Metropoulos Forum

I want to build a cascading preamp with a fixed gain (no volume pot between the stages). What should I use instead of the pot?
thanks --Gary

You need to study some schematics that use cascaded gain stages for your own benefit, then you'll understand. The 2203/2204 and SLO100 schematics are a good place to start.

However, if you use a 470k voltage divider between stages you won't go far wrong. If you want some midrange crunch, bypass the 'top' 470k resistor with a 250pF-1000pF cap.

papawoofer wrote:What should I use instead of the pot?

First you should 'use' some good books - from Kevin O'Conner maybe, or from Dave Funk, aso.
Parallel you should study lots of other schematics of well known amps and try to get the idea in the schems with some help of the books.

And after this you can use your solder iron/station.

That's the way to go

I've moved this topic to the forum "General Beginner's Questions" now - where it belongs

Larry

novosibir wrote:

papawoofer wrote:What should I use instead of the pot?

First you should 'use' some good books - from Kevin O'Conner maybe, or from Dave Funk, aso.
Parallel you should study lots of other schematics of well known amps and try to get the idea in the schems with some help of the books.

And after this you can use your solder iron/station.

That's the way to go

I've moved this topic to the forum "General Beginner's Questions" now - where it belongs

Larry

Sorry Larry I swore I put this in the restorations and mods section

HTH wrote:You need to study some schematics that use cascaded gain stages for your own benefit, then you'll understand. The 2203/2204 and SLO100 schematics are a good place to start.

However, if you use a 470k voltage divider between stages you won't go far wrong. If you want some midrange crunch, bypass the 'top' 470k resistor with a 250pF-1000pF cap.

that voltage divider is what I need, how do I build that?

papawoofer wrote:that voltage divider is what I need, how do I build that?

papawoofer wrote:Sorry Larry I swore I put this in the restorations and mods section

Yes, I know and I confirm - but that's been the wrong place for this

Larry

axeman wrote:

papawoofer wrote:that voltage divider is what I need, how do I build that?

google voltage divider and all will become clear.

HTH wrote:

axeman wrote:

papawoofer wrote:that voltage divider is what I need, how do I build that?

google voltage divider and all will become clear.

Or as I've already already said - use some books and first get some fundamental theory & knowledge!

What do you think, what people would reply, if I'd ask in another forum: "How can I pilot a Boeing 747? Which handle how and where?"

Larry

Read Butterfly.

axeman wrote:

papawoofer wrote:that voltage divider is what I need, how do I build that?

I have read somewhere that the 470/470 voltage divider is like a 1meg pot turned 1/2. I havent seen a layout or anything, although physically isnt it like the mixer section? and if so.....

A. the point where the 2 resistors meet, that connects to pin 2 (or 7)?
B. one resistor is connected to the .022 from the first stage and the other is connected to ground
C. if I add a cap, it goes on resistor that is connected to the first stage?

Thats all I need to know. I can figure it out from there

papawoofer wrote:I have read somewhere that the 470/470 voltage divider is like a 1meg pot turned 1/2.

That's valid for a linear pot.

But Volume pots are not linear, they've a logarithmic taper...

... and 470K/470K equals a 940K logarithmic pot set to about 6.5.....7.0

Believe me, the recommended books don't hurt!
But the high voltages inside amps might.....

Larry

thanks

OK, in no way am I meaning to sound self righteous here but why is it that people don't like to read anymore? They just want you to give them the answer...the same answers we all had to go through and read the shit to get...almost like a kid that would rather have his parents give him the answers to his homework rather than actually study the material his homework is about and maybe learn something.

Like everyone else above mentioned...for your own health and safety I highly recommend you start reading books and acquire some general basic electronics knowledge before you go poking around in amplifiers that have deadly voltages higher than what comes out of your wall socket.

And if you're not willing to read and learn about this stuff, then you don't need to be doing it and should leave it to those of us who have a degree of respect for the science. Electricity requires a high degree of respect for it and IMHO, messing around with high voltage stuff such as guitar amplifiers while showing no interest in wanting to read up and acquire even a basic understanding of it shows great disrespect for the science. If you're not willing to respect electricity, then you deserve everything you've got coming to you if you get zapped.

Just my $0.02.

flemingmras wrote:OK, in no way am I meaning to sound self righteous here but why is it that people don't like to read anymore? They just want you to give them the answer...the same answers we all had to go through and read the shit to get...almost like a kid that would rather have his parents give him the answers to his homework rather than actually study the material his homework is about and maybe learn something.

Like everyone else above mentioned...for your own health and safety I highly recommend you start reading books and acquire some general basic electronics knowledge before you go poking around in amplifiers that have deadly voltages higher than what comes out of your wall socket.

And if you're not willing to read and learn about this stuff, then you don't need to be doing it and should leave it to those of us who have a degree of respect for the science. Electricity requires a high degree of respect for it and IMHO, messing around with high voltage stuff such as guitar amplifiers while showing no interest in wanting to read up and acquire even a basic understanding of it shows great disrespect for the science. If you're not willing to respect electricity, then you deserve everything you've got coming to you if you get zapped.

Just my $0.02.

Well here is my nickel---I have been a member of this forum for almost two years, and I have supported this business every since I found Metro. I buy everthing I need from George, this is my SECOND build and I have some electronics knowledge SO I KNOW HOW NOT TO GET ZAPPED all I need is to make sure I get this voltage divider done so I can finish. YA KNOW THIS IS SUPPOSED TO BE A FORUM FOR THE DIY TO HELP PEOPLE BUILD THIER OWN METRO, YA KNOW SHARING INFO. BUT IT SEEMS THAT MORE AND MORE I GET NOTHING BUT SMART ASS TECHIES WHO WANT GLOAT OVER HOW MUCH KNOWLEDGE THEY THINK HAVE SO.....IF YOU ARENT GOING TO HELP ME WITH THE VOLTAGE DIVIDER THAT GOES BETWEEN TWO CASCADING STAGES DONT POST! I DONT WANT TO HEAR COMMENTS FROM THE PEANUT GALLERY. I READ ALL THE TIME, BUT I USUALLY START HERE FIRST I DONT NEED THIS SHIT.