Quote from: JB074 on June 13, 2018, 08:42:52 PM
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I was unashamedly asking for *opinion* on heads you may have used that you like the sound of or conversely do not like.
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My apologies, but I plead the hive-mind of the internet.  Ask opinions on a ham sandwich and by the second page it's a full-blown smackdown on whether French Crullers are better than Danishes.

What kind of music do you play?  I am assuming something Rock-oriented but I don't like to assume.  If you lean towards the harder side, I don't think you can go too wrong with a Randall RG series.  I can personally vouch for pretty much any Peavey heads for clean tone, and some TransTube heads have switchable loads. Beyond that, not sure.

Quote from: phatt on June 11, 2018, 07:58:27 AM
Hey Ed,,
Those TDA2050's are a 28Watts @ 4Ohms Watt chip,,Depending on load and PSU. 35Watts if you want to push 4 Ohms with 10% Distortion.
The 50Watt crap is music power which is a fancy fan-dangled way of making it look more powerful. That is what happens when marketing geeks use maths. :duh
Back at a less stressful 8 Ohms and it's somewhere between 18 ~22Watts RMS in the real world.
So I'd call that what it actually is,, about 20Watt Chip.

Yep, I know the marketing-speak and I got the 35 watts at ±30V from the Volts-to-Power chart on the datasheet.  I know they are simple-but-tough little critters and you can push them to get better power, and bridging them is even funner, but I'm trying to keep it simple.  For the moment they are out of stock at Tayda, so I won't be trying them anytime soon.

QuoteFrankly you sound like you are over thinking this whole thing. 8|

HA! Ya think?  :dbtu:

QuoteA SS power amp of any type normally used is a world away from a Valve equivalent. The rare circuits that might be able to compete will cost $$$.

I stated in my first post I'm not trying to concoct a magic equivalent of tube amps, and I think that's a lost cause anyway, for reasons I am not interested in discussing.  Seems to me, the only things truly in common between tubes and silicon is they are both made from hot glass and they can both amplify.  After that, there's a lot of dead horses being beaten, and I want no part of that.

QuoteWith SS all your tricks are easier and a lot $$Cheaper$$ to do in the preamp.

Pre-zactly.  The one thing I do like about tube amps is their innate habit of soft-clipping even when running clean, and that mostly holds for the pre-amp triodes.  Output pentodes can clip just as ugly as their 3-legged cousins.  Well, so can triodes if you abuse bias them properly, but I digress.  My pre-amp tricks aren't new, but hopefully pleasant as I try and avoid hard-clipping (I may say more about that later).

QuoteThat TDA7294 is likely the best bet and just follow the data sheets.
Though LM3886 has less pins and likely a bit easier to make a PCB.

Chip amps can run just fine for years if used as intended.
i.e. a proper heat sink and conservative loads.

I got those because they were dead cheap, and my favorite supplier is currently out of stock of 3886s. I will probably pick up a few at some point, just trying to avoid fakes.

QuoteI've built a few discrete pwr amps like ESP's P3A and they run fine. About as simple as it ever gets 8|. They have no Short protection and as Rod states in one of his pages the current protect circuits are not fool proof anyway and can fail.
So I just use a PTC on the output as they negate all the extra current protect circuitry which makes life easier for a home builder.  These are poly thermal switches and are sold as speaker protection devices BUT they can also protect the amp from shorts IF inserted right at the output of the power amp pcb. :dbtu:
They look like a disc cap.
https://www.jaycar.com.au/rxe075-ptc-fuses-speaker-protection/p/RN3460

I've built about a dozen amps using these for protection and had no trouble. <3)

I guess it's kinda silly of me to complain about the complexity when I've built more than one Big Muff  :loco , but I can't help but get just a little freaked out looking at those glorious schematics.  I'll probably opt for Project 27 if/when I decide to do a discrete power section, and I am intrigued by the whole "current drive" thing anyway.  Thanks for the PTC suggestion, I'd wondered about that myself.  I've got a good handful of them in my parts buckets...

QuoteBack to preamps,, Go purchase a bread board or 2 and start experimenting with a few simple preamp circuits.
I have a few circuits on here which are simple but quite effective, some are on my pedal board some tricks are in amps I have built.

My pedal chain is a fet preamp>> a couple of dirt pedals (never maxed out)>> mictesters (from FSB) compressor circuit (Brilliant) >> my own cab sim design>> my not Famous but very potent PhAbbtone and the amp is actually an old Laney keyboard amp. I have owned and built many amps, Valves as well and the above line up is still my go to rig. It just works.  <3)
I can plug my acoustic into this,, I can use my Strat and when needed I plug in keyboards as well.
I can pull country clean,, to ZZtop thick OD with ease.

As much as I always wanted to have  all this in one Amp I've had revert to pedals as it's just more versatile.
Most of my circuit schematics are on this site.
If it interests you I'll take some pictures?
Hope it helps ,, Regards.. Phil.

