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Messages - edvard

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Amplifier Discussion / Re: What makes for a good clean channel?
« on: February 20, 2021, 02:51:02 AM »
For me the short of it is yes, sparkly clean but with tone shaping.  Normally a -10db dip in mids, centered around 600hz.  After that it is up to preference if you drop lows or highs.
Hi Joe, Your observation is correct but sadly it is only one piece of a much larger jigsaw puzzle.
If you insert that tone curve into a generic SS amp it won't sound like it's valve equivalent.

He asked for a clean channel, I figured he meant just preamp.  If that is the case, I stand by my argument.  Of course, taste/preference is relative.

I do agree about what you said though.  I've not tried using a transformer for speaker output, but I've thought about it because I constantly hear about it's magical properties.

Per my (admittedly limited) knowledge, since it's SS, much of the "magic" has to happen in the preamp.  If one wants to mimic power supply 'sag', or speaker reactance, it's gotta go before the power amp because that thing is linear all the way, toots... 

Transformer output is particularly intriguing, because in my mind, it promises to deliver just a little of that non-linear "magic" we hear so much about with tubes.  I am leaning toward a MOSFET power amp due to MOSFET designs being relatively simple to build, but I think it might also be a little easier to design around a transformer output.  However, I don't doubt I may be plenty wrong about that.  Searching around the internet, the general consensus reaction to the idea of transformer output on a Solid State amp is "But why?", and I guess they kinda have a point, I mean why use a transformer if the chips can drive a speaker directly?  MOJO, that's why!   :trouble

That said, if anybody has any MOSFET-with-transformer circuits, send them my way, especially if it uses one of those 70-volt PA system transformers; I have one, and they are pretty cheap as far as audio transformers go if I want another.


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Amplifier Discussion / Re: What makes for a good clean channel?
« on: February 15, 2021, 07:02:29 PM »
Oh, and look at the response curves of popular guitar speakers.

Ya know, I was looking at speaker response charts, and they told me a lot less than what my ears could tell me.  I can look at the steepness of the low- and high-end rolloff and judge how bassy or trebly they might be, but beyond that they don't tell me anything about any give speaker's fundamental character that I can't pick up immediately with a brief listen.  I have a few ideas for what I'd like in a speaker, but that'll require more money than I have at the moment, and even then it'll probably be a Harley Benton twin cab.  Cheapest in their class and they are genuine V30s, you know...

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Amplifier Discussion / Re: What makes for a good clean channel?
« on: February 15, 2021, 05:54:11 PM »
Hi Ed,,Try to keep in mind that there is no one section of a complete system that will reap magic,,
You build the sound/Tone you want out of what is mostly basic circuits most of which have been around for years.
If you want Clean then I take it you are talking about electric guitar?

In that case the clean will benefit from a little edge. (As Enzo just mentioned)
(My Cab sim, compressor, Phabbtone does that for me)

Regards OD and multi channels on amps,,, Been there done that and failed?
Pedals are far easier to get to where you want. It will depend on what styles you want to emulate.
For me it's just older rock and blues which is built from the little rattle of *Mictesters* Comp which is always on.
Then I add a home designed germanium clipper (that is my clean boost with a little more edge and OD) sweet. :tu:

For MORE heavy rock stuff (think ZZtop) I add a Boss OS2.
For all out scream I add a Boss SD1 (not totally happy with that but it does the job)

OK by now the bass and drums are playing louder so I press my Level Shift which just lifts the volume enough to lift it over the top.
Except for the Level Shifter all the added dirt pedals are set at much lower gain than most players I've known.
This helps a lot as with 3 Drive pedals it's way to easy to end up sounding like Mud or buzzing fizz with to much gain on any of those pedals.  The Compressor is AFTER those 3 pedals and that keeps it all within a SET SPL of my overall volume,, without that it's a nightmare trying to keep them all within a certain SPL range.

If heavy metal is your taste then you might only need to add the pedal of your desire. 8|

Of course there are many ways to do similar things but this has worked well for me over the last ~10 ish years.

All that is running thru my crappy old Laney which I think I mentioned to you once before is not even a guitar amplifier,   :lmao:

To do all that in one amp chassis is a tall order. :-X :-X Once you realise that all that would need many relays and a pedal board with many switches.
AND you are still stuck with a friggin pedal on the floor,,,, Naah xP
As much as I hate pedal boards it's just a lot easier to use pedals.
And if you don't like one you just swap it out,,, you can't swap out things in a complicated amp chassis in a few minutes??  xP

Let me clarify: I've tried a lot of dirt pedals and amps (too many to mention) that never left the music shop in my hands, the few that have I don't have any more, and I am not financially flush enough to do any further experimentation with that, and frankly, I'm not all that interested.  If I were to name my dream rig, it would be a Mesa Boogie Mark IIc+ or the Bedrock twin combo I tried out in 1992 or so, but didn't have the cash to swing at the time.  I still don't, so that's that, but the point is I'm a "set it and forget it" sort, which means once I find something that makes me happy, I'll likely be happy with it for a while.  Right now, I'm on a chase of a good clean tone that's not boring, but not over-complicated either.

