Page 1 of 4
#1
EDIT: The build really starts here (page 5): https://www.ultimate-guitar.com/forum/showthread.php?t=1136168&page=5&pp=20 and ends on the next page.


Okay, here's the amp building thread that I promised in the thread here: https://www.ultimate-guitar.com/forum/showthread.php?t=1135281

Basically, what I'm going to do is walk through the construction of a small, 5-7 watt single ended amp, in kit form. Some day I may make a tutorial for an amp from scratch. We'll see.

Disclaimer: Yes, working on amps is dangerous. You can be shocked. I will point out as many areas as I can where danger lurks, but I cannot get them all, so please use common sense. And if you don't have common sense, do a bunch of google reading before you get involved...I know google is a poor substitute for common sense, but it's better than nothing. Really...what it boils down to is, when you're working on stuff, take your time, think before you move you hand or place the probe or whatever. And, I cannot and will not be held liable for any injury you get by working on amps. I'm just some guy who likes working on this stuff, am not officially licensed or trained, and have made this stuff up as I go (in short, I'm not an expert).

Background on myself: I'm a metallurgical engineer, working full time for an aerospace firm, 24 years old. I've been building amps for 5 years, seriously for about 2 years. I'm married, with a baby on the way, due Jan 10th. I'm also trying to get a Master's Degree online through USC in Materials Science (Metallurgy). And I do 2-4 amp repairs a week. So, if posts are irregular/don't come too often, that's why.

My wife rides horses a fair bit, so I'm frequently out at a horse stable in the evenings...I will probably be posting/answering questions from my cell phone, so if some times I appear to spell correctly and whatnot and other times it's horrible, it's not because I'm an intermittent alcoholic, it's because my phone is hard to type with.


My intentions on this is that I build this thing, posting every little detail of what to do/whatever/etc (nice and specific, huh? ). Ask questions as I go, I will do my best to answer them all. Please please please check out other FAQs and stuff first, to keep questions on topic, pertinent, and "fresh". Once it's done, I'm going to compile everything into a word/PDF document, along w/ the Q&As for each section, and post that as the "final tutorial".

As the title says, I'm going to build a smaller 5-7 watt single ended amp from a kit, as this is the typical starting amp. After this whole mess is done with, I'll do something similar with a 20 watt PP amp that's a bit more complex.

So, yeah...here we go...
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Last edited by DLrocket89 at Aug 20, 2009,
#3
Quote by inkandlead
I'd like to begin the questioning...
What is a single ended amp?


In a nutshell, it's a the simplest of all poweramps. Usually just 1 tube, no phase inverter. Think Fender Champ, Epi Valve Jr, etc.

It's quite inefficient, so it works well for low wattage, not so much for high wattage.

I'll get into this more during construction. Also going to post links to some other places...
Quote by kcdakrt
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#4
Okay, places to get amp kits:

http://www.ceriatone.com/index.htm
http://www.allenamps.com/kits.php
https://taweber.powweb.com/store/kits.htm
http://shop.dobermanamps.com (which is an offshoot of AX84.com)
http://www.chappellamps.com/ (amps also on AX84.com)

I'm sure there are others, post them if you know them, I'll add them to the list.

I'm partial to the last two on the list. AX84.com (doberman amps) is where I got my start, and the forum there is great, and the kits are great. For this tutorial, I'll actually be building one of their Single Ended Lead amps. The bottom one is a good friend of mine...his two amps are a bit more complex, I'll be building one of his for the 2nd tutorial.

The other three are clones of amps, for the most part. That isn't my cup of tea, but there they are if it is your cup of tea (and that's cool, to each his own).

It looks like Ceriatone amps having already finished boards and stuff...to me, this would take away some of the satisfaction. But like I said, whatever.

One thing I will note, I will be working with a prepunched chassis (already has all the holes in it) because I HATE drilling holes in sheet metal.
Quote by kcdakrt
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#5
Places for information/books to read:

General good series of books: http://www.londonpower.com/catalog/index.php?cPath=3

I don't agree with a bunch of what KO'C writes, but the books are good for learning the basics, so have at them.

