I'm tired of anemic guitar amps!

[scruffy]

I'm going to build an amp. And post the whole thing on YouTube. Show the world how it's done.

My ear has had it with anemic amps. I like thump, I like an authoritative sound. I like the power tubes to break up at full volume, none of that saggy blues stuff.

My other requirement is it has to be bulletproof. It has to be able to fall out the back of a truck and survive. So no PC boards, all old school point to point wiring. The worst thing that happens is a tube blows and then you replace it and you're done.

If you're into guitar amps, check out the schematic of this 200 watt Marshall. Notice the 12AU7 driver, in front of the power tubes. That's there because the KT-88's require 50 V rms to reach full power. They sound great when they do, they're thumpy and they have great dynamics, but they need some beef backing them up.

https://schematicheaven.net/marshallamps/major_1967u_lead_200w.pdf

So I'm going to have a 400 VA toroid that can supply almost an amp at 560 volts (the tubes draw 640 mils at full power), but it weighs less than half as much as a big metal power transformer.

And I'm going to make it a dial-an-amp, so you can get any sound you want just by flipping a few switches. If you want a Fender sound with reverb and the tone stack up front you can get that, and if you want a Marshall sound with the tone stack in back you can get that too. And anything in between, and above and beyond.

By using a 12AU7 as a phase inverter, ahead of the driver, I get a combined gain of about 60 for the power amp, which is just about perfect, that means about 0.8 volts will drive it to full power. With a long tailed pair, it'll have the same sparkle as a Marshall Major about halfway up, and then it'll get really aggressive when it's cranked.

I want to blow some windows out this year. It's one of my New Year's resolutions.

 

[JGalt]

I'm going to build an amp. And post the whole thing on YouTube. Show the world how it's done.

My ear has had it with anemic amps. I like thump, I like an authoritative sound. I like the power tubes to break up at full volume, none of that saggy blues stuff.

My other requirement is it has to be bulletproof. It has to be able to fall out the back of a truck and survive. So no PC boards, all old school point to point wiring. The worst thing that happens is a tube blows and then you replace it and you're done.

If you're into guitar amps, check out the schematic of this 200 watt Marshall. Notice the 12AU7 driver, in front of the power tubes. That's there because the KT-88's require 50 V rms to reach full power. They sound great when they do, they're thumpy and they have great dynamics, but they need some beef backing them up.

https://schematicheaven.net/marshallamps/major_1967u_lead_200w.pdf

So I'm going to have a 400 VA toroid that can supply almost an amp at 560 volts (the tubes draw 640 mils at full power), but it weighs less than half as much as a big metal power transformer.

And I'm going to make it a dial-an-amp, so you can get any sound you want just by flipping a few switches. If you want a Fender sound with reverb and the tone stack up front you can get that, and if you want a Marshall sound with the tone stack in back you can get that too. And anything in between, and above and beyond.

By using a 12AU7 as a phase inverter, ahead of the driver, I get a combined gain of about 60 for the power amp, which is just about perfect, that means about 0.8 volts will drive it to full power. With a long tailed pair, it'll have the same sparkle as a Marshall Major about halfway up, and then it'll get really aggressive when it's cranked.

I want to blow some windows out this year. It's one of my New Year's resolutions.

That's really neat. You should make it monolithic, shaped like the Obama library.

But with a 15" on the bottom, two 12" speakers in the middle, a horn near the top, and a 3-way passive crossover.

 

[hjmick]

 

[toobfreak]

My ear has had it with anemic amps.

I've not heard many Marshall amps described as anemic.

So I'm going to have a 400 VA toroid that can supply almost an amp at 560 volts (the tubes draw 640 mils at full power), but it weighs less than half as much as a big metal power transformer.

Unnecessary. The thing will still be a big hulking block of wood, glass and metal. There are no light tube amps.

And I'm going to make it a dial-an-amp, so you can get any sound you want just by flipping a few switches.

I'd keep any unnecessary circuit shit out of the direct circuit path of the amp and keep it as an effects box between the guitar and the amp.

I want to blow some windows out this year. It's one of my New Year's resolutions.

Genalex makes a great KT-88 if you can find them, but as an alternative, you might also look into considering some Tung-Sol 6550s. Also, consider your choice of output transformer. Acrosound makes some oil-filled killers.

Do post your video here.

 

[Chuz Life]

I'm going to build an amp. And post the whole thing on YouTube. Show the world how it's done.

My ear has had it with anemic amps. I like thump, I like an authoritative sound. I like the power tubes to break up at full volume, none of that saggy blues stuff.

My other requirement is it has to be bulletproof. It has to be able to fall out the back of a truck and survive. So no PC boards, all old school point to point wiring. The worst thing that happens is a tube blows and then you replace it and you're done.

