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MagnaWatt 1Watt tube amplifier development thread

PostPosted: 29 Dec 2018, 21:58
by mj_sound_cubed
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Hello All :),

[center]"Parva Res Magna"[/center]

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. :)

Br,
MJ

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 31 Dec 2018, 01:12
by 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/file/d/1iMzbXTVAv9dac7rK7KM-0nF8UVqHRS__/view?usp=sharing


Here what`s inside:

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Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 31 Dec 2018, 09:11
by 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:

[img width=1000 height=405]https://lh3.googleusercontent.com/euVsg-q9kIZwvNjc5Mlk92DPhqKE85WoN4ZN1kOYrdocunrLT3NkMrdrmx3URNTLOZu4JfRUn2A7MzIGlylZ-eqKg19do0cHZDuD9y0oaPexjUdt_2Mo0G3KaBgcux4xl---YEfz=w1516-h615-no[/img]

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 05 Jan 2019, 00:06
by 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.

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

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 05 Jan 2019, 01:28
by ppluis0
Hola MJ,

You can avoid the LTP phase splitter at all implementing an output like this:

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The value of the cathode resistor is adequate for a 12AU7 but perhaps a little tweaking is needed.

Also, you can use a single triode phase splitter:

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This way you have a triode section available for another tasks as dual channel, clean/crunch mode, etc. 8)

Regarding the diagram you posted:

Move C9 between pin 2 of U2B and GND
Connect one end of R31 to 12.6V
Connect the negative leg of C14 to GND but C14 correct value must be 2200 picofarads
Connect one side of the O/P tranny to GND (Left the speaker floating can cause instability)

Saludos,
Josè

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 05 Jan 2019, 15:18
by mj_sound_cubed
Hola José,

Thank for you help and ideas. Gracias :)

I was working on designing a SMPS based tube amplifier for a couple of years already. I will share my comments.

ppluis0 wrote:Also, you can use a single triode phase splitter:

[ Image ]

This way you have a triode section available for another tasks as dual channel, clean/crunch mode, etc. 8)



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


ppluis0 wrote:
You can avoid the LTP phase splitter at all implementing an output like this:

[ Image ]




I attempted that method, and realized that it was behaving like a single ended amplifer. The PP configuration made a big difference in volume and PSU efficency.


ppluis0 wrote:
Move C9 between pin 2 of U2B and GND
Connect one end of R31 to 12.6V
Connect the negative leg of C14 to GND but C14 correct value must be 2200 picofarads
Connect one side of the O/P tranny to GND (Left the speaker floating can cause instability)



Thanks im checking. :)

Can you please let me know about any spanish speaking foruns?

Saludos,
MJ

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 05 Jan 2019, 16:31
by mj_sound_cubed
Revision 2.

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[url=KiCAD file here.]https://drive.google.com/open?id=10p4wVcGcIsf1aVbPdxBhTkF_RViXDKY0[/url]

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 06 Jan 2019, 03:29
by ppluis0
mj_sound_cubed wrote:Can you please let me know about any spanish speaking forums?


Hi MJ,

There is a section here to post in several other languages but the vast majority of information are placed here, at the main body of the forum.
If you wish, feel free to send me PM to continue this subject in our native language 8)

Looks from your responses that you have already breadboarded several topologies for PI and output stages and selected what work best for this design.

Regarding this revision on the schematic: I see 3 electrolytics (C1, C2, and C10) connected in parallel at the 15V supply line... is this correct ?

Cheers,
Josè

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 08 Jan 2019, 08:33
by mj_sound_cubed
ppluis0 wrote:
mj_sound_cubed wrote:Can you please let me know about any spanish speaking forums?


Looks from your responses that you have already breadboarded several topologies for PI and output stages and selected what work best for this design.

Regarding this revision on the schematic: I see 3 electrolytics (C1, C2, and C10) connected in parallel at the 15V supply line... is this correct ?



Yes, those 3 capacitors, stabilized the whole amplifier much more.

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 09 Jan 2019, 09:34
by mj_sound_cubed
3D model almost finished.

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Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 09 Jan 2019, 10:23
by Dirk_Hendrik
If you want to go for a reliable design, move away from the idea the tubes should be visible and fully enclose them. Go figure; There's no serious manufacturer of tube based devices that makes stuff with the tubes sticking out in the open. However, there's loads of boohteek DIY-ers who do because they think it looks great. It's a strange thought that the component that is the most vulnerable for mechanical damage is deliberately put in the open. Go figure from there, what's goodlooking about a broken tube when you are about to strike your first chord and your audience is waiting.

