Cascading gain stage with a fixed level

[flemingmras]

OK don't get defensive and don't take it personal. We're not "gloating" over anything. We're simply recommending that you get some books and read up on the subject of electronics. We're trying to tell you that you could have this knowledge too if you'd get some books and read up on the subject of electronics. If we were just simply bragging and not trying to help you, we would've just simply told you to take it to a tech rather than offered suggestions.

A voltage divider is nothing more than 2 resistors connected in series. One end of the series string gets grounded, the other end goes to the coupling capacitor at the output of the gain stage, then the signal is taken from where the resistors connect to each other. No rocket science behind it whatsoever.

Your preamp stage is nothing more than a voltage controlled voltage divider. The input signal causes the internal plate resistance of the preamp tube to fluctuate at the same frequency as the input signal, which causes the voltage across the preamp tube to fluctuate at the same frequency as well. The fluctuation margin of the voltage across the preamp tube is higher than the fluctuation margin of your input signal (i.e. if your input signal is 200mV peak to peak, it may cause the voltage across the tube to vary by 2-4 volts), hence the amplification. The coupling cap filters out the DC voltage on the plate of the tube, so you end up with just the 2-4 volt fluctuation at the output of the cap.

Learning from the experience of others will only get you so far in this hobby. To truly learn what you're doing, you have to acquire some book knowledge. Relying on others to simply just tell you "what to connect where"...you don't learn anything from that...and good luck trying to troubleshoot the circuit should you have any problems...which gets into the "throw parts at it" method of troubleshooting. The people who practice this method is where I feel a lot of the myths and misinformation in this industry comes from.

They say you can give a man a fish and he'll eat for a day, but teach a man to fish and he'll eat for a lifetime. This is the difference between learning from others' experience and taking the time to read and learn what actually happens in an electronic circuit.

The Wiki on this site is a wealth of information that I'm currently working on expanding...here's an article I highly recommend reading up on that talks about series circuits to help you gain an understanding of how electronic things work. It uses a voltage divider type circuit to explain how series circuits work.

http://metroamp.com/wiki/index.php/Series_Circuits" onclick="window.open(this.href);return false;

[papawoofer]

A voltage divider is nothing more than 2 resistors connected in series. One end of the series string gets grounded, the other end goes to the coupling capacitor at the output of the gain stage, then the signal is taken from where the resistors connect to each other. No rocket science behind it whatsoever.

thank you for the info and suggested reading

[HTH]

^ +1

For the record, I would never term myself a tech or a gloater at my 'superior' knowledge

I started building amps after first teaching myself to build fuzz pedals for a few years. Once I'd got enough study time under my belt and got my hands dirty, I started on amps - just modding to start with, then gutting amps and rebuilding them, then designing amps on paper. You've really got to do this stuff for yourself and some basic electrical knowledge is essential if you want to avoid (a) killing yourself or (b) killing your expensive amp parts.

Nobody is gloating here, all I can see is folks trying to give you sound advice to put you on the right path. If you can read a schematic, everything you want to know about cascaded preamps is in a 2203/2204 Marshall and a SLO100. Get the Marshall 2204 schematic from Schematic Heaven, have a look at the two 470k resistors labelled R10 and R11 - thats a voltage divider. Typically you want a gain pot after the first gain stage, then some like another gain pot after the second stage for more control, others are happy with a voltage divider to have the gain levels 'fixed'. If you change the R11 resistor to 1M you'll get more gain and bass, if you change it to 220k you'll get less gain and less bass, but a faster attack to the note. You might also want to mess with bypass caps around R10 for some snarl in the midrange (try 250pF - 1000pF).

In future, try not to spit your dummy out, its not the best way of asking for help.

[flemingmras]

^ +1

For the record, I would never term myself a tech or a gloater at my 'superior' knowledge

I started building amps after first teaching myself to build fuzz pedals for a few years. Once I'd got enough study time under my belt and got my hands dirty, I started on amps - just modding to start with, then gutting amps and rebuilding them, then designing amps on paper. You've really got to do this stuff for yourself and some basic electrical knowledge is essential if you want to avoid (a) killing yourself or (b) killing your expensive amp parts.

Nobody is gloating here, all I can see is folks trying to give you sound advice to put you on the right path. If you can read a schematic, everything you want to know about cascaded preamps is in a 2203/2204 Marshall and a SLO100. Get the Marshall 2204 schematic from Schematic Heaven, have a look at the two 470k resistors labelled R10 and R11 - thats a voltage divider. Typically you want a gain pot after the first gain stage, then some like another gain pot after the second stage for more control, others are happy with a voltage divider to have the gain levels 'fixed'. If you change the R11 resistor to 1M you'll get more gain and bass, if you change it to 220k you'll get less gain and less bass, but a faster attack to the note. You might also want to mess with bypass caps around R10 for some snarl in the midrange (try 250pF - 1000pF).

In future, try not to spit your dummy out, its not the best way of asking for help.

Whew...thanks. After that I think I'll sit on the apples & pears and light up a fag.

[OnTheFritz]

^ +1

For the record, I would never term myself a tech or a gloater at my 'superior' knowledge

I started building amps after first teaching myself to build fuzz pedals for a few years. Once I'd got enough study time under my belt and got my hands dirty, I started on amps - just modding to start with, then gutting amps and rebuilding them, then designing amps on paper. You've really got to do this stuff for yourself and some basic electrical knowledge is essential if you want to avoid (a) killing yourself or (b) killing your expensive amp parts.

Nobody is gloating here, all I can see is folks trying to give you sound advice to put you on the right path. If you can read a schematic, everything you want to know about cascaded preamps is in a 2203/2204 Marshall and a SLO100. Get the Marshall 2204 schematic from Schematic Heaven, have a look at the two 470k resistors labelled R10 and R11 - thats a voltage divider. Typically you want a gain pot after the first gain stage, then some like another gain pot after the second stage for more control, others are happy with a voltage divider to have the gain levels 'fixed'. If you change the R11 resistor to 1M you'll get more gain and bass, if you change it to 220k you'll get less gain and less bass, but a faster attack to the note. You might also want to mess with bypass caps around R10 for some snarl in the midrange (try 250pF - 1000pF).

In future, try not to spit your dummy out, its not the best way of asking for help.

Whew...thanks. After that I think I'll sit on the apples & pears and light up a fag.

Whoa Jon! You've got your Cockney slang down pat!
Frog and toad!

[papawoofer]

^ +1

For the record, I would never term myself a tech or a gloater at my 'superior' knowledge

I started building amps after first teaching myself to build fuzz pedals for a few years. Once I'd got enough study time under my belt and got my hands dirty, I started on amps - just modding to start with, then gutting amps and rebuilding them, then designing amps on paper. You've really got to do this stuff for yourself and some basic electrical knowledge is essential if you want to avoid (a) killing yourself or (b) killing your expensive amp parts.

Nobody is gloating here, all I can see is folks trying to give you sound advice to put you on the right path. If you can read a schematic, everything you want to know about cascaded preamps is in a 2203/2204 Marshall and a SLO100. Get the Marshall 2204 schematic from Schematic Heaven, have a look at the two 470k resistors labelled R10 and R11 - thats a voltage divider. Typically you want a gain pot after the first gain stage, then some like another gain pot after the second stage for more control, others are happy with a voltage divider to have the gain levels 'fixed'. If you change the R11 resistor to 1M you'll get more gain and bass, if you change it to 220k you'll get less gain and less bass, but a faster attack to the note. You might also want to mess with bypass caps around R10 for some snarl in the midrange (try 250pF - 1000pF).

In future, try not to spit your dummy out, its not the best way of asking for help.

Whew...thanks. After that I think I'll sit on the apples & pears and light up a fag.

Whoa Jon! You've got your Cockney slang down pat!
Frog and toad!

ya know you guys kill me, after all the insulting remarks I finally get good info

[papawoofer]

I want to illustrate my point here---
There are guys on this forum who just pissed off their wives and spent 1500.00 on an amp kit and a big box of parts show up I remember that "Oh shit" feeling and you can tell it in their post. But they are paying customers who are told this forum will help them.
And it will, it helped me! I know I might have asked a really dumb question, but if this was my first build and I got replies like you need book knowledge before you go poking around in an amp you'll get yourself killed or they just want to be told how to do it or dont respect the science ( I am an audio engineer and I dont mean a computer geek I can actually align a 2" tape machine) I would send that kit right back to Metro.

George has done an amazing thing here and I owe him a mountain of gratitude, but if your going to present yourself as someone to help you are a representive of his business,----lets be a little more mindful of his customers and treat the stressed out on the verge of divorce new guys with a little more compassion.

My second build is almost done--- a 12XXX that switches from a 1959 pre to a 1959 cascaded (at first I was going to do 1959 to 2203) I will post pics this week
I hope I make George proud.

[flemingmras]

I've gone back through the entire thread and I honestly can't see anywhere where insulting remarks were made.

Realize this...you're a beginner. End of story. But that's not a bad thing at all. We all had to start somewhere at some point. We weren't all born doing this. As for me, I didn't have anyone to teach me along the way...my knowledge was not given to me. Nobody in my family was an electronics enthusiast. I literally had to read lots of books and do research on the internet as well as experiment with circuits to get the knowledge I have. When you look at the amount of time I have invested in it, it definitely didn't come free.

I'm sure you read too...however, the questions you're asking are more along the lines of "how do I do this" rather than "how does this work". You expect us to tell you how to do everything...that's not "sharing knowledge". Sharing knowledge would be you coming on and stating "Hey guys, I'm new at this whole amplifier thing, I'm looking for such and such tone, and I'm curious to learn how such and such works" rather than asking questions like "how do I build this" and "how do I build that". You won't gain any knowledge with us simply telling you the physical steps required to build certain circuits...but you will gain knowledge and figure out for yourself how to build things by asking how things work. We're more than happy to guide you in the quest for actual knowledge...simply wanting us to tell you how to build it though will get you nowhere.

Example...you want us to tell you how to make a voltage divider. If we just told you where to connect the parts, what knowledge did you gain from that? All you gained would be the physical connections of the parts...without knowing how or why the thing works the way it does, or for that matter, where you can and can't use that type of circuit. What good is that "knowledge"?

What happens when you do something wrong and run into a problem? Well, knowing how to build the circuit won't tell you where you went wrong and you'll have to come back on here and ask where you went wrong. Whereas if you try asking about how things work, you'll be able to figure out what's wrong on your own. An amplifier with a problem will exert a symptom...however, many different parts within the amplifier can cause the same symptom. It's not a "if the amplifier is doing this, it's that part causing it" kinda thing. That's where learning how the circuit works comes into play...you'll know which parts can cause the same problem and you'll know where to look for the problem, and chances are you'll find your problem by checking those parts.

Again, we're not insulting you in any way and we're more than willing to help you learn how amplifiers work. But you'll never learn how they work if you don't read up on basic electronic theory and just expect us to tell you how to build and fix the thing. You will get nowhere with that.

Now in regards to being on your second build, usually people on here who are on their second build...by then they're reading up on electronics material and asking "how do things work" type of questions...not asking how to build their second amplifier...they figure that out on their own through the experience they gained building the first one as well as reading books and doing research on the internet to learn how the thing actually works...not how to connect the parts together.

[jerrydyer]

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.

ill help you..PM me. or
jerrydyer2003@yahoo.com

some people didnt even bother to read the caption of the thread. Beginners questions ? ? lets not make this HCAF

[HTH]

^ +1

For the record, I would never term myself a tech or a gloater at my 'superior' knowledge

I started building amps after first teaching myself to build fuzz pedals for a few years. Once I'd got enough study time under my belt and got my hands dirty, I started on amps - just modding to start with, then gutting amps and rebuilding them, then designing amps on paper. You've really got to do this stuff for yourself and some basic electrical knowledge is essential if you want to avoid (a) killing yourself or (b) killing your expensive amp parts.

Nobody is gloating here, all I can see is folks trying to give you sound advice to put you on the right path. If you can read a schematic, everything you want to know about cascaded preamps is in a 2203/2204 Marshall and a SLO100. Get the Marshall 2204 schematic from Schematic Heaven, have a look at the two 470k resistors labelled R10 and R11 - thats a voltage divider. Typically you want a gain pot after the first gain stage, then some like another gain pot after the second stage for more control, others are happy with a voltage divider to have the gain levels 'fixed'. If you change the R11 resistor to 1M you'll get more gain and bass, if you change it to 220k you'll get less gain and less bass, but a faster attack to the note. You might also want to mess with bypass caps around R10 for some snarl in the midrange (try 250pF - 1000pF).

In future, try not to spit your dummy out, its not the best way of asking for help.

Whew...thanks. After that I think I'll sit on the apples & pears and light up a fag.

lmao, nobody within 200 miles of me talks like that. Actually, you'll be hard pushed to find anyone in London who talks like that.

If you've ever heard Brian Johnson of AC/DC talk, thats how I sound (though not as broad an accent) - he's from Newcastle too.

[flemingmras]

Yeah I knew he was a Brit and not an Aussie...just wasn't sure where in Britain he was from. Would love to visit England one of these days...I'm a sucker for British hotties.

Ever been to Milton Keynes (for those not in the know, it's pronounced "Milton Keens") and toured the Marshall factory yet?

[papawoofer]

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.

ill help you..PM me. or
jerrydyer2003@yahoo.com

some people didnt even bother to read the caption of the thread. Beginners questions ? ? lets not make this HCAF

you da man

[HTH]

Yeah I knew he was a Brit and not an Aussie...just wasn't sure where in Britain he was from. Would love to visit England one of these days...I'm a sucker for British hotties.

Ever been to Milton Keynes (for those not in the know, it's pronounced "Milton Keens") and toured the Marshall factory yet?

Milton Keynes isn't supposed to be 'all that' - mostly an industrial region from what I can gather. Will have to drive down there and get the Marshall tour one day. The worst thing is that I'm jaded with Marshall, they just don't seem interested in making amps that have a good standard of build-quality like the JMPs and JCM800s (the early ones anyway).

[flemingmras]

Yeah I knew he was a Brit and not an Aussie...just wasn't sure where in Britain he was from. Would love to visit England one of these days...I'm a sucker for British hotties.

Ever been to Milton Keynes (for those not in the know, it's pronounced "Milton Keens") and toured the Marshall factory yet?

Milton Keynes isn't supposed to be 'all that' - mostly an industrial region from what I can gather. Will have to drive down there and get the Marshall tour one day. The worst thing is that I'm jaded with Marshall, they just don't seem interested in making amps that have a good standard of build-quality like the JMPs and JCM800s (the early ones anyway).

That's because they figured out a cheaper way to build them while keeping the prices the same = more profits per unit.

Unfortunately, sad but true, everything's all about money these days.

[Structo]

I agree.
They established a brand name built on the backs of the biggest acts in rock and roll but it seems their recent amps of the last ten years or so (maybe even further back) just aren't the quality that Marshall was known for.
Thus the cloning companies success, since they tend to build them the way Marshall used to.
The cloners have to be taking a bite out of Marshall's profit margin.

But there will always be the kid that just has to have that Marshall script logo on the front if his amp.

They went from pretty decent pcb amps with good component separation and wide traces to stuff you would expect to see in the Asian built amps so prevalent nowadays.

Sure they reissued some and hand wired a few.
I understand how labor intensive that is verses a machine or two that can insert the parts then wave solder the boards.

I doubt that they will ever go out of business unless it's due to very bad management after Jim and family fade from the scene but I often wonder if any of the management or employees check out the Marshall forums to see what real guitar players think of the amps and how they could improve upon them before it is too late.