Radio to guitar amplifier

[sluckey]

4Ω, 5Ω, 8Ω... It's all the same to that little radio.

[Synchu]

With SE EL84 radio as a base, you could build a decent 3-4 Watt amp. I did TW Rocket pre into the said config recently (see the Trainwreck section) and it sounds great, I also tweaked a SE EL84 based 5F1 with some Tweedle Dee mods (see the Dumble files section) and it also sounded great.
For the TW Rocket, I used a 12AV7 for the third gain stage and the half PI and it sounded even better.

So EL84 SE radios will be a good donor, if you manage to find one.

Niki

[dotfret]

4Ω, 5Ω, 8Ω... It's all the same to that little radio.

That is not a bad guess. Running the radio output transformer into a 4 ohm load could cause problems with sustained output at full power. Into 8 ohm you would not have a problem, but it would be a little quieter, and likely add a little grit to the tone.

[TomJS]

With SE EL84 radio as a base, you could build a decent 3-4 Watt amp. I did TW Rocket pre into the said config recently (see the Trainwreck section) and it sounds great, I also tweaked a SE EL84 based 5F1 with some Tweedle Dee mods (see the Dumble files section) and it also sounded great.
For the TW Rocket, I used a 12AV7 for the third gain stage and the half PI and it sounded even better.

So EL84 SE radios will be a good donor, if you manage to find one.

Niki

Just asking would a single ended el84 be loud enough to gig with? Of course, il be micing it like I said I'm an aspiring audio engineer. Would I need to get a really high-efficiency speaker for it to be a decent volume or would a normal speaker be just fine?

[TomJS]

With SE EL84 radio as a base, you could build a decent 3-4 Watt amp. I did TW Rocket pre into the said config recently (see the Trainwreck section) and it sounds great, I also tweaked a SE EL84 based 5F1 with some Tweedle Dee mods (see the Dumble files section) and it also sounded great.
For the TW Rocket, I used a 12AV7 for the third gain stage and the half PI and it sounded even better.

So EL84 SE radios will be a good donor, if you manage to find one.

Niki

O and how would I be able to add multiple gain stages? Wouldn't I need to totally rebuild everything and if so do you have schematics that can help me?

Thanks and regards,

Tom

[Synchu]

Hey Tom,

At 3-4 watts it won't be enough for gigging without micing for sure, no matter the speaker. With micing, even a 0.5 watt will do.

Here's the last amp that I built, using scavenged radio transformers (it was a SE EL84 power amp ) :
https://ampgarage.com/forum/viewtopic.php?f=1&t=31462

It is the said TW Rocket preamp with SE EL84 power amp.

I still have to do the schematic for this one, but it will take some time for me to get to it, but it is not much more than what I said already

Niki

[tubeswell]

I think the talk about 240 vs 230 or 220 volts is confusing you a bit Tom.

What matters in this instance, is that you put an isolating (power) transformer between the amp and the mains. (You can build it into the same cabinet as the amp). So a 1:1 power transformer with a minimum 60VA (60W) rating will work. 100VA or 120VA etc is even better as it will experience less heat stress. A 1:1 power transformer reproduces the same voltage on the secondary, as whatever the wall voltage is on the primary.

All you need to do is:

1) hook the power wires in the stock amp circuit directly to the secondary winding of the 1:1 transformer.

2) run the primary wires of the PT to a mains connection socket mounted on the amp chassis - via a mains switch and a mains fuse. At 60VA, the mains fuse wants to be rated at: (60/230) x 2 = 0.5A. The switch needs to be a 250VAC rated switch that can carry at least 1A - available through most electronics suppliers.

3) securely clamp a multi-strand wire to a ring terminal for your earth connection and secure this to the chassis with dedicated grounding bolt secured firmly with a lock-nut. Run the other end of this wire to the ground lug on your chassis-mounted mains socket). Flow solder into the ring terminal - after you have clamped it first to secure a tight mechanical connection.