Single Ended Solid state preamp

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
If you download the program this .asc file of your preamp (unzip the folder) will run straight off.

You can see the amp is inverting. The response extends to many Mhz. Bottom end is poor due to the 0.047uf cap.

I forgot to add the decoupling cap after the 1K resistor which will slightly alter the AC characteristics... but I'll leave that for you to add :)

If you get stuck then ask.
Thanks for simulating :)
I'm an old type pencil and paper Engineer (started Engineering in 1969 :eek: ) and "old dog learns no new tricks" but it's nice to see that simulation confirm classic design performance.
Just one small detail, "0.047uF" was a typo, corrected in the following answer to:
Sorry, I intended to write 0.47uF, which would have a cutoff frequency below 10 Hz.
1uF is fine, of course.
so if you want to re-simulate with 0.47uF , fine.

Maybe this old dog should practice some Spice, after all.

As a side note, original Spice was available way back then ... but we run it in an IBM1620 computer
IBM1620-Tuck1960s.jpg

No monitor, of course :eek:
Curves/answers were drawings made out of asterisks " * " on a blanket size sheet of paper *or* long lists of numbers.
Not exactly user friendly :mad:
So it was ***much*** faster to simply use one of these:
sexySlideRule_w.jpg


Thanks again :D

EDIT: did we have a *mouse* way back then?:eek:
Of course!!, what did you think?
....................
We called it "Mickey", it used to live behind a bookcase and we fed it cookies :p
 
Last edited:
Administrator
Joined 2007
Paid Member
hi i see the output is inverted, must is change this.
or just play inverted or change the + to - and - to + on the output

You can't really swap the outputs because of the grounds. An inverting amp (and many are) isn't a problem although some claim to be able to sense absolute phase.

Try an experiment. Listen to some music and then reverse both speaker lead polaritys and listen again. Can you tell any difference ?
 
Administrator
Joined 2007
Paid Member
All it means is that as the input voltage rises, the output voltage falls and vice versa. Forget signals and AC. Think about it at DC. The base of the transistor is biased to some set voltage by the resistor network. If the voltage at the base is "altered" the collector voltage alters too. Base voltage goes up, the transistor conducts more, the collector volts fall. Base volts fall, the transistor conducts less, the collector voltage rises.
 
Jempie, a simple single stage amplifier, whether transistor, Fet or Tube, *will* invert the signal phase.
No big deal since it does not change the sound at all.

There are some situations where it matters, because you are using 2 amplifiers or speakers or mix different channels in an amp, so those 2 signals interact, and even in that case, *absolute* phase never matters , but *relative* phase, meaning one of them relative to the other.

And about "original" phase?

Who knows? .... Who cares?
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.