How Valve Guitar Amplifiers Work Part 1

[@michaelevans3852]

It seems I'm spending much time watching your videos. Always informative and entertaining. Thanks again.

[@stuartukguitarampguy5830]

I'm glad you are enjoying them. Only another 100 to watch....

[@smartquark]

A very interesting and knowledgeable in-depth description of how two different valve amplifiers work (Marshal JMP and Fender Super Reverb). Fascinating to see the simple but elegant solution for vibrato through photo resistance.

[@KitchenBuddha]

Stuart, I noticed (not this vid) you need a 9 pin tube pin straightener. I got some a couple of years ago, and I assure you it will brighten your day everytime you use it, and no glass cracking just perfect straight pins.

[@stuartukguitarampguy5830]

Hi Bob. Ah that's interesting, I haven't come across one of those. Any idea where you get them?

[@Roy-xe9is]

Thank you for this! Can't wait to keep going.

[@stuartukguitarampguy5830]

Cheers Roy

[@stuartukguitarampguy5830]

Hi I did a degree in electronics at Uni. But I learned most of what I know through running my own electronics design company in the 1980s. Even then I didn;t know anything about valves. I learned most of that through trial and error and watching channels like mine on KZbin.

[@Roy-xe9is]

@@stuartukguitarampguy5830 Well, This is what I'm doing on your channel. Glad I found you. Cheers from sunny Seattle.

[@kitwarren2493]

Exactly what I was looking for - very informative, engaging and well explained. Thank you very much!!

[@stuartukguitarampguy5830]

Excellent thanks Kit

[@curious_atoms]

Excellent video. Thank you.

[@stuartukguitarampguy5830]

Many thanks

[@ottomans2876]

I enjoyed that Stuart. I will keep an eye out for the others in the series.

[@stuartukguitarampguy5830]

Excellent I'm pleased you enjoyed it.

[@philchapman1463]

Great videos! Thanks for making and sharing! I had a Marshal TSL 60 tube amp that I changed coupling capacitors on to remove some low bass, this tightened the amp up and this mod worked well. Do you know much about the Marshall solid state tone stack for the MG HDFX 100 head? Does a transistor amp use a similar style tone stack as a tube amp and would one be able to change coupling capacitors to create a tonal change (such as removing some bass)?

[@stuartukguitarampguy5830]

Hi Phil Glad you enjoyed it. I couldn;t answer your question I'm afraid without considerable research. All the best.

[@garygratzer9670]

Thank you so much for this series. Generous of you. The Vibrato/Tremolo confusion will never end thanks I believe to Leo Fender mislabeling his amps as having vibrato. These and have tremolo, not vibrato. I believe tremolo is the oscillation of amplitude and vibrato varies pitch. Please correct me if I’m wrong. Thx

[@stuartukguitarampguy5830]

Thanks Gary, yes I always have to think which is which!

[@ianbradford8581]

Fender get it the wrong way round on their guitars where the tremolo actually changes pitch and is really vibrato I can't help thinking that there will be a fun story behind getting the names backwards.

[@stuartukguitarampguy5830]

@@ianbradford8581 Yes I had heard that but haven;t ever heard the story about how it happened!

[@billconrad201]

Hi I have a red Bear amp, worked fine ,then I plug in and very little sound no volume changed tubes same stuff, wondering if you could help?

[@stuartukguitarampguy5830]

Hi Bill I don;t know that amp. TBH it's very hard to diagnose a fault over the internet. Do you have a local tech?

[@tomfoolery2082]

Why is ac transformed to DC , I'm sure there's a good reason but I don't know what it is . Great channel .

[@stuartukguitarampguy5830]

Good question. AC is basically 100% hum and it would be impossible to use that as a power supply in an audio amplfier.

[@mila8400]

Hi Stuart, may I please ask you another question regarding the connection of the three-prong cord at about 17:00, of course the green/yellow wire goes from the mains to the earth, from the mains comes the brown wire that you connect via a pink wire to the right side of the AC switch, then from the mains comes the blue wire that you let go via a black wire to the primary winding of the main transformer. From the sleeve of the fuseholder a white wire leaves to the primary winding of the main transformer and from the tip of the fuseholder a white wire leaves to the left side of the AC switch. I see no connection with the gray wire of the primary winding. Am I seeing this correctly? Thanks in advance for your answer ! Best regards, Mila

[@stuartukguitarampguy5830]

Hi Mila I cou;dn;t see that at around 17:00 I'm afraid.

[@themrtomward]

Noticed on these Fender schematics the voltages are sometimes noted as + or - 20 %! On an amp running 420 volts that means anywhere between 336 and 504! What do you think Stewart?

[@stuartukguitarampguy5830]

I've never noticed that. I doubt they will be anything like that far out. Makes you think though! UK mains voltage alone had quite a wide range and that would make a bit difference to HT voltages for example.

[@themrtomward]

@@stuartukguitarampguy5830 For me it means … if it sounds good the voltage is close enough.Don’t have to squander time chasing an exact voltage.

[@stuartukguitarampguy5830]

Exactly

[@mchammer655]

Tganks for the helpful video!

[@stuartukguitarampguy5830]

Cheers Matt!

[@edwardhannigan6324]

Very informative..Thanks for sharing..Ed..Herts..😁

[@brentmydland5176]

Very knowledgeable however you misspoke and said that the smoothing caps covert ac to dc when their actual job is to smooth out dc ripple from already rectified dc. The rectifier stage creates dc from your ac PT secondary output.

[@stuartukguitarampguy5830]

Hi Brent. Sure. It's easy to make that sort of error live!

[@brentmydland5176]

@@stuartukguitarampguy5830 sorry for nitpicking

[@mila8400]

Hi Stuart. Could it possibly be, by 15:35 that you mean red green red, because the green is the center tap ? Thanks and greetings, Mila

[@mila8400]

I am sorry, I just see that you make it clear by 15:40, sorry !

[@stuartukguitarampguy5830]

Hi Mila The two reds are the HT and the yellow/green is the centre tap. The two green are the heaters.

[@mila8400]

@@stuartukguitarampguy5830 Thank you very much Stuart for your expert and pedagogical explanation!

[@ukenbike]

At 10:45, do you mean 6L6 valves, or are they 6v6?

[@stuartukguitarampguy5830]

I'm pretty sre they're 6L6 in that amp. Might be wrong.

[@djangoknight]

Thank You

[@stuartukguitarampguy5830]

Glad you liked it. Damn, I wish I was called Django Knight instead of Stuart Smith. Such a cool name!!

[@Davyfb75]

Condensers when I started

[@stuartukguitarampguy5830]

Leyden jars when I started...

[@codelicious6590]

This is titled inappropriately, it is not an explanation of how valave amps work but simply a look inside of two venerable valve amps with lots of mystifyong terms and descriptions of things, of which the functions are never explained. Id love to see a second try however.

[@stuartukguitarampguy5830]

Try part 2. Also see my vid where I go through an amplfier schematic.

[@bryannorris]

First glance V6 is a bit hotter