Good Mosfet Amplifier for HeadPhones?

[Mod_Evil]

I´m searching for the best possible ( and simple ) mosfet based headphone amplifier for my Philips HP800. the music will be preferably old rock, like Pink Floyd and Black Sabbath
I have a Philips HP800 headphone and its impedance is 32Ohm, so the amplifier must be compatible with this

Thanks!

Rulez!!

 

[00940]

http://www.amb.org/audio/mmm/ one solution, with opamp gain stage and three channels structure. There is a pcb available

http://headwize.com/projects/showfil...lerano_prj.htm another one, full mosfet, based on the Zen amp of Nelson Pass.

http://headwize.com/projects/showfil...szeke1_prj.htm and of course the good old mosfet buffer. Simple if you don't need gain.

 

[Mod_Evil]

Hi!
I have this. http://headwize.com/projects/showfil...szeke1_prj.htm , and the Zen? Do you have pcb to her? I not have the ci's to M³ because in the Brazil i not found this

Thanks for your reply.

 

[00940]

I forgot this : http://headwize.com/projects/showfil...murdey_prj.htm and this : http://headwize.com/projects/showfil...stokes_prj.htm (but the M³ I pointed earlier is basically an improved version of this last amp).

For the Szekeres and the the Murdey, there are no pcb I know of, but those are easy to deal with, even without pcb.

For the Zen, Digi01 ran a group buy on diyaudio, i don't know if pcb are still available. You could contact him (he's in China) : http://www.diyaudio.com/forums/showt...784&highlight=

Sheldon Stokes : you can find the layout in the article, if you can etch your own boards.

For the M³, Amb is selling the pcb on his website.

 

[Mod_Evil]

They send a PCB to brazil? The cost of the shipment is very expensive, to send one pcb to Brazil.

J-fet is a buffer? I need one simple... amp.

Thanks. mod.

 

[rickcr42]

you could also look at the Borbely hybrid Amp in the "designing a headphone amp with opamps" article at headwiz.It uses a low voltage 6GM8 as the fron end to the mosfet output stage.

the szekeres is a nice design but extremely power supply sensitive and should be thought of like you would a SE triode stage if you want to optimise it (Gate =Grid etc).It is also intput sensitive and gate capacitance or gate drive are also factors that come into play.

So simple,so easy to build,so cheap,so complex to really get it to sing as it can.Hint-a jfet "Buffer" before the gate to isolate it and increase the input impedance to the actual amp is a plus because it takes the interconnecting cable and volume pot out of the gate capacitance equation (think of this if in tube terms as the miller capacitance and what that does to high frequency response of an amp).
Not like the Murdey amp but more a dual jfet white follower type.Check the jfet series pdfs (two of them) at the borbely site for details

 

[00940]

just send Amb an email, I've no idea if they ship to Brazil but the email is free

The basic szekeres (and the j-fet version) are just buffers, they don't add volume, just more power (current actually). If you drive your cans from a high level sources like a cd-player or a soundcard (the standard is 2V), you should have no problems, since the philips have a low impedance and don't require much voltage swing. If you source has a weak output and you need more volume, then pick an amp with gain.

 

[00940]

Quote:

Originally Posted by rickcr42 you could also look at the Borbely hybrid Amp in the "designing a headphone amp with opamps" article at headwiz.It uses a low voltage 6GM8 as the fron end to the mosfet output stage.

Speaking of low voltage tubes, you just remind me that there's a big thread for the moment on headwize on a very easy hybrid tube+mosfet. See here for the schematics and the layout : http://headwize.com/ubb/showpage.php...d=5395&fpage=6 But there are three different threads for this thing on headwize

A bit easier than the Borbely but needs an output cap.

 

[rickcr42]

Quote:

The basic szekeres (and the j-fet version) are just buffers, they don't add volume, just more power (current actually).

Exactly right.they would be better labeled headphone drivers and not headphone amps.You can ad a gain stage by doing a jfet version of the borbely hybrid front end but if you use the szekeres with a CD player you need no extra gain but just the volume control.I use mine after my line stage so that provides the gain even though not needed with CD as source.
with poertables you will need gain because they drive the "driver" absolutely teribly.you will NOT like the results straight out of a portable.

My most recent version of the "simple" szekeres has a 2:1 line level transformer to a simple jfet buffer/gate isolator and finally the mosfet which is still the original capacitor coupled single supply SE version.The DC version will have a DC offest unless you trim the supplies and the single cap never bothered me anyway.