If you're into guitar amps, check out the schematic of this 200 watt Marshall. Notice the 12AU7 driver, in front of the power tubes. That's there because the KT-88's require 50 V rms to reach full power. They sound great when they do, they're thumpy and they have great dynamics, but they need some beef backing them up.

https://schematicheaven.net/marshallamps/major_1967u_lead_200w.pdf

So I'm going to have a 400 VA toroid that can supply almost an amp at 560 volts (the tubes draw 640 mils at full power), but it weighs less than half as much as a big metal power transformer.

And I'm going to make it a dial-an-amp, so you can get any sound you want just by flipping a few switches. If you want a Fender sound with reverb and the tone stack up front you can get that, and if you want a Marshall sound with the tone stack in back you can get that too. And anything in between, and above and beyond.

By using a 12AU7 as a phase inverter, ahead of the driver, I get a combined gain of about 60 for the power amp, which is just about perfect, that means about 0.8 volts will drive it to full power. With a long tailed pair, it'll have the same sparkle as a Marshall Major about halfway up, and then it'll get really aggressive when it's cranked.

I want to blow some windows out this year. It's one of my New Year's resolutions.

I can't hate the idea, but looking at the schematic, I don't see any way to adjust the bias on the tubes in the final stage.

I would add pots to adjust the bias, maybe also add a negative feed back that is switchable (on or off,) or even variable.

Get you one of these.

 

[toobfreak]

maybe also add a negative feed back that is switchable (on or off,) or even variable.

Generally, the less NFB the better the amp sounds dynamically, even if THD goes up. Pay no attention to THD, but it also tends to become more unstable, so, the best NFB is usually a fixed point where only the minimum NFB is applied just enough as needed to keep the amp from going into oscillation.

 

[Chuz Life]

Generally, the less NFB the better the amp sounds dynamically, even if THD goes up. Pay no attention to THD, but it also tends to become more unstable, so, the best NFB is usually a fixed point where only the minimum NFB is applied just enough as needed to keep the amp from going into oscillation.

I don't disagree. That's why I would make it (NFB) bypassable.

I can only add. As much as I like the idea of designing and building my own "anything." It's very hard to 1. Actually do anything original and 2. Have that effort be significantly better than anything else that is out there.

 

[1srelluc]

In 1986, Motorhead played a legendary show at the Variety Theater in Cleveland, Ohio - a concert that would enter the history books as one of the loudest of all time. Levels of 130 decibels were reached during the show, and journalist Joseph Lanza recalled the event following the passing of the band's legendary bassist Lemmy in 2016.

"It was wild seeing them playing as plaster was coming down," Lanza said. "Everyone was looking up - even the band was pointing at the plaster coming down during the songs."

 

[toobfreak]

That's why I would make it (NFB) bypassable.

You almost always need at least a little NFB applied. A little usually doesn't hurt anything.

As much as I like the idea of designing and building my own "anything." It's very hard to 1. Actually do anything original and 2. Have that effort be significantly better than anything else that is out there.

There I have to disagree. Guitar amps are a bit different because they fall under professional audio but consumer gear suffers designed obsolescence and I've spent much of my life in pursuit of making stuff that blew most anything I could find in the consumer market out of the water.

Pro audio is different because pros want the best that can be made and if you don't offer it, they'll get it somewhere else, whereas consumers are chumps who fall for the annual "new model" to be released each year with the latest "improvements."

Since we are talking about bias, here is a power amp that has output trim pots mounted right on the board, you can see them between the output tubes, along with a pair of special adapter plugs I made to reach the very inconveniently-located jacks so that I can measure the bias current while trimming the pots.

 

[Chuz Life]

You almost always need at least a little NFB applied. A little usually doesn't hurt anything.


There I have to disagree. Guitar amps are a bit different because they fall under professional audio but consumer gear suffers designed obsolescence and I've spent much of my life in pursuit of making stuff that blew most anything I could find in the consumer market out of the water.

Pro audio is different because pros want the best that can be made and if you don't offer it, they'll get it somewhere else, whereas consumers are chumps who fall for the annual "new model" to be released each year with the latest "improvements."

Since we are talking about bias, here is a power amp that has output trim pots mounted right on the board, you can see them between the output tubes, along with a pair of special adapter plugs I made to reach the very inconveniently-located jacks so that I can measure the bias current while trimming to pots.

View attachment 1148096
View attachment 1148097View attachment 1148099

Pretty much what I was talking about with the bias pots and all.

 

[toobfreak]

In 1986, Motorhead played a legendary show at the Variety Theater in Cleveland, Ohio - a concert that would enter the history books as one of the loudest of all time. Levels of 130 decibels were reached during the show, and journalist Joseph Lanza recalled the event following the passing of the band's legendary bassist Lemmy in 2016. "It was wild seeing them playing as plaster was coming down," Lanza said. "Everyone was looking up - even the band was pointing at the plaster coming down during the songs."

