Ha!  Now I can get on with my St. Anger cover band 
Now all I need is a "Trash Can Lid" snare effect, and I'm all set. 

EDIT: I listened to the video, and I get it now.  The "Rip" knob sets the bias, which explains the gating effect.  And the tone is a "tilt" tone, which was a bit of a failed experiment in Hi-Fi world, but it works for pedals?  Hmmm...
https://www.edn.com/implement-an-audio-frequency-tilt-equalizer-filter/

I think the effect might sound better if there were also a control to blend in with the clean signal.  After all, that's why folks were slashing speakers; to get a distorted sound out of the clean amps of the time.  But I'm not a big pedal company, so...

Sounds exactly to me like hard rail clipping from overdriving the op-amp itself and is a reason why I don't like circuits that do that.  I don't know of any remedy that doesn't involve a few invasive mods to the circuit, but you can try something a little less complex;
Replace the 1458 with a socket and test out a few different dual op-amps to see if any are better for avoiding the fizzle. 
Try a TL072, NE5532, RC4558, and LM358. 

Quote from: joecool85 on February 02, 2021, 11:22:47 AM
Personally I have settled in on KiCad.  Available on Linux, Mac, and Windows.  Plus you can do PCB design in there, even having a 3d layout view!  And a lot of PCB houses accept KiCad files natively for PCB production.

https://kicad.org/

Woops... forgot that one.  As a 20-year Linux user, I should have remembered, but then I also remember all the time I spent trying to get it to work, giving up, and eventually firing up Eagle, LOL.  Now Eagle got sold to the dark side so KiCad is back on the menu.  It's much better now.

ExpressPCB has software for drawing schematics and it works well.
https://www.expresspcb.com/

Any of the free simulator tools out there work to draw schematics, but they are geared more for simulation than making clean schematics:
https://www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html#
https://www.ti.com/tool/TINA-TI

Fritzing and DIYLC both have a similar look:
https://bancika.github.io/diy-layout-creator/
https://fritzing.org/download/

Lots of online schematic capture tools as well:
https://www.digikey.com/schemeit/project
https://www.schematics.com/
https://easyeda.com/
https://www.circuitlab.com/

Take your pick!  I've tried them all, and they all work well, but evaluate them against your own preferences as far as functionality, look & feel, features, etc.

Quote from: dogbox on December 20, 2020, 04:42:04 PM
Hey guys, haven't been here in a while or played around with electronics and electric guitars for couple years. Been on an acoustic odyssey lol. Feel like I'm starting from scratch again. Dragged out my MIM strat and red knob superchamp..thats downstairs in the man cave and too loud for the living room.

I was wanting to build myself a small stereo coffee table guitar amp. I have seen plenty of cheap amp boards on ebay, pre soldered with surface mount components with stereo 3w output. That would do me, anything much louder would annoy the missus, and we don't want that and I don't want make a real amp with power transformer..i don't do AC.

I need a preamp...but before I get to that stage I have some really obvious things that I don't know/ forgotten.

1. Could I just use an effects pedal as a pre?
My intuition says no because guitar amps have an input stage ( i remember that part)

As Loudthud said, it depends.  A chorus pedal?  No.  A 5- or 10-band EQ with boost?  Yes.  Some dirt boxes are full-fledged preamps in themselves, consisting of a gain control, multi-band tone control, and output volume.  That's about the bare minimum for what you'd want in a preamp, even a clean one.

Quote2. Would pedals work directly into a line level inout if i placed a DI box between pedal and amp? What would it sound like? Would a cabsim pedal or amp in a box work?

You don't need a DI between a pedal and a line input.  One thing that pedals are very good at is taking your high-impedance guitar input and producing a low-impedance output, which more-or-less is compatible with line level inputs.  A standalone cabsim would work well after your preamp if you want some color to the sound that more resembles a "real" amp, or you could get one of the Tech21 "Character" series or Joyo pedals that simulate amps.  They are a preamp and cabsim all in one.

Quote3. Is there a schematic on here or elsewhere that gives a simple clean channel, with maybe basic tone controls that you could point me to, that may be suitable for these ebay amps. Fetzer valve was one i used in the past and I remember Phil(Phat) had some great preamp designs floating around here. Would there be a way to modify one of those to work with the ebay amp?

Any preamp with at least 2-band tone controls (bass & treble) and a volume or output control will work.  The only mod you may need is to make sure the output is low-impedance, but I don't think that's a problem with most schematics you can find here and elsewhere.  You can message Phatt, he's still around; I'm sure he won't mind at all sharing anything that might help.

Quote4. Should I stay away from those chinese prepopulated boards on ebay, and build a proper deigned practice amp? If the latter option, Which one?

Use what works for you.  I'd say if you get a small stereo amp or kit that you plan to run regular hi-fi speakers with, then definitely a cabsim as mentioned before will help the sound, especially with headphones.  The same stereo power amp hooked up to a bona fide guitar speaker is not all that different from any production Solid State guitar amp.

Quote5. If it was Ok to have a preamp board ( that i would perf) and the ebay amp side by side in a box, and i didn't need a D/I circuit in between, could I use a single 9/12v wall wart to power both boards, or would I need a seperate supply for both pre and power amp?

As long as the power supply has enough juice to run the power amp and then some, you'll be fine.  Say you have a circuit or amp module that's 10 watts; you'd need something that was at least between 10 and 15 watts, and some will even say don't run the amp with anything less than 2X the power demands of your amplifier.

QuoteAm i barking up the wrong tree with the D/I box..i just remember having a need for a DI box when plugging into my mixer years ago..sounded terrible without it, and it had line level inputs. When it comes to electronics I know enough to be dangerous. I can solder ok and use a dmm. I used to build pedals 10 years ago, then had sporadic forays back into electronics but only limited understanding. Sorry for the dumb questions, and rambling in advance

A D/I box would be useful if you are simply plugging your guitar into something low-impedance with no pedals or preamps at all.  If you know how to build pedals, you already know all you need to tackle this one, it's just a bigger box with a speaker.  I don't think your questions are dumb at all.

QuoteLooking for your input
steve

Quote from: willpirkle on January 21, 2021, 07:19:54 AM
I'm using this TDA1517 stereo amp kit in one of my audio electronics classes. I built and tested it over Christmas and it is stable at 4 ohms. For $12 (Jameco, $27 on Amazon) it might be worth a try for your application. The output power will depend on the supply voltage and current capabilities.

https://www.jameco.com/z/MK190-Velleman-2x5-Watt-Amplifier-for-Portable-Audio-Player-Kit-6-14VDC-1A_2196588.html

- Will

I second the vote for TDA1517; 2 channels, 6 watts per, though they recommend heat sinking if you try to bridge it.  I used to have a habit of finding old ISA soundcards that are loaded with TDA1517 chips, or TEA2025B for the lower-power ones.  Also check the Craigslist "Free" ads or any friends with old broken computer speakers or one of those cheap mass-produced stereos from the '90s; they often have usable power chips hiding inside. 
Or go for broke and get a handful of LM1875s.  They are rated for 20 watts, but that's edge case; at 12 volts with an 8Ω speaker you'll get more like 6-8 watts.

JoeCool85's suggestion to go with a Class D chip is solid though, much less heat to deal with.

If you know of someplace where you can find or buy an old-style float and arm style toilet valve, that arm is often copper or brass, and the diameter will fit in most soldering irons.  Cut off small sections and file one end into a tip. 

If you want REALLY budget tips, I have been known to buy a screwdriver or two from the local hardware store that sells cheap junk.  Found one with a shaft diameter that fit and cut it into sections with my Dremel.  No, it doesn't work as good as a proper tip, but it'll get you by while you save up for a nice tip.

Make sure you buy from a reputable seller; there are some counterfeits ever since the MN-series bucket-brigade delay chips went out of production, though on eBay you're more likely to encounter salvage chips, which are a good deal if they aren't dead.  If they're actually listed as salvage and are cheap enough, I'd order two or more to make sure you get at least one good one. 


YouTube link: (Part2) Detecting Fake Ebay ICs Chips - Sound Test




Smallbear carries genuine NOS stock at somewhat of a premium ($10.95 at the time of this posting), but at least you know you're getting the real deal. 
Xvive is making re-issues, but they may be a little hard to find, and are on the expensive side ($25 and up from what I could find).  They sound as good as the originals, from what I hear.

Quote from: shasam on September 10, 2020, 05:30:09 AM
...
Do you think Spice simulations would differ a lot from reality?
What I find annoying, is what is a practical signal for testing a guitar amp? An hifi amp won't have to produce continuous square waves. But for a guitar amp, for exemple, a larsen with a super fuzz type pedal is a possible situation, and look really more painfull for the amp.
...

The biggest drawback to using simulators is that they will consistently give you an ideal result; that is, any given part will have real-world variations due to many factors, but the simulation will run at exact specs every time.  That can lead to disappointing results with real parts, but as long as you're aware of that, it's not so bad. 

In LTSpice (and probably others), you can use a sound file as input to your simulation, so I sometimes record a 1 or 2 second clip of a strummed open E, or plucking of a high note as "real-world" input (the clips are short because the simulation with a sound file takes quite a bit more time to process, as you can imagine).  Your guitar and pre-amp will NEVER produce a perfect sine wave, so though a sine wave can be used as a useful baseline to see if the circuit is doing what you think it is supposed to do, it won't show you how the circuit will react to an actual guitar signal.

If you are doing your testing on a "real-world" amp, I would suggest investing in a looper pedal.  That way you can strum a few chords into it, start it looping, then jack it directly into the amp and it will repeat until you stop it while you take measurements or gawk at an oscilloscope trace.  You could even run it through a pedal of your choice.

QuoteFurthermore, what would you use for practical load? Results would vary a lot in fonction of the load used for measurments, with different impedance dips and phase shifts between real speakers.

There are circuits that simulate a speaker load with varying impedances, etc. that are very close to how a real speaker will affect the operation of the circuit it's connected to.  Try this one:
https://www.aikenamps.com/index.php/designing-a-reactive-speaker-load-emulator
Whether you build a real one, or run it through a simulation, I think something like this will work fine.  Tonal differences between speakers are often down to the material and construction of the speaker cone itself; the engineering of the power amp is only concerned with the magnet/coil part.

The tab is connected to V-.

If you can avoid, or have no intention of, grounding the heat sink by attaching it to a metal chassis (most common)or other scheme, you can get away with mounting the chip directly to it with some thermal grease.  CAVEAT: Make absolutely sure that there isn't or won't be the opportunity for some wayward part to short the heatsink to ground or the V+ rail. 
Or just use an isolation pad.  For breadboarding, I wouldn't risk going without one.  For final assembly in a box, use some common sense (and a barrier between the heatsink and the rest of the circuit) and you can get away with it.

By the way, I've heard all the cool kids are using 1mil Kapton Tape for isolating their semiconductors nowadays.  Good thermal conductivity (not as good as Mica, better than Sil-Pads), pretty tough, and one 36 yard/~33 meter roll oughta last you a while...

P.S. All you ever wanted to know about attaching something to a heat sink:
https://www.eg.bucknell.edu/~dkelley/eceg351/FairchildHeatsinkMountingGuide.pdf
http://www.junradio.com/Discretes/TI/9701.pdf

You'll find that most chipamp packages do not line up to any pre-drill hole patterns, unless it's a DIP, and there's no such thing as a pentawatt socket as far as I can find.  I wish I had thought of that when I was younger, I bet it'd make a few bucks.

My best suggestion would be to solder solid lead wires to the legs of your chipamp, so they go from your heatsink to your breadboard; you don't want to flex the legs of the  chipamps themselves too much.  They tend to weaken and break at the chip body.  Ask me how I know...  

Quote from: Oooscar on May 11, 2020, 10:47:11 AM
Hello,

I am studying different preamp schematics. I am inclined to minimal amps or amps with not so many parts, just the ones needed to produce a given sound for guitar practice/bedroom playing purposes. I have several questions:

1.- Is it good to add a boost stage initially before any overdrive/soft clipping in terms of sound?

It depends on the circuit.  Some circuits sound just fine creating their own gain, like discrete transistor designs and most Op-Amp designs, but oftentimes boosting into a circuit that is wired for low gain will get better tones than the circuit itself wired for high gain.  In my experience, MOSFET inverter stages are like this, perhaps some others.  Counter-intuitive, I know...

Quote2.- Is it better to add a tone control stack before any clipping or after, in terms of sound?

Again, it depends on the circuit and what you want it to do.  Personally, I've found that tone controls before the clipping/gain stage work best with low- to mid-gain circuits, for Blues and Classic Rock.  High gain circuits can tend to be noisy and "mushy" sounding with the tone control in front, though that might sound good if you want more of a Fuzz effect from your high-gain channel.  Post-clipping tone controls can sound "sterile" with lower gain circuits (but not always, there are many exceptions, I'm sure), but can be powerful tone shaping tools after a high-gain stage.

