3T HeadPh Amp. JFET-BJT-MOSFET - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 27th May 2009, 01:59 AM   #1
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north
Default 3T HeadPh Amp. JFET-BJT-MOSFET

Hi
I am working on a 3 Transistor hifi headphone amplifier.

1. Input uses N-JFET, like 2N4416 or 2N3819, which is more easily found.
2. One bipolar PNP turns the signal to correct phase
and drives the output stage.
3. Output IRF610 N-Channel MOSFET follower powers the load resistor into several 100mA Class A.

Be back with schematics, AC-analyses and Fourier for discussion/evaluation.
All is properly tested in virtual circuit with some of the best instruments we can find.
On the commercial ground my simulator costs way too much.
---

From this we can forsee, that this topic will not discuss my circuit.
But people will do more postings of the usual debate on using sims, paper or calculator
or design by listening to transistors output through headphones of different qualities
after throwing it quickly together with solder.
And hope you have a lucky day and that your luck will stay with you
as you change this and that capacitor or resistor.

So just another good amplifier idea is completely ruined by these off topic posters.
Those that are not really interested in design,
but only to show how clever they are and how good diyaudio builders
and how golden their audiophile ears are.
Those they were born with and have finetuned to perfection in many a sessions with a bunch of them other audio-jet-setters.


lineup
__________________
lineup
  Reply With Quote
Old 27th May 2009, 02:17 PM   #2
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north

I wont change the basic concept = 3T
Neither I want any changes to my original idea
like fooking CCS ideas.
If you want to make your own ravishing unique amplifier
start your own topic and start worrying about problems in that circuit

But suggestions regarding what transistors are very welcome.
In such very basic and simple designs
we can not just throw in non-fitting devices
and think any 'tons' of feedback will cover up for a bad design idea.

/lineup
--

Attached is the first public version.
Running @ the important first milli watt level, 1 mWatt into speaker.
Of course by trial and error there were version before this one.
They simple were nothing much to publish and get my well deserved critic for.
From all you fooking knowledege besserwissers out there
Attached Images
File Type: png 3t_jfet-bjt-mos_v-3c_pub.png (7.9 KB, 941 views)
__________________
lineup
  Reply With Quote
Old 27th May 2009, 03:00 PM   #3
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
lineup, How do you adjust the DC bias point? J305's can work here too.
__________________
"This logos holds always but humans always prove unable to understand it, both before hearing it and when they have first heard it."
  Reply With Quote
Old 27th May 2009, 04:59 PM   #4
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north
I am beginning to think we could become good friends
- if ever we meet.

One good friend, not fiend, is enough to miss my dead mother less.
(passed away in a heavy brain stroke at 29 October,
I carried her wooden box to the hole my self on Friday 28 Nov 2008)

Any good man reading a lineup post is worth notice.
Any good man posting a comment, Nelson or Scott, is remembered for ever .. I have a daarn good memory for things!
Dont you mistake me for old and hard-to-remember syndrome
eventhough i just at the 22nd of May
celebrated my 2-years-before-60 birthday totally alone in my 1-room-flat
without a bdaycake or even one candle to light up my day.

You want proof I am not just talking, but I'm alive and living, too?

Here you are (in perfect destroyer X - Carlos M. fashion).

There is always one in a crowd.
One that does not give a daaaamn about not wearing a yellow jacket.
Perhaps he doesnt even have the money to buy suitable dull black tuxedo ..
And he is not very much afraid of crying out loud his tears
.. if and when they want to come down his cheeks
Attached Images
File Type: jpg my_mother_is_dead_1jpg.jpg (88.5 KB, 762 views)
__________________
lineup
  Reply With Quote
Old 27th May 2009, 05:28 PM   #5
jam is offline jam  United States
diyAudio Member
 
jam's Avatar
 
Join Date: May 2001
Location: Auburn, CA, USA
Lineup,

Sorry to hear about your mother.

Looks like a good design.......how about current sourcing the output stage?

Hey, my birthday is also on the same day.

Regards,

Jam
  Reply With Quote
Old 27th May 2009, 08:15 PM   #6
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north
Default Scott Wurcer suggestion J305 input

I have, as John Curl usually like to put it (and from a scientific point of view this makes good sense)
maintained 'all things else equal'.

