MagnaWatt 1Watt tube amplifier development thread

[MJ_Sound_Cubed]

Hello All  ,

"Parva Res Magna"

This Latin expression translates to English, as the small greats. The perfect inspiration to build a small low power amplifier with great tone.

This is the first step of a pleasurable journey, of crowdsourcing ideas, visualization of concepts, experimentation of possibilities, design of prototypes and enjoying the final amplifiers.

Currently there are a few options in the market, with a wide variety of tubes ranging from the current production ones to the NOS sub mini sorts. In the tiny head shaped tube guitar amplifiers, we have the Zvex Nano, the Wangs VT1-H or the Surprise Sound Lab: Rock Block.

Some years ago, DIY versions came out such as the Frequency Central Superfly amplifiers or the DeXTeR's SFA.

The whole project will be created using a Creative Commons Attribution-ShareAlike 4.0 International License (Not the blog )

The URL for the project post series at my blog: http://soundcubed.com/category/projects/amplifiers/magnawatt/

As full disclamer I will try to gather as many DIY minds as possible with your help. I will share the progress in a few places.

Br,
MJ

[Marcos - Munky]

So... where's the project? Schematic?

[thomasha]

interested!

I'm currently working on another submini amp but why not?

Can we make it powered by LiPo batteries?
Imagine Frequency Centrals Obsession amp running on rechargeable LiPOs!
Would probably run for hours before one would have to charge it again.

[MJ_Sound_Cubed]

So... where's the project? Schematic?

I will share all the research I made for this project later in today.

interested!

I'm currently working on another submini amp but why not?

Can we make it powered by LiPo batteries?
Imagine Frequency Centrals Obsession amp running on rechargeable LiPOs!
Would probably run for hours before one would have to charge it again.

Submini tubes would make the whole project harder to reproduce for a lot of people in some parts of the world, even though I like them a lot for the compact size.
Why not a clip with a rechargeable 9V battery?

[thomasha]

Submini tubes would make the whole project harder to reproduce for a lot of people in some parts of the world

Check out the obsession amplifier! 12ax7 followed by a 12au7 in SE. It is similar to the Rock block or  Wang VT1 with only 2 tubes and no PT.
Heaters run at 12V 300mA and SMPS converts from 12V 250mA to 250V at 10mA.

Unfortunately there are only a few 12V batteries, but with a 4 LiPo you can make a 12V-ish battery.
And at 550mAh I would suggest a battery with at least 2700mAh, for 5 hours of playing time, which is the average charge of a 18650 battery. And you can always use a 12V power supply when playing at home.

[printer2]

I have some ideas that would use a pair of 6AK6's for a couple of watts. Run off of a laptop brick with an off the shelf HV module. Probably not in the lines of this project, it might be worth its own thread.

[SpencerPedals]

Submini tubes would make the whole project harder to reproduce for a lot of people in some parts of the world

Unfortunately there are only a few 12V batteries, but with a 4 LiPo you can make a 12V-ish battery.
And at 550mAh I would suggest a battery with at least 2700mAh, for 5 hours of playing time, which is the average charge of a 18650 battery. And you can always use a 12V power supply when playing at home.

This wheel has already been invented, in my opinion.  It is comprised of the Milwaukee M12 (12 volt) rechargeable batteries and corresponding "compact charger and power source."  See:  https://www.milwaukeetool.com/Products/Batteries-and-Chargers/M12-Batteries-and-Chargers/48-59-1201

The M12 batteries come in different sizes, and that charger/power source has a 5.5mm 12V out port on it that you can use to plug into external devices.  The amp just needs a male adapter to plug into it.  I'm already planning on using this setup for a 386 (12V version) amp.  I got a heated jacket that has this battery and charger/power source with it recently, and so I will be experimenting this winter.  NOTE:  THE OLDER VERSION OF THE COMPACT CHARGER/POWER SOURCE—Model 49-24-2310—DOES NOT HAVE THE SAME 12V OUT PLUG AND SHOULD BE AVOIDED.

[MJ_Sound_Cubed]

Submini tubes would make the whole project harder to reproduce for a lot of people in some parts of the world

Check out the obsession amplifier! 12ax7 followed by a 12au7 in SE. It is similar to the Rock block or  Wang VT1 with only 2 tubes and no PT.
Heaters run at 12V 300mA and SMPS converts from 12V 250mA to 250V at 10mA.

Unfortunately there are only a few 12V batteries, but with a 4 LiPo you can make a 12V-ish battery.
And at 550mAh I would suggest a battery with at least 2700mAh, for 5 hours of playing time, which is the average charge of a 18650 battery. And you can always use a 12V power supply when playing at home.

I remember those, you kinda made one and distributed the schematic?

