How A Valve Guitar Amp Works.

[DrNomis_44]

Hi Everyone,

I think we all have a bit of an idea how a guitar works, so I thought that I would start a thread about how a Valve Guitar amp works, I'm going to try and keep it relatively simple to understand, but I'll have to include a simple scientific principle which I think should help.


Here's the simple Scientific principle:


Like charges repel, un-like charges attract.


Okay, so, when we discuss how a Valve Guitar amp works, we need to first discuss how a Valve works, a Valve is an Electronic device which is used to control the flow of Electrons in an Electronic circuit, so what is an Electron?, an Electron is a very small atomic particle which has a Negative charge, in a basic atom, such as a Hydrogen atom, there is one Electron orbiting a nucleus made up of one Proton, a Proton is a very small atomic particle like an Electron but it has a Positive charge, so it attracts the Electron to it because the charges are un-like.


Back in around the late 1800's, Thomas Alva Edison, an American inventor, was trying to find a way to stop his recently invented Incandescent lamps from developing a black film on the insides of the glass envelope, incandescent lamps had an electrode called a Filament which glowed brightly when an electrical current was passed through it, Edison tried introducing a thin metal plate into the glass envelopes in an attempt to stop the blackening, and it was while he was doing some experiments that he noticed an interesting phenomenon, when the plate was made Negative, he noticed that nothing happened, but, when the plate was made Positive, he observed a small current-flow, this discovery led to the invention of the very first Electronic device, called a Diode (two-electrode), this new Electronic device was put to use in a device called a Radio, in 1907, Lee De Forest, another American inventor, created a new Electronic device, called a Triode (three-electrode), by placing a third electrode in between the filament and the metal plate in the glass envelope, Lee De Forest found that he could control the flow of current from the filament to the plate by applying a Negative-charge to the third electrode which he called a Grid (it was literally a grid of fine wire), he found that his new device, the Triode, could amplify, or make louder, weak signals, so it ended up being used in the early Valve Radios from the 1920's onwards, right up until the invention of a device called a Transistor in the mid 40's.

As it turns out, the Electron Valve proved to be a good device for making guitars louder, most guitarists these days seem to like the sound they get from a good Valve amplifier, although there are also some that like the sound of Solid-State amps too.


Anyway, going back to how a Valve Guitar amp works, when an electrical-current is passed through the filament, the filament heats up and glows a dull-orange colour, but something else also happens, the Electrons in the filament boil-off the surface (this process is called Thermionic Emission) much like how water-vapour boils off water when it's heated, you might have noticed this happening while making a hot cup of tea or coffee on a cold day, now because the plate is held at a high positive-charge, the Electrons (negatively charged) are attracted to the plate and a current flows, but if a negative charge is put on the grid, this repels the Electrons back to the filament, effectively stopping the current-flow.


I'll be continuing the discussion tomorrow, might also post some pics, so stay tuned


Note: if this thread needs to be moved to a more appropriate forum-section, please do so mods.


Note that if there are any forum members who wish to contribute to this thread, you're welcome to do so.

[Brendan]

Looks great DrNo... I've moved it to the PitBull Amps section - figured although it's a general thread, it fits nicely in here.

[DrNomis_44]

Looks great DrNo... I've moved it to the PitBull Amps section - figured although it's a general thread, it fits nicely in here.


Cheers mate, in hindsight, the amp section is where I should have put it in the first place, anyway, no harm done so it's all good.

[DrNomis_44]

Following on from my last post, I thought that I would post a pic of some Valves which are commonly used as Preamp Valves in Valve Guitar Amps, so here you go:


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On the left is a 12AU7A, it produces the lowest gain of the three Valves you see in the pic, the 12AU7 Datasheet gives a figure for gain-factor of 19, so theoretically, the output signal is 19 times bigger than the signal at the input, next is the Valve in the middle and it is a 12AT7 with a gain-factor of 60, i.e. output signal is 60 times bigger than the input, and the Valve on the right is a 12AX7 with a gain-factor of 100, i.e. output signal is 100 times bigger than the input.


