DIY Tube Amp - Beginner

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Alinithin
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Joined: Tue Dec 10, 2019 3:38 am
Location: Livermore

DIY Tube Amp - Beginner

#1 Post by Alinithin » Wed Dec 11, 2019 3:51 am

I've been thinking a lot latly, about trying to build my own tube amp. I'm not 100% sure where I should start, so I've come here to ask the experts!

I've seen kits for sale in the $300 price range, but I'm trying to keep this project as cheap as possible; I was thinking of just finding a good schematic, and sourcing the parts myself.

I should state that I'm by no means an electronics expert (thats why I'm here), basically, I have a fairly deacent understanding of electronics theory (I took a few courses in college), and I can solder.

For this project, I'm not as focued on building an awesome tube amp (It would be nice though), as I am focued on learing how the amps work, and learning how to build better ones.

I found a schematic for a 17 watt 6L6 and a 12-50 watt amp.

Basically, I'm just looking for some imput, and suggestions as to where I should start, and what direction to go in. I'm not completly set on using either of those schematics, so if someone has a better suggestion, by all means shoot it to me. I'm not planning on starting this project for another month or so, but I'd like to have all my ducks in a line before I do start!

Grant Bunter
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Location: Ilfracombe Queensland Australia
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Re: DIY Tube Amp - Beginner

#2 Post by Grant Bunter » Wed Dec 11, 2019 4:51 am

Hello, and welcome to the forum :)

There will be some people here who know about amplifiers, how to repair them etc, and there is a reasonably recent thread about building one as well, but really, more than 90% of the focus here in the forum is after the output stage, in other words, about speaker cabs, and in particular, Bill's speaker designs.

Don't be discouraged if not many people respond with help. Better to say nothing than lead people astray I reckon.
The is a lot of amplifier designs and theories, and, much of that is reasonably easy to explore on the net I imagine.
Tube amps came first, because that's what was available. Not any longer though, so I reckon check out all the theory you can find first, you might end up with your own ideas before your first amp build that way...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

Grant Bunter
Posts: 6400
Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
Contact:

Re: DIY Tube Amp - Beginner

#3 Post by Grant Bunter » Wed Dec 11, 2019 4:54 am

Oh, BTW, kits are often pretty good in terms of pricing, especially if there's something a little unusual in the parts list.
The kit supplier has done all the hard work chasing everything down, and, unless your time is worth nothing at all, that's a saving within itself...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

tallevan
Posts: 46
Joined: Sun Oct 20, 2019 12:15 pm
Location: London, England

Re: DIY Tube Amp - Beginner

#4 Post by tallevan » Wed Dec 11, 2019 8:40 am

Welcome.

What Grant says is true, this is mainly a forum dedicated to the discussion of BFM speaker designs and other related matters

I design, build and tinker with valve (tube) amps and preamps. I hope you don't mind a few starting tips:

1) It's not cheap.
2) Kits are normally pretty good value, because you won't buy parts in error (admit it.. we all do it) nor be obliged to buy 10 instead of the one you need, nor pay over the odds for small quantities and postage. Nor wait for out of stock, out of country providers.
3) Building from scratch is rewarding, but error-prone and much more expensive, but if your goal is to come out the other end smarter, it's the better way.
4) Good quality transformers are crazy expensive.
5) It's very dangerous. Voltages can get up to 400+ volts. Even when you unplug it, there are the big capacitors sitting there, storing their electricity for days.. just waiting ..
6) If you don't understand how to dress (route) wiring in a tube amp or preamp, it will hum. This will drive you mad.
7) You might want to start with a preamp first. You can always add this to your integrated amp project later.
8) If you get serious, test equipment will start to add up. A 'scope, variac, bench power supply, function generator, and And AND!!
9) Get stuck into www.diyaudio.com, diyaudioprojects.com, http://www.valvewizard.co.uk/ and even www.diystompboxes.com.
10) Buy Merlin Blencowe's excellent books "Designing Tube Pre-amps for Guitar and Bass" and/or "Designing High-Fidelity Tube Pre-amps"
11) Buy a copy of the "Radiotron Designer's Handbook" by Fritz Langford-Smith. No need to worry too much about the edition, but aim for the latest one you can find.

Being a bass player, I've just gotten rid of my last valve power amp, though I still use and love valve preamps. I find the power amps don't suit my use case as well as solid state. The bottom end can be a little soft, they are massively heavy, and I don't appreciate distortion from my power section (though many do).

Good luck. And try to keep your left hand in your back pocket.

Bruce Weldy
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Location: New Braunfels, TX

Re: DIY Tube Amp - Beginner

#5 Post by Bruce Weldy » Wed Dec 11, 2019 8:44 am

I'm assuming you are talking about a tube amp for guitar and not your stereo....

I've been looking at the kits from Mojotone. They have really good instructions and videos available for helping to build one. There are a couple of other sites that sell kits - but they are not nearly as easy to navigate as Mojotone as far as picking a kit and having all the parts there.

I play in a band with two guys that have built the 5E3 amps and they sound amazing. I'm seriously considering building a Princeton type myself.

If you are a beginner, I seriously suggest a kit over trying to just build from a schematic and sourcing all the parts yourself.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Bryan Cox
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Location: Minot AFB, ND

Re: DIY Tube Amp - Beginner

#6 Post by Bryan Cox » Mon Dec 16, 2019 7:01 am

If you're going for a guitar amp, a 5E3 Champ kit is the way to go IMO. Super simple, can be 5 or 15 watts (just have to change the PT and switch from a 6v6 to 6L6), sounds great, and you learn a ton along the way. Some suppliers of the kit:

Mojotone
Triode Electronics
Ceriatone
There are others. Just Google it

If you don't care much about the aesthetics and are using this as purely a learning experience then you can save $$$ by building it as a chassis only to drive a speaker cab (assuming you have one).
Otop 12 x 4 (Delta Pro 12-450a) 2x melded, 2x straight
Titan 39 x 4 (3012LF) 20" wide

jimbo7
Posts: 705
Joined: Fri Dec 28, 2012 10:45 am
Location: St. Louis

Re: DIY Tube Amp - Beginner

#7 Post by jimbo7 » Mon Dec 16, 2019 11:29 am

As your first amp, I'd suggest not building anything more than 10w. The price, complexity and hazards go up exponentially. Check out the 5e3 kits like everyone's recommended.

I've been wanting to build this for years: http://www.olcircuits.com/olc_tubecricket.html (fyi Beavis Audio has a schematic to build it yourself)

What about getting a Valve Jr. and modding that? I got 2 (with cabs) and they're still pretty cheap and fun to mod.
BFM builds:
XF212
T24 BP102 24"
2x SLA's 6-5" mids, 9- gt-302's
2x AT 14" MCM 55-2421
TrT 5" MCM 55-2421
AT 18" JBL GTO804
2x OT12 flat array
2x SLA Pro 2-Alpha 6's 2-Goldwoods
2x T39 24" 3012lf
Simplex 10 BP102

NukePooch
Posts: 352
Joined: Mon Jun 30, 2014 8:07 pm
Location: Berea, Kentucky

Re: DIY Tube Amp - Beginner

#8 Post by NukePooch » Sun Dec 22, 2019 2:48 pm

Lots of good info above.
I just finished my first amp project, researched the daylights out of it first, made the construction/assembly easier.
I did a 5E3 Deluxe (Champ is much easier to build).

Did a short thread about it here:
viewtopic.php?f=7&t=25530

Biggest takeaway of my thread is to go here:
https://robrobinette.com/Amp_Stuff.htm
This guy (Rob Robinette) has a wealth of knowledge on the site.

Study schematics and layouts of well-known amps. Keeping certain parts away from other parts is a must, and isn't shown on schematics. Layout / component placing is vital to noise-free amps.

DIYLC (DIY Layout Calculator)
http://diy-fever.com/software/diylc/
https://bancika.github.io/diy-layout-creator/
Software that allows you to place/move/modify amp layouts. Very useful. Also made gorgeous electronics geek 'art' that I printed off and will frame/hang on the wall once I get to it.

Duncan Amps Tone Stack Calculator
http://www.duncanamps.com/tsc/
Software that allows you to see the EQ/Tone curves that result when using specific tone stack wiring and part values. Not necessarily for beginners, but as a beginner, I found it useful to see what is going on in preamp tone controls, as well as incorporate mods.

Might want to build a light-bulb current limiter. Limits the current when first powering up the amp to avoid blowing up the works. I ended up buying a Variac and using both it and the light-bulb limiter for first power-up.
https://antiqueradio.org/dimbulb.htm

I strongly would consider adding an effects loop...It's probably the best non-model specific mod I made.
Built:
4 Jack 112L- 3012HO, melded array
17.5 wide AutoTuba with Infinity 860w
6 Wedgehorn W6 w/ Panel Mount Piezos
2 T48 Slims (15" wide) with 3012LF
4 T48 Fattys (32" wide) with 3015LF

Bruce Weldy
Posts: 7116
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: DIY Tube Amp - Beginner

#9 Post by Bruce Weldy » Sun Dec 22, 2019 10:39 pm

NukePooch wrote:
Sun Dec 22, 2019 2:48 pm

I strongly would consider adding an effects loop...It's probably the best non-model specific mod I made.
Both of my buddies that built the 5E3 did the master volume mod.....helps tame it a little since it's pretty much off or balls to the wall with just the volume control.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

NukePooch
Posts: 352
Joined: Mon Jun 30, 2014 8:07 pm
Location: Berea, Kentucky

Re: DIY Tube Amp - Beginner

#10 Post by NukePooch » Tue Dec 24, 2019 2:10 pm

Bruce Weldy wrote:
Sun Dec 22, 2019 10:39 pm
NukePooch wrote:
Sun Dec 22, 2019 2:48 pm

I strongly would consider adding an effects loop...It's probably the best non-model specific mod I made.
Both of my buddies that built the 5E3 did the master volume mod.....helps tame it a little since it's pretty much off or balls to the wall with just the volume control.
+1
Yep. I did that too. Forgot that I've usually got the Master on "1" for practice...
Built:
4 Jack 112L- 3012HO, melded array
17.5 wide AutoTuba with Infinity 860w
6 Wedgehorn W6 w/ Panel Mount Piezos
2 T48 Slims (15" wide) with 3012LF
4 T48 Fattys (32" wide) with 3015LF

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