Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => The Newcomer's Forum => Topic started by: Lex on February 04, 2020, 06:38:40 AM

Title: Introduction, a question and a hope for some insight / help
Post by: Lex on February 04, 2020, 06:38:40 AM
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
Title: Re: Introduction, a question and a hope for some insight / help
Post by: joecool85 on February 04, 2020, 10:32:15 AM
Quote from: Lex on February 04, 2020, 06:38:40 AM
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 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

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.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Lex on February 04, 2020, 11:07:22 AM
Quote from: joecool85 on February 04, 2020, 10:32:15 AM

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
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Lex on February 10, 2020, 05:24:28 AM
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
Title: Re: Introduction, a question and a hope for some insight / help
Post by: phatt on February 10, 2020, 05:43:43 AM
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.
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.
Phil.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Lex on February 10, 2020, 03:05:31 PM
Hello Phil,

thank you for the reaction.


Still a few questions;
   
QuoteJust 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.


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 ?


QuoteWith 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.


Greeting
Title: Re: Introduction, a question and a hope for some insight / help
Post by: joecool85 on February 10, 2020, 08:33:49 PM
Quote from: Lex on February 10, 2020, 03:05:31 PM
Hello Phil,

thank you for the reaction.


Still a few questions;
   
QuoteJust 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 ?


QuoteWith 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

CR1 and CR2 are 1n4148.  These are very similar to the old 1n914.  While there is nothing wrong with these diodes, I know from experience that they tend to have a more "fuzz" type of distortion.  If you would like more of an "overdrive" sound, try replacing those two diodes with red LEDs.  Make sure you have them with one facing one direction, and one the other (just like the original diodes).  An even better idea is to solder in two sockets and then you can swap diodes at will and see what sounds best.  Some circuits, like my own 5th Gear Overdrive, use two different diodes.  In my case, 1n914 and a red LED.

Here are some diodes that you could try: http://smallbear-electronics.mybigcommerce.com/silicon-signal-1/ and http://smallbear-electronics.mybigcommerce.com/led-t-1-3-4-5mm-diffused/

And the sockets: http://smallbear-electronics.mybigcommerce.com/single-in-line-mill-max/
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Lex on February 12, 2020, 07:13:16 AM
 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;
....
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
Title: Re: Introduction, a question and a hope for some insight / help
Post by: phatt on February 12, 2020, 07:16:32 AM
Quote from: Lex on February 10, 2020, 03:05:31 PM
Hello Phil,

thank you for the reaction.


Still a few questions;
   
QuoteJust 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.




  • 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

Small Amp ; means small wattage and small speaker = not much clean headroom.
small chip amps distort very quickly once you try to get a large volume due to the simple fact that they run small transformers and low wattage chips.

Regards to how diodes work to create dist just study some of the OD dist pedal circuits.
The Back to back diodes has been around long before distortion pedals were invented.
basically they limit/clamp the signal swing to the voltage breakdown of whatever diode you use.
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.
Phil.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Lex on February 12, 2020, 07:38:35 AM
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.

QuoteAs 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
Title: Re: Introduction, a question and a hope for some insight / help
Post by: joecool85 on February 12, 2020, 08:51:24 AM
Quote from: Lex on February 12, 2020, 07:38:35 AM
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.

QuoteAs 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

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.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Lex on February 12, 2020, 09:21:00 AM
QuoteThat 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
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Lex on February 15, 2020, 11:11:44 AM
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


Title: Re: Introduction, a question and a hope for some insight / help
Post by: joecool85 on February 15, 2020, 06:54:54 PM
Quote from: Lex on February 15, 2020, 11:11:44 AM
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

This should work with the exception that it looks like all diodes are facing the same way.  The diodes in the "S1" section should face the opposite direction as the ones in the "S2" section.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: phatt on February 16, 2020, 02:03:24 AM
Yes,, what Joe said.  You wire them back to back in that loop.
lay them side by side and they should look like this;
  + -
<     >
  - +
Just be aware that there is no magic diode involved here it's the combination of distortion (Dirt) or whatever diodes you use. The secret to great OD/Distortion/Fuzz is in the tone shaping of the circuits NOT so much the diode type.

So Leds might work for one circuit but sound crap in another amp circuit.
There are just so many combinations of how to do these tricks and then add to that; Each player might want something quite different.
Hence you see Utube clips where someone raves about how good the latest Dirt pedal sounds but you get it home and it sounds nothing like what you heard.
Because your guitar-Amp- speaker- style of music you play- talent level-blah blah.