Personally, I haven't actually come across a Guitar Amp that uses a 12AU7A Valve in it's preamp, but I think the closest would probably be an original Fender Bassman (the yellow tweed model from the 50's) it used a 12AY7, which has a similar gain-factor as compared with the 12AU7A (they both have the same pin-out), on the other hand, the 12AT7 was used a lot in Fender amps as a Reverb Driver Valve, the Fender Twin Reverb is a classic example, and finally the 12AX7 was used a lot in the early Marshall Amps due to their high gain-factor of 100, the 12AX7 was also used in the Fender Twin Reverb, but Fender used the 7025, which is the lower-noise version of the 12AX7, you will also see a Valve called an ECC83 used in Marshall amps too, this is the British/European equivalent of the 12AX7, with the same technical specs, the 12AU7, 12AY7, 12AT7, 12AX7, 7025, and the ECC83 all have the same pinouts (the way the internal elements are connected to the Valve Base pins), and is as follows:


If you look at the base of the Valve with the pins facing towards you, you will notice that there is gap where a pin should be, the left-most pin to the gap is pin one, and the pins are numbered in a clockwise direction from pin one, each pin serves the following function:

Pin 1, Plate of Triode 1.

Pin 2, Control-Grid of Triode 1.

Pin 3, Cathode of Triode 1.

Pin 4, Heater Filament.

Pin 5, Heater Filament.

Pin 6, Plate of Triode 2.

Pin 7, Control-Grid of Triode 2.

Pin 8, Cathode of Triode 2.

Pin 9, Heater Centre-Tap Common.


Incidentally, because these Valves have two-identical Triodes within the glass envelope, they are all known as Twin-Triode Valves.


Here's a pic of a larger Twin-Triode Valve, called a 6SN7GT, it uses what's called an Octal-Base (8-Pins), from looking at the data sheet, it has a gain-factor of 70 for each Triode, i.e. the output is 70 times larger than the input, they can be used as a preamp Valve or as a Power-Valve, I have actually built a working Valve amp that used one of these as a Power-Valve so it does work:

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[DrNomis_44]

Here, we will take a look at some commonly used Power Valves:


Firstly, here's a 6V6GT Valve which is used in some Fender amps, you could think of it as a lower-powered version of the 6L6 which is also used in Fender Amps:


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Next is an EL34 Valve, these are commonly used in most Marshall amps:

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And finally here's a KT66 Valve, these are apparently very similar to the 6L6, the KT66 was used in the Marshall Bluesbreaker Combo Amp, made famous by Eric Clapton during his tenure as a guitarist in John Mayall's Bluesbreaker band:

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Unfortunately, I don't happen to have an EL84 Valve in amongst my stash of Valves, so if anyone can chime-in and post a pic of one, feel free to do so.

[DrNomis_44]

Here's an interesting little bit of trivia for you, did you know that the first Marshall Valve Amp, the JTM45, was based-on a certain Fender amp from the 50's?, yes, the JTM45 was based-on the Tweed Fender Bassman 4 X 10 Combo Amp which was originally intended as a Bass Guitar amp, but guitarists soon found out that it worked equally well as a guitar amp, as the story goes, Jim Marshall, who founded the Marshall company, asked his techs, Ken Bran and Dudley Craven to design a new amp after listening to some suggestions from local guitarists who frequented his shop, Ken Bran and Dudley Craven chose to base the new amp on the Fender Bassman because guitarists said that it came closest to the new sound of Rock they were hearing in their heads, and the rest is history.

[Muzza]

The Fender Bassman was is also very popular for blues harp.

I'll post a pic of an EL84 tommorow, unless someone beats me to it. I THINK one of my Orange amps has EL84's.

[DrNomis_44]

The Fender Bassman was is also very popular for blues harp.

I'll post a pic of an EL84 tommorow, unless someone beats me to it. I THINK one of my Orange amps has EL84's.


Cheers mate, yep, I would have to agree with you on that, the Fender Bassman in my opinion, has to be one of the most versatile amps of all time, I think that's probably due to the simplicity of the circuit, I certainly wouldn't mind building one from scratch, I guess it's versatility is one of the reasons why original 50's Bassmans command such high prices.

