Quote from: Loudthud on January 08, 2025, 07:56:04 PMSorry for the delay but here's what I got from my guy at TI. He's not an actual employee as far as I know, more of a paid consultant. The TI engineers are talking about those designs where you use two chips in parallel or two chips in a bridge drive configuration. I think Marshall has a design that uses four chips for amp. Hard to keep working blowing up chips all the tome.

Yea LM3886 is back in stock. I've printed a few PCB batches
for a guitar and Bass power amps to build with them but after
talking with TI engineers they steered me away from them to
use Class D. I've yet to build any amps with the LM3886.  They
pretty much implied it was designed for single module application
or dual in stereo and not recommended for multi modules designs
to double the power. They said rail voltages needed to achieve the
result I expected would exceed the maximum continuous voltage
and cause them to fail. So I get they exaggerated the true power
output and adding additional chips don't increase total power
output in expected quantities. They also exaggerate about the
Class D chips. In reality the advertised output is at 2 ohms and
maximum rail voltages before it burns!! So if you want 200 watts
in the real world you must get 700watts to come close.

I think a single LM3886 chip amp at 50-ish watts would be plenty for a guitar amp.
Especially if it's going through a 2x12 or 4x12

I think it would be better to use class d for bass amps.

If the TI chips can't really achieve their listed wattage, I bet the ICEPower modules can.

There are other options too.

Actually, I just looked and DigiKey has LM3886T and LM3886TF. Are these not the same?

LM3886T

LM3886TF

Quote from: J M Fahey on December 30, 2024, 07:31:41 PMI love LM3886 but they are out of production for years now.

Only non original ones freely available.

Most are straight junk; *maybe* a honest chip factory (in Asia of course) cloned one or makes something which reasonably works, who knows?, but that is still betting on unknown horses, how would you know who is who?

For "just one" not worth the risk.

The real ones are made by TI; they are not "officially" discontinued but typically on heavy backorder because they have WAY more profitable products to make, think car, solar energy, electric vehicles, etc. stuff.

A hobby type (commercial factories have switched to Class D) market is not even a drop in a bucket.

There is a specific tread on LM3886 unavailability on DIY Audio.
Currently 29 pages long, maybe that means something

https://www.diyaudio.com/community/threads/whats-going-on-with-lm3886-availability.386577/

Now and then a few appear at Mouser or Digikey or Farnell, they are swept out within hours.

*Maybe* you get lucky, I commercially make amplifiers and can not work with that uncertainty.
 

I had no idea they were so rare now.

I guess I should look for TDA7293/4 or transistor based boards.

I wish that I could find one that was designed with guitar in mind, is in the 50-100 watt range, and works well to "replicate" tube amp behavior (current drive/feedback or some other manner of raising output impedance and lowers damping).

Maybe I should try to have PCBs made and use schematics from an existing guitar power amp (Yamaha G100/50, Randall RG, Peavey Transtube, etc)

Quote from: J M Fahey on December 29, 2024, 10:06:39 AM

Quote from: Tassieviking on December 28, 2024, 04:12:32 AMI think that PCB is not well designed, you will need a good heatsink on the power transistors but the transistors are right in the middle of the PCB, right behind the transistors where you should mount the heatsink bracket are 2 small footprints for 7 watt resistors.
Have I been asleep for centuries and 7 watt resistors have now shrunk right down in size ?
I would throw that PCB in the bin, I would never try to build that amp since it will undoubtedly lead to heartache.
You can buy a 100 watt class D amp for less then the cost of the components you need to complete it, and the transformer will be expensive as well. There are so many better and cheaper options out there.

Fully agree.

Checked KM Tech site out of curiosity, thinking it might be a Chinese site, it reeks of it.

To my surprise, it IS UK based, but otherwise the description fits .

There is a Business Model based on ordering stuff in China , wholesale, and reselling it.
PCBs can be ordered from fabricators such as PCB Way and others for peanuts, think 10 boards for $5 or so.
https://www.pcbway.com/
https://www.pcbway.com/orderonline.aspx?x=100&y=100&num=10&Layersquote=2&Thicknessquote=1.6

KM seems to be a hardworking PCB design office, churning out tons of PCBs.
Their catalog shows over 200 different designs, they have sold over 20000 empty boards, so the Business model is working.

