JLH 10 Watt class A amplifier

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DomKo

Member
Joined 2003
formachine.com
bee ...... @ Right channel

Hi DIY,

I built a JLH High Power Version. I find bee when I connect right channel to a preamp. Left channel is absolutely quiet.

Exchange the input from preamp. Right Channel also has bee. Left Channel is absolutely quiet.

The input volumes are turned off.

I use CLC filter. 100000uf 2.5mH 100000uf dual supply.

Is there any suggestion & advice ?

Thank you for your assistance.


DKO
 
DarkHorse

DarkHorse

Member
Joined 2005
x-pro said:


Hi millwood and tschrama. I think I can feed you some information on this circuit and post here my own version of MOSFET development, somewhat based on JLH class A idea, which I've designed in 1992 and this amplifier still working quite happily in my daughter's room :) . The sound of this amp is very sweet... .


Have a look at my circuit here and ask questions :) - I would be happy to answer.

Cheers

x-pro (Alex)
Click to expand...


:D
hello,dear Alex:
I am so intresting in your circuit,and I make some of simulation with your circuit...perfeat!THD=0.0025%(oh,god!)...
but I have a qustion:should we choose more smaller value of R11 R13,as we know the power mosfet has more than 1700pF's input capacitor,if you want to drive it well,your voltage driver stage must need more Iq...but in your circuit the Iq of R11 or R13 just only about 10mA,it is too small,isn't it?
and I have modify the Iq be much bigger,but the THD increase too!!!???
your works so great!I admire you for your creative circuit!

best regards!
WINCO

here is your circuit which you have posted in this thread:
 

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mikelm

mikelm

Member
Joined 2003
DarkHorse said:
hello,dear Alex:
I am so intresting in your circuit
Click to expand...

Me to Alex,

I missed your cct the first time round.

I also have been using a ccs in the i/p cct in a JLH amp that I built about 4 years ago. This does reduce the distortion quite a lot.

But I found that if I changed the driver transistor for a small mosfet in conjuction with this, the distortion drops even more....but this is with BJT o/p devices.

Dark horse - try dropping a zvn4424a or similar into your simulation. You may have to do some adjustments but if if is like my cct the distortion should drop quite a lot.

I'll try it aswell but I will have to build alex's cct in spice first.

I have also found that increasing the current in the driver cct has pros and cons - more speed & more distortion.

mike
 
DarkHorse

DarkHorse

Member
Joined 2005
mikelm said:


Me to Alex,

I missed your cct the first time round.

I also have been using a ccs in the i/p cct in a JLH amp that I built about 4 years ago. This does reduce the distortion quite a lot.

But I found that if I changed the driver transistor for a small mosfet in conjuction with this, the distortion drops even more....but this is with BJT o/p devices.

Dark horse - try dropping a zvn4424a or similar into your simulation. You may have to do some adjustments but if if is like my cct the distortion should drop quite a lot.

I'll try it aswell but I will have to build alex's cct in spice first.

I have also found that increasing the current in the driver cct has pros and cons - more speed & more distortion.

mike
Click to expand...

thanks,mike:
Alex is a genius,he collecting choose the B******* transistor is wise!
I have try to using IN5551/5401 BD139 BD140 etc instead of them.but not as good as using B*******...
the driver stage's Iq,I don't know why Mr Alex set it to about 10mA,maybe as he said:"The sound of this amp is very sweet... "
this is because of lower Iq...
waiting for your Pspice result!
regards!
WINCO



:smash:
 
L

Luke

Member
Joined 2001
But I found that if I changed the driver transistor for a small mosfet in conjuction with this, the distortion drops even more....but this is with BJT o/p devices.
Click to expand...

Dark horse - try dropping a zvn4424a or similar into your simulation. You may have to do some adjustments but if if is like my cct the distortion should drop quite a lot.
Click to expand...

The ZVN4424a is a small signal device, it woudlnt have the grunt to bias the output would it?
 
mikelm

mikelm

Member
Joined 2003
Luke said:
The ZVN4424a is a small signal device, it woudlnt have the grunt to bias the output would it?
Click to expand...

Well, I have been using something of that of that order ZVN.........eline package...for the last 4 years - no problem. On 24/7 mostly.

But if you want to crank up the bias current try a vn66afd or vn88afd. To my ears they generally sound nicer - more smooth but they do cost a bit more.

In my cct the big benefit comes from the i/p CCS & MF driver together, but with this arrangment you may need a little compensation for stability.

Recently I changed the gain from 16 to 31 and the dynamics are quite something.

mike
 
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ericfe1975

Member
Joined 2005
comparating 2 equal sounds?

Hello,

after looking and reading lots of information about the jlh amp, specialliy the version that has an output capacitor, and comparating with DoZ amp, its evident that both amps a extremely similar, as geoff said in his site, the main diff is that rod elliott has aded a transistor to stabilise the current.

my question is : this modification has an influence on the sound?
is the sound softer smoother or it remains the same?

i think it should be no difference at all in the sound, but then i ask... if there is no difference in the sound why doesn't everybody builds the rod's version? there is a very good pcb in this site : http://diyaudio.8m.com/Bebet/bebet_sch.html

i'm buildig it, now i only have to solder the power transistors,but i have a lot of existencialists doubts :rolleyes:

so if anyone coul answer to me, saying if there is or not a difference of sound between DoZ an jlh this schematic of jlh :
http://www.tcaas.btinternet.co.uk/jlh2000.pdf

well i'm anxious expecting yours answers guys! see you soon!

:confused: :confused: :confused:
 
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ericfe1975

Member
Joined 2005
thanks for the answer

thanks for the answer edl,

i think as you, the simpler the better. once i finish my doz , i will build the jlh version that you have posted, btw it is the same that i have posted.
i someone can share the pcb of this version :

http://www.tcaas.btinternet.co.uk/jlh2000.pdf
:D

i will be very apreciative of it , and alson if someone has an opinion about the diff of sound between DoZ and JLH ( the version on the link) i will be very happy to read it.
 
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