[DrNomis_44]

A couple of other types of Power Valves that you might see in some guitar amps are the 5881, and 6550, I seem to remember seeing a set of six matched 6550 Valves used in a Bass Amp once, I think it was the venerable Ampeg SVT, or I could be mistaken, Marshall used 6550 Valves in their Marshall Major 200 Watt amps.

One interesting observation is that, as guitar amplification evolved from the relatively low-powered models from the 1940, the Power Valves not only increased in power output, amp designers were using more of them in the power-amp sections of the amps, in the 40's most guitar amps used either a single Power Valve, or a couple of them, these early amps produced anywhere from 1 watt to about 5 or 10 watts at the most, during the 50's and 60's more powerful amps were designed and built due to the demands of guitarists wanting to be able to be heard clearly over the noise the drummer and crowds were making, Vox are a good example with their Vox AC15 and AC30 amps, the AC15 used two EL84 Valves to generate 15 watts of audio power, in response to requests for a more powerful amp, Dick Denney, who designed the AC15, designed the AC30 which used four EL84 Valves to generate 30 watts of audio power, the Vox AC30 circuit is much like the AC15 in other respects, the Vox AC30 was used by famous bands, like The Beatles, The Shadows, and The Rolling Stones to name a few, Queen's Brian May used a total of 18 Vox AC30 amps while on tour, the Vox AC30 has a very musical chiming sound to it.


Another thing to mention is that in the early days when Rock music was evolving, bands didn't have access to the high-powered P.A. systems that we have today, so they had to use high-powered guitar amps to be able to be heard, as a consequence, or maybe because bands could be heard better, the music became louder and heavier, apparently loud music tends to generate feelings of excitement in humans.

[stan]

great thread DrNo, good read

[Chuck]

Great informative post Doc, especially as I'm about to embark on building a tube amp for the first time ever. I'm using a kit from Valve Heaven (http://www.valveheaven.com/) - the Lamington Junior that uses a 12V plugpack to minimise the risk of higher voltages that a rookie like me could encounter. Should be interesting...

[Dan]

Great informative post Doc, especially as I'm about to embark on building a tube amp for the first time ever. I'm using a kit from Valve Heaven (http://www.valveheaven.com/) - the Lamington Junior that uses a 12V plugpack to minimise the risk of higher voltages that a rookie like me could encounter. Should be interesting...

I've been thinking about doing similar and have looked at those amps. I don't understand how the 12V plugpack option really makes it any safer. Sure you don't directly need to connect anything to the mains, but the first thing in the circuit is a transformer to convert the 12VAC to 240VAC to bring the voltage back up to generate the +270VDC high tension supply...

[Chuck]

I've been thinking about doing similar and have looked at those amps. I don't understand how the 12V plugpack option really makes it any safer. Sure you don't directly need to connect anything to the mains, but the first thing in the circuit is a transformer to convert the 12VAC to 240VAC to bring the voltage back up to generate the +270VDC high tension supply...

Good point Dan, not that I have any real understanding of these things! Have you seen the weekend courses that Grant at Valve Heaven runs? Two days, $500, kit supplied and supervision! He's based in Adelaide too these days. I used him years ago when he was in Sydney to service an SWR Baby Blue amp I have and he's a really good guy.

[Muzza]

I'll post a pic of an EL84 tommorow, unless someone beats me to it. I THINK one of my Orange amps has EL84's.
Sorry, they're EL34 tubes in both.
I've heard that the Orange Rocker 30 was based on a Vox AC30, so I assumed it had EL84's in them.

EL34 on the left from Orange Rocker 30, EL34BHT on the right from Orange Rockerverb 50 mkII on the right. (I have no idea what the difference is!)

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[edit:] here's some EL84's courtesy of Dr Internet...
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[Muzza]

As a bonus, for those that are interested, here's the 5 watt single ended harmonica amp I made that I sold for $600.

In the final stages...
13966 13967

...and finished!
13968 13969

(Cab dimensions based roughly on a Blues Junior.)