Most are for the Retro Gaming market, think Amiga, Playstation, Atari, Amstrad, etc. but they also offer some Audio boards.

Most look reasonable, but when being so broad banded sometimes a lemon sneaks in.

Their LM3886 power amp looks fine, the Chipamp is "heat sink mountable" along an edge, they show a populated picture, proof it is "buildable":





Now the "150W Darlington Amp" looks like it was hastily thrown together.
It may meet the "electrical" connections but layout is ludicrous, the thing is unbuildable; so much so that they show a *simulation* where to boot Power Transistors are NOT inserted 
Because they can´t.



Bonus points:
* as noted above, real 7W resistors will NOT fit there, no way.
* speaker ground return track is impossibly thin, it will explode on the first drum roll or something.

Funny notice: LM 3886 board has the "Use heat sink" warning printed on the silkscreen side ; "150W" one does not even mention them. 

That said, IF you already bought it and have no option, it *may* be built, sort of (assuming design is fine, of which I am not sure) by mounting TIPs on a heatsink proper, and running wires to PCB holes.
Same with 7W resistors.
But why bother to correct a botched board design which to boot is also poor electrically?

If you want the hands on build challenge, fine with me, just get the Velleman board, either as a kit or on its own, use your own heatsink and transformer.

If you find another kit that looks suitable, feel free to post/link it here so we can have a look.

That's a lot of good information and I am going to take your advice and shelve this one, at least for now.
I haven't bought any parts for it, so I'm only out the money for the board.
I may come back to it once I have a little more experience.

The LM3886 board is really interesting to me.

Knowing that they aren't as careful or worried about making tested and functioning amplifier PCBs I think I would rather buy from someone who is.

If you (or anyone else) can recommend a good LM3886 and/or a good Darlington or MOSFET PCB that would work well as a guitar power amp, please send links!

I would like it to be in the 60 - 100 watt range.
Ideally it will be used for playing live.

Thanks everyone for the info and advice. I really appreciate it and hope you have a great New Year!

Quote from: Loudthud on December 28, 2024, 02:12:30 AMA few words about the need for short circuit protection. In addition to the bad speaker cable as mentioned by J M Fahey above, there is the very real possibility of a momentary short occurring when using Switchcraft brand jacks (or similar) on the speaker cabinet. Cliff type jacks don't have this problem.

Most Guitar amps use Phone plugs to connect speakers. When a cable with Phone plugs is inserted into a Switchcraft jack, a momentary short occurs across the cable. If an amp is Powered On and you first plug the cable into the amp, no problem yet, until you plug the cable into the speaker cabinet. The amp sees the momentary short and could blow up. Best to leave the amp off while you connect the speakers or always plug into the cabinet first, then the amp.

Those 60s solid state Thomas-Vox amps didn't have short circuit protection. How did they get away with that ? First, they used XLR type connectors for speaker connections. Those won't short the signal. Second, they used an Off - Standby - Play power switch that didn't connect the amp to the speaker until you were in the Play mode. Pretty clever

Thanks for the info!

Would I experience that issue if I used Cliff jacks on the amp and the cabinet has phone jacks?

The standby switch sounds clever and I might have to look into using that too just as an extra safety precaution

Quote from: J M Fahey on December 27, 2024, 11:14:33 PMYou are lucky: exactly that same basic amp but properly made (not much more added, yet ...)is offered in kit form with an *excellent* 20 page assembly manual.

Enter the Velleman k8060.

Proper biasing, short protection, very flat assembly (board,  supply,  power transistors at the ends) make it easy to mount inside a Guitar amp chassis or a powered speaker back aluminum plate.

Circuit:  (eerily similar to the crude one):



Full  manual :  https://cdn.velleman.eu/downloads/0/illustrated/illustrated_assembly_manual_k8060.pdf

from:  https://www.velleman.eu/products/view/?id=360242

They even offer a heatsink, custom drilled or not, and a suitable power transformer.

Of course you can buy only the PCB and parts kit and mount it on your own heatsink or aluminum chassis and get a cheaper and maybe closer to home ANTEK toroid.

Anything from 26+26 to 30+30 VAC, 2.5 or 3A will do fine.

Amp marketing is "optimistic" as usual, forget the meaningless "200W peak power", it has honest 70-80W RMS into 8 ohms, which is perfect for live use.

You're the man! Thanks for sharing.

Quote from: Tassieviking on December 28, 2024, 04:12:32 AMI think that PCB is not well designed, you will need a good heatsink on the power transistors but the transistors are right in the middle of the PCB, right behind the transistors where you should mount the heatsink bracket are 2 small footprints for 7 watt resistors.
Have I been asleep for centuries and 7 watt resistors have now shrunk right down in size ?
I would throw that PCB in the bin, I would never try to build that amp since it will undoubtedly lead to heartache.
You can buy a 100 watt class D amp for less then the cost of the components you need to complete it, and the transformer will be expensive as well. There are so many better and cheaper options out there.

The board is 2 sided so components can be mounted on the under side.

You're right that I could pick up an ICEPower module (or an even cheaper class d module) for less than the cost to build this amp, but that wouldn't be a challenge at all

Quote from: J M Fahey on December 27, 2024, 12:51:04 PMbeware it has NO short protection.

Mr. Fahey you have helped me in the past on DiyAudio.  I appreciate your advice and knowledge.  I have read lots of posts you've made helping others, especially related to guitar amps you have built.

Do you recommend a way to include protection for the amp?  I have seen a few PCBs on ebay for speaker and DC protection. 

I haven't ever designed my own PCB so I would prefer to either buy a PCB or wire it up using another kind of board.

Thanks!

Thanks for the reply!  I assumed 150 watts was overstated.  60 - 80 watts is perfect.

I did actually want to build this as a stand alone head, so I think I should add in some kind of protection circuit.

Hey all!

I was recently given an interesting power amplifier PCB based around a Darlington TIP41/TIP147.

I haven't built it yet, but since its a pretty simple circuit, I wanted to see if anyone had any suggestions for how I could make it work well as a guitar power amp?
Ideally, I'd like to experiment with making a hybrid amp.

You cannot view this attachment.
You cannot view this attachment.


Would this be an opportunity to add current feedback from the speaker? 

Could any of the component values be changed to help the response?

Or is it fine the way it is and I should just focus on the preamp?


Thanks!

Quote from: phatt on February 20, 2024, 08:59:41 PMhi Megatrav,

Wise not to focus on one aspect like Efficiency.
Heck, Valves waste a lot of energy as heat yet they are still considered the holy grail of tone for a lot of guitar players.
There are just so many rabbit holes in this field that are mostly a waste of time.
I have 3 Valve Amps but my main setup is a pedal board which delivers a great sound into an old 70's 80's era Keyboard Amp.

If you research how Valves actually work you will realise that a lot of the magic is due to a very poor Power supply.
Depending on the design With no signal the HT voltage might read 400VDC in a valve amp. Turn up the volume and hit a big power chord hard and that 400V will drop like a brick, You might see it drop by 100V or more, depends on The ability of the PSU design.
As that signal fades away that voltage rises back up.

This is effectively causing compression so the sound level actually drops and limits the absolute SPL and as the Voltage rises back up it gives the impression of more sustain.
But with SS amps the supply voltage is very stiff and hence no magic sustain.
A SS 40 volt supply might only sag 2 or 3 Volts and by then you get into hard clip which is ugly, so hence SS gear gets a bad reputation.

So to recreate that effect with SS gear you will need a compressor.
I do all of that with my pedal board and the Amp just makes it louder.
The Amp adds very little colour to the final sound although it does have a spring Reverb which adds a final touch. I use 3 OD dirt pedals into my Compressor.
the Gain of all 3 dirt pedals are set fairly low and as you turn each one on you get more drive. And the compressor does 2 jobs obviously it adds compression but it also keeps the absolute SPL in a set range so when I play leed parts nothing gets too loud.
I use an optical compressor as they tend to work very well for OD rock guitar sounds.

As for Class D stuff I've noticed that the freq response often goes down way too far and that can be a big problem if you are trying to reproduce the classic sounds.

