guilty of spreading "ignorant audiophile pampering nonsense" ?
Looking very much to your expert advice,
Patrick
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Obviously Mr. Pass deliberately added 'extras' so that the sentiment-driven tweakers have something to discuss, play-with, and worry about.
Having read many of your previous posts I am surprised that you have not understood that.
My advice stands firm. Disagreement is fine; you are welcome to it.
See updated version & comments at :
http://www.diyaudio.com/forums/pass...urce-follower-configurations.html#post1603771
http://www.diyaudio.com/forums/pass-labs/128571-some-other-source-follower-configurations.html
http://www.diyaudio.com/forums/headphones/154053-dao-follower-vs-f3-headphone-amp.html
http://www.diyaudio.com/forums/pass-labs/139907-downscaling-zen-v-9-use-headamp.html
Patrick
.
http://www.diyaudio.com/forums/pass...urce-follower-configurations.html#post1603771
http://www.diyaudio.com/forums/pass-labs/128571-some-other-source-follower-configurations.html
http://www.diyaudio.com/forums/headphones/154053-dao-follower-vs-f3-headphone-amp.html
http://www.diyaudio.com/forums/pass-labs/139907-downscaling-zen-v-9-use-headamp.html
Patrick
.
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No output decoupling capacitor, if that was what you meant.
I don't build amps which are not DC coupled.
The LU1014 can draw quit a bit of gate current, so you will need a low impedance source.
If you want to use a pot at the input for volume control, I would say 10k max., but you are probably better off using a JFET buffer in between, like the Curl Follower (also know as B1 from Nelson Pass, among other names).
Patrick
I don't build amps which are not DC coupled.
The LU1014 can draw quit a bit of gate current, so you will need a low impedance source.
If you want to use a pot at the input for volume control, I would say 10k max., but you are probably better off using a JFET buffer in between, like the Curl Follower (also know as B1 from Nelson Pass, among other names).
Patrick
I don't use a cap at the output. I matched the active components very close and used the source resistors to zero output DC-offset. After some fiddling I ended up with around 5-10mV.
No pot at input..
I also tried to build the taylored version but couldn't get it to work properly. I didn't spend alot of time with the Taylored version and plan to return to it when I find the time. Also wanted to listen some time to the "basic" version first.
For power supply I use PCB from chipamp.com in following config:
Trafo 225VA 2x18V
Rectifiers MUR860
Panasonic TSHA Caps
10000µf + 47000µf + 2.2mH + 47000µf + 2,2µf MKP.
I also suggest first building the standard version. It is easy and can hardly go wrong.
The Taylor version is quite a bit more complex in principle and not for beginners.
It looks very simple in the schematics, but there are many factors linked together, and you need to know which one to trim if you devices (both LU1014 and 2SJ103BL) are not quite the same as mine, which will be 99% the case.
Patrick
The Taylor version is quite a bit more complex in principle and not for beginners.
It looks very simple in the schematics, but there are many factors linked together, and you need to know which one to trim if you devices (both LU1014 and 2SJ103BL) are not quite the same as mine, which will be 99% the case.
Patrick
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