Hybrid low-voltage tube pre-amp to TDA2030 Poewr amp

[pdavis68]

First of all, I'm an electronics hobbyist with little real experience. I used to play around with robotics and now I'm trying to build a little guitar amp.

I'm about to build this tube pre-amp. Yes, I know it's low voltage and won't sound like a high voltage pre-amp. I'm okay with that. I'll do a high voltage pre-amp another day...

So what I want to know is if there are any concerns I need to have running the output from that into an amp built on a TDA2030A chip? Can I just run it straight into the non-inverting input of the TDA2030A?

I was actually going to build an LM1875 based power amp, but I have this crappy little Crate practice amp (GFX15) that I opened up and managed to salvage the 2030A with a heatsink from it, so I'll just use that instead. In fact, I'm going to use the chassis, transformer, speaker and case from the Crate and just replace the electronics with something that sounds less crappy (hopefully).

 

[Bigun]

I think this Ruby Tuby preamp will have too much gain for you and it's some kind of guitar thingy besides. I think something like a simple cathode follower will be a better choice for you if you want a tube on the front.

http://www.decdun.me.uk/gainclone3.html

 

[sreten]

Hi,

IMO you can find find wild and wacky transistor power amplifier
schematics in service manuals that are clearly godawful hifi
amplifiers, but are ten times better than any chip amplifiers.
Peavey schematics are a good place to start.

rgds, sreten.

 

[pdavis68]

Bigun, this is for a guitar amp.

 

[johnr66]

The tube preamp in your link has high output impedance and will have trouble driving the TDA2030A input. You would need a buffer or some circuit changes.

 

[JMFahey]

Use it as-is, I guess you want some distortion anyway, but replace the straight A100K volume pot with an attenuated version.
100K in series with a 10K or 22K Audio/Log pot will be fine.
Will solve both level and impedance issues.
Please post some MP3 or even better, some YT video 😉

 

[pdavis68]

Thank you, thank you, thank you. That's exactly the kind of stuff I wanted to know. Impedance is something I'm struggling with. In the Ruby Tuby, is the output impedance the 100K + whatever the pot is at + the capacitive reactance of the 0.01uF there? A lot of the material I've read is kind of hard to follow on this topic, but I'm under the impression, in this case, that it's the impedance from the +12V down to the output. A lot of stuff uses vague terminology like "the impedance of the circuit". (I really need to go back to school and take an electronics class).