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Newbie…kinda - idea for first build

Started by Maddus, December 17, 2023, 12:29:53 PM

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Hello there,
my name is Martin and I joined here because I have this design idea, and I bet there will be more to come after that. Although I'm an electrics/electronics professional, my knowledge is more about energy distribution, generation and sensors/actors. So I'm not necessarily an expert in signal processing, that's where this forum comes into play.
I have this vision to make a small practice amp, where I use a Drive55 pedal pcb as a preamp and the Vellemann K4001(TDA2003) as the power amp. This will be built into a combo cabinet with a 10" speaker. For the power supply I would like to use a toroidal transformer (2x 6V/1,25A secondary, can be bridged).
My first question is, how do put this all together, what is additionally needed impedance-wise between the modules and modifications on the Vellemann board?

Components links:




G'day and welcome to the forum.
In my opinion the Drive-55 will not have enough output to drive the power amplifier properly, you will still need a pre-amplifier as well.
You can incorporate the Drive-55 in it like a dirty channel but it wount have enough gain by itself. (In my opinion)

PedalPCB have a lot of Preamp pedals and many of them will most likely drive that amp.

There is the Honey Amp project designed by people on this site (Thanks JoeCool) that is a great starter amp, and you can use the Drive-55 pedal with it as well.
Just look at the top right of the page for the link to the shop.

BAJAMAN on the FSB forum designed many preamps that sound like nice amps for stompboxes, and there are vero board layouts for them as well.They should be able to drive the amp.

Aion effects have the Sunn Beta and the Lab Series L5 which are nice.https://aionfx.com/projects/

The Preamp pedals are usually able to plug into the return jack on a normal guitar amp and totally bypassing the preamp stage in the guitar amp itself, basically making it a different guitar amplifier.
Hope I make sense, audio circuits are not my area neither, I am a retired electrician myself but I have extensive electronic experience in industry.DC drives,AC drives PLC interfacing etc on machinery that had up to a hundred motors and pneumatic and hydraulics all tied together.
There are no stupid questions.
There are only stupid mistakes.


Thanks for your suggestions. The drive55 is basically a Fender 5e3 Tweed Deluxe in a box (Catalinbread Formula 55 clone), it has a hi/lo gain switch so it can be also played clean - so it should also count as a preamp pedal. A tonestack is also integrated. So if just the output could be an issue, couldn't I just build a little gain stage (j-fet or opamp) on a perfboard and put it in between? Or somehow beef up the last gain stage on the drive55?


Hi Maddus,
Well be prepared to be disappointed if you think it will sound like a real Fender 5E3.

Some real world understanding is needed before you waste time and effort on ideas like this.

The reality is thus;
What is hardly ever mentioned by all these utube experts trying to sell a new pedal is that a lot of these over hyped pedals rely on the Valve amps they run through.

Rule of thumb for you, even a pedal with Valves will sound crappy through a lot of SS guitar amps.
While even a simple transistor pedal will likely sing when used in front of a well built Real Valve Amp.

WHY you ask?
You only need to send a good valve amp a bigger signal and the power section will gracefully OD/Distort. All that the pedal really does is make the signal a bigger which makes the valves drive harder. it's a magic combination that few seem to understand. the pedal can add a bit of dirt and tweak the tone but it's the Valve Amp that does the magic.

This does not happen with most SS circuits they just clip hard, part of the reason why Tranny Amps got a bad name.

If you want all SS then you have to do all the tricks in the preamp sections. So don't be surprised if the end result you build is a disappointment.

Tassieman has given some options for you and you can also download Teemu K's book on this site on this page and start learning;

I've been building gear for 30 + years and trust me it takes a lot of reading and testing to build a decent rig.

My best advice is to invest in a bread board and start building simple circuits and experiment.

I'm not a teck just a novice who refused to except the hype so I went out and spent the time learning to DIY.
in those years I have only has a handful of success circuits,, the rest was me learning how NOT to waste time building land fill.

While reading and breadboarding I used Cad Sim programs and that was a huge help for me to understand just where in these circuits the mojo is won and lost.
Hope it helps you out.  ;) Phil.


Thanks Phil, yes, Teemu's book is really a treasure for the fact that it is free. I also try to get inspiration from the schematics of the 80s Marshall, Peavey and Lab Series ss amps, but the often use now obsolete components.
My main amp is a Vox AC30, so I don't depend on the builds I'm trying to make, they would be just some grab&go gimmicks - as long as there tubes available.
Breadboards are a good idea, I have them for Arduino stuff, but I didn't think yet of using them for the audio circuits  ::) .


Quote from: phatt on December 20, 2023, 03:00:47 AMthe rest was me learning how NOT to waste time building land fill.
Have you figured out Phil ?
No more landfill ?
Please tell me the secret, I have been doing it since the mid 1970's and I am still working on landfill all the time. :)
There are no stupid questions.
There are only stupid mistakes.


Quote from: Tassieviking on December 21, 2023, 10:29:13 AM
Quote from: phatt on December 20, 2023, 03:00:47 AMthe rest was me learning how NOT to waste time building land fill.
Have you figured out Phil ?
No more landfill ?
Please tell me the secret, I have been doing it since the mid 1970's and I am still working on landfill all the time. :)

Yep tiss easy to just dive in and build stuff but I think most of us fail to realise that it may have worked for the bloke on utube but we forget that while his guitar/amp setup might sound good,,, our setup will likely not reproduce the same results.
There are just way too many variables so you are just shooting arrows into the air and missing every time because you have no full knowledge of the target.

So I always BBoard test ideas first through as many amps & speakers as I have.(even head phones)
While it's all on the BB I also simulate it as well.
This is where you can clearly see just how each section is winning or loosing the magic.
You might find one section is hard clipping too early.
You can also tell where there is too much, to little bass or treble.
You then adjust the test circuit until you get a good balance.

If you put in the time for the R&D then you build far less land fill.

Same goes no matter if it's Pedals, SS Amps or Valve Amps.

I recently modded a small Mesa amp.
The balance between the 2 channels was unusable.
Again I could have wasted hours or dayze changing component values and guessing.
Just by using a simple sim of the preamp stages it only took 2 days to work out how to tweak the circuit to bring the 2 channels closer to a usable balance of drive and tone shaping.

I have built many circuits in my garage that I thought sounded great only to find that on stage they just turned in to crud. :'(

I think my brain has trained itself over the years to pick tone and harmonics.

A bit of trivia;
Some years back I was watching as SBS doco on the study of music where they had 20 or so Conservatorium students in a massive cathedral in Europe. (Names escape me)
The Cathedral housed one of the largest pipe organs on the planet. wow 8)
A blind test was setup for the students where they had to pick the REAL Organ from a Digital Organ which had been setup in the same cathedral.
The samples for the Digital organ were taken from that very same organ.

The same organist played the same piece on both the real and digital organs

Before the second piece had finished I picked the real one.
My Wife was struck by my ability,,, she asked how on earth could you tell?

I said that was easy to pick because the digital organ had far more bandwidth,, the real organ does not have all those hi freq artifacts.
(I may have had a slight advantage because I've heard a few big pipe organs in my youth)

This is why I keep trying to tell guitar players that they will never sound like the old amps because most gear now has way too much bandwidth.
Those old famous Valve amps had very limited bandwidth.
So modern gear including a lot of fancy pants Valve rigs suffer because of that very same issue.
hope it helps folks who are chasing the many secrets of amplification of musical gear.