Suggestions for a DIY amp?

[knutolai]

Hi! Hope everyone is doing well.

So I've finally had it with repairing my Fender Princeton 65 transistor amplifier, and thought it could be a fun project to keep the cabinet, speaker (8 Ohm) and amplifier compartment and swap the amplifier for something else. What I'm looking for is a minimalist clean amp for testing guitar pedals in my workshop at a comfortable level (I have very close neighbors). I'd actually be fine with just a master volume knob as far as parameters go and I wish to stay away from tube designs.

Any recommendations?

In case anyone is interested in the manual for the 65 solid state:
https://www.fmicassets.com/Damroot/Original/10001/OM_leg_gtramp_Princeton_65.pdf

[patrick398]

Following.
I'm in a similar position actually. Picked up a Gem Mars 30 for free but there are no schematics for it anywhere and i've been told it's a pain in the arse to fix and the costs exceed the value of the amp, which is a shame, they're cool amps.

[stallik]

This lockdown and the accompanying need to keep the noise levels down have led me to start using Deadastro's Astrosim and some headphones to do my pedal auditioning. Clean sounds through the phones sound remarkably close to my amp and distorted tones are close enough to do the lions share of work before firing up the amp.

[soggybag]

I built a Weber kit. They have a lot to choose from. The kits don't provide much help, just parts, schematic, and layout. You can get them with a chassis only, or with a cab and speaker.

[marcelomd]

I'm building (very slowly) a modded Fender 5e3. It's the simplest tube amp I know.

The hardest parts were sourcing everything and making a custom chassis+cabinet.

There are kits if you want all the fun and none of the chores.

[willienillie]

5F1 Champ is simpler, cheaper to build, sounds great, and only has one knob.  Not much headroom, but with the right speaker(s) can be good for low volume pedal testing.  Not sure if OP wants to build a tube amp though.

[vigilante397]

I've built a handful of amps, and I agree 5F1 is a great one for a beginner. Not a lot too it, hard to mess up, and frankly a great sound. I built mine into a 1x8 combo, and lately it's been the only amp I really play as it's the only one I can get away with playing when kids are asleep

A headphone amp is also a great idea, and the Astrosim is top-notch.

[Marcos - Munky]

I think that, if the purpose it's just to play at low volume and to test a few pedals, it's better to just build a small amp based on some chip-amp (like the 386) or a headphone amp and use a cheap speaker/whatever headphone you have on hand. Those cabinets and speakers will have a better use as a nice amp, like a tube amp or a good solid state amp.

Btw, Marcelo, there's the 5f1, which is simpler than the 5e3. You can say the 5f1 is kinda a smaller 5e3 with just one 12ax7 and a single 6v6 to get about 5W on single ended configuration, while the 5e3 uses two 12ax7 and two 6v6 in push pull to get about 15W. One is suited for lower volume (but 5W is way louder than some may thing) while the other is suited for smaller performances/stage mic'ed amp. I'd say the difficulty difference between them is something like a difference on building a bufferless tube screamer and a buffered tube screamer. And both are great amps.

For the 5f1, I just finished one 2 days ago (well, it's still missing the power switch and cabinet but anyway). It's my 8th tube amp and, despite it's simple design, it sounds very good! Actually, for a clean and low volume strato playing, I liked more the sound of the 5f1 plugged in a cheap 5" or 6" speaker than the sound of my P1 plugged in a 12" Jensen speaker!

[slashandburn]

Lm386 amps were my route into pedal building and how I ended up here pestering you lot.

What's to lose? A small handful of components, runs off a 9v battery, minimal risk of electrocution. If the words "clean"  and "headroom" don't figure into your vocabulary id recommend it.

The novelty has worn off a bit now - theres plenty other chips that can drive an 8ohm speaker without having to mess around with transformers - but it was a fun introduction that cost me less than the price of a 4-pack. I still use some of them occasionally. Mostly as desk/test amps but also occasionally when I'm wandering around the house, thanks to a friend of mines who saw an early Smokey Amp type build and said "you should get a belt-clip and hook that thing to your guitar strap".

All that said, I've been looking for a headphone amp build for all the same reasons stallik mentioned so I've just just taken note of the Deadastronaut circuit he mentioned.

Edit: on second thought, a 386 is no real substitute for a Princeton. Unless of course your issues with the Princeton are that it's too loud and doesn't sound like a very poor man's plexi.

[marcelomd]

Nice. Didn't know the 5f1.

Well, if you want clean volume, there are those cheap class D amps on eBay. I bought one to use with both bass and guitar. Just change the preamp.





Still missing the power switch and a step down regulator to provide power to pedals.

60W a into 8 ohms is a lot for guitar. Ok for practicing with the bass.

[Elijah-Baley]

My problem with solid state amp that need higher voltage is the way to power up.
It's ok if I built amp based on LM386, but I would like to build something powerful. I just omitted in my cart in the last order the 60w amp PCB because I don't know what PSU I have to use.
A good one could be something come for laptop (19v-24v, 3A or even more), but I don't have any. And those are not built for audio device, and sometime them can make noise that can't be filtered, as someone told me.
It's hard for me buy something used and to pay just a few money. But even if I buy a new one it's a bit like a lottery.

If you want some mini amp but loud enough and working at 9v try to take a look at this:
http://www.diyguitarpedals.com.au/shop/boms/10%20Min%20Amp.pdf
It seems very nice.

I would like to build it by my self on veroboard but I didn't built it yet, because there's something I can get in the schematic and the PCB.

[cab42]

I have built this, based on a tda2050. Pretty much data sheet circuit. Single supply, powered by a laptop power supply.

https://www.diystompboxes.com/smfforum/index.php?topic=57018.0

works great.

I actually have an almost finished vero laying around. Just need to solder in the tda2050. My last one died due to poor mechanical construction of the enclosure.

[bluebunny]

A good one could be something come for laptop (19v-24v, 3A or even more), but I don't have any. And those are not built for audio device, and sometime them can make noise that can't be filtered, as someone told me.

The Tiny Giant was designed to use a laptop PSU.  Take a look at the schematic to see what was done to minimise noise reaching the rest of the amp circuit.

[Elijah-Baley]

Well, the Tiny Giant Amp seems have about a common noise filter in the power supply: a 100nF to the ground after the power and before a regulator, then a big 470uF electrolytic cap.
Anyway the Tiny Giant Amp works kind of at 12v. That class D 60w amp can work well, I guess even at 19v or something more.

The thing that some guys told me is that some laptop PSU are noiser because doesn't have the noise filter in the input, so doesn't care how much we can filter our circuit.

[Marcos - Munky]

I have a very small 30W class d amp based on some tda I don't recall the number and I can't check because I glued a heatsink (not really necessary, but safer than sorry). I'm powering it using a laptop power supply @ 19V. Then I'm using a dc step down converter to low down the voltage to 6V, which powers a 555 smps (to get high voltage for a tube preamp) and the tube heaters. All fits a 1590B (well, I had to put the class d board outside of the box, no big deal). And I have no noise at all, it's quieter than a Hi Octane I built.

Maybe I was lucky to get no noise even with all those power conversions, then I took another shot: the same class d board and a UC2842 smps to get 200V and power a mesa boogie preamp, everything powered by a different brand laptop power supply. Besides the expected tipical noise from the (very) hi gain preamp, this one is also quiet.

Maybe I'm lucky. But I'd say to give it a shot and see what happens.

[tubegeek]

I've been VERY happy with this, and my application is exactly what you are talking about.

https://www.diystompboxes.com/smfforum/index.php?topic=123650.msg1170231#msg1170231