Tube Amp for Beginners

[pablogilberto]

Good day!

I'd like to learn more about Tube Amps by building one. Preferably using a tube amp kit like the one from mojo tone.

I have some knowledge in solid state electronics and basic tools.

I have few questions.

#1 Do you know references like books / videos / tutorials that I can read  about this subject (vacuum tubes for guitar amp applications)?

#2 Any recommended tube amp kit supplier?

#3 Any tips are welcome

Thank you!

[newey]

Lots of info, resources and discussion here:

ax84.com

Our "Links Page" is woefully out of date, with lots of dead links, but there are links to most of the tube amp kits there. Also check out Dan Torres' site here, he wrote a book years ago on tube amps:

Torres Engineering

Note that I have never done business with any of these entities, so the above are just starting points, not recommendations, necessarily.

[gckelloch]

This is great resource: robrobinette.com/index.htm

Mojotone is good stuff, but Ceriatone has many more model options and is also excellent quality and well reviewed. I don't think you need to read tube amp books to assemble an amp kit, but you should learn safety practices and wiring techniques b4 starting a kit. Wire placement alone can affect hum, tone, etc. I'd just go with the stock kit parts. Any improvements from more expensive caps made of the same materials are dubious, but you can swap parts later. From my understanding, changing tone stack cap types makes the most audible difference -- some being smoother than others. Also, Carbon Comp resistors in the signal path have been shown to generate less odd harmonics near thier V limit than metal film, but they do generate some noise. I think it only matters in the signal path. Ceriatone has thier transformers custom made in England. They seem to do the job well from what I've heard.

[reTrEaD]

Sept 30, 2021 7:01:31 GMT -5 gckelloch said:

I don't think you need to read tube amp books to assemble an amp kit, but you should learn safety practices and wiring techniques b4 starting a kit.

imho, this is crucial. The voltages present in a tube amp are lethal. They can literally kill you.

While it isn't necessary to understand how vacuum tubes work or even basic electronics to build a kit, learning makes the juice worth the squeeze. You mentioned Ceriatone. Their kits are excellent and very complete. However, they are quite expensive.

---

Resource sites I recommend:

Basic electronics and vacuum tube theory: FUN WITH TUBES - Max Robinson
Particularly the sections: The Basics of Electricity and Electronics. ~and~ Audio Amplifiers: How They Work.
Max is an antique radio guy, there will be much on the site that won't be of interest to an amp guy. But what is of interest, is well presented.

Duncan's Amp Pages
The Tube Data Sheet Locator and ToneStack Calculator are awesome.

Aiken Amps White Papers and Aiken Amps Technical Q&A
These are very advanced and most of it will go right over the heads of beginners. Still, worth being aware of.

[thetragichero]

i'm not sure your expertise level but would highly suggest a pedal kit or two under your belt before attempting an amp kit build. something like a simple fuzz and then a pt2399 delay would help practice needed skills at 9v instead of 300+ volts. much nicer to discover your soldering skills need work when you're not blowing fuses/setting off circuit breakers

once you've got some nice effects to play with, i'd suggest a simple champ as a first tube amp build. much easier to follow your signal in a single-ended amp and getting a single-ended build to be virtually hum-free will make you a better builder (push/pull amps will naturally cancel out some hum at the output stage)

valvewizard is a great site for breaking down amps. rob robinette has good information, although it is obvious he does not have an engineering background so when in doubt defer to merlin/aiken

[unreg]

Honestly, I have no experience building amps.

Sept 29, 2021 22:18:36 GMT -5 pablogilberto said:

#2 Any recommended tube amp kit supplier?

www.stewmac.com/kits-and-projects/electronic-kits/amplifier-kits/

Recommending StewMac bc they provide excellent instructions and they say:

Need Help? Our trained staff is standing by!
If you get stuck don't worry, we're here to help. Our amp team is just a phone call away.

Read a few of their amp kit reviews; those have made me want to try a StewMac amp kit. Some of the reviews provide helpful links too.


Note: the '65 P-Reverb 15W Amp Kit is a tube amp; and the kit is expensive.

[reTrEaD]

Sept 30, 2021 11:45:36 GMT -5 unreg said:

Recommending StewMac bc they provide excellent instructions and they say:

Need Help? Our trained staff is standing by!
If you get stuck don't worry, we're here to help. Our amp team is just a phone call away.

The only reason I'd ever recommend StewMac for anything is if it couldn't be sourced anywhere else. They're overpriced.

Sept 30, 2021 11:45:36 GMT -5 unreg said:

Note: the '65 P-Reverb 15W Amp Kit is a tube amp; and the kit is expensive.

Rumor has it, the tube amp kits from StewMac are sourced from MojoTone, then rebranded.

StewMac's '65 Princeton Reverb clone kit: '65 P-Reverb 15W Amp Kit $1,104.10

MojoTone's '65 Princeton Reverb clone kit: ‘65 Blackface 15W P-Reverb Amp Kit $875.00

[thetragichero]

Sept 30, 2021 12:52:43 GMT -5 reTrEaD said:

The only reason I'd ever recommend StewMac for anything is if it couldn't be sourced anywhere else. They're overpriced.

100% this. stewmac/lmi are a last resort for items that cannot be found elsewhere

[pablogilberto]

Hi All!

Thank you for all the suggestions and recommendation.

I have started reading on them.
There is surely a lot to learn.

I hope I can build a kit and do some mod before the year ends.

Cheers!

[Jaga]

Share results!

[youka]

There are two sources set up in overwhelmingly most respectful educational manner.
These sources don't start from the middle of trunk but from the beginning in very interesting manner. 
I have created two playlists just this question on mind. For myself.
But there is few things to get familiar with first and
the first of the first is this:



Follow the numbers like Part 2. 

1. Uncle Doug who is the authoritative source on old tube amps tutorials documented the whole project to build the simple tube amp and all that comes with full explanation of every stage:
www.youtube.com/results?search_query=youka+naava+Uncle+Doug%27s+Boutique+Amp+Build+Tutorial
This is larger Uncle Doug playlist weighed to have educational content:
www.youtube.com/results?search_query=youka+naava+Uncle+Doug+Education

2. Valve Wizard has similarly highly comprehensible important chapter from his book available for everyone. This is the chapter explaining how tube works in amp circuit and from what facts the delicious distortion originates:
www.valvewizard.co.uk/Common_Gain_Stage.pdf

When you mix those two sources you will understand all the basics. I was able to get grasp in three months working 24/7. I did not know much about tube amps but ohms law was familiar to some extent. Ohms law is must and LTSpice helps alot to make sure you get it.
(Guitar)Tube amps are all very similar and that is why there is lot of welcomed repetition.

As part of the project I did Uraltone Deluxe 5E3 kit(for europeans) which is similar to Mojotone kit:
en.uraltone.com/uraltone-5e3-tweed-deluxe-rakennussarja-2-0.html
Mojotone: 
www.mojotone.com/Tweed-Deluxe-Amp-Kit

I also did simulate whole thing in free LTSpice circuit simulator. That accelerates the understanding very much but be aware of somewhat steep learning curve if you are new to LTSpice.
In any case it is recommended to learn LTSpice - maybe little by little.

Building the Kit was not fun as noobie but it is quite necessary to accelerate learning. I had not proper soldering iron which I purcased later and it is night and day difference to have nice 90W-120W soldering station to manage quite thick kit wires.
Xytronic LF-3500 will do. I have LF3200 but it is no more listed.

That tubeamp is very dangerous thing. At any given moment the power is on there are 500v capacitors ready to bite. When you turn power off you must be sure that all those caps are set to bleed empty - normally within few seconds. Also learning to see automatically where are the big potentials close to low ones is nice training session. You should have similar attitude like driving a car and keeping out of the way of semi-tracks. There is this movie
en.wikipedia.org/wiki/Duel_(1971_film) which show cases the right attide with tube amps safety.
You better get the kit building right.
So I made also my own alternative safe kit-system by connecting 9v batteries directly together and without any capacitors I was able to reach 200v for smaller 12AX7 tubes.

In fact I was also able to record some power tube distortion with my battery kit. 
The whole thing starts to be quite fun when you learn to read schematics and check out some 'tone stack' frequency responses and bias voltage fact checking with LTSpice without need to test build every idea. 

[cooltone]

Here's another vote for the valve wizard site and the book on building guitar pre-amps.

The book is just excellent and I read over and over to digest all the nuances.

In the end I started by modifying an existing amplifier to achieve what I wanted. Maybe I'll design and build my own one day, but it's a big job.

Don't forget to buy the correct tools. The PS voltages are high and the transformer input goes higher. Since I was doing simple things I used a meter that could take 1000v max. If it gets more complex and you need to use a scope, the probes need to be high voltage and compatible with the scope input.

As others have said keep the first project simple and be careful.

[thetragichero]

i do suggest a scope for troubleshooting purposes, although thankfully as we really care about seeing on the scope is the AC signal so as long as your probes are ac-coupled (passed through a capacitor) you shouldn't have to worry much about high voltage probes (you probably shouldn't be probing the plates directly anyway), although probes with x1 x10 switch can be useful. old slow analog 'boat anchor' scopes can be had for relatively cheap and should more than suffice for audio work