[Dan]

Good point Dan, not that I have any real understanding of these things! Have you seen the weekend courses that Grant at Valve Heaven runs? Two days, $500, kit supplied and supervision! He's based in Adelaide too these days. I used him years ago when he was in Sydney to service an SWR Baby Blue amp I have and he's a really good guy.

I have seen that and been tempted... but I think I need to build a cab first before I get onto amps.

[DrNomis_44]

Sorry, they're EL34 tubes in both.
I've heard that the Orange Rocker 30 was based on a Vox AC30, so I assumed it had EL84's in them.

EL34 on the left from Orange Rocker 30, EL34BHT on the right from Orange Rockerverb 50 mkII on the right.

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That's alright mate, it's good to include some more examples of EL34 Valves anyway, cheers for that.



With those Lamington amp kits that are powered by a 12V plugpack adaptor, there'll most likely some circuitry included to convert 12V AC (I'm assuming) up to a suitable high-voltage to run the Valves properly, I might have a look at these Lamington kits cause they sound pretty interesting.

[wokkaboy]

cool amp Muzza, so you built that from scratch ?

[DrNomis_44]

As a bonus, for those that are interested, here's the 5 watt single ended harmonica amp I made that I sold for $600.

In the final stages...
13966 13967

...and finished!
13968 13969

(Cab dimensions based roughly on a Blues Junior.)



That's a cool looking amp, perhaps that could be a good design template for the PBG guitar amp.

[Muzza]

cool amp Muzza, so you built that from scratch ?
Yep. Cabinet, circuitry, logo, everything, including the amp chassis itself - all made from scratch. (I have access to a sheet metal bender at work.)

The logo on the front is an offcut of brushed stainless. I printed the logo in reverse on the back of some sticky back plastic, then cut it out with a really sharp Xacto knife. Stuck the logo on the stainless and hit it with a few coats of flat black.

When it was completely dry (I allowed 24 hours) I peeled off the stick back plastic and voila... I was pretty pleased with the result. It was going to cost about $50 to get one cut on a CNC machine.

[Muzza]

That's a cool looking amp, perhaps that could be a good design template for the PBG guitar amp.
If you put it next to a Blues Junior, it's almost exactly the same height, width and depth. It just doesn't have the sloping front face - all sides are parallel.

[Muzza]

If anybody wants to build an amp and you have no electrical experience, I would suggest you get assistance from somebody who does. There are voltages in excess of 350V dc in some of these amps, some as high as 600v I believe. (Doc, correct me if that's an exaggeration.)

I'm not sure why anybody would bother with a 12 volt / 240 volt initial input transformer, unless you want to use it for busking.

The danger of these amps isn't the 240v AC primary winding voltage, ('tho that IS lethal...) it's the high DC voltage in the circuit wiring that catches people out. Even if you had a 12 volt transformer feeding the amp, the circuit voltages would still be in the 300-400 volt range.

[DrNomis_44]

If you put it next to a Blues Junior, it's almost exactly the same height, width and depth. It just doesn't have the sloping front face - all sides are parallel.


I think I remember hearing a Blues Junior Amp at some stage, they're great little amps, wouldn't mind owning, or building one.

[DrNomis_44]

If anybody wants to build an amp and you have no electrical experience, I would suggest you get assistance from somebody who does. There are voltages in excess of 350V dc in some of these amps, some as high as 600v I believe. (Doc, correct me if that's an exaggeration.)

I'm not sure why anybody would bother with a 12 volt / 240 volt initial input transformer, unless you want to use it for busking.

The danger of these amps isn't the 240v AC primary winding voltage, ('tho that IS lethal...) it's the high DC voltage in the circuit wiring that catches people out. Even if you had a 12 volt transformer feeding the amp, the circuit voltages would still be in the 300-400 volt range.


You're actually correct, the voltages in a Valve amp can easily be anywhere from about 350 V DC to 600V DC, I have even seen one design for a 150 Watt Valve amp that had voltages as high as 750V DC which is scary to think about, and I totally agree with your safety concerns there, there is a very thin margin for errors when building a Valve amp, and the errors could prove fatal if you're not familiar with the procedures you need to follow when working on a Valve amp, I definitely would advocate getting help from someone more experienced if you're a first-time Valve amp builder.

