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June 27, 2022, 05:47:11 PM

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Battery-Powered-Tube-Amplifier

Started by Tassieviking, March 02, 2022, 05:38:41 AM

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Tassieviking

I came across this when I was doing something on the net, I think it is cool enough to post it here for everyone to check out.
I especially like how he generates the high voltage for his designs, could be useful for tube pedals.
I think the design can easily be adapted for a stomp-box pre-amp, 
The portable bluetooth tube amp uses a 12AX7 and a 12AU7 tube, the JCM800 uses 2 tubes in the pre-amp.
I wonder if a JCM 800 pre-amp into a LM386 would sound ok ?
Anyway, I found it interesting, and thought provoking. I just wish I was good at using Spice programs so I could play with the idea more.
I think it would be too hard for me to get into Spice, my Dr keeps pumping me full of opioids for pain, messes with the head too much.

https://www.instructables.com/High-Gain-Subminiature-Amplifier/
https://www.instructables.com/Battery-Powered-Tube-Amplifier/
https://www.instructables.com/How-to-Build-a-Portable-Bluetooth-Tube-Amplifier/
There are no stupid questions.
There are only stupid mistakes.

phatt

#1
Some years back I built and messed around with this idea and yes the 555 circuit works.
I also built the Silicon Chip Valve kit and integrated it into a circuit.
Just keep in mind that there are a few things to consider.

A valve pedal or stand alone preamp is not going to have the same interaction for the player as a full valve Amp.

The magic of a full rig is partly due to the Power supply and the way in which it sags under load. (more notable with lower power rigs)
As the power section supplies the WHOLE amp then there is a lot of interaction with the preamps as well as the power section. It all works together to create the magic. 8)

Just altering the voltage drops from Power stage to preamps can alter the way in which it responds to signal.
You get the triodes as well as the power stage all interacting.
This interaction does not happen if the preamps are run from a totally separate power supply. :'(

To make matters worse SMode supplies don't sag as th feed back keeps it Stiff. yes you still get a triode rattle but it's Stiffer which is harsher to my ears. (for want of a better description)

I have done the above test and it was obvious that running the preamp section from my Smode supply while the power stage run from it own separate supply,,changed the way the Amp responded.
With all else same, I then reconnected the preamp back to main Amp supply and the magic returned.
the Smode voltage was close to same reading as main Amp, about 240volts.

If you care to compare all the early Fender Deluxe schematics you will note the power supply voltage drops changed a lot over time.
Those first ones were lower wattage due to voltage drop/sag, add to that they were K biased.
Over time voltage drops were changed to give more watts,, and eventually they used Fixed bias giving cleaner power more headroom.
There is a point where you can have a nice balance where the Amp runs clean but still breaks up at just the right place and it's magic. ;)

You can make a Valve circuit as stiff as a big SS rig and it won't sag but by the time it does start to deliver some valve mojo it's ear bleeding loud.

As a Great teck chap once told me when I first started messing around with circuits, "Small Cathode biased amps are great because they break up at just the right place and are not too loud."
I now see why that is so.

But try it out if you wish,, oh yeah I'll have a dig around for the 555 circuit i built as it has a pot which allows adjustment of the output voltage. That might take a while as I've got tons of schematics I've built over the years.
Phil.

Tassieviking

I would love to see the circuit you have of that power supply Phatt, I have never played with vale circuits except HV sparktesters in industrial situations.
Sparktesters are used in cable manufacturing to check the insulation when the cable is made, I worked as a maintenance sparky most of my career.

Is that the 10 Watt stereo amp from Silly Chip you mentioned ? From about 2014 or so.
I keep thinking about making a valve amp but the transformers are pricey just for playing around with something for a hobby,
valves aren't cheap neither when you need a bunch of them in one hit.

But that valve bug keeps nibbling in the back of my mind.  :)
There are no stupid questions.
There are only stupid mistakes.

phatt

Just google nixie smps there are many showing the adjustment pot.
Just make sure you use an Ultra fast diode.
Silly chip valve kit was the preamp one, can't remember the name? But the 555 is far easier and less parts.
I'll have a dig through all my elecro junk box. Major flooding up here right now in south east Qld but we are up high, just roads cut.
Phil.

phatt

Regards cost of a valve amp you can purchase a lamington kit for $350 at Valve heaven.
https://valveheaven.com/  (by Grant Wills in barossa valley SAust)

If you wish to do it even cheaper go here; https://ozvalveamps.org/

DIY ideas here;  https://ozvalveamps.org/ava100/ava100project.html

The site is the work of an amazing aussie chap (Roly Roper) who collected almost every Aussie amp circuit that was made in Aust and NZ.
Plus a ton of high voltage info. :tu:

Regards the "Valve mojo thing"
Valve amps by design (at least the older ones) distorted simply because they were very simple basic design. The HiFi brigade would never dream of building such a pathetic design.
But as guitar has a relatively limited range it actually beneficial to have a limited bandwidth especially if you are wanting the classic OD breakup effect.
Distortion through a full bandwidth circuit is the last thing you want for electric guitar.
So rule of thumb is, if you want a great Amp don't build a hifi spec circuit. That's half the reason why a lot of later digital stuff sounds Krass as they often have way to much hi Freq content. so they sound harsh and fake.
Yes there are good ones that deal with bandwidth but they will cost bigger bucks.
So your little Gorilla amp is an ideal setup as it's older and by the looks of the schematic you posted will sound sweeter than the latest hi teck digital stuff.

Yes Valves are great but I've found you can pull some stunning sounds just using a few well designed pedals and some basic amplification.

My main Amp is actually a Keyboard amp and with some pedals and some reworking of the Amp I'm happy. ;)
I have basically designed most of my system by trial and error (lots of Errors but that is how one learns). you don't need hi teck,, you need to learn to understand what your Ears Are Actually hearing.

Take distortion,,, dead easy to do that but it's the TONE shaping that makes it sing.
Example, a common Guit player complaint; I want to cut through I need more MID.
      WRONG!!!  what he really needs is less bass.
The trick is Subtraction THEN turn up what is left and it cuts through.

It's what you DON'T hear that makes great guitar sound/tone
This goes for both SS and Glass
Phil.

Tassieviking

Good to hear you are not affected too bad by the flooding phatt, way too many people have died from it.
I have been keeping an eye on it as my dad lives in Casino NSW.
I think Lismore went right under with the river rising 14.4m,
I remember being there a few years ago and saw all the markers high up on buildings from previous floods, worse this time.

There are no stupid questions.
There are only stupid mistakes.