As mentioned before, a lot of small bedroom amp designs are off the shelf circuits and they don't tend to put much effort into tone shaping to suit the speakers used.

I'm not trying to put you off ,, by all means experiment as that will slowly teach you how to interpret sound/tone.
I've been experimenting for years and it takes a while to find what works and what is a waste of time.
Phil.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Lex on February 16, 2020, 04:16:32 AM
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
Title: Re: Introduction, a question and a hope for some insight / help
Post by: phatt on February 16, 2020, 09:02:54 PM
Yes much better :tu:

There are 2 basic ways to do this Distortion trick.
1/ across the signal path and 2/ in the feedback loop.
Although your setup is in the Fb loop this page might help you understand that it's not just about what fancy pants diodes are used.

This explains the finer details of how diodes work across the signal, often driven by an opamp stage.
https://sound-au.com/articles/soft-clip.htm

In your case you might do well to back off the gain of the input stage as that will slow down how early the amp goes into distortion.
That may well be easier to do that muck around with a whole lot of diodes.
Phil.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: phatt on February 17, 2020, 12:30:17 AM
Oh I forgot the obvious page,
Here is a good explanation of the TS9 circuit by R G Keen of Geofex;
http://www.geofex.com/Article_Folders/TStech/tsxtech.htm
It explains how BB diodes work in the fb loop of an opamp which is the type your circuit uses. :tu:

FWIW,
I've come to the conclusion that I'd rather work with a single CLEAN channel amplifier and just use pedals for all the other FX.
My main working amp is not even a guitar amp,, it's an old Keyboard amp with treble bass and volume, but does have a real spring reverb. All the fancy tricks are on my pedal board and forgive me for blowing my horn here but half of those pedals are my own designs or modified brand name units. Took many years to work out what I wanted,, an sure many of those designs ended up as land fill but in the end I got exactly what I wanted.

WHY pedals?
Cause I'm yet to meet a player who uses multi channel amps and totally happy with all channels. :lmao:
Unless you are rich and can afford to have someone custom build exactly what you want then it's likely most of the off the shelf shop rigs will leave you less than impressed. :(

I spent years trying to get an ALL in ONE amp to work for me but in the end I resorted to pedals. I don't like pedals but for me I'm playing many different styles of music and the pedals cover most of what I need.
Sadly pedals are an evil necessity for me,, it's a love hate thing. :-X

Reason 2/
It's a heck of a lot easier to swap out pedals than it is to have to rebuild amplifiers all the time until you find the sound you want.
My rant over for now,, hope it helps
Phil.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Enzo on February 17, 2020, 12:39:40 AM
Well you don't have to turn all the diodes around, just turn the two-pin connector around.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: phatt on February 17, 2020, 07:16:49 AM
Quote from: Enzo on February 17, 2020, 12:39:40 AM
Well you don't have to turn all the diodes around, just turn the two-pin connector around.

Ha Ha very good. :P
Thanks Enzo trust you to see the simple way to do it. :tu:

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.  xP
Maybe I've missed something but might be a mistake.
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.
Or maybe I'm just not tecky enough to know what I'm doin,. :lmao:
Phil.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Lex on February 17, 2020, 08:49:18 AM
 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;
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
Title: Re: Introduction, a question and a hope for some insight / help
Post by: phatt on February 17, 2020, 08:59:02 PM
Hi Lex, this might be helpful.
Basic opamp designs explained,,minimum maths.
https://neatcircuits.com/op_amp.htm

It's beyond the limits for most of us to give a blow by blow description of how it all works but briefly;
You signal which is an AC voltage floats on a DC voltage potential. (your DC supply Rails)
Each stage amplifies that AC audio signal.

From left to right,
U1 is the input pre,,,U2 is the clipping stage,, u3 makes up for the losses created by having a passive tone control.
U4 is likely not needed but hey they don't make a chip with 3 opamps so why not use the 4th as another buffer. :lmao:
the 4th chip on the right is the power chip which is just a much higher current opamp to drive the speaker. this is the one that bolts to a heat sink. In some small cheap amps it's just a slice of alloy.

The 130k fb resistor on the pwr chip sets the gain of the power amp along with other parts. If that is what is in your amp then no wonder you can't get a clean sound.