QuoteLet's say you make: guitar, boost, tone control/tone stack, soft and/or hard clipping, out.
3.- Does it worth to add a classic tone stack with bass, trebble, mid respect a single pot tone control, or a BMP with some mid control (Jack Orman mod I believe...)?

The best answer I can give is to simply try it.  I've used single-knobs, two knobs, 5-band EQs, they all have their advantages and disadvantages.  If you want to keep it simple, then a BMP with mid control sounds like it could be nice, but as joecool85 said, it can be TOO limiting.  Give it a shot, start breadboarding and take notes on which ones you like.

QuoteIt seems to me that with a simple tone control (or maybe two pots) you can get a wide range of sounds, but I am learning, and I would like to understand how many stages can have a guitar amp, and the purpose of those, to see how can I simplify or minimize them, and still get a good and wide range of sound. For instance, adding preamp stages to an LM386 can give you a good sound with control. I have tried hard clip diodes with a TL072, and the sound to me gets better. Nicer.

Thank you very much for your attention.

Regards, cheers.

Most of the "extra" stages and parts of a preamp have to do with either tone shaping, bandwidth limiting, or protection.  Solid state gear is really good at simply re-creating whatever is put into it, but that includes signals you didn't intend, and so we have a thousand schemes to clamp oscillations, eliminate sub-sonics, and protect an op-amp from frying itself.  Many of those can be eliminated, but it is oftentimes what gives certain circuits their "feel".  Would a Tube Screamer sound like it does without that famous mid-hump?  Nope, it'd sound like any other generic OD/Distortion boxes out there, but maybe that's what you like; only YOU can make that distinction.

For the record, I prefer: Op-amp clean boost to a tight (2-pole) hi-pass at about 100Hz into a chain of low-gain MOSFET inverters, just about any FMV tone control circuit, (pre-gain for clean channels, post gain for dirt), make-up gain and single pole low-pass at ~5-7kHz depending on the circuit

Quote from: solidstate2199 on March 09, 2020, 02:54:37 PM
To me the most obvious difference in the preamps ss vs tube
Is the onset "fizz" of the opamp or generally transistor when it
Starts to clip. At least i figure this is from transistors because all ss
Amps that i have do it.  I have a marshall 3203 which, if it wasnt for
That fizziness would sound rather close to a marshall 2204 or similar.
Maybe its just bad design from the old marshall ss amps.
Maybe jfet dont fizz.

I'm inclined to believe the "fizz" is from "ringing" when the signal gets clipped.  Tubes naturally go from clean signal to squared-off clipping in a very gradual manner that doesn't "ring" like squared-off waves do.  Transistors are clean until they hit the limits, then *BAM*... Gibbs Phenomenon.  This is why people like (ab)using CMOS chips (and JFETs, to a lesser extent) for "tube-like" distortion; they exhibit a gradual onset of clipping as the signal approaches the limits, though not completely analogous.

Quote from: joecool85 on March 02, 2020, 08:38:39 PM
D'Addario has released their "casein" picks.  These picks are suppose to be reminiscent or tortoiseshell picks but instead of being made of plastics, they are made of dairy proteins.  Sounds cheesy to me, but if they work, I'm all for it!  That said, at $21.99 for a single plectrum, I might stick with my Dunlop Nylons!

https://www.guitarworld.com/news/daddarios-casein-picks-aim-to-replicate-tortoiseshell-tone-using-dairy-proteins

In all seriousness, that sounds cool.  Not 22 bucks cool, but cool nonetheless.

I've seen this posted around the forum, but it should be here.

Schematics for Crate amplifiers (and others):
https://supportloudtech.netx.net/loud-public/#category/10641

Also, for those who have a schematic for the Sunn Beta Lead and disappointed that the power amp schematic is unreadable, the schematic for the Sunn "Alpha Series" mixers is the exact same thing.  Page 3 here:
https://support.fender.com/hc/en-us/article_attachments/115007761663/Alpha_Series.pdf
can drop in to page 1 here:
https://support.fender.com/hc/en-us/article_attachments/115007663026/Beta_Lead.PDF