The ideal solution would be an external battery pack made with LiPo´s that could be plugged to the amp and even power pedals.

I have some ideas that would use a pair of 6AK6's for a couple of watts. Run off of a laptop brick with an off the shelf HV module. Probably not in the lines of this project, it might be worth its own thread.

The 6AK6 isnt produced anymore. I would like to use the common and current production 12AX7 and 12AU7 in a push pull configuration. A bit like the Firefly with a SMPS.

[thomasha]

You're right, I tried it before, just need to make or buy such a battery pack.

The push-pull approach is also interesting. Have you seen the amplifiers at Tube-Town?
https://www.tube-town.net/ttstore/Kits/Verstaerker:::64_436.html

They have different amps to mimic famous amps using the 12au7 or the ECC99 in PP. Even  a trainwreck style amplifier.
Using a SMPS will be difficult at higher current requirements, as for the ECC99. Maybe it will be interesting to have a different kind of SMPS, from mains to 12V or 200V, using a small transfomer, as found in some pedal power supplies.

[iainpunk]

Eyy man,

The project sounds great!
Im wondering if you are set on using tubes or if you are open for transistor/solid state?

I've had some great experience with tinkering/building single ended inductor coupled class A transistor amplifiers! Especially when using germanium transistors, it can give a really smooth distortion from the power amp!

Am currently working on a 18watt all germanium power amplifier
The preamps (2 channels) are going to be semi-modular. Im building a lot of "building blocks" of the amp on different boards, so i can swap order and/or replace building blocks. But maybe the idea of semi-modular amplifiers is a usable one for guitarist so they can "invent" their own tone, like the synergy but more focused on unique sounds rather than popular sounds.

[MJ_Sound_Cubed]

You're right, I tried it before, just need to make or buy such a battery pack.

The push-pull approach is also interesting. Have you seen the amplifiers at Tube-Town?
https://www.tube-town.net/ttstore/Kits/Verstaerker:::64_436.html

They have different amps to mimic famous amps using the 12au7 or the ECC99 in PP. Even  a trainwreck style amplifier.
Using a SMPS will be difficult at higher current requirements, as for the ECC99. Maybe it will be interesting to have a different kind of SMPS, from mains to 12V or 200V, using a small transfomer, as found in some pedal power supplies.

Yes I do know that store its cool.

Eyy man,

The project sounds great!
Im wondering if you are set on using tubes or if you are open for transistor/solid state?

I've had some great experience with tinkering/building single ended inductor coupled class A transistor amplifiers! Especially when using germanium transistors, it can give a really smooth distortion from the power amp!

Am currently working on a 18watt all germanium power amplifier
The preamps (2 channels) are going to be semi-modular. Im building a lot of "building blocks" of the amp on different boards, so i can swap order and/or replace building blocks. But maybe the idea of semi-modular amplifiers is a usable one for guitarist so they can "invent" their own tone, like the synergy but more focused on unique sounds rather than popular sounds.

Ultra set on hybrid !

[MJ_Sound_Cubed]

The First block Diagram. I used and app called Dia Diagram Editor ( Free and multi-platform, link: http://dia-installer.de/ )

Here is the original .DIA file if you want to make your own twist,download it from this link:

https://drive.google.com/open?id=1epMGB0vdRBGmj6BRz2mLU1UMaHyDlRj7


Here what`s inside:

[MJ_Sound_Cubed]

I used KiCAD to create the schematic (http://kicad-pcb.org/).

First version of the schematic. It might have a few errors. Help to check.



If you want to help with the PCB layout - https://drive.google.com/file/d/163WfDpMYKvSOI0zYaawF-IXAxBswxJgD/view?usp=sharing

[MJ_Sound_Cubed]

Revision 2.



The Kicad project.

[thomasha]

Nice schematic, that was fast. I have some suggestions!

- Why not use a proper voltage multiplier chip? the 555 is Ok, but there is no correct way to control it, where other chips have feedback pins. I would go for the cheapest/easiest to find.

- The ECC82 is much more sensitive than the el84 or the el34, but you used a standard PI found in amplifiers with those tubes. It is much stronger than required, a simple cathodyne would do the job and you can use one triode for an extra gain stage. With the 2k2 resistor the bias must be somewhere at 2 volts?

The FX-loop is a nice touch, using transistors makes things easier too. No need to waste two triodes.

Last, why use a 15v power supply? You could use a 12v one and avoid the voltage regulator. Or use 18v (sometimes even available as laptop PS) and have all the filaments in series. Would use less current. How high can the 555 go? Higher VCC reduces the required current, resulting in less heat.

[Marcos - Munky]

- Why not use a proper voltage multiplier chip? the 555 is Ok, but there is no correct way to control it, where other chips have feedback pins. I would go for the cheapest/easiest to find.

