Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Thanx Phil,

u got a msg back

Cheers

Quote from: Lex on February 22, 2020, 05:13:16 AM

Thanx all for your reply,

it's obvious .. buy them all, try them all .. and probably keep them all !!!

Cheers

I like the way you think lol.   

yeah .. have the same with the cars, bikes, ski's .. and probably other stuff

still much cheaper than keeping a women around

Hi Phil,

thanx .. im overwhelmed with your reply and need time to read and understand.

Mostly intrigued my the last 2 schematics, as I can see you have changed the positions of 4 diodes / resistors within the circuit ?

So this gives different amplitudes (and the sound as the final output).
What does represent the 1st simulation and what the 2nd in terms of sound?

Regards

 ok Gent's, thanx again.
 
 I fully understand comments.
 
 Those links are very usable. I need some time to read it and understand it, its not easy.
 
 And yes I agree about the single channel amp.
 Im running álso  Laney K30 single ch. keyboard/guitar amp (their first SS amp from 4 decades ago, got it almost unused) and Zoom FX thingy.
The sound is much much better than playing through those 2 small 15W Fenders on 12 inch speaker.
 Difference like day and night.
 However, tweaking that Champ Squier remains as a challenge to me.
 
 Enzo, yeah that's obvious!
While drawing didn't recognise that solution (not used to draw circuits) but in the real life I think I would see it myself.
 Thanx for your comment.
 

Now the second reply based on Phil's last comments;
 

BTW I've just been studying the Schematic for this Amp and it's dawned on me that the output of power chip (pin1) connects to both +&- terminals of the speaker. 
 Maybe I've missed something but might be a mistake.

Unfortunately I cant see that on this schematic.
 But I suppose it's a weird construction?

 
 

Also regards to the amp distorting even at low volume;
I just simulated the preamp and a 100mV signal at input does not distort until you turn up past halfway.
But I notice the FB resistor around power chip is 130k.
surely that is rather high and I'm guessing would distort even at low gain. (And that was the main reason for *Lex's* initial post)
The schematic is not very clear and I can't read the part number on the power chip.

Out from my curiosity, how do you simulate a pre-amp ?
Some software where you put and connect all the components and then observe amplitudes .. ? (cant imagine sound)

And yes there is a slight distortion on the clean channel, in combination with a 'flat' sound.
Second Gain pot all the way turned to 0.
I did not drive this amp more than 1.5-2 on the volume pot.

If you could point to this 'power chip' so I know where and what is it, then I could make some tweaks in the photoshop to get more clear reading of schematic?

Im enjoying emojis too, they are great !!!

Greetings

Phil & Joe thanx,

the purpose of re-building this old cheap Champ amp is purely to learn, understand and improve the sound and my knowlegde, if possible. 
Im re-entering music again after many years.
This time Im gonna learn to understand and not just interpret someone elses music. Or gear..

While drawing I did not pay attention to the polarity of diodes as Im not used on their graphical appearance.
But I do assume that all diodes should be wired in the same way, probably positive (+) as input and negative (-) as output.
I think this was a wrong assumption now.

So this explains where I made a mistake:

" wiring back to back in the loop" and
  + -
<     >
  - +

I have attached changed polarity for S1 section of diodes, I hope I understood your comments gent's,

Thanx

Greetings

That experiment would work, but I think what Phil means is that it may not sound great with anything due to the way the rest of the circuit is built.  I still suggest the sockets.  Then you can swap as much as you'd like.  If you find that you like more than one combination, you could build a little daughter board with switching to swap between the combinations as you talked about.  My guess though is that you will find one combo that works best and you'll stick with that.  Most circuits end up with a kind of "sweet spot" where things just fall in place.

Ok thanx, Im getting it.

I think most of my assumptions were correct.

So what I think that I need is 8 sockets, 2 switches, wire's, and few diodes, exchange them in the search for that 'sweet spot' (lucky me, I have just around the corner a shop with a lot of old school electric components) - the socket/diode Mod.

At the end, I still have a Zoom FX thing for all kind of sounds however I appreciate old school analogue handling and control.

Thanx all again, I got the answers.
I'll come back with the report over my achievement.

Please do not hesitate if you have other idea's about this small amp and possible mod's.

Greetings

Hi,
as far as I know you will need an USB interface between FX and a PC.
When I got mine Zoom I got Behringer U-Controll UCA202 as a smallest and affordable for learning / experimenting.
It works good with Audacity.

Also very handy with the Zoom;
ToneLib ZOOM https://tonelib.net/zoom-quick-start/
It gives you the full control over the Fx box from your computer.

Cheers

Hello Phil,

thank you for the reaction.


Still a few questions;
   

Just remove CR1 & CR2 for clean.
   Or you could wire up a switch to switch those 2 diodes in or out of circuit for clean or dirt.

•   this means for each diode 1 off/on switch?
   so when the switch is OFF, that means that same diode is disabled ?
• for my purpose of learning: are those CR1 and CR2 a 'bad' diodes, are there a 'better' one for possible replacement - or it's just old school SS amp design?

edit: found an info at  http://www.tpub.com/neets/book7/27m.htm ,  is this diode mod about same/similar thing - "Rectifier action of CR1 and CR2. NEGATIVE / POSITIVE ALTERNATION ?
 
 

With diodes out of circuit you will find there will be a lot more clean but being a small amp it will still distort when volume is high.

• being a small amp as 'small' aka SS 15w or small because of the speaker?
  I will use a single 12" or (2x) 10" - so to an external cab.

Greeting