As an example, before my Marshall MA100C amp was fixed I remember measuring voltages as high as about 600 V DC in it, the guy who fixed it managed to bring the voltage down to about 450V DC, still high enough to be very lethal though.


Our Australian 240V AC mains power that we get from the 3-pin wall sockets is actually not 240V AC, that is what's call the Root Mean Squared Voltage, in reality it is something more like about 678.9V AC, and considering that most 3-pin wall sockets are capable of supplying anything up to about 15 Amps, this makes it even more lethal.

[Muzza]

I have to correct your last point Doc. 240V rms is, in layman's terms, the 'average' of the AC sine wave. The 'peak' voltage of 240V rms is about 340 volts. (339 point something).

(To clarify, as well as rms value of the sine wave, there is also something called the 'average' value. I used the term 'average' in the above explanation so non electrical people have a better chance of comprehending these concepts.)

Even if you accidentally touch one phase of a 3 phase system, you're still 'only' going to get a 240 volt (rms) wake up call.

If if you're ever unlucky enough (or stoopid) to touch 2 different phases of a 415 volt 3 phase system, you're gonna cop a peak voltage of about 586 volts. I don't know where you got the value of 678 volts from.


Just to explain a little further to those who are still awake and still following this, Australian mains voltage is 240v rms @50hz.
This means the 'average' (sic) voltage is 240 volts, but the actual voltage is like a wave. In one 'cycle' of this wave it starts at zero volts, in 5 milliseconds (mS), it rises to +340volts (ish) 5mS later drops to zero volts again then rises to -340volts (ish) and back to zero. This whole cycle takes 20mS and happens 50 times every second, which is where the 50Hz comes from.
If you get a 240volt 'kickinthepants', you're actually copping 340volts one hundred times each second. The good news is, your also getting zero volts one hundred times every second. (Gives you a break)

[DrNomis_44]

I have to correct your last point Doc. 240V rms is, in layman's terms, the 'average' of the AC sine wave. The 'peak' voltage of 240V rms is about 340 volts. (339 point something).

(To clarify, as well as rms value of the sine wave, there is also something called the 'average' value. I used the term 'average' in the above explanation so non electrical people have a better chance of comprehending these concepts.)

Even if you accidentally touch one phase of a 3 phase system, you're still 'only' going to get a 240 volt wake up call.

If if you're ever unlucky enough (or stoopid) to touch 2 different phases of a 415 volt 3 phase system, you're gonna cop a peak voltage of about 586 volts. I don't know where you got the value of 678 volts from.



Cheers for that, I obviously got my maths wrong so thanks for clarifying things for us.

Here's how I got my value, I started by dividing 240V AC by .707 to get the peak voltage, then multiplied the resulting figure by two to get the peak-to-peak voltage, maybe I took the wrong approach, maths was never my strongest subject at school.

[fender3x]

cool amp Muzza, so you built that from scratch ?

1+ Cool amp!

[DrNomis_44]

I'll see if I can add some more info on Valve Guitar amps in the morning, maybe what we could do to continue the discussion is to have a look at one of the many classic designs of Valve Guitar amps, the Fender Champ, since it is a relatively simple circuit, I'll see if I can do a simple explanation of how the circuit works, together with a hand-drawn schematic and block diagram, I'll try and make it easy enough to understand, might also include some info on it's history too, so stay tuned.

[FrankenWashie]

If you get a 240volt 'kickinthepants', you're actually copping 340volts one hundred times each second. The good news is, your also getting zero volts one hundred times every second. (Gives you a break)

I'm not so sure you're going to benefit greatly from that break Muzz! Seriously though, great stuff from both of you. its all great and valuable information, especially the safety aspects.

[DrNomis_44]

I'm not so sure you're going to benefit greatly from that break Muzz! Seriously though, great stuff from both of you. its all great and valuable information, especially the safety aspects.


Cheers, personally the safety aspects of working on Valve Guitar amps cannot be stressed enough, which is what I was originally getting at, I've had some pretty close calls when working on Valve circuitry in the past, and know from first-hand experience just how dangerous it can be if you're not careful, but as long as you follow certain procedures you can minimize the safety-risks involved.