Which means
~1mA input (the default J305 is a 6mA IDDS)
~20mA in second BD140 stage to drive the input capacitance of MOSFET
~360mA in output IRF610


This below is the resulting circuit for Scott Wurcer suggestion to try
= one J305 N-Fet for input.

difference in gain is now almost x10
vs. ~ x5 in Lineup original PN4416A (almost equivalent to 2N4416 JFET)

In next post I will show the compare of Fourier analysis
at output level of First Milliwatt = 1 mW into 32 Headphone (fully resistive!)
Attached Images
File Type: png 3t_jfet-bjt-mos_v-3d_j305_scott-w.png (14.5 KB, 753 views)
__________________
lineup
  Reply With Quote
Old 27th May 2009, 08:24 PM   #7
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north


The fourier show almost the same.
Only fractionally higher distortion in Scotts circuit,
with a lower level of even order harmonics especially 4th, 6th, 8th etc.

Conclusion:
If we want to have, need as high voltage gain as x10 ( +20dB)
then go for J305 as Scott suggests.
This can be most suitable for HP:s with an impdance at 300-600 Ohms.
Like the very good best ones by Sennheiser.
Among world's finest, but very expensive, HeadPhones.

Otherwise, you get a more decent gain of x5 with 2N4416
as suggested by Lineup.

This is suitable for lower impedance HP:s like 32-100 Ohm.
Think for example Grado classics series of HiFi phones.

/lineup, circuit design - May 27th 2009
Attached Images
File Type: png 3t_jfet-bjt-mos_v-3d_j305-vs-2n4416_fourier.png (17.1 KB, 655 views)
__________________
lineup
  Reply With Quote
Old 27th May 2009, 11:30 PM   #8
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north

This is a rather interesting analysis.
I think my few readers, pupils if you like, will agree totally

AC Analys = Frequncy response + Phase behavior within the audioband.

We are most interested, of course, how one machine that is involved with sounds behave vs. audiable signals.
In this case via one pair of Headphones.

More specifically we are concerned with what we can hear.
We leave other things to the bats and the supersticious

Usually most music takes place between 50 - 10.000 Hz for a normal middleage white man.
Black women, according to tests, has got a slightly better hearing = larger spectrum they can hear.
John Curl, syn08 and older white skinned men like Scott and me
.. we just have to be happy with what we still can perceive.

Inside the audioband, we strive for a stright line, 'stright wire' behavior.
The ideal Amplifier is said to be like a very short wire


Well, friends ---
... using 2N3819 (25VDS) + BC560C(45VCE) for 2nd stage, I think we have come very close.
At least me my self. Maybe later you. too

Comments are welcome.
This one uses 0.5mA in JFET and
~ 5mA in the PNP BC560C low noise high gain device.
Attached Images
File Type: png 3t_jfet-bjt-mos_v-4c_2n3819_bc560c _ac.png (4.4 KB, 606 views)
__________________
lineup
  Reply With Quote
Old 27th May 2009, 11:38 PM   #9
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
What if to remove that Miller cap, but to add a gate stopper?
__________________
The Devil is not so terrible as his math model is!
  Reply With Quote
Old 28th May 2009, 12:26 AM   #10
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally posted by lineup
I am beginning to think we could become good friends
- if ever we meet.

lineup - Don't take such a simple component substitution so seriously. A lot of FET's would work in that position, just plug them in and see what you get no big deal.

You have yellow jackets and I had one of my father's best friends come to his wake after a whole liter of vodka so we suffer our friends because there is no other way.
__________________
"This logos holds always but humans always prove unable to understand it, both before hearing it and when they have first heard it."
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Jfet/Mosfet cascode with OPT Fuling Pass Labs 10 3rd December 2007 05:53 PM
MOSFET or JFET Faust3D Solid State 17 29th November 2007 04:46 PM
10W JFET/MOSFET SE Class A, no Feed Back widowmaker Solid State 9 26th November 2006 01:00 PM
Need good current sink JFET or MOSFET? rlaury Tubes / Valves 7 22nd November 2005 06:14 AM


New To Site? Need Help?

All times are GMT. The time now is 11:50 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2