I've got more breadboards than I can shake a stick at, so I'm good there.  Being a former pedal junkie, I got pre-amps pretty much covered, though if you have links to some of your favorites, I'm always interested, thanks.
I'm focusing on the power section at the moment because I know I can whip up a pre-amp practically in my sleep, and power has always been an afterthought; the job of whatever amplifier I'm unhappy with at the moment.  It's a challenge and I want to learn.
In fact, that's the whole point of this experiment, to make a standalone amp that I'm happy with because I put all my best ideas in one package.  Yes, a chain of pedals can be quite versatile, but if I wanted to fiddle with pedals, I would have kept the old Peavey I sold because I hated the distortion channel.  I want the simplicity of just plugging in and cranking up without having to worry if my batteries are fresh.  I built my own guitar because for the same reasons; I have two others that work just fine, but now that I've built one, it's my favorite, and I'm going to build another based on what I learned with the first one.

Yeah, I'm overthinking it, and I probably can't compete with what the "big guys" have already done and been doing for the last 50 years, but dangit, I'm having FUN...

P.S. My guitar project, if you're interested: https://imgur.com/a/7Vo5F

I've heard of Sloane's book, but haven't picked up a copy yet.  I've also amassed a large collection of datasheets for TI and other chipamps, as well as many Application Notes from TI, National Semi and others.  I've also pored over collections of schematics and have built quite a few stompboxes, so I'm not exactly new to the subject, I just have never before assembled the required parts into a cohesive unit, AKA a solid-state amplifier that is tweaked to MY tastes and preferences.

My first hurdle is going to be power, as in how am I to feed current into this collection of parts.  That means starting with the power amp.  In that regard, we have a few choices:
-Chipamp
Pros: Simple to design for, and can be inexpensive if you shop around.
Cons: Many good chips are now obsolete, and current production will someday be obsolete as well.  Not sure I want to chase that dragon, so if I settle on one, I should probably buy 3 or 4 more as backups. Or perhaps make the power section a separate module, so I can simply replace it with whatever the cool kids are using that month.
-Discrete
Pros: LOTS of designs freely available on the web to suit many tastes and power output needs.
Cons: Can be complex, which can lead to expensive, depending on what bells and whistles you want.  Speaker protection? Power-on muting? Even more complexity.
-MOSFET
Pros: Most common circuits are less complex than Discrete designs overall. 
Cons: Lateral MOSFETs (that means the GOOD kind) are designed for audio, and are VERY rare/expensive.  Cheaper vertical MOSFETs are not designed for audio, so they can be more "touchy" to work with, but see International Rectifier's Application Note AN-948 "Linear Power Amplifier Using Complementary HEXFET Power MOSFETs".  Very informative.  Also, heat... so much heat.
-Class D
Pros: Same pros as chipamps, but with vastly reduced heat concerns.
Cons: REALLY not targeted to guitar, and need to be protected from transient input spikes.  Overdriving a Class D chip is not pleasant.  At all.

I happen to have a few different chipamps, so I'll roll with that for this first project.  For the TDA7294 I have, ±30V should give me ~50 watts.  The Triad Magnetics F8-24 should get me there, is within budget, and has a 100VA rating, which Rod Elliott might argue is a bit under-powered for a 50-watt guitar amp, but anything more than that gets spendy pretty quick.  Besides, I don't plan on gigging with it any time soon; I'm not THAT good...  Alternatively, if I can find a good source of TDA2050s, I suppose I could live with the 35 watts it can put out with a ±18V supply and a 4-ohm speaker load.

Two thoughts:
Can the cab not be re-wired for a lower load?  From pictures I was able to look up, the speakers are 16 ohms each, wired series/parallel.  If you wired it all parallel, it would come down to 4 ohms.

See illustrations below.

While that would bring the overall load down to something more useful, it won't magically transform the individual speakers into 4-ohm units, so the frequency response will likely be somewhat different from a standard 1960 cab.
I realize that would also limit your choices to amplifiers that are capable of handling a 4-ohm load, but as JM stated, that's at least more common.

Second thought:
While a 16-ohm load would reduce the power available from a solid-state head, isn't that what you want?

Quotewhile I love a plexi as much as the next guy, I'll need a decent reactive load to keep the peace with the neighbours if I want to get the right crunch out of one - not to mention I like having my hearing.

Though I agree with JM's opinion,

Quote"too much cabinet for too little driving power".

it might still work for your purposes.

I would NOT plug a 16-ohm cab into a tube amp that doesn't have a 16-ohm output.  There are all kinds of reasons why not that I won't get into here.  Suffice to say that it's not good for the output tubes or the output transformer to mis-match loads.  Solid-state is a little more tolerant, just with the afore-mentioned imposed power capability limitations.

Yep, just the thinking part for now, though I already have most of it worked out.

Here are my first thoughts:
1 - Start with the speaker and power section.  I get the nagging feeling that designing a SS amp is akin to pairing up a distortion box with a 3-band EQ and power amp, so we start with the limitations (power watts and budget) and work down from there.  I'm thinking 50 watts is a good compromise between "I might have to gig with it someday" and cranking it up to a dull roar while the wife is out shopping.  I want the best speaker I can afford that doesn't have "British Voicing" (to my ears that means "sounds like a box"... sorry, that's just me).  I am also torn on the issue of the power section; basically I have 3 choices: Discrete, Chip amp, and MOSFET.  They all have their pros and cons, but that's for further discussion...

2 - Single channel.  In the '80s I cared about channel switching.  These days, I don't need to go back and forth; I have re-discovered my guitar's volume control so I can go from "Really Crunchy" to "Not So Crunchy" without having to set up two different tones. 
However, just writing this paragraph is making me think I may change my mind.  More about this later...

3 - Don't try too hard to emulate tubes, except for soft limiting in all clean gain stages.  An elegantly designed overdrive stage doesn't do much good if your signal hits the rails before it even gets there.

Thoughts?  Opinions?  I've read a good part of TeemuK's excellent book, so that's given me some good groundwork.  I'll lay out details in following posts, and give a complete schematic at the end for any other intrepid solder junkies.

The Crate board was cannibalized for pedal parts years ago.  I was never 100% happy with the preamp anyway; I had to crank up both volume and gain to get a decent sound out of it.  At one point, I had audacious plans to house a tube amp in the head, but those plans never panned out (power transformers are spendy!), and I'm not in the mood to deal with tubes these days anyway.  The amp was rated for 20 watts output (2 TDA2030s at ±12 volts to make ~10 watts each), so the original transformer will have to go to something else.

Quote from: phatt on June 05, 2018, 06:31:09 AM
Well tel us what those other Amps are that you have laying around because you may find you already have got most of what you need. :tu:
They may only need small mods to better suit your needs.
And maybe add a link to schematics of same if you can.

Amps I own at the moment:
-My grandfather's 1952 Fender Deluxe 5A3, which is a great tube amp, but it doesn't do the Rock thing so well, and I'm a metalhead from way back.  It's amazing how much this thing doesn't distort.
-Park Bass GB 25-12. It's a bass amp, no more, no less, and doesn't distort either.  Currently doing duty as the speaker for my science experiments.  More about that later...
-First Act MA214.  Small practice bass amp that came with the bass my wife got me for Father's day a few years back.  It sounds OK with guitar, as long as you've got a good dirt box in front of it, and even then it's just OK.

For my current plans, I've got the cabs and head of a Crate G200C XL "Mini-stack" that I bought new in '89 and gutted YEARS ago after the power section blew, and I couldn't find the chips for it.  This was back before the internet could have gotten me 2 TDA2030s to fix it for less than bus fare downtown.  The cabs are loaded with four 6"s each and they sound awful; imagine shaking a sackful of marbles and that's what distortion sounds like through these cabs.  My current goal with that is to replace the arrays of 6s with one 12" each for true girth.  I need to find ones that will do OK in smaller-than-average sealed cabs though.

QuoteAlso if you want an easy 50 Watt power amplifier then look at the LM3886 power chip, there are many circuits and PCB's on the net for that chip.
Phil. 

Yep, I've looked at that one many times but could never afford it, and I had the hots for some TDA2050s before they went out of production.  At the moment, I've managed to snap up a couple LM1875s and a TDA7294 with some Christmas money, so I'm not out of options.

I'm thinking I've finally got my thoughts straight on what I'm going to do with all this silicon and hubris; I'll post in the relevant section later. 

Hadn't thought of that, thanks.  I've also found a guy on eBay who sells old speakers pulled from organ units and the like.  Many of them look like re-branded Jensens and others, and many are dirt cheap.  I haven't seen any 'victim of an upgrade' speakers on my local Craigslist, but I'll keep looking...

All I want is 50-75 watts, with no "British Voicing", tight but not absent bottom end, with not overly harsh high end.  Oh, and less than a hunnerd bucks as well (emphasis on "less").  I know, compromises abound, but "good enough" is what I've lived with most of my life.  Either way, I have a couple amps here that I can hijack their speakers for experimenting, so I'm not immediately lacking. When I have the budget for some "real" speakers, we'll talk...

Undoubtedly, which means yet another expense, and I really don't know about speakers, so I'll have to be careful.  Seems like the cheapest "good" speakers are upwards of 60 bucks, so I gotta spend wisely.  Too bad most speaker descriptions are as full of marketing-speak as the rest of it.  I'll save speaker questions for another thread.

Thanks, see ya around...

Howdy folks, I'm here because I want to learn about building and modifying solid-state amps.  I have used many SS amps, but was never satisfied with any of them (probably because I never had the money for a decent one).  These days I still don't have the money, but I do have buckets of parts and a soldering iron (and I know how to use it!!).

I've built pedals for myself and friends, and lately I've built my first guitar.  I've been reading a LOT and I think I'm now ready to explore the world of high(er) power guitar foolery.  I have a LOT of questions (for other threads), so let the hijinks ensue...

I've read Teemuk's book (or at least, most parts of it; great resource, my hat is doffed), perused Elliot Sound Products, and bought a handful of chip amp modules just to make noise with until I can get something better built.
Anyways, onwards and upwards...