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 09 Jan 2019, 19:41
by mj_sound_cubed
Dirk_Hendrik wrote:If you want to go for a reliable design, move away from the idea the tubes should be visible and fully enclose them. Go figure; There's no serious manufacturer of tube based devices that makes stuff with the tubes sticking out in the open. However, there's loads of boohteek DIY-ers who do because they think it looks great. It's a strange thought that the component that is the most vulnerable for mechanical damage is deliberately put in the open. Go figure from there, what's goodlooking about a broken tube when you are about to strike your first chord and your audience is waiting.


Great advice, but im more visual. :)

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 09 Jan 2019, 20:37
by ppluis0
Dirk_Hendrik wrote:There's no serious manufacturer of tube based devices that makes stuff with the tubes sticking out in the open...


Hi Dirk,

Perhaps, since the tubes are somewhat inside the cabinet and do not protrude so much, they can be protected in this way:

Image

Personally I consider that this is an example of a serious tube fx manufacturer, but is not my intention to begin an argue with you... :thumbsup

Cheers,
Jose

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 10 Jan 2019, 11:32
by mj_sound_cubed
ppluis0 wrote:
Dirk_Hendrik wrote:There's no serious manufacturer of tube based devices that makes stuff with the tubes sticking out in the open...


Hi Dirk,

Perhaps, since the tubes are somewhat inside the cabinet and do not protrude so much, they can be protected in this way:

[ Image ]

Personally I consider that this is an example of a serious tube fx manufacturer, but is not my intention to begin an argue with you... :thumbsup

Cheers,
Jose


Hey José,

Tottaly agree. :) Day by day, part by part. :)

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Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 10 Jan 2019, 12:41
by Dirk_Hendrik
ppluis0 wrote:
Dirk_Hendrik wrote:There's no serious manufacturer of tube based devices that makes stuff with the tubes sticking out in the open...


Hi Dirk,

Perhaps, since the tubes are somewhat inside the cabinet and do not protrude so much, they can be protected in this way:e


Jup...
that's the standard boohteek way of thinking the tubes are protected.

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 10 Jan 2019, 15:48
by ppluis0
Dirk_Hendrik wrote:Jup...
that's the standard boohteek way of thinking the tubes are protected.

Agree. The usual way to display tubes pointing out from a box is using forniture handles... :D

The solution using in Sweden requires intense metalwork but is more resistant:

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The solution using in Argentina (in one of my prototypes) : simply a laser engraved plexiglass... :lol:

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Cheers,
Jose

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 10 Jan 2019, 21:36
by mj_sound_cubed
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Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 10 Jan 2019, 21:42
by mj_sound_cubed
Dirk_Hendrik wrote:
ppluis0 wrote:
Dirk_Hendrik wrote:There's no serious manufacturer of tube based devices that makes stuff with the tubes sticking out in the open...


Hi Dirk,

Perhaps, since the tubes are somewhat inside the cabinet and do not protrude so much, they can be protected in this way:e


Jup...
that's the standard boohteek way of thinking the tubes are protected.


Image

ppluis0 wrote:
Dirk_Hendrik wrote:Jup...
that's the standard boohteek way of thinking the tubes are protected.

Agree. The usual way to display tubes pointing out from a box is using forniture handles... :D

The solution using in Sweden requires intense metalwork but is more resistant:

[ Image ]

The solution using in Argentina (in one of my prototypes) : simply a laser engraved plexiglass... :lol:

[ Image ]

Cheers,
Jose


Those are also great ideas :)

Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 10 Jan 2019, 21:58
by Cub
Since nobody's going to stomp on it, why not look beyond the die cast stomp box enclosures and use something that already looks like an amp head?
Hammond has some really nice chassis with optional perforated covers.
https://www.hammfg.com/electronics/small-case/chassis/1441

Then you can also have a much more elegant layout of the controls instead of just cramming them wherever is space and you could even put some nicely designed control panels and a logo on there.

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Re: MagnaWatt 1Watt tube amplifier development thread

PostPosted: 11 Jan 2019, 17:45
by mj_sound_cubed
Not a bad idea, the Lunch Box amplifier look. If it was cheaper I would use it. :)