Whenever I work on any piece of electronic equipment that's mains-powered, I follow this procedure to ensure my personal safety:


1, First thing I do is turn off and completely disconnect the piece of electronic equipment from the 240V AC mains outlet, I usually do this by pulling the 3-Pin mains plug out of the wall socket after switching the wall socket and the piece of equipment off, if it uses an IEC "Kettle-Cord" I completely disconnect that from the equipment I'm working on.

2, I use my Digital Multimeter set to read DC Volts on it's highest DC Volts range to check for any residual voltage in the circuit, I attach the black multimeter probe to a suitable grounding-point in the piece of equipment, and I put my left hand either behind my back or in the back pocket of the shorts or trousers I'm wearing, and I hold the red multimeter probe in my right hand while I probe for voltages, this ensures that I don't get any dangerous shocks going across my chest, if I do accidentally happen to get a shock.

3, If I do get any significantly high voltage readings, I use a resistor of a suitable value and a couple of alligator-clip leads to discharge any power-supply filter caps to ground while monitoring the voltages with my multimeter.

4, Once I am satisfied that there are no dangerous voltages present in the equipment I'm working on, I consider it safe to work on, then I commence working on it.

5, Once I have finished doing the work I Double, and Triple-check that I have done everything correctly before I plug the equipment into the mains wall socket prior to testing the equipment for correct operation.

[dave.king1]

This is a great thread.

I built a poor AC30 clone in 1965 in my 2nd year at college can't remember what the output tubes were (807 power tubes) but they had 385v on the anode cap, for reasons that should be obvious I remember the voltage figure very well.

Speakers were a pair of 30w Etones which seemed to be the speaker of choice with the Oz amp manufacturers at the time, my 150w Lenard had 8 of them

I've been thinking of building a 5f3 clone or one of the 18 watt Marshall clones over on 18watt.com.

[DrNomis_44]

This is a great thread.

I built a poor AC30 clone in 1965 in my 2nd year at college can't remember what the output tubes were (808 maybe) but they had 385v on the anode cap, for reasons that should be obvious I remember the voltage figure very well.

Speakers were a pair of 30w Etones which seemed to be the speaker of choice with the Oz amp manufacturers at the time, my 150w Lenard had 8 of them

I've been thinking of building a 5f3 clone or one of the 18 watt Marshall clones over on 18watt.com.


Cool, I'm not sure if I've ever heard of 808 Valves, let alone seen any, but I'm guessing that they were probably similar to the EL84 Valves, a good friend of mine, who's a Luthier, is in the process of having a 5F3 built for him by someone, the 5F3 is another one of those classic Fender amps.

[dave.king1]

Cool, I'm not sure if I've ever heard of 808 Valves, let alone seen any, but I'm guessing that they were probably similar to the EL84 Valves, a good friend of mine, who's a Luthier, is in the process of having a 5F3 built for him by someone, the 5F3 is another one of those classic Fender amps.

Just googled and edited my post, the power tubes were 807 pictured, although there was such a beast as an 808

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[DrNomis_44]

Just googled and edited my post, the power tubes were 807 pictured, although there was such a beast as an 808

13988


Geez, that's a pretty hefty Power Valve, I bet your AC30 build put out a decent amount of power and was pretty loud, how many of those 807's did you use to build your AC30?, that looks like a standard Radio-Transmitter Valve.

[dave.king1]

Geez, that's a pretty hefty Power Valve, I bet your AC30 build put out a decent amount of power and was pretty loud, how many of those 807's did you use to build your AC30?, that looks like a standard Radio-Transmitter Valve.

It was a very basic single channel amp with simple tone controls and no effects 2x807 in PP, 30watts rms.

In 1965 it was a very loud amp but by about 68 and the birth of heavier rock it had nothing, hence the hike up to the Lenard 150W

[DrNomis_44]

It was a very basic single channel amp with simple tone controls and no effects 2x807 in PP, 30watts rms.

