Portable DIY valve amp for beginner?

[Andy123]

First things first: I know SFA about electronics.

I've seen a few Cigar Box amps etc and thought "wouldn't it be cool if you could jab a valve or two in there?"

This got me thinking: is there such a thing as a DIY valve amp kit for beginners who are as low on cash as they are on brain cells? A low powered practice amp that might not kill me dead if I stuff it up?

[wazkelly]

Check this out.... https://www.valveheaven.com/diy-amp-...unior-amp-kit/

THE LAMINGTON JUNIOR AMP KIT
Build your own valve guitar amplifier with our 2W Lamington Junior Amp Kit, just $195 + postage (includes $49 construction manual).

Uses a 12v power supply which I believe lessens the chance of getting oneself fried.

Once you factor in a speaker and enclosure it starts to make some of the ready made combos look really good value, unless of course you want to play mad scientist and create your own.

The sound demos and be found here.... https://www.valveheaven.com/diy-amp-...e-sound-clips/

[Andy123]

I definitely want to play mad scientist. I like the idea of a custom made cab, and all the cheap/low power amps I've found are a bit odd on the controls fronts.

I'd like to have something with a single input, on/off switch, gain, T/M/B, and Master volume.
It looks like if you want a three band EQ you have to pay close to $1000 and get something high powered.

If I'm going to get something small, low powered, with that^ control lay out, I may have to make something from scratch.

[wazkelly]

Doc & Marcel should be the best ones to help you out as they both seem to dabble more in this than most folks.

Sent from my SM-A520F using Tapatalk

[DrNomis_44]

@ Andy123 There's one other website I could recommend you checking, and that's the AX84.com website, there's tons of info about building guitar amps on that website, one of the simplest designs on that website that i can think of is the P1 amp, which uses two valves, a 12AX7 and an EL84, and has a master volume and 3-band tone control on it.

http://ax84.rru.com/

[Andy123]

Thanks Doc, that P1 looked like just the ticket until I realised they don't ship to Aus.

I've found this but don't know if it would be appropriate:
https://www.ebay.com/itm/KLD-vintage...0AAOSwON5bmPzD

For a bit less than the price of the Lamington Jr you get a 15w kit with a 3 band EQ and reverb, all on a PCB.

Looks like its BYO cake tin, cab and speaker, but other wise thumbs up?

[Simon Barden]

Not that much DIY about the circuit itself as you get the PCBs pre-assembled. You aren't really going to learn much about building a valve amp from this. You'd need to get your own ceramic valve holders and valves, and make a decent chassis for it to fit in. Their black metal chassis shown in the pictures doesn't have room for the reverb tank, so your head would either have to be much larger than shown, or else you build it into a combo and have the tank at the bottom of the combo.

The design, although Fender 'Vintage Amp' is mentioned, is of unknown provenance as Fender made no such amp and has no valve rectifier, so if it is a copy of a Fender, then it's likely to be a later design rather than from a tweed or blackface era amp. It's got an input gain and master volume, so definitely not a tweed or blackface. From the 15W and the controls it maybe a modified Blues Junior circuit.

YouTube demos for what I assume is the same basic, but factory assembled amp, here: https://www.youtube.com/results?sear...d+Pilot+15+amp

Some sound nice, some rather tinny, but that's probably down to the variation in audio recording methods. The cleaner sounding demos are probably using plug-in reverb rather than the amp's spring reverb, which I know on a real Blues Junior, sounds quite different.

[Andy123]

Thanks for looking into it Simon. I suppose I should clarify my goals here.

I saw some examples of cigar box amps where people took cheap & simple (cheap & nasty?), pre-manufactured solid state amps and mounted them in cigar boxes. Most of their efforts went into the aesthetics of the box and the speaker grill etc.

I was inspired by that but was looking to do a valve version. Although inspired by the cigar box movement, I'd be building a cab myself and maybe go for a 10" speaker instead of a 6". Not having to learn much about electronics prior to commencing the project is a plus for me.

I wasn't looking for reverb, so if it's there it's a bonus. I'm not fussed about what era inspired it, or if it's an authentic Fender clone. If it's cheap and makes noise it passes the first test. If it has half-way respectable valve tone instead of solid state toy-amp tone, that's what I'm shooting for.

I guess my main concern here was that the same ebay shop sold similar bundles which were just some combination of parts but not the whole kit. I think the one I've linked to has everything I need minus the chassis/cab/speaker but wanted to check.

Also, it looks to my untrained eye like a bit of a bargain, coming in at a bit less than the cheapest equivalent, the Lamington Jr (which is only 5 watts, has only one tone knob, no reverb, and requires getting one's hands dirty with the circuitry). I'm wondering if there's an expense I'm overlooking before getting too excited about this being a legit option for me. You've pointed out valves and valve holders, but I suspect I could get those at a cost that would still make this a decent option.

[Dedman]

https://www.ebay.com/itm/KLD-Pilot-1...8AAOSwbpVbeD8g

Chassis is available and they will ship to Aus

[Simon Barden]

Things you'll certainly need to get are: IEC mains input connector, knobs and valves. It's not shown, but it struck me that the the amp sockets are probably on the underside of the board. So as shown in the pictures, the amp is shown is a chassis suitable for combo mounting where the valves hang down from the chassis. In a head, you'd rotate the chassis so the valves pointed upwards and the inputs would be on the left of the knobs. You may want to get shielding cans for the pre-amp valves and spring retainers for the power valves if you make a combo.

If you want to make a combo then you'll need a speaker (at least a 10", though I'd go 12" myself) and wood for the enclosure. Don't underestimate the complexity of making a suitable amp chassis as it needs to reasonably strong and you'll need to be able to either bend metal or find a suitable sized chassis where you just need to drill and punch holes etc. The transformers would sit in holes cut in the chassis, normally outside the chassis hanging down in a combo. Ideally the chassis would be fully metal enclosed to reduce the electrical noise emitted and picked up by the guitar.

The input transformer might be an issue with 240v as it's primarily a 110v or 220v transformer. With 240v rather than 220v, the output voltages will be 9% higher, so the internal 260v supply will now be 283v etc, which could possibly be an issue with some component ratings or their longevity. The valves will also be driven that bit harder. Someone like Marcel would be better to advise you on this.