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SurfGuitar101 Forums » Gear »

Permalink New DIY amp day

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I like music and playing guitar, but I also like to tinker with things that make music. I lately thought I should understand how vacuum tubes work. I first learned the basics of electrons flowing in tubes--diodes through pentodes. I bought a few old 78 record players from the 40s and 50s with tube amps to repair, mostly just replacing old capacitors with modern, safe equivalents. In every case, the old tubes themselves worked just fine.

I then thought I should make a practice guitar amp for my little music room where not much volume is needed. There’s lots of info on the internet, and I thought Robrobinette.com was particularly good. He recommends starting with a Fender Champ build, because it sounds good and is a relatively simple amp with just a preamp tube and one power tube.

I approached this build with the desire to use as much stuff as I had lying around. I rewound some 12-volt AC transformers to be an isolation power transformer and an output transformer. I used a silicon bridge rectifier instead of a tube rectifier. I had a 12AX7 twin triode tube available. I bought the requisite resistors, capacitors, tube sockets, pots and DC filament transformer. I bought a 12AL6 pentode that seemed like it would work well with the lower voltage from my isolation transformer. I also bought an old Fender Frontman 15 for its cabinet and 8” speaker.

The build was pretty straightforward but I spent a long time chasing down some loud hums. The solution ultimately was shielding the transformers and grounding the filament negative supply line to the chassis.

In the end, the amp sounds great, though more distortion than surf would probably like. Especially with some boost ahead of it, it gets plenty loud.

A Champ-style amp is a great first build for any of you thinking about such a project.

image
(Awaiting a pot for treble.)

If I'd stop buying old guitars to fix, I might actually learn to play.
Bringing instruments back to life since 2013.

Last edited: Nov 14, 2021 18:37:13

Let me just say, this is no small feat. You have really accomplished something here. It looks really cool, and I bet it sounds great as well. I have been checking out that guys website lately, and have learned a lot from him. I would love to be able to build a Champ style amp one day, but it takes a lot of time and dedication (like anything else). Anyway, awesome job my friend!

Guitar player for The Driptones surf band.
https://www.driptones.com/

very nice! i built a champ as my third amp just for something quick. i’m not crazy about the champ sound, so i added a tone control ala 5f2 princeton which made it more versatile.

my first amp is a 6g2 princeton that’s a little more challenging but still easy enough.

cosmonaut wrote:

very nice! i built a champ as my third amp just for something quick. i’m not crazy about the champ sound, so i added a tone control ala 5f2 princeton which made it more versatile.

my first amp is a 6g2 princeton that’s a little more challenging but still easy enough.

Not that I need another amp, but I'm getting the parts together for a 6V6 push-pull based on a Princeton amp. After that, I think my amp-building days are over. I might think about making a 6G15 Reverb.

If I'd stop buying old guitars to fix, I might actually learn to play.
Bringing instruments back to life since 2013.

Great amp build!
Especially with the transformer re-winds and such, much respect.
I too built my first amp this year and used Rob Robinette's site for quite a bit of information and guidance.
I built a 5E3 Deluxe but with some of the Fender Edge model mods and absolutely love the amp.
I've known enough about tube amp circuits to be dangerous for years but also wanted to slowly and methodically understand an entire circuit in both electrical and signal flow concepts.
It's a very rewarding experience and with all of the kits and online information available I highly suggest it.

Cheers,
Jeff

http://www.facebook.com/CrazyAcesMusic
http://www.youtube.com/user/crazyacesrock
http://www.reverbnation.com/crazyacesmusic

Great project. I love small amps; they can really produce some great sounds. I use a 5 watt amp around the house, myself. I love home-builds too, but lack the time to follow through on one.

The artist formerly known as: Synchro

When Surf Guitar is outlawed only outlaws will play Surf Guitar.

Cool. I just finished a home brew amp myself and it is a satisfying feeling for sure (all octal 5D3). Rob's site is LOADED with reliable info. Post more pics down the road!

ldk wrote:

cosmonaut wrote:

very nice! i built a champ as my third amp just for something quick. i’m not crazy about the champ sound, so i added a tone control ala 5f2 princeton which made it more versatile.

my first amp is a 6g2 princeton that’s a little more challenging but still easy enough.

Not that I need another amp, but I'm getting the parts together for a 6V6 push-pull based on a Princeton amp. After that, I think my amp-building days are over. I might think about making a 6G15 Reverb.

the brown princeton is quite lovely. there is nothing like bias-vary tremolo to my ears. the later princetons are also great. i have built three 6g15s now. It’s the one piece of equipment I need to have in my signal
path. They can be tricky to get the grounding correct.

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