project: mini amp

makepeace

So I have my deluxe and it sounds fantastic, but there's a problem. For most of the year I stay in a small flat in Cape Town, and true to form, the neighbors have been neighing about volume.. Thus the need for a small amp to play at +- TV sound levels.

I would ultimately love a 5W attenuable tube amp, something along the lines of a Champ, but I'll leave that project in the pipeline until I've saved a bit of cash. My goal now is to build a small SS amp, that will put out between 0.5 and 1W, with the capability to run on a battery.

The circuit will be based on the Ruby, a 9V audio amplifier designed for guitar based on the LM386 audio amplifier IC.

I will also be including a tone control based on the Baxandall tone shaping circuit, wired on a dual concentric pot.

I'll be using the 386-4 IC, which is rated up to 18V supply so that I can use a higher supply voltage to somewhat minimize the losses of the tone circuit.

I'm going to build a nice mini head and cab arrangement with some stuff I have left over from my deluxe build.

I will be using 2x 4ohm Pioneer 6' drivers in series. They're obviously not ideal as they're car speakers and not voiced for guitar, but I have them lying around and hopefully they will sound ok. I will always be able to replace them later.

All in all I'm anticipating a cost of about R200 excluding the stuff I already have.

More soon.

ezietsman

Instead of building another amp, why not install a VVR control onto your 5E3? They're pretty simple on cathode biased amps. You'll need a 12V zener diode, two 100k resistors, 1 10ohm 5 watt resistor, a NTE2973 mosfet and a pot to control the voltage. That way you can have TV levels on your big amp (OK it won't sound as good as it usually does at these low levels) and it will sound better than a little toy amp.

You may need another diode or two if you want to scale only the PI and power section instead of the whole amp.

bottledtone

I'm still wanting to get some pencil valves and build a dc to dc step-up and build a tiny valve amp.
But for now i'm building a more traditional 2watt with three valves. The power amp is a 12AU7.
Its a hybrid of the lil night train and a tiny terror.

makepeace

ezietsman wrote: Instead of building another amp, why not install a VVR control onto your 5E3? They're pretty simple on cathode biased amps. You'll need a 12V zener diode, two 100k resistors, 1 10ohm 5 watt resistor, a NTE2973 mosfet and a pot to control the voltage. That way you can have TV levels on your big amp (OK it won't sound as good as it usually does at these low levels) and it will sound better than a little toy amp.

You may need another diode or two if you want to scale only the PI and power section instead of the whole amp.

What?! And contaminate my beautiful already vintage incorrect amp with SS tone suck?! ? Jokes, yeah I have spoken about the VVR with Mike and tbh, I don't have space in that chassis for any more knobs or components. Just commissioned the final chassis to be cut and plus, I really dig it like it is.

Also this is more of a bargain build if you will, mainly its just something to do that doesn't need a whack of cash thrown at it.

bottledtone wrote: I'm still wanting to get some pencil valves and build a dc to dc step-up and build a tiny valve amp.
But for now i'm building a more traditional 2watt with three valves. The power amp is a 12AU7.
Its a hybrid of the lil night train and a tiny terror.

Cool project BT, what are you using as a preamp and recto? I thought the tiny terror was more powerful. Doesn't it run off cathode biased PP EL84's?

I'm quite interested to hear what this ruby circuit sounds like, they say it does a valve reenactment pretty well.

Somewhere down the line I might even build a new baffle and put a bigger speaker in and throw in a lil valve amp.

bottledtone

The tiny terror does use the EL84's but will steal the preamp, PI and toggle a tone stack in and out of the circuit. Just using a bridge rectifier ss.

How about making a outboard reverb unit and then have a jack output that bypassed the reverb tank that you can put straight into a 8 ohm speaker? Reverb for existing amp switching to low powered amp itself?