120 Volt psu PreAmp - lowest possible G-FeedBack
will soon be posting schematic and my simulation results
and should sure be very good sounding
as lots of neegative global feedback
is very well known to ruin good musical sound
120 Volt 2SC2240 & 2SA970, from Toshiba
and 2N5551 + 2N5401, from OnSemi
Here is first image.
2SC2240 & 2SA970 superb low noise transistors
from Toshiba in JAPAN
from OnSemi in JAPAN
is a very useful NPN transistor
You can see the pin configuration here.
120 Volt preamp
below you can see the input stage
is one pair of 2SC2240
they each work at 1.0 mA
- 220 Ohm base stopper resistors
these 'protect' the input from acting as antennas
should be placed very close to transistor BASE
- 10 pF capacitor at the input transistor
will increase stabilty of the amplifer
by let input 2SC2240 get negative feedback from its own collector
at higher frequencies
- each emitter resistor is at 3000 Ohm
together this makes one 1500 Ohm resistor to feed the pair
the voltage at the transistor emitters is
(1 mA + 1 mA) x 1500 Ohm = 3 Volt
Any questions, so far?
From normal www.diyaudio.com Members or or Guests.
I would like very much to all besserwissers (E.E. or Amateur)
to stay away from here.
Thanks. Very kind of you.
I could make one list which ones these are at our forum.
it is a pretty long list, I'm afraid, people.
As well as I could easily make a list with those
that see themselves as Audio Gurus. True or not.
This list is a bit shorter with all well known names.
But it wouldn't be very polite and nice of me to publish such lists.
I leave it up to you & your self mind
to decide if you are welcome in this topic.
Hope you respect to stay away, if you should.
6mW of dissipation in the paralleled emitter resistors (tail).
Why do you need a parallel pair 3k0 when most would use a single 1k5?
Is my enquiry welcome or am I on either of your lists?
Just for information, Perreaux (from New Zealand) used a similar approach in some of their pre-amp designs in the 1980s - these had a fairly high voltage rail which gave them enormous overload margins, and hence fairly low distortion at normal levels.
C2 is a nice way to ruin PSRR.
BTW: Are you sure that you didn't get fakes?
120 Volt Pre Amplifier
- no global feeedback or
- very low global feedback
one NPN transistor follower 2SC2240 .. for first version
Now, I maybe will use 2N5551 here (for more power output)
or even, several 2N5551 in parallel Class A
for high output power (read: lower load impedances)
1. This output follower is OUTSIDE the voltage feedback loop
to the input pair of 2SC2240 differential stage
2. There is the possibility to break Global Negative FB loop completely.
In this case, the THD distortion actually gets lower.
right now my prtotype shows these figures:
Okay, even if the THD goes up ( especially 2nd ) with feedback
the rest of the harmonics are considerably lower,
than Without Feedback.
The mixture of distortion changes when using feedbac vs. not using feedback.
3. Also for the output follower I use BASE STOPPER resistor, with value 220 Ohm
|All times are GMT. The time now is 12:46 AM.|
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio