Newbie needs suggestions for component order

[antonis]

I'm thinking a TS clone of some-sort, I'm not at all fussy, but best I can gather, I'll be able to use a 4558 which I have, and I have enough diodes that I figure I should be able to sit here and try pairs until I like it. This is the first schematic I found that seems reasonable; anyone have a comment or suggestion one way or another?
https://www.diystompboxes.com/smfforum/index.php?topic=77835.0

Let's make it more "plain" for the beginning..



https://www.muzique.com/tech/scream.htm

[GibsonGM]

Then you will want to modify it to make it a "Timmy"   

[Phend]

Never built an effect, get your bread board and start with this.
Note at the bottom of the site is a , in red text "click to download pdf."

https://www.premierguitar.com/diy/pedal-projects/build-your-own-guitar-pedal

[ThePracticalPeasant]

Billions of schematics online!  Watch out that they're verified good, though. There are some in the forum, and lots in topics (use the search function)

You hit exactly upon my problem - knowing whether what I've found is worth the energy [required to even render the schematic] or not: I don't know what I don't know!

Let's make it more "plain" for the beginning..

I like it. We have a winner.

[antonis]

Let's make it more "plain" for the beginning..

I like it. We have a winner.

Beware of what Sir Mike pointed out..

Then you will want to modify it to make it a "Timmy" 

https://www.diystompboxes.com/smfforum/index.php?topic=121481.0

which might result into an addition of a Baxandal EQ plus a phase splitter + octave up plus + plus + plus..

[GibsonGM]

The TS has a mid hump that's useful for blues tones; but because of this, I find that it doesn't work for 'traditional' hard rock guitar, at least with my rig and a Les Paul.   The Timmy does away with this, and the bass and hi cut controls give a lot more versatility, to my way of thinking.   

Both have their place (so you'll have to make at least one of each!)

[duck_arse]

this is your thread now, so if you supply the popcorn, sausages and coffee, you can just scope-out a circuit diagram, post it here and ask questions, compare and contrast. and we'll all pile in and give you helpful hints ......

[Clint Eastwood]

Get some j113 jfets. Versatile, not expensive and available. I have never understood the J201 hype. Can anyone give me an example of a circuit that will only sound good with a J201 and cannot be adapted for another Jfet? I'd like to listen for myself.

[GibsonGM]

^  That's the one.  I'd forgotten that the 113 is a good replacement, thanks for the reminder Clint!

[ThePracticalPeasant]

They should make these components in jumbo-sized packages for people with chunky stumpy "mechanic hands" like me...



Used 1N4007s as clipping diodes and RC4558 for the op-amp.
Skipped the volume pot and hardwired to 50% gain for testing.

I spent an hour trying to figure out why it wouldn't work before hooking the guitar to the input and the amp to the output instead of the other way around



But, it works! Now to learn how/why...

[Phend]

What's that cool looking stringed instrument?

[ThePracticalPeasant]

What's that cool looking stringed instrument?

It's one of of a few cigar box guitars built without actual cigar boxes; here's a wider angle.

[Phend]

I bought, at a junk store, a super cheap cardboard one for super cheap, just to try. I have fun with it but have not plugged it in since I don't trust the super cheap whatever may be inside the thing.

[antonis]

But, it works! Now to learn how/why...

http://www.geofex.com/circuits/what_are_all_those_parts_for.htm
http://www.geofex.com/article_folders/tstech/tsxtech.htm

Further studying (optional)..
https://www.tutorialspoint.com/linear_integrated_circuits_applications/linear_integrated_circuits_applications_log_and_anti_log_amplifiers.htm
(concerning NFB loop clipping diodes..)

[ThePracticalPeasant]

I bought, at a junk store, a super cheap cardboard one for super cheap, just to try. I have fun with it but have not plugged it in since I don't trust the super cheap whatever may be inside the thing.

What is there to distrust? Unless there was something wrong with the amplifier that caused a dangerous potential to be put on the input, I can't see how a failure of the electronics in the guitar would be an issue. Am I missing something?

[ThePracticalPeasant]

http://www.geofex.com/article_folders/tstech/tsxtech.htm

This was great, once I got through a very basic doc on op-amps in general. This is what we've got built, and I've got a couple questions if anyone can help me declutter my understanding. Also a neat project just came about...



1. This configuration is cutting/boosting only the "tone" but generally leaving the signal at the same level? If I were to delete this part of the circuit, I'd only lose the tone control? Do I also need to delete R4? If so, I'm suddenly unsure what C4 is for....

2. Other audio amplifier circuits I've previously worked with had +/- supply rails, I basically understand in this circuit, the waveform's "zero crossing point" is actually at half the amplifier's supply voltage, and this DC must be blocked. I realized after drawing the image...

3. Depending how much of the output gets fed back via the diodes (versus shunted via the pot), we get more/less clipping (from the diodes)? Removing R3/R10 gives a very clean tone. My thought is to put a switch that flips between zero resistance and a 250k pot with a 250k resistor in front of it. This gives a boosted clean and drive tone in the same unit. Thoughts/comments? (the why is coming)

4. Isn't the 4.5V blocked by C2? I don't get what's happening here, but perhaps related to:

5. What's the relationship between the voltage supplied via the 470k here, whatever is happening via C2/R2, and the overall gain of this part of the circuit?

I have a long-standing complaint that drive pedals of all kinds have an output volume shift as the amount of drive is changed. In normal practice it's a non-issue as one could balance the drive and gain pots against the bypassed volume, but this is about to be abnormal.

The first thing I tried once I had a circuit that worked was to put a small speaker across the output and somewhat surprisingly, this circuit was able to drive it directly [albeit very quietly]. This got me wondering:

If I can balance out the "driven" and "clean" tones a bit, and then boost the outputted signal a bit to better drive this little speaker; I have a box of salvaged 18650s to power everything; I think I can build this all into a cigar-box guitar as one self-contained electric instrument.

I actually have amplifier boards based around an LM1875 that I could slap at the end of the whole pedal circuit, but I think that's a bit overkill, power hungry, etc; plus they want a +/- supply. The speaker is only rated 2.5W and fairly responsive; TL022s are rated 680mW; Could I just drive both in parallel?

Whatchall think?

Edit: I said TL022s because I have some, and by both I mean both on the same chip, though the rating might be for the whole package rather than each op-amp. Open to any/all suggestions/ideas!

[ThePracticalPeasant]

So I guessed and I'm not sure how I should judge my results. I need a hint.
Fuuuugettabout the active tone circuit, I made this tweak (1k/220 is gain of 4.5, correct?) ...



...and it got louder, but has funny behaviour whereby it's only loud when the input is really high, otherwise it's super quiet. Also, more clipping. So I took a guess, the datasheet says in the 100s of nA for the input/bias currents; presumably I need exponentially larger resistors at R5/R6? Also, if whatever was going on wasn't hurting the chip, there might be a "crunch" effect in there somewhere. I'd have to rig an actual guitar through other effects and into more than a little practice amp if I wanted to investigate that further... the Mad Hatter better watch out... 

Edit: TLDR: I'm shooting to take the input from a guitar pickup, volume pot for driven tone, volume pot for clean tone, tone pot, microswitch to flip between "channels", running off 12V, outputting half a watt across 6 ohms.

[antonis]

So I guessed and I'm not sure how I should judge my results. I need a hint.
Fuuuugettabout the active tone circuit, I made this tweak (1k/220 is gain of 4.5, correct?) ...

Actually, gain is x5.5 (1+ 1k/220) 'cause it's a non-inverting configuration..

BUT

that gain stands for DC also (no cap in series with R6) resulting into op-amp saturation..
(output multiplies +4.5V with 5.5 pushing itself up to 24.75V - but it can't go higher than +9V..)
Only negative part of "loud" inputs can be heard (it's subtracted from +9V) and it's "more clipped" due to asymmetrical clipping..

[antonis]

As for previous post questions:

1. R4 & C4 form a Low Pass Filter of -3dB cut-off frequency calculated from : 1/(2πR4C4) where π = 3.14

2. 

3. That's a unity buffer configuration..

4. See my reply on previous post..
(We DO want to block 4.5VDC - here 4.5V point acts as AC ground 'due to C8)

5. No relationship at all..
R1 "brings" +4.5V to non-inveting input and sets particular stage input impedance..
https://www.diystompboxes.com/smfforum/index.php?topic=129863.0
(bottom posts)

[ThePracticalPeasant]

Actually, gain is x5.5 (1+ 1k/220) 'cause it's a non-inverting configuration..

BUT

that gain stands for DC also (no cap in series with R6) resulting into op-amp saturation..
(output multiplies +4.5V with 5.5 pushing itself up to 24.75V - but it can't go higher than +9V..)
Only negative part of "loud" inputs can be heard (it's subtracted from +9V) and it's "more clipped" due to asymmetrical clipping..

I suspect the majority of the gaps in my understanding are related to this magical voodoo of mixing AC and DC in the same circuit. I need to remind myself that some components are invisible to certain aspects of the circuit. You've pointed me on a path that I can fiddle with; thanks!