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Old 8th September 2006, 03:41 PM   #1
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Arrow OTH -> One Transistor HeadPhone

This is a scheamatic without gain, for Head-Phone or BUFFER use.

This is a PURE Class-A schematic without FEEDBACK!

This is my frist design in pure class-A for HeadPhones.
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Old 9th September 2006, 04:34 PM   #2
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hey - this look nice - maybe to try to use it with dual power supply - in that way you will not have the need for the output capacitor.....i don't like them (sorry) - but hte amp is nice - it should work nice for low frequency load ......
right?
have you try it allready
how it is sounding

regards
daniel
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Old 9th September 2006, 04:46 PM   #3
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I haven't it allready.

It is only a simulation to in the future I make them.

I need to evaluate this circuit to make a very very good head-amp. =]

Best Regards,
Felipe
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Old 9th September 2006, 07:48 PM   #4
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Hi Felipe,

I built a headphone amp like this a while back (but I did have a bit of feedback).
I started with an emitter follower, like yours but on dual rails, and then replaced the emitter resistor with a current source. It made quite a difference, and is really worth trying.

Then I changed the one transistor with two in a complimentary feedback pair, and that helped as well, but it did introduce feedback.

I drive my grados with it and I'm really pleased with it.
I totally agree that, you don't need voltage gain to drive headphones, more a buffer to provide the current, and relieve the source.

Cheers,
Phil
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Old 9th September 2006, 07:56 PM   #5
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I'm thinking to drive mine headphones with this new circuit:

http://www.diyaudio.com/forums/showt...postid=1001572

A buffer with 6sn7GT and a HEAD-AMP.

Best regards,
Felipe
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Old 13th September 2006, 03:57 AM   #6
suiraMB is offline suiraMB  Norway
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Try using an LU1014D power JFET as the active device instead, and replace the load resistor with another LU1014D. And put the rails at +/- 12V.

That is:
Lower JFET - drain to output, source through a small resistor to negative rail, gate to negative rail.

Upper JFET - drain to positive rail, source through another small resistor (same value if the devices are matched) to output, gate to input.

If you want some feedback, use a 10K resistor in series with the input, and a 100 ohm resistor from the output to the gate of the active device.

With proper matching, the DC offset should be negligible (meaning no coupling cap), and distortion negligible. A 3 ohm source resistor would give about 500mA bias at +/- 12V rails.

Then you can drive a low-impedance headphone as well. Either way, the performance should exceed that of the bipolar.

For high-impedance headphones, the 2SK389V (or LSK389C) should perform admirably with a 75-300 ohm source resistor.
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Old 13th September 2006, 01:53 PM   #7
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Suira,

I can't buy a LU1014D, because I can't import this in Brazil. I haven't international credit card to buy it.

And... IF I PUT a IRF610?

In what circuit design software can I simulate mosfets? I have the circuit maker professional and I can't simulate mosfets in this =[.

I have changed the 1000ohm resistor to a CCS with 2 BC549.

Thanks,
Felipe
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Old 13th September 2006, 05:00 PM   #8
suiraMB is offline suiraMB  Norway
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Quote:
Originally posted by mod_evil
I can't buy a LU1014D, because I can't import this in Brazil. I haven't international credit card to buy it.
Ah. That's a pity. You may want to keep an eye on the "Lovoltech Group Buy" thread, then.

Quote:
And... IF I PUT a IRF610?
The IRF610 is not a depletion mode device, so it will not self-bias like the circuits I suggested. Also, it is a MOS FET, not a JFET, so its transfer characteristics are different.

Quote:
In what circuit design software can I simulate mosfets? I have the circuit maker professional and I can't simulate mosfets in this =[.
You could try LTSpice, Orcad, etc.

Though with such a simple circuit, it will probably take less time to build it and listen to it.

Quote:
I have changed the 1000ohm resistor to a CCS with 2 BC549.
That should give lower distortion, so probably a smart move

I would also suggest trying to build the circuit with a dual monolithic JFET, such as the 2SK389V (Toshiba), LSK389C (LIS), 2N5911 (Vishay), IF3602 (InterFET) or similar.
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