If you want a good "here's how everything works", here's my favorite site, one I refer to often: http://www.freewebs.co.uk/valvewizard/index.html <--- Merlin just wrote a book...I haven't seen it yet, but people who've read the advance copies say it's great.

I'll get other stuff up here too, if people have suggestions, let me know.
Quote by kcdakrt
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#6
Tools you'll need:

-Wirecutters (most wire strippers have wire cutters..)
-Wirestripper : http://www.radioshack.com/product/index.jsp?productId=2062787 the time and frustration that that thing saves make it worth it's weight in gold
-soldering iron (recommend one 25-40 watts)
-solder (I recommend 60:40 or 63:37 tin: lead solder, rosin core)
-your brain and some patience
-chopsticks (serious...at least one, preferably two)
-a good multimeter capable of going to 500 Volts DC

Extra parts you'll need:

(depending on kit) - wire (18-22 gauge, I'll have notes about voltage rating...suffice it to say, the stuff at radio shack probably won't work).
-heat shrink tubing (available at hardware store)
-a hot glue gun is optional, but a nice thing to have around.


As always, this list will be growing/changing/etc, and if you see anything missing, let me know.
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Last edited by DLrocket89 at Jun 1, 2009,
#7
*Stickied for me*
I know next to nothing on this topic, and this looks like the perfect place to start learning it.
Quote by bangoodcharlote
^Owned.

I suggest not screwing with the UGer with the best name on the site.


Quote by Albino_Rhino
I don't see how prostitution is going to help out your string buzz...
#9

Stickied. This is brilliant mate.
So this single ended amp, it's basically just going to have a volume knob and that's it?
#12
Quote by james4


I thought the SEL kit from ax84 was 20W...

are you just pairing the lead preamp with their single ended 5W poweramp?
or.. ?



Sorry for the confusion. Yes, the SEL is supposed to be about 20 watts, when it's driven by a KT88. I'm using a KT77, which develops less wattage.

OK, quick lesson here. I had mentioned single ended amps are inefficient. The general rule is that the average power of the amp will never be more than 50% of what the tube is rated for (called "max power dissipation"). A KT88 is usually 35-40watts, a KT77 is usually about 25 watts. So, on a good day, a SE KT88 amp will be about 18-20 watts, a KT77 will be more like 10-12 watts. In actualyity, it's a bit less, so I call it 7 watts. IT could be 8 1/2, could be 11, whatever.

Datasheets for tubes are your friends. I usually use JJ tubes, so I get stuff from their website: http://www.jj-electronic.com/index.php?option=com_content&task=view&id=17&Itemid=11

There's another website that's get for tube data, that's this: http://frank.pocnet.net/ I work with a lot of oddball tubes and haven't yet found one that wasn't in that collection.


EDIT: and I picked the KT77 owing to it's sweet tone, which I call a mix between a 6L6 and an EL34...check the tubes sticky for more description there. It's my favorite tube.
Quote by kcdakrt
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#13
So, I had a request to contribute donations to me for making this thread. I will take it as some of the cost is out of pocket for me, but I'm not going to hold this thread hostage to donations or anything. This has always (and will always) be a free endeavor, because I like seeing people build amps. If you'd like to contribute, paypal it to my email account.

To be clear, I'm not asking for or soliciting donations. This will be the last you hear of it.
Quote by kcdakrt
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#14
Quote by idontgrillonwed
This is going to be amazing. A friend of mine and I are already saving to buy kits now!


Sweet! That's what I like to hear!
Quote by kcdakrt
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#16
Are the places you linked us to to buy kits reliable? Have you actually ordered from them? I'm over protective of my money.
MY GEAR!
Amp
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Guitars
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-Squier Stratocaster
Pedals
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-Fender PT-100
-MXR Phase 90
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-MXR Carbon Copy
#17
Quote by fender4482
Are the places you linked us to to buy kits reliable? Have you actually ordered from them? I'm over protective of my money.


Yes all of those websites are reliable. Ax84 is the best to get a starter amp kit.
#18
Quote by XgamerGt04
Yes all of those websites are reliable. Ax84 is the best to get a starter amp kit.


concur 100%. AX84.com has a great forum for discussing things too, and they have a nice "theory" document for explaining stuff.
Quote by kcdakrt
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#19
Quote by DLrocket89
Places for information/books to read:

General good series of books: http://www.londonpower.com/catalog/index.php?cPath=3

I don't agree with a bunch of what KO'C writes, but the books are good for learning the basics, so have at them.

If you want a good "here's how everything works", here's my favorite site, one I refer to often: http://www.freewebs.co.uk/valvewizard/index.html <--- Merlin just wrote a book...I haven't seen it yet, but people who've read the advance copies say it's great.

I'll get other stuff up here too, if people have suggestions, let me know.
same here. he seems to be the "authority" on power-scaling, though.

a couple of other guys with some free info available on the web:

Max Robinson. Has a site called "Fun With Tubes "
Mostly targeted at old radios but all the basic audio stuff translates just fine to guitar amps.
Lots of info on the different flavours of PI's, too.

Randall Aiken. He's a boutique amp builder and has plenty of good tech info you can learn from, whether you're newbie or advanced. Click Tech Info on his site

There are rare few things he has written that I don't agree with wholeheartedly.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#20
Quote by SomeoneYouKnew
same here. he seems to be the "authority" on power-scaling, though.

a couple of other guys with some free info available on the web:

Max Robinson. Has a site called "Fun With Tubes "
Mostly targeted at old radios but all the basic audio stuff translates just fine to guitar amps.
Lots of info on the different flavours of PI's, too.

Randall Aiken. He's a boutique amp builder and has plenty of good tech info you can learn from, whether you're newbie or advanced. Click Tech Info on his site

There are rare few things he has written that I don't agree with wholeheartedly.


I don't even agree that he's the power scaling authority... Easier ways to do it, that's for sure.
Quote by kcdakrt
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#21
Quote by DLrocket89
I don't even agree that he's the power scaling authority... Easier ways to do it, that's for sure.
i use the term "authority" rather loosely.
I don't think there's anyone who has written more (quantity, not quality) about it or made more money writing about it than he has.

He invented powerscaling.
(just like I invented the internet.)
/A.Gore
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#22
Quote by SomeoneYouKnew
i use the term "authority" rather loosely.
I don't think there's anyone who has written more (quantity, not quality) about it or made more money writing about it than he has.

He invented powerscaling.
(just like I invented the internet.)
/A.Gore


Hah!

*shrugs* I'm sure he knows his stuff, just that his view on things tends to be somewhat limited in my mind. That and (judging from his book showing how to design poweramps) he could design a proper poweramp to save his life. But that's just MHO.


UPDATE: Kit is being assembled right now, he's waiting on the prepunched chassis, so this might be a bit. We'll see...I have a list of things to go over in the mean time, like SE vs PP differences, how to read a schematic, etc. When I get the time.
Quote by kcdakrt
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#23
Quote by DLrocket89
Sorry for the confusion. Yes, the SEL is supposed to be about 20 watts, when it's driven by a KT88. I'm using a KT77, which develops less wattage.

OK, quick lesson here. I had mentioned single ended amps are inefficient. The general rule is that the average power of the amp will never be more than 50% of what the tube is rated for (called "max power dissipation"). A KT88 is usually 35-40watts, a KT77 is usually about 25 watts. So, on a good day, a SE KT88 amp will be about 18-20 watts, a KT77 will be more like 10-12 watts. In actualyity, it's a bit less, so I call it 7 watts. IT could be 8 1/2, could be 11, whatever.

Datasheets for tubes are your friends. I usually use JJ tubes, so I get stuff from their website: http://www.jj-electronic.com/index.php?option=com_content&task=view&id=17&Itemid=11

There's another website that's get for tube data, that's this: http://frank.pocnet.net/ I work with a lot of oddball tubes and haven't yet found one that wasn't in that collection.


EDIT: and I picked the KT77 owing to it's sweet tone, which I call a mix between a 6L6 and an EL34...check the tubes sticky for more description there. It's my favorite tube.

ooh, k
thanks for all the info, too

regarding the money situation:
you could always consider selling the amp once you've finished the build/tut, if you dont already have your heart set on keeping it

I dunno what your intentions with the amp are after you've finished it, but just another suggestion..


but thanks again for posting this. I"ve done a bit or research into tube amp builds/ done a bunch of modding on my VJ, but knowing what does what, when it goes a certain place will really help, too. I know what some parts of the amp do, and why they do what they do, but like ..some things, I just know "ok, if I put a bigger resistor here, then it has [x] effect on [y]"
..but I want to learn like, why that happens.

tl;dr: thanks
#24
Quote by DLrocket89
Hah!

*shrugs* I'm sure he knows his stuff, just that his view on things tends to be somewhat limited in my mind. That and (judging from his book showing how to design poweramps) he could design a proper poweramp to save his life. But that's just MHO.
I think we're on the same page. I was being slightly facetious. Read Randall Aiken's stuff. I think you'll probably enjoy his writings. If he ever writes a book, I would highly recommend it.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#25
Quote by SomeoneYouKnew
I think we're on the same page. I was being slightly facetious. Read Randall Aiken's stuff. I think you'll probably enjoy his writings. If he ever writes a book, I would highly recommend it.


I've talked with Randall some, nice guy, knows his stuff. He has a really nice "first time you fire up the amp" guide to making sure you don't die that's going to be one of my crib sheets for that stage of the tutorial.
Quote by kcdakrt
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#26
Quote by james4
ooh, k
thanks for all the info, too


Thanks. And I realized, I should've stated that a SINGLE ENDED amp will never be more than 50% efficient. Push pull amps can get up there, with a pure class B being theoretically close to 100%.

regarding the money situation:
you could always consider selling the amp once you've finished the build/tut, if you dont already have your heart set on keeping it

I dunno what your intentions with the amp are after you've finished it, but just another suggestion..

I intend on selling the amp, mostly to pay back the guy who's giving me the kit for free...


some things, I just know "ok, if I put a bigger resistor here, then it has [x] effect on [y]"
..but I want to learn like, why that happens.


That's why I'm doing this. Will show how to build, and wil hopefully get into modding too. At minimum, I'll swap some caps and resistors out, recording them, so people can see what they do.
Quote by kcdakrt
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#27
Quote by SomeoneYouKnew


Max Robinson. Has a site called "Fun With Tubes "
Mostly targeted at old radios but all the basic audio stuff translates just fine to guitar amps.
Lots of info on the different flavours of PI's, too.




That really was... fun .....
#28
Okay...lunchbreak, time to write stuff.

I'm going to write a bunch about various topics, as kind of a "here's the background on electronics" and whatnot while I'm waiting for the kit to arrive.

Today: Ohm's law, Voltage, Current, Resistance

First, let me link to one of the greatest engineering resources out there:

http://en.wikipedia.org/wiki/Ohms_law

In a nutshell, ohms law describes how a resistor works. You have a resistor of known resistance "R". You apply a voltage "V" across it, you get a current flow through it, of a current "I".

R is measured in ohms, V in volts, I in amps.

Typical R values seen in guitar amps is 1 ohm to 1 megaohm, which is 1,000,000 ohms.

Typical V values seen in guitar amps is 5 volts to 500 volts (and higher).

Typical I values range from 10 amps (for heaters) down to .5mA (mA = milliamp, or 1/1000 of an amp).


The V across a resistor is measured by putting the probes on each side of the resistor. You know the resistance. You back out current by the equation I= V/R.

From there, the power that the resistor is dissipating (in watts) is P = VI. This is critical to know, because there are 1/4 watt resistors, 1/2 watt, etc, so you need to know how big to get. The kit builders should take care of this for you.


To better understand the concepts of current and voltage, I think of a set of water pipes. Current is akin to the amount of water flowing through the pipes (more water = more current), voltage is the pressure the water is being pushed by (higher pressure = higher voltage), and by continuation, resistance would be the size of the pipe (small = high resistance).


Resistors: you know the value of them by the color banding system (usually).

http://en.wikipedia.org/wiki/Resistor_color_code

In a nutshell, there is this color coding system:

Black = 0
Brown = 1
Red = 2
Orange = 3
Yellow = 4
Green = 5
Blue = 6
Purple = 7
Grey = 8
White = 9

There will typically be 4 bands on a resistor. The gold/silver on one end is the "tolerance", meaning + or - 10% or whatever.

The rest of the colors you read starting at the side opposite to tolerance band, progressing towards the tolerance band.

The first two numbers you write down in order, the 3rd band tells you how many zeros to tag on the end. For example:

Brown Black Brown ( 1 - 0 - <add 1 zero> = 100 ohms
Red Red Yellow (2 - 2 - <add 4 zeros> = 220,000 ohms
Brown Black Green (1 - 0 - <add 5 zeros> = 1,000,000 ohms

There is a shorthand for resistors... if you have say, 3.5Kohm (3,500 ohms), you shorten it to 3K5. Similarily, 1,000,000 (1 megaohm) is shortened to 1M. If you have something under 1 Kohm, you tag an R on the end so people know you're talking less than 1K, so 600 ohms would be 600R.
Quote by kcdakrt
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#29
Quote by DLrocket89
Sweet! That's what I like to hear!



He will probably get his before the end of the summer, but it will take longer for me because I am going to a more expensive school than he is.

Oh and thanks for going into theory here and using analogies that other people can understand.
Last edited by idontgrillonwed at Jun 2, 2009,
#30
Quote by DLrocket89
I've talked with Randall some, nice guy, knows his stuff. He has a really nice "first time you fire up the amp" guide to making sure you don't die that's going to be one of my crib sheets for that stage of the tutorial.
IRL or on the net?
either way, me = jealous.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#31
Quote by SomeoneYouKnew
IRL or on the net?
either way, me = jealous.


net
Quote by kcdakrt
DLrocket89 makes my ug experience better!


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#32
Quote by SomeoneYouKnew
IRL or on the net?
either way, me = jealous.


He's one of the nicest guys you'll ever meet. I ran into him up at school once.
#33
Will you go into modding a little as well? Like the small Blackstars and Blackheart push-pull type amps?
#34
Quote by idontgrillonwed
Will you go into modding a little as well? Like the small Blackstars and Blackheart push-pull type amps?



I'll be modding this one, yeah. won't be like the blackstars though, totally different power amp topology.

Preamp mods will make sense though...
Quote by kcdakrt
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#35
OK, today's lunchtime blurb: Tubes, what they are, how they work.

General idea: http://en.wikipedia.org/wiki/File:Triode_tube_schematic.svg

Things to remember: Opposites attract. So, a postive voltage will attract electrons, which are negatively charged. And likes repel.

All (most really, there are some "cold cathode" regulators out there...whatever) tubes have heater filaments in them. This is the central rod in that picture. Heaters are used because some metals (tungsten in particular) give off electrons when they are heated.

In some tubes ("direct heated" tubes) the heater is just there and the electrons come off of it. In most guitar amp tubes, we have "indirectly heated" tubes that have a separate cathode - the heater heats the cathode, which then gives off the electrons.

So, you turn the heater on and electrons boil off of the cathode. What then? Well, the plate (anode) is held at high voltage (anywhere from 100-600+ volts). This voltage is the voltage that can kill you in a tube amp. Recalling that opposites attract, the electrons are pulled to the anode by the positive voltage. So, we have electrons flowing, which constitutes an electrical current ("I" from before).

So...we now have a tube that has current flowing through it. Great. Not a whole lot of good for us. What if we want to say, control that current flow? That's what the "grid" in that picture is for. It's a loosely wound thin wire that is placed between the cathode and anode. If you put a voltage on this grid (or rather, a varying voltage from something like a guitar pickup for instance) it changes how much current flows. Namely, if you make it negative, it will repell electrons (because likes repel) and prevent electrons from making it to the anode from the cathode, so the electrical current in the tube drops. Likewise, if you make it more positive, it will allow more electrons to flow and current increases.