Oh yeah.Run the mosfet "hot" and not at the +9 to +15 vlts in the article.This will mean some bias changes but in the long run mosfets like the juice and 24-40 volts is far better than 12-15 in sonics (30 a good happy medium)

 

[rickcr42]

I am always a bit leary of low voltage tubes.they sound OK but to me,at least the designs i have either built or heard.sound lacking in life.

There is periodically a bit of chatter on making a tube headphone amp and i have done this and it really was not hard.What WAS hard was getting it to sound good enough to make it worth the hassle and that never happened.

I used hearing aid "pencil" tubes and in fact got the basic schematic from old hearing aid designs then added modern parts and some new twists like a CCS.
no matter what parts and what tweak I tried they were bettered by a simple opamp gain stage every time.If i tackle this again it will be a hybrid tube/mosfet mu-stage design for lower output impedance but the sound may never beat a simple opamp so really not worth the hassle

 

[Mod_Evil]

Hi friends, in the Brazil, is more difficult to found not discrete componentes, because this i need one simple amp... I have two pairs of IRF640 mosfets ( N-channel ) I need one amplifier for use this

... Money is not problem, i need quality.

I dont use Texas Chips because is very dificult to found in the Brazil.

National send the samples, this is Free? And the import custs?

And the class D amps? Schematics?

Thanks for attetion.

 

[00940]

Well, I trust you on that. Never played myself with low voltages tubes. Only with my RKV-like amp (320VDC) and a simple line stage (250VDC). Why go low voltages when life can be full of danger ?

 

[rickcr42]

When i was young it was common to have a tube radio in the car.we mostly listened to AM back then becasue FM was either all talk radio or what we considered "weird" music-classical and operetic,some jazz and free form.

so it was AM with a mono amp to front and rear speakers and it sounded damn good with Motown playing !

the temtations the rocked AM dial !

so 12VDC power is possible in a tube amp with fair power and sound but a car battery has GOBS of current available for powering the tubes.something a tiny portable amp can not have so already these tubes are either eliminated or operated out of there sweet spot in the current delivery.There are tricks to fool the tubes such as monolithic current pumps that take a little bit of current and increase it output but so far my experiments were dismal enough sounding to be put away for another day.I have some ideas but it just is not important to me as it once was

 

[Daroid]

Quote:

Originally Posted by Mod_Evil Hi friends, in the Brazil, is more difficult to found not discrete componentes, because this i need one simple amp... I have two pairs of IRF640 mosfets ( N-channel ) I need one amplifier for use this ... Money is not problem, i need quality. I dont use Texas Chips because is very dificult to found in the Brazil. National send the samples, this is Free? And the import custs? And the class D amps? Schematics? Thanks for attetion.

A "simple" amp might not necessarily be a mosfet output stage amp then. Sheldon Stokes sell his own PCBs too for the SDS labs amp if you want to give it a whirl. Build version 1.2 and not the older 1.1 on Headwize. I think it is an excellent amp - at least surprisingly good for the money spent. With that amplifier you can use IRF610, 620 and 640 n-ch. mosfets, but you will of course need the p channel mosfet from the same family (the ones with 9 in front). There are certain "bugs" about the SDS labs amps which can be quite a hassle if you do everything yourself:
1) On the PCB layout he did he kept changing between grids, not just 0.1" grids.
2) He still hasn't made it very official that the mentioned mosfets manufactured by harris are no longer available. He doesn't really recommend a substitute.
3) Input impedance is unnescesarily high (1 MOhm), accordingly a 100 kOhm pot was chosen.
4) Everywhere he goes oversize with the electrolytics, especially 4700 uF isn't needed. I found 1000 uF to be quite sufficient.
5) Making a star ground on this thing in the right spot is essential to even hope for a hum free result. This PCB design uses long traces too which might be a cause.

AMB's (and Morsel's) M³ does NOT suffer from any of the above-mentioned bugs. PCB design is more functional, and parts aren't overkill. (From what i've seen in the construction thread). However i'm not sure (or can't remember) if the IRF640 would fit in the M³, but chances are high that it will since it uses a standard pinout, and has a wide specification - i.e. high drain to source voltage of max 200V, drain current of 16A. It's truely overkill

 

[aphex944]

http://www4.head-fi.org/forums/showt...threadid=50478

Mine is very simple, but I couldn't tell you how to build it. It was designed and built by a friend. This probably doesn't help you much, but the schematic is there. All I CAN tell you is that it still sounds great