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Messages - Lex

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1
The Newcomer's Forum / Re: Some wisdom regarding speakers
« on: Today at 05:13:16 AM »
Thanx all for your reply,

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

Cheers

2
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

3
The Newcomer's Forum / Re: Some wisdom regarding speakers
« on: February 17, 2020, 08:54:35 AM »
Thanx Enzo,

this means: there is no way to be reasonable but to try it all ..

was a bit afraid of that. It's a justification of GAS ...

Cheers

4
 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 ├ílso  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;
 
Quote
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?

 
 
Quote

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. :loco
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

5
The Newcomer's Forum / Some wisdom regarding speakers
« on: February 16, 2020, 09:09:41 AM »

 
 Any worth of getting used 10 inch speakers from old Peavey Backstage (late '70, CST), so called 'squareback' for an external cab?
 I mean, Im 'educating' my self and trying many things just to understand what Im hearing (and why of course).
 It brings (un)necessary costs with it.

 So, would I be just better to go for a new modern speaker(s) or take a risk and spend less money (about 1/3 of the price of the new one) for my 'tests'?

 Im I reasonable ..?

 Greetings

6
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:

Quote
" 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

7
Hi all,

got carried away with this thought about multiple diodes and after some brainstorming I made a simple schematic (according to my knowledge based on auto-moto electronics) .. with some on-line schematics tool.

I would like to hear if my thinking is logical or not.

CR 1 & 2 are removed, there comes a socket (J1 & 2),
2 x switches (S1 & 2),
repeating diodes D1 - D10

Greetings



8
Quote
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

9
Hi Phil,

thanx for your explanation.

I had to read it 3 x to really understand what you meant.
Im not that good within electro-language-slang.

But I got your message.

Quote
As Joe has already mentioned you can use Leds if you want as they have a higher breakdown voltage so distort later. the big gotcha with any diode dirt circuit is the dreaded fizz that often comes with the dirt and most of the low wattage bedroom amps don't bother to filter out the fizz and they often sound quite harsh.

Do you want to say just it's a too small / 'bad' amp for such experiment ?

Cheers

10
Software / Re: Zoom G5 software
« on: February 12, 2020, 07:21:40 AM »
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

11
 Thanx, got it.

 This socket is a great thing, I was not aware of it.

 After your message I did my own research around this mod and I have learned that a lot of old SS amp's are based on the same principle.

 And I found out that there are mode diodes / combinations that could be used;
  • 1N4001 silicon
  • 1N34A germanium
  • 1N4148/1N34A
  • Red LED/1N34A 
  • Red LED
  • Yellow LED
  • Yellow LED/1N4148   
  • 1N4148/2x1N4001
....
 So if I understand it good, all this possibilities makes it kind of a pedal.
 Now I wonder (only if my understanding is right) if would be possible to make an extra circuit board, to put different diodes and combinations and to have switch(es) for selecting?
 Please, if this sound's silly .. it's only a thought of an amateur.
 
 Thanx again,
 
 Greetings

12
Hello Phil,

thank you for the reaction.


Still a few questions;
   
Quote
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 ?
 
 
Quote
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

13
Hello,

got schematics from Fender, however its not really good read (for an amateur)  .. cant find those 2 GAIN pot's for the orientation ..

It's in the attachment so I hope some good ppl would understand it and being ready to advice,

Greetings

14

You'll need the proper schematic.  According to Fender's list, you can get a PDF copy: https://support.fender.com/hc/en-us/articles/212774686-Fender-Guitar-and-Bass-Amplifier-Owner-s-Manuals-and-Schematics-Hard-Copy-Archives

There is an email address to write to linked at the top of that page.  Send them a message and they'll send you the PDF.

Thanx , I'll check it there first

Greetings

15
Hello good people from SSGuitar forum.

It's nice to see enthusiasts and professionals who are still in love with old stuff.
I've been reading for a few days several treads and now decided to post mine.
But first about my skills;
- Im a mechanic by default,
- I have some experience with electronics. I can repair electronic stuff, solder, exchange components and such.
But I dont know why certain resistor or diode or capacitor is placed somewhere and what that particular part is doing there.

I have one Fender Frontman / Bullet 15W Reverb Pr-241.
It's doing good, exept this well known BUZZZ ..
Found out that I need a really good grounding and I took a wire from the radiator and connected to the chassis.
Buzz gone.
Then I removed the wires from the speaker, removed (external) ground wire and connected to 12" Celestion. No Buzz and very good sound.
Well done Fender, this amp sounds good.

Now I have the second small SS amp, a Squire Champ 15GR Pr-CPR1.
Overall is working good, however it does not sound good as it's brother- the Frontman. A difference in sound as night and day.
This model has 2 GAIN pot's and no distortion switch and no AUX input.
Also Im not sure about the schematics, If I found on-line a good one as non of them are with 2 GAIN's.

Now what I would like to change or improve on this Champ amp:
 1. First and most important:
 - there is a 'light' distortion sound all the time, with or without Reverb, I can hear it all the time so also on the clean channel (the matter of a setup of 2 GAIN pots),
 2. the overall sound is kind of 'shallow' .. 'flat'.., I miss the richness of the Frontman. Tried it also on 12" Celestion.
  - so a bit nicer, fuller, richer sound would be appreciated.

Both amps will be NOT PLAYED on stock speakers but on a external cab.
 
I found on this forum some good stuff about diferent kind of diodes and swapping them, however I could not spot the right part on my board to compare it.

So my humble question would be:
 - if someone could 'guide' me to the right place on the board for exchanging diodes / resistors ... like I found in other treads regarded to Squier 15w.
 
I hope I was clear with my explanation (and my English).
If there are some other / more questions Im more than ready to answer them - only way to lean new things!

Greetings

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