Last, why use a 15v power supply? You could use a 12v one and avoid the voltage regulator. Or use 18v (sometimes even available as laptop PS) and have all the filaments in series. Would use less current. How high can the 555 go? Higher VCC reduces the required current, resulting in less heat.

The 555 can go up to 18V, I believe. When using a laptop power supply (18V-19V), you can use the UC2842 IC.

[MJ_Sound_Cubed]

Nice schematic, that was fast. I have some suggestions!

Thanks man    If you have one for the footswitch circuit , let me know 

- Why not use a proper voltage multiplier chip? the 555 is Ok, but there is no correct way to control it, where other chips have feedback pins. I would go for the cheapest/easiest to find.

I agree, there are better IC options for the SMPS, I only tested this one, feel free to build the circuit and let me know how it behaves and sounds. I also add, that it worked well, was cheap, very quiet and easy to build.

- The ECC82 is much more sensitive than the el84 or the el34, but you used a standard PI found in amplifiers with those tubes. It is much stronger than required, a simple cathodyne would do the job and you can use one triode for an extra gain stage. With the 2k2 resistor the bias must be somewhere at 2 volts?

I also attempted cathodine versions,but the clean sound was very dull, the overdriven tone was not harmonically rich even using that extra triode as a boost, lost a tiny bit of volume, somehow loaded the PSU more. I also realized that it sounded amazing with a mosfet boost powered with 15V in front of the pre-amp and the LTP phase splitter. Maybe I will add it.

The FX-loop is a nice touch, using transistors makes things easier too. No need to waste two triodes.

It works well.

Last, why use a 15v power supply? You could use a 12v one and avoid the voltage regulator. Or use 18v (sometimes even available as laptop PS) and have all the filaments in series. Would use less current. How high can the 555 go? Higher VCC reduces the required current, resulting in less heat.

Tried 9VDC- Worked but sounded dull and dirty. Max HV was 190VDC.
Tried 12VDC - Worked and the full gain sounded good, clean not so much. Max HV was 225VDC.
Tried 15VDC - Worked and full gain and clean sounds really good because the HV was around 250VDC.


The main purpose of this quest, is to build a small amplifier that sounds great clean and has crunchy sound.

- Why not use a proper voltage multiplier chip? the 555 is Ok, but there is no correct way to control it, where other chips have feedback pins. I would go for the cheapest/easiest to find.

Last, why use a 15v power supply? You could use a 12v one and avoid the voltage regulator. Or use 18v (sometimes even available as laptop PS) and have all the filaments in series. Would use less current. How high can the 555 go? Higher VCC reduces the required current, resulting in less heat.

The 555 can go up to 18V, I believe. When using a laptop power supply (18V-19V), you can use the UC2842 IC.

Depends in the version, the one I used was good for 16VDC.

Do you a working SMPS schematic with the UC2842 IC?

[Marcos - Munky]

Do you a working SMPS schematic with the UC2842 IC?

http://www.cackleberrypines.net/transmogrifox/BoostConverter/250V_SMPS.png
There's this one designed by Transmogrifox. It's not the simplest one, but it's tested and working great, I just didn't tried it with higher current (waiting for some pots for a tube circuit to arrive). It can be simplified a little bit, but I don't know where I did put the annotations on how to do it. Keep in mind this IC needs a higher voltage to work (16V), but there's the UC2843 which works with 8.something volts.

Voltage is set by Vout = 2.5*(R3/R1 + 1) so, with those values (10K and 1M), you'll get 252V.

[MJ_Sound_Cubed]

Do you a working SMPS schematic with the UC2842 IC?

http://www.cackleberrypines.net/transmogrifox/BoostConverter/250V_SMPS.png
There's this one designed by Transmogrifox. It's not the simplest one, but it's tested and working great, I just didn't tried it with higher current (waiting for some pots for a tube circuit to arrive). It can be simplified a little bit, but I don't know where I did put the annotations on how to do it. Keep in mind this IC needs a higher voltage to work (16V), but there's the UC2843 which works with 8.something volts.

Voltage is set by Vout = 2.5*(R3/R1 + 1) so, with those values (10K and 1M), you'll get 252V.

Hey man, Thanks for the schematic

I like the idea but it seems like it was designed with a 25K load, so it wont provide as much current as the 555 SMPS, moreover the IC costs the same as 10 NE555.

I will stick with mine, but I would appreciate a footswitch circuit , for a boost or the effects loop.

[Marcos - Munky]

I like the idea but it seems like it was designed with a 25K load, so it wont provide as much current as the 555 SMPS, moreover the IC costs the same as 10 NE555.

This one was designed to supply up to 50mA, while the regular 555 smps provides around, don't know, 10mA?