In 1965 it was a very loud amp but by about 68 and the birth of heavier rock it had nothing, hence the hike up to the Lenard 150W


You probably could have been able to increase the output power by upping the HT and upgrading the output transformer, I think from the looks of it, you probably could have been able to easily get something like 100 Watts from out of two 807 Valves in Push-Pull, I've seen a single-ended Valve amp that uses a single 813 Valve and the HT was something like 1000V DC, or there abouts, but the amp was a high-end HiFi amp.

[DrNomis_44]

Okay, so how about we have a good look at a classic Valve Guitar amp from Fender, the Fender Champ, since it is a relatively simple design, it uses three Valves in the circuit, before I go any further I'll post a pic of the circuit for you:


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Tomorrow, I'll see if I can post a write-up on how the Fender Champ circuit works, will try and make it fairly easy to understand, stay tuned.


Might also go into some history of the Fender Champ too.

[Muzza]

...will try and make it fairly easy to understand, stay tuned.
To quote our old friend Yoda...
14000

[DrNomis_44]

To quote our old friend Yoda...
14000


Cheers Muzza, some very wise words there, I shall re-phrase it to "I shall make it easy to understand".

[dave.king1]

Nice stuff doc, pity I don't have my Electronics 3 text book from 1st year at college I could have scanned the relevant bits.

It broke simple circuits such as that one into the various stages and explained how each worked how each of the stages interacted and how to calculate the component values for a given outcome.

I'm going to enjoy this thread because it will jog the memory, not only of the technology and associated maths but also some great times

[DrNomis_44]

Nice stuff doc, pity I don't have my Electronics 3 text book from 1st year at college I could have scanned the relevant bits.

It broke simple circuits such as that one into the various stages and explained how each worked how each of the stages interacted and how to calculate the component values for a given outcome.

I'm going to enjoy this thread because it will jog the memory, not only of the technology and associated maths but also some great times



Cheers mate, when I do the write-up I'm going to deliberately keep the explanations simple and fairly easy to understand without going too deeply into the mathematics, this is so that those who aren't that well versed in electronics can follow it.

[dave.king1]

Here's a pretty good site that's fairly easy on the grey matter :o

https://robrobinette.com/How_Amps_Work.htm

[DrNomis_44]

Here's a pretty good site that's fairly easy on the grey matter :o

https://robrobinette.com/How_Amps_Work.htm


Cheers for that mate, that link has just saved me a whole heap of typing on my computer keyboard so it's definitely worth including in this thread.

[dave.king1]

Cheers for that mate, that link has just saved me a whole heap of typing on my computer keyboard so it's definitely worth including in this thread.

No worries, I was researching something else on TDPRI in the Glowing Bottle sub forum and stumbled across it.

Make sure you credit the source as you work your way through it for stuff to share, folks get very narky over on the car club forum when something is obviously copied and pasted

[Muzza]

I've made 3 valve amps so far and all have had the exact tone I was looking for.

Funny thing is, I have absolutely NO idea how they work, even though my knowledge of electricity is way above average. (I'm an electrical trades teacher at TAFE)

[DrNomis_44]

No worries, I was researching something else on TDPRI in the Glowing Bottle sub forum and stumbled across it.

Make sure you credit the source as you work your way through it for stuff to share, folks get very narky over on the car club forum when something is obviously copied and pasted


Definitely a good idea, I try to put the info in my own words so that any issues with crediting can be minimized, but still giving credit where it's due is a good thing and honorable too.

[dave.king1]

Gday Doc,

Have you got another chapter ready to go yet, I need some prodding to get into building a Trainwreck clone

[DrNomis_44]

Gday Doc,

Have you got another chapter ready to go yet, I need some prodding to get into building a Trainwreck clone

Not yet, but I'll see if I can do another chapter soon, had some other things occupying my attention, one other forum member added a link to a website that pretty much covers how Valve amps work in a lot of detail, hence the reason why I haven't done another chapter yet.

[dave.king1]

Sorry about that link, I only had a quick scan and didn't realise how deep it went

[DrNomis_44]

Sorry about that link, I only had a quick scan and didn't realise how deep it went


No worries, no harm done, the website article is actually really informative and definitely worth including in this thread.