130dB is just about right. I reach about 135dB all the time when I'm cranked as an ideal volume for R&R. My gear sounds better the louder it is and at 130dB, its it lights out awesome. No strain or clipping at all.

Of course, I've had a few things fallen off book shelves across the hall, a few pictures knocked crooked on the walls, and a neighbor across the street and up the road a bit called the police once when I was jamming at 4AM.

But I don't think it was the volume as much as the bass. With my sub on, the bass goes down at least to 12 Hz (that's as low as I can measure) and it is pretty flat with the midrange (all by design).

Bass that deep tends to carry.

 

[Chuz Life]

Anyway, good luck on the build scruffy. It looks like you have help here if you need it or want it.

I also recommend https://techtalk.parts-express.com/

It's the builders forum on "Parts Express's" website. They also sell a lot of parts, speakers, etc.

Not sure if they still do, but they used to host the "Midwest AudioFest" where builders could compete and show off their designs.

 

[scruffy]

I can't hate the idea, but looking at the schematic, I don't see any way to adjust the bias on the tubes in the final stage.

I would add pots to adjust the bias, maybe also add a negative feed back that is switchable (on or off,) or even variable.

Get you one of these.

View attachment 1148083

Good ideas! Thanks all for the comments and suggestions.

Yeah, I'm going to run a separate bias supply, I found a 36v transformer that'll fit in the inch-and-a-half space under the chassis, gonna voltage double it to about -95 vdc. Tunable NFB is good, there has to be "some" to make the presence control work right.

I have the old school analog bias toy, mine looks like this:

 

[scruffy]

BTW, Guitar Amp Design Books for Professional Builders has a nice set of tube calculators, very helpful.

The power amp will run completely clean till breakup, I'm going to use the Soldano trick to get low volume grit. They drive a 12ax7 "really hard" and put a 39k resistor in the cathode so the tube is biased "really cold", it sounds excellent in front of a cathode follower (you can play with the resistor value, 22k works good, so does 10k).

 

[scruffy]

This is what I'm going to start with.

This company AIMS was in Arizona from '67 till about 72 or so, it was started by some ex Fender employees who left after the CBS sale.

It's not going to look anything like this when it's done, gonna rebuild it from the ground up.

This is the back:

You can see the reverb spring hiding in the back there, that's the only part I'm going to keep. (Because it's an original Accutronics tank, sounds great). Plus it has the right number of tube sockets, save me some drilling work.

But y'know... anemic... that's a pair of 6550's but they're running at 450 volts, non ultralinear, there's no way they're getting 100 watts out of that. Maybe 70, tops. So I'm gonna put KT-88's at 560 volts with an ultralinear OT to get an honest 100 tube watts, which is very loud. Giant 350 uF filter caps to prevent sagging.

Maybe I'll build a practice amp with the leftover parts, but this one has to compete with a loud rock drummer so it has to be correct.

 

[Harry Dresden]

In 1986, Motorhead played a legendary show at the Variety Theater in Cleveland, Ohio - a concert that would enter the history books as one of the loudest of all time. Levels of 130 decibels were reached during the show, and journalist Joseph Lanza recalled the event following the passing of the band's legendary bassist Lemmy in 2016.

"It was wild seeing them playing as plaster was coming down," Lanza said. "Everyone was looking up - even the band was pointing at the plaster coming down during the songs."

the loudest concert i ever was at was in about 72-73 Anaheim Convention Center.....West,Bruce & Laing....a monster wall of amps.....holy shit was that loud....

 

[toobfreak]

the loudest concert i ever was at was in about 72-73 Anaheim Convention Center.....West,Bruce & Laing....a monster wall of amps.....holy shit was that loud....

All that has changed. Years ago, a friend of mine who was a Rush fan, dragged me to go see them and I was like in the 6th row right in front of the speakers; I always take cotton to concerts to stuff in my ears as needed in case things are too loud to protect my ears but the music wasn't even loud. I bet the SPL wasn't anymore than 85-90dB, if even that.

I could have stayed home and put a Rush album on and heard a much better rendition of the music.

 

[Sherlock Holmes]

I'm going to build an amp. And post the whole thing on YouTube. Show the world how it's done.

My ear has had it with anemic amps. I like thump, I like an authoritative sound. I like the power tubes to break up at full volume, none of that saggy blues stuff.

My other requirement is it has to be bulletproof. It has to be able to fall out the back of a truck and survive. So no PC boards, all old school point to point wiring. The worst thing that happens is a tube blows and then you replace it and you're done.

If you're into guitar amps, check out the schematic of this 200 watt Marshall. Notice the 12AU7 driver, in front of the power tubes. That's there because the KT-88's require 50 V rms to reach full power. They sound great when they do, they're thumpy and they have great dynamics, but they need some beef backing them up.

https://schematicheaven.net/marshallamps/major_1967u_lead_200w.pdf

So I'm going to have a 400 VA toroid that can supply almost an amp at 560 volts (the tubes draw 640 mils at full power), but it weighs less than half as much as a big metal power transformer.

