| sparkle |
Hi!
This thread is for people that still don't have a nice little headphone amplifier and don't want to spend a lot of money to get one.
Amplifier below is VERY cheap and it works nice for me. I use it with my MBQuart QP450 Professional as a portable amplifier when I work on my computer or somewhere I don't need Hi End but good sound. They are 300 Ohms. My friend use this amplifier with his Grado SR80 with even better sound.
The circuit is very simple (the idea comes from my friend – he use the same topology only a little bit bigger to drive his loudspeakers- thanks Darko).
He gets all the credits.
Regards
daniel |
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| sparkle |
some pictures:
The output cap's are Roe 2200uF/40V - nothing special. Cap's in power supply are 4700uF Matshushita- all of them. I have a little hum from the power supply so one should consider a better power supply :) |
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| sparkle |
Potentiometer is blue burns and the wires are silver with teflon insulation......
regards
daniel
p.s. it is not an high end but it works very nice - so nice that no one could complain about it- it has everything what a nice little amp should have in a sound and it is CHEAP |
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| tschrama |
Hi Sparkle,
250mA bias and 47K//47K resistor ... shouldn't that be 47R//47R?
greetz,
Thijs |
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| millwood |
one small suggestion to you: split the collector resistor into, and connect the pot to the junctionof the two resistors. This way, there is certain level of feedback to maintain very stable bias for the transistor.
the schematic is posted under "simple preamp". except that I used just one mosfet but you can try various medium power bjts with no ill effect. |
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| azira |
Nice simple CE amp...
1uF input capacitance seems kind of low. Using 2.5k impedance to gnd you would have a cutoff around 60Hz... I think you might want to raise that to 5uF or 10uF.
Do you hook up the headphone reversed polarity like on the zen amps? |
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| destroyer X |
Good looking machine..... wood made it full of "class"
very good!
Carlos |
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| sparkle |
OOOPPS!
Resistors are two 47R/5W in paralel :D
Millwood - thanks....
Azira- I have thought to add little more of the input cap. Thanks for the suggestion.
I have forgotten to say - my recitifier diodes are MR824 form motorola and input cap is wima 1uF (will change that to something bigger.;)
regards
daniel |
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| lineup |
:)
nice little project, sparkle!
Very!
for headphones amplifiers are many ways to go
from
- very advanced Op-amp based
- extremely complicated discrete amplifiers
to
- simple 1 OP-amp circuit
- a few transistors
- one single power transistor follower ( buffer )
I like this project.
You have built any other amplifiers?
Or new version of this one?
PICTURE of Circuit in box:
http://www.diyaudio.com/forums/attachment.php?s=&postid=376302&stamp=1082498251
regards
lineup |
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| destroyer X |
Now we have more informations....very nice from you.
And the schematic is optimum!
regards,
Carlos |
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| sparkle |
oh guys....this little amp was something that i was playing with....it sounds nice with Grado's that have 32ohm impedance - but the problem is that i have 300R impedance and this little amp didn't work with them good.....
but with Grado's it sings preety nice - a very nice start for the guys that don't want to invest much, want nice preamp for their Grado's.....
unfortunatelly - since this unit was not good for my needs i dismounted it.....:(
thanks also for Your kind words....:) |
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| chrispenycate |
If this works (which it might well not) it's the circuit for my standard (unbalanced) line driver, which works more than adequately as a headphone amp, or even (reducing emitter resistors and putting in slightly oomphier transistors) a small speaker amp. I still have lots of PC boards for this, and run one up (with components for particular job) when needed. The bootstrapping is perhaps a little over the top for this job, and generally AC feedback separated from DC gives a slightly better noise performance.
Still, the output drive is symmetrical, and performance is pretty much independant of transistors chosen. |
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| lineup |
hi
good circuit, chrispenycate
hard to make it better if using only 3 T
I am sure it does a good job
and makes good quality sounds
makes me think of some of of Nelson Pass amps
same nice simplicity
even if he makes it with MOSFETs for POWER Amps |
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