What I DO have is a few buckets of spare parts, a little time, and a certain tone I'm chasing. I have designed a solid state dirt circuit that I'm about 99.9% happy with, and further tweaking is getting diminishing returns so I know I'm about done.  My ultimate plan is to make everything modular (separate boards with connectors between them), so If I get REALLY unhappy with a preamp or tone control, or if the power amp dies and I can't find a replacement, I can simply swap it out.  It might take a couple of days, but I'm not gigging, so I don't mind.

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I just read your other posting and it seems I promised you some of my circuits  :-[
I'll try and get some up soon,,, life is very busy at the mo but I WILL get something for you. :tu:

Phil.

No problem, this endeavor has gone on for more years than I'd like to confess, so I'm OK.  ;)

So, the concensus so far is a bit of compression and judiciously chosen tone control to add some tone shaping and non-linearity to what would otherwise be no different from a monophonic Hi-Fi or PA.
Anything else?

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Amplifier Discussion / Re: What makes for a good clean channel?
« on: February 15, 2021, 04:36:41 PM »
Crystal clean clarity?  Foo, that would simply be a PA system, and we know that does not make a good guitar amp.   What you think of as clean in a guitar amp is not really very clean.  It just doesn't have the shrill raspy edges of dirt channels.

Agreed.  The problem is, that tube amps have an inherent non-linearity that everybody knows is the bees knees whether clean or dirty, while us SS guys are pretty much stuck with basically a PA powering a Celestion, and I want to do something about that without involving hot glass...  ::)  Hopefully without going down the tube emulation rabbit hole that many before me have plumbed to its depths already.

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Go to DUncan amps and download the tone stack calculator and explore the tone stacks, you will see their response curves are not flat.  Putting all the tone controls at center on your old Fender is NOT the flattest setting.

Yep, done that, and looked up and tried at least 10 or 15 various tone controls trying to find the one that hits my ears just right.  Right now, the Brownface Bass/Treble control has my attention for the longest, so I'm sticking with that, but still researching an active Mid EQ to mitigate the -15dB mid scoop.  FWIW, it doesn't sound all that scoopy to me, so maybe I'll leave it.

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Amplifier Discussion / What makes for a good clean channel?
« on: February 15, 2021, 05:10:37 AM »
Back in 2018, I was pondering creating a basic SS amplifier that had all my best ideas in one box.  Now it's 3 years later and I still haven't built it, but I've been breadboarding!  I've re-thought my opinions on 2-channel amps, and eventually came around to a new question... Is the clean channel nothing more than the default when you turn off the dirt?  Like the wire that goes straight from input to output when you switch a pedal off?  That sounds so boring, but can there be more to it? 

I worked up an idea of making the clean channel run through a tone control and then through a single gain stage, which is how tube amps of yore were laid out.  I'm not trying to purposefully emulate tube anything, it just struck me as a novel design decision that will alter the response of the gain stage and maybe introduce some pleasing audio anomalies.  Or at least, that's what I'm hoping...

What do you folks think are essential elements of a good default clean channel?  Squeaky-clean crystal clarity?  Just a little grit on the top for flavor?  Tone shaping ideas?
  Some simple compression/limiting maybe? (Yes, Phatt, I remember your suggestion of the simple compressor.)   

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Guitar News / Re: EHX Ripped Speaker - Make your rig sound broken!
« on: February 14, 2021, 02:55:36 AM »
Ha!  Now I can get on with my St. Anger cover band  :lmao:
Now all I need is a "Trash Can Lid" snare effect, and I'm all set.  8)

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...

7
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. 

8
Software / Re: Drawing schematics
« on: February 03, 2021, 10:18:13 PM »
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.

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Software / Re: Drawing schematics
« on: February 02, 2021, 02:33:27 AM »
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.

10
Preamps and Effects / Re: Old newb questions
« on: January 23, 2021, 02:05:12 AM »
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.

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2. 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.

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3. 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.

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4. 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.

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5. 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.

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Am 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.

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Looking for your input
steve

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Amplifier Discussion / Re: Simple 3W amp IC? (for 4ohm speaker)
« on: January 22, 2021, 10:10:02 PM »
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.

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The Newcomer's Forum / Re: Soldering Iron Tips
« on: January 18, 2021, 08:36:10 PM »
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.

13
Amplifier Discussion / Re: Peavey VSS-20 amplifier with chorus noise problem
« on: September 19, 2020, 03:38:00 PM »
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.


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Amplifier Discussion / Re: Peak dissipation in class B output stage
« on: September 13, 2020, 01:24:45 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.

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Furthermore, 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.

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The Newcomer's Forum / Re: Tda ICs Pentawatt PCB
« on: May 31, 2020, 11:48:32 PM »
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

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