And I'm going to make it a dial-an-amp, so you can get any sound you want just by flipping a few switches. If you want a Fender sound with reverb and the tone stack up front you can get that, and if you want a Marshall sound with the tone stack in back you can get that too. And anything in between, and above and beyond.

By using a 12AU7 as a phase inverter, ahead of the driver, I get a combined gain of about 60 for the power amp, which is just about perfect, that means about 0.8 volts will drive it to full power. With a long tailed pair, it'll have the same sparkle as a Marshall Major about halfway up, and then it'll get really aggressive when it's cranked.

I want to blow some windows out this year. It's one of my New Year's resolutions.

High spec audio amplifiers are easy to come by, what specification are you aiming to meet with the one you intend to design?

 

[Fort Fun Indiana]

I'm going to build an amp. And post the whole thing on YouTube. Show the world how it's done.

My ear has had it with anemic amps. I like thump, I like an authoritative sound. I like the power tubes to break up at full volume, none of that saggy blues stuff.

My other requirement is it has to be bulletproof. It has to be able to fall out the back of a truck and survive. So no PC boards, all old school point to point wiring. The worst thing that happens is a tube blows and then you replace it and you're done.

If you're into guitar amps, check out the schematic of this 200 watt Marshall. Notice the 12AU7 driver, in front of the power tubes. That's there because the KT-88's require 50 V rms to reach full power. They sound great when they do, they're thumpy and they have great dynamics, but they need some beef backing them up.

https://schematicheaven.net/marshallamps/major_1967u_lead_200w.pdf

So I'm going to have a 400 VA toroid that can supply almost an amp at 560 volts (the tubes draw 640 mils at full power), but it weighs less than half as much as a big metal power transformer.

And I'm going to make it a dial-an-amp, so you can get any sound you want just by flipping a few switches. If you want a Fender sound with reverb and the tone stack up front you can get that, and if you want a Marshall sound with the tone stack in back you can get that too. And anything in between, and above and beyond.

By using a 12AU7 as a phase inverter, ahead of the driver, I get a combined gain of about 60 for the power amp, which is just about perfect, that means about 0.8 volts will drive it to full power. With a long tailed pair, it'll have the same sparkle as a Marshall Major about halfway up, and then it'll get really aggressive when it's cranked.

I want to blow some windows out this year. It's one of my New Year's resolutions.

Sounds awesome. But enjoy looking at it at home, because at no gig ever will you be able to use it and get those good tones and breakup. Unless you're a national act who is in charge of the gig, anything over 50 watts can just be left at home. And even most 50W amps will be too loud.

If you keep the amp too quiet to get the good coloration or breakup, then there isnt much point in messing with an all tube amp. Just use solid state or a modeler. It will probably sound better.

This is just my recent experience as a working musician.

Make it 20 or 30 watts. Then you can get those sweet tones without the sound guy unplugging you and without your neighbors calling the cops.

 

[Fort Fun Indiana]

I'm going to build an amp. And post the whole thing on YouTube. Show the world how it's done.

My ear has had it with anemic amps. I like thump, I like an authoritative sound. I like the power tubes to break up at full volume, none of that saggy blues stuff.

My other requirement is it has to be bulletproof. It has to be able to fall out the back of a truck and survive. So no PC boards, all old school point to point wiring. The worst thing that happens is a tube blows and then you replace it and you're done.

If you're into guitar amps, check out the schematic of this 200 watt Marshall. Notice the 12AU7 driver, in front of the power tubes. That's there because the KT-88's require 50 V rms to reach full power. They sound great when they do, they're thumpy and they have great dynamics, but they need some beef backing them up.

https://schematicheaven.net/marshallamps/major_1967u_lead_200w.pdf

So I'm going to have a 400 VA toroid that can supply almost an amp at 560 volts (the tubes draw 640 mils at full power), but it weighs less than half as much as a big metal power transformer.

And I'm going to make it a dial-an-amp, so you can get any sound you want just by flipping a few switches. If you want a Fender sound with reverb and the tone stack up front you can get that, and if you want a Marshall sound with the tone stack in back you can get that too. And anything in between, and above and beyond.

By using a 12AU7 as a phase inverter, ahead of the driver, I get a combined gain of about 60 for the power amp, which is just about perfect, that means about 0.8 volts will drive it to full power. With a long tailed pair, it'll have the same sparkle as a Marshall Major about halfway up, and then it'll get really aggressive when it's cranked.

I want to blow some windows out this year. It's one of my New Year's resolutions.

BTW, I often use 40w Hughes & Kettner, set at only 20 watts, for my gigs.