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Old 28th May 2009, 03:22 PM   #21
lineup is offline lineup  Sweden
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Default Gettin' better with the output follower MOS

.

adding a fix for more John Curlish output
via the MOSFET (note! mos still not within feedback)

Now we are talking!
Suddenly the input stage will totally dominate the harmonics
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Old 28th May 2009, 03:27 PM   #22
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Hi Lineup,

First thank you for sharing your ideas here ... i just followed youre thread, since im on the go for a diy amp for my new cans (AKG K702) They have an impedance of 62 Ohms so i guess they'll fit well to this amp ...

My question:
Will this circuit work also perfect with a power supply lower than 24 VDC ? How low could someone go, that it still works that good ?

Thx in advance for your reply

regards
artQuake
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Old 28th May 2009, 05:15 PM   #23
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lineup,
your deep sorrow really does elicit sympathy. Time certainly softens grief through the change we undergo, but some wounds never heal. Hopefully, you can find the strength to go on, bustling with activity is probably the best way.
The recent design version is much cleaner, that ugly comp cap and diode are gone, but R5 could have a value around 100 Ohms and I would run the JFETs at considerably larger current, using types with high Idss here.
IRF610 is an easy-to-find nonlinear device and it does not get more linear by the load. Improvements are possible.
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Old 29th May 2009, 04:44 PM   #24
lineup is offline lineup  Sweden
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dear friends in audio

This is a remarkable milestone.
Because first time ever actually one transistor stage shows (a virtual)
improvement of signal.
Some harmonics are improved after passing one mosfet.

Am I going carzy or what the fook?

Maybe my software are trying to play jokes I can not believe in.
Any explainations, of course, are most welcome

At your service - for free, Lineup 58
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Old 29th May 2009, 09:21 PM   #25
lineup is offline lineup  Sweden
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Any explianation
why a signal harmonics can show lower dist after passsing one transistor stage
is welcome.

Fourier testing with one/two harmonics shows improved values,
after passing one single stage
1. is this possible?
2. how come?
3. can we design to achieve this
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Old 29th May 2009, 09:22 PM   #26
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Quote:
Originally posted by lineup
Of course, me and other DiyAudio guys will answer any questions
and guide you perfectly on your way towards a very well sounding amplifer.
No matter what headphones you use.
Well, are there any suggestions about the lower PSU-Voltage or was it such a dumb question to overlook it ?
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Old 29th May 2009, 09:39 PM   #27
lineup is offline lineup  Sweden
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You should be able to use as low as 9 or 12 or 18 VDC.

9 Volt Battery is not suitable. Not as ithis ciecuit is.
Because this draws 360 mA per channel
... one alkali 9 Volt Batt would be empty 2-4 hours like.

15, 18 or 12 Volt DC and thereabout
All you need to do is adjust 440 Ohm resistor
... you increase this value by using one 1k (1.000) trimpot
until you have output at around 40-50% = 5-6 VDC.

See this post:
4. Red resistor 440 ohm sets the output to Close 12 Volt (50% of V+24V)
Temporarily you can use one 1k trimpot to find out what you need.
Start at setting the trimmer at 50% and work from there.
This is an asjustament done to suit for your 2N3819.
JFETs have a bit different parameters for each and every single Transistor we buy

---



But better
you could try my HIFI Class A transistor Headphones Amo
especially designed for 12V.
I myself has got one stereo prototype built fo 15 years ago. Still sounding excellent.
This one really sings in your ears

It has been built by some guys in our forum and even I think some guy made and built PCB card for it:

Solid State >Discrete Single End TRUE Class A HeadPhone Amplifier
PCB by Nordic

Here Stereo, 2 Channels, PCB made by Nordic:
http://www.diyaudio.com/forums/attac...amp=1180701258


Regards
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Old 29th May 2009, 09:50 PM   #28
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Quote:
Originally posted by lineup

[i]4. Red resistor 440 ohm sets the output to Close 12 Volt (50% of V+24V)

It is very suboptimal for a source (or emitter follower) loaded on resistor. Guess, why?


Quote:
Originally posted by lineup


Ask Wavebourn!
He is using same type of circuit idea in his headphone amplifiers ...

Sorry, my circuit idea was a bit different: to load the preamp on more linear input resistance of the output follower, and to load a follower on a counter-modulated current source. As the result, the whole thingy had less distortions, especially high order ones, and the order of them as well as level of them goes down as sounds decay, that's why they are inaudible.
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Old 29th May 2009, 09:58 PM   #29
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lineup,
no explanation, just a recommendation: delete that stupid software pretty soon.
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Old 30th May 2009, 01:27 AM   #30
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Default Version 7b .. with 1N4148 diode

.
Version 7b .. with 1N4148 diode

Fourier analys of output from version 7b.
This version I have put the 1N4148 back.
The reason is it makes BC560C stage, bipolar,
act more in a current mirror mode.

This changes the harmonics content of circuit.
The characteristics will lean more to the JFET.

The input N JFET, in this case I use one 7mA BF245B.

This is a HF radio FET that can be found to buy.


The digram
Analys is compared before & after the 2 parallelled output polarized Capacitors.
We can see they do not hardly distort anything.
They possibly will add a tiny bit higher 2nd order harmonics dist.
More specifically you can see this in my image as 6th and 8th.

- The output level is as usual 1 first mW into 32 Ohm.
- PSU is 12 VDC (was asked for)
- DC level before output caps is set to 6.75 VDC .. for this test.

/yours Linie
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