As the schematic is likely drawn wrong, i.e. pin 1 of power chip connects to both Pos & Neg of the speaker terminals so as drawn it can't work. :duh
Of course it obviously does work so I have no way of being able to work out how the circuit is actually wired up. :loco

The resistor I mention looks like it reads R19- 130k but who knows what is actually in your circuit. looks like it joins pin 1 and pin 8 on the power chip.
(I think)???

I've added this pic to show what I think is a mistake on the drawing.
If the red marked link was removed then the circuit makes more sense.(R19 is just to the left of that red cross.
Phil.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: phatt on February 18, 2020, 06:50:12 AM
regards to sims,, FANTASTIC learning/ teaching tool for noobs like me who wish to understand what the hell goes on inside amplifiers. :dbtu: :dbtu: :dbtu:
And you can't  blow them up if wired wrong or burn yourself with hot irons  :lmao:
Your preamp circuit looks like this with Circuitmaker,, it's not top shelf sim but it's all you need to come to grips with basic amp circuits. (even does Valve circuits if you want)
Cheers Phil.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Lex on February 22, 2020, 05:11:23 AM
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
Title: Re: Introduction, a question and a hope for some insight / help
Post by: phatt on February 22, 2020, 07:34:48 AM
Hi Lex it's ok ,, i've got time at the mo as I'm waiting for a bathroom reno to be finished so can't do much else cept wait. :'(

Although some parts might be in a slightly different position you will find it is electrically the same thing.

Pic2 just shows how the signal swing gets bigger and smaller as it passes through each section.
in this case the ,,gain 1 pot (R6) is set at 70% rotation, while gain pot 2 (R8) is set at 40% rotation.
The input voltage is 100mV and the output at U4 (Yellow trace) is still under 200mV so the preamp is basically clean until gain2 (R8) passes 60% rotation.
Which is why I'm fairly sure the preamp is working mostly clean so if you have distortion at low level then  I would look at the schematic of power amp and see that R18 which sets the gain around the powerchip is 130k and my guess is that resistor is way too large and hence the amp distorts long before the diodes conduct in the preamp. Normally R18 would be about 20k~ 50k max.
the other screen shot is the tone response curve at different points on the schematic which gives you a clue as to what frequencies are being amplified.
The tone controls are set with Bass Full up Mid full off and Treb Full up.
so the output at U4 (top of R17) is the purple trace of the frequency curve from the preamp. 
Phil.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Lex on February 23, 2020, 05:12:45 AM
Ok Phil thanx,

still looking for the time to get into it.

Tell me please, that piece of the software is 'Circuit Maker 2000' ?

Could you share with me the 'project' file so I could import after the installation and test / learn / play .. ?

Im still not so familiar with the signs so it will take me weeks figure out

Greetings all and have a good Sunday

Title: Re: Introduction, a question and a hope for some insight / help
Post by: phatt on February 24, 2020, 06:59:29 AM
No worries Lex, Happy to help. :tu:
Yes mate That is the program I use.
How fast you learn to use it depends on how much you already understand about electronic circuits.
But as I mentioned what's to loose because you can't blow anything up and you can't kill yourself by touching high voltage or burn your fingers on a hot soldering irons.  :lmao:
You will still need to read up on some of the basics of audio circuits, a lot can be found on the dub,dub,dub and help is also here of course. 8|

The program comes with a whole library of circuits for you to learn from, some of which will be useless for Audio but no matter just start using it and don't expect to understand it all in a few weeks. It took me 6 months to fully grasp what the hell I was doing and it does send you loco at times.  :loco
Be warned it's a highly addictive hobby, And I'm just so grateful for the friend who introduced me to simulations years back. Even though i already had a fairly good grasp of how amps worked, sims just saved me years of building land fill.
As they say "a picture is worth a 1,000 words"
check your pm's, Phil.
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Lex on February 29, 2020, 05:44:31 AM
Thanx Phil,

u got a msg back

Cheers
Title: Re: Introduction, a question and a hope for some insight / help
Post by: Lex on April 01, 2020, 05:38:54 PM
Hi all,
I can't report any progress as I lent this amp to a friend and he is enjoying it like it is.
So I'll be back with more stories .. if I dont sell it to him.
I'm discovering the wonderful world of amp's so I would not be surprised if I just move to something else. (this means more amp's, not less..).
Actually Im quite interested in a vintage Peavey Studio or Bandit .. well will see,
Stray strong all and away of Corona (beer is quite refreshing tho!)
Cheers
Lex