Okay, so we can now vary the current through the tube. Also good, but not entirely helpful unto itself. Next, look at the diagram here: http://www.freewebs.com/valvewizard1/gainstage.html And don't freak out over the "bias" thing.

(As an aside, the ciruclar looking thingy is the tube. The cathode is the bent solid plate on the bottom, the grid is the dotted lines through the middle, and the straight solid line on the top is the anode).

Now, looking purely at the tube, recall Ohm's Law from yesterday, which states that the voltage drop across the resistor is: V=IR Now...the square box above the tube is the anode resistor. One side is connected to the high voltage supply (+HT), the other side is connected to the anode of the tube. So, current flowing through the tube also flows through that resistor. At "idle", there is some current flowing through that tube...so, if there is current flowing through the tube, there must be current flowing through that resistor. And that means that there is a voltage drop across the resistor. So, if +HT is at 300 volts (very common for preamp tubes), there is probably only about 180 volts on the anode of the tube, because the rest is lost in the resistor (so, the resistor would be dropping 120 volts).

Now, what happens if the grid voltage goes negative, so less current flows through the tube? Well, less current flows, so there is less of a voltage drop across that plate resistor. That means that the voltage on the plate then goes up. Similarily, if the grid voltage goes down, current goes up, the voltage drop across the plate resistor goes up (because current is up), so the voltage at the plate goes down.

The thing that lets you actually have gain is that the grid is VERY effective at its job...namely, a 1 volt swing on the grid will give you 20-100 volts out. Each tube data sheet (for triodes at least) will list a "mu", which is the greek letter that looks like u. This is the "idealized" gain, with a 12AX7 being 100, 12AT7 being 70. In reality, it never gets that good.

That type of tube is called a triode (tri = 3 elements, the plate, grid, and cathode). Later, I'll get into tetrodes, pentodes, beam pentodes, etc, going to leave it here now though. Triodes are the most common preamp tube. Usually, in one tube ("envelope") there are two triodes. So, a 12AX7 tube actually contains 2 12AX7 triodes. Each triode is that full internal structure described above.

Also, if you look at a triode, the big grey boxy thing that you see - that's the anode/plate.
Quote by kcdakrt
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#36
this is all very hepful and easy to understand. i hope the actual build tutorial is this easy.

this sounds like it could be fun and very interesting.
#37
Quote by TheBuddhistPalm
this is all very hepful and easy to understand. i hope the actual build tutorial is this easy.

this sounds like it could be fun and very interesting.


Glad it's making sense. I'm doing this now because once I get the kit, I'm going to be saying stuff like "the anode resistor *blah blah*" and I want people to know what I'm talking about.
Quote by kcdakrt
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#38
Quote by DLrocket89
Glad it's making sense. I'm doing this now because once I get the kit, I'm going to be saying stuff like "the anode resistor *blah blah*" and I want people to know what I'm talking about.

Thats a real good way to start. I am definitely the kind of guy who prefers to learn book theories first so the hands on makes more sense. I'm liking this.
Thank you.
#39
I love when someone who is knowledgeable is able to put across their knowledge in an easy to understand fashion (great job and thanks basically ). Out of interest, why does there need to be an anode resistor?
#40
Quote by 21Fretter
I love when someone who is knowledgeable is able to put across their knowledge in an easy to understand fashion (great job and thanks basically ). Out of interest, why does there need to be an anode resistor?



Because if you didn't have an anode resistor, you wouldn't have anything to get a voltage drop across. Meaning...if you didn't have a resistor, the anode of the tube would be at +HT. End of story. Doesn't matter how much current you flow through it, it'll still be at +HT, which means you have no votlage swing (meaning the amplified signal) coming back out.

This'll probably make a bit more sense when I do something on reading a schematic.

Another way to look at it is that without the resistor there, the tube is in neutral. IE...it's revving full throttle, but there's nothing for the tube to "work against". Put the resistor there and the tube now has something to apply it's force against.

That's getting out there in the analogy realm, but I think it works.
Quote by kcdakrt
DLrocket89 makes my ug experience better!


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Kit Amp Building Tutorial
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