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Old 13th October 2012, 02:41 PM   #1
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Default My E5 Class A hifi headphone amp

Hello all,
I design three headphone amps: E3, E4, E5

E4 is the upgrade version of E3, E5 is the upgrade version of E4, E5 sounds more pure and natural. And better performance in the heat sink and protection.

They own different characteristics. (E3 refer to the beyerdynamic A1 headphone, E4 refer to the JC2 dual differential FET input construction, E5 using Marantz HDAM input structure)
Some audiophiles in my domestic discuss these headphone amps, they like the E5 best.

Here are the pictures of E5 headphone amp, work on class A.
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File Type: jpg DSC05366.jpg (318.7 KB, 1512 views)
File Type: jpg DSC05368.jpg (296.8 KB, 1432 views)
File Type: jpg DSC05370.jpg (341.8 KB, 1423 views)
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Old 26th October 2012, 03:45 PM   #2
cotdt is offline cotdt  United States
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got schematics?
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Old 26th October 2012, 06:50 PM   #3
qusp is offline qusp  Australia
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so these are basically just copies of commercial designs?

fancy that...
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Old 10th November 2012, 01:22 PM   #4
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Hello, attached the schematics, I refer some famous structures, their performance are great.
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File Type: jpg E5 headphone amp schematics-1.jpg (87.8 KB, 1355 views)
File Type: jpg E5 headphone amp schematics-2.jpg (63.5 KB, 745 views)
File Type: jpg E5 headphone amp schematics-3.jpg (77.4 KB, 665 views)
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Old 18th November 2012, 03:39 PM   #5
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Don't like the look of this one.

Firstly, it's clearly not a Class A amplifier, it actually uses a Class AB output stage, it may use a heavy class A bias, but it still isn't a class A amp.

It also looks like you are going to have some real stability issues here because you aren't compensating for the dominant pole by using a frequency compensation cap in the voltage amplification stage. Judging by the combination of transistors that you have used its a nearly dead cert that this amp is going to oscillate.

Why would you use an LED string in series with the Vbe multiplier to set the bias current , it's completely unnecessary and pointless and a much better solution (in terms of thermal stability) can be found by simply changing the resistor values of the Vbe multiplier.

Also, why the need for the 75 ohm output resistor? It ruins the damping factor and means you have to increase the closed loop gain, resulting in more distortion.
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Old 21st December 2012, 05:09 PM   #6
phase is offline phase  United States
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Well I now have one, one issue with making any comparison is that I simply don't have anything to compare it to, besides my laptop soundcard.

I am letting it run on the bench for a few days, with some older fisher-price headphones, just in case something goes awry.

So far it has DC offset of 25, and 27 mv, and appears stable in that respect.

Will have to wait for Santa to deliver some better headphones in order to really check it out...

Also have a DAC in the same chassis to confuse things further; Coaxial DIR9001 WM8740DAC Decoders USB Coaxial G 1 | eBay
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Old 28th December 2012, 12:19 AM   #7
phase is offline phase  United States
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Well, I don't know which component is contributing what to the overall sound, but it sounds great, no complaints, plenty of headroom, very gradual breakup.

The heatsinks are warm, can't be too much over 100 farenheit though, my experience has told me that 135 is about the max you can stand to touch for any amount of time, and these are nowhere near that.

There is 18, and 21 mv of dc coming through at idle.

I might swap the opa275 out for a dual opa627au on the DAC, but that can wait.

I ran the output through my home stereo, an SAE2300, and some old Dahlquist speakers, and it sounded very good.

Couldn't really ask for much more, considering the usb source, and of course, the price!

This isn't an end all setup, is for work to drown out the ambient noise so I can work, and not get fatigued by my setup.
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Old 24th April 2013, 03:36 AM   #8
phase is offline phase  United States
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So how low can I safely go with the output resistors?
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Old 29th April 2013, 04:55 PM   #9
Telstar is offline Telstar  Italy
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Which Jfets are used in the output stage (LQ1, LQ2)?
This circuit would probably sound good with the lovoltechs...
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Old 13th March 2014, 10:35 AM   #10
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Hi! What are the values ​​of resistors LR3 and LR11? In my constructor to 5.6 ohms. Is that right??
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