Understanding and limiting the bandwidth of your gear will help refine your sound.
Too much Low and High freq will just frustrate you and drive you crazy.
There are many ways to great tone and even when you get there you will find that different venues and rooms can give different results. I have built many circuits and thought I had cracked the holy grail only to find that when I played live it sounded like crap.

If it interests you I posted a recording of my gear on here a while back.
This will give you some idea of what can be done with all SS gear.
https://www.ssguitar.com/index.php?topic=5309.msg41595#msg41595
Regards from an old bloke who has spent lots of time down these rabbit holes, Phil

I get what you are saying.  I definitely understand voltage sag being part of classic tube amps.  I don't think that is usually the case with more modern high gain tube amps.  It is also not the case with amps like HiWatt that had very well-designed power transformers and output transformers.

But yes, there is definitely something about the way an output transformer will affect frequency response and interact with the speaker. Solid State amps have to have that built in as emulation (compressor circuits and/or post preamp EQ) or sometimes additional voltage regulating circuits that work similar to tube amps but don't actually affect the power or output.

Efficiency is important if the end goal is smaller, lighter, and cooler (temperature).
As for Class D frequency response, I can't agree that this is the case 100% of the time.
2 real solid examples of great sounding Class D amps are Quilter and the Victory V4 amps which have tube preamps running at high voltage (I assume at least 250v) that go into a power amp emulation, then a Class D output stage.

If you listen to any clips of them, I don't think you can say they sound bad or have bad frequency response.

As for recording, I have no problem using plugins or my HX Stomp. They sound great to me.  I would really love to build my own hybrid amp with a tube preamp and solid state power amp for gigging.  Class D seems like the obvious choice given what I stated above.

Quote from: phatt on January 13, 2024, 04:34:38 PMJust a note on Digi Amps and SMode supplies.
Ok they are cheap, light weight, and so so convenient.
But keep in mind, Unlike Smode supplies Iron and Copper Transformers have an indefinite life span, if used within spec.
Jezzus Not even god could make a more bullet proof design.

 I doubt that in 50 years from now that these SMPS circuits will still be running as they are far more complex and hence far more prone to failure.
Notice how many Dead computer Power boxes fill bins in repair shops.

Now I'm not up to speed on Digi amps but the few I've had the displeasure of working with leaves me thinking that it's hard to beat a basic old school transistor poweramps.
Well designed unit go for years without issue. Of course Can caps dry out eventually but simple to replace.
with most things now surface mounted and hard to work with it's a throw away item. But by then you find out OH sorry they don't make them anymore.
 and you are left with land fill.  

If it interests you Rod Elliot has a ton of info on Amp design, a lot of which is aimed at muso gear.
Start here;https://www.sound-au.com/

I have found him to be very helpful while trying to build Analog Power Amps.
Phil.

Hey Phil,

Thanks a ton for the response.

I agree with you on the idea that building things with the intention of them not lasting is never a good idea. It's wasteful and isn't good for anyone.

I have nothing against transistor amps other than the lack of efficiency.
The most appealing thing about Class D is that if someone wanted to build a high wattage bass amp they could keep the weight lower because they wouldn't need as large of a heat sink.
I've looked into Class H amplifiers but they seem even more complicated and with only slightly more benefit over Class AB.

I actually think that when it comes to building an amplifier, a power transformer is a better idea because it will last longer and probably have less failure (potentially?). This may be a silly question, but can one use a power transformer with a Class D amp?


Lastly, these small SMD modules were sort of my Segway into learning about Class D amps. If I were ever smart enough to build my own, I would want to use through hole components.
That's how I build everything I make now. 

I will check out those power supplies.

This is basically the board I have https://a.co/d/66I0eA7

There is no heatsink attached. I suppose I thought since it's Class D it wouldn't need a heatsink because of the high efficiency.

Can you recommend one to use with it?

Thank you for all of the information

Quote from: Tassieviking on January 10, 2024, 04:55:37 AMThe ICE power modules are well priced for what you get, you can get cheaper modules from China but often you have to buy a power supply and an amplifier and put them together.(And most likely not run them anywhere near the advertised power without dropping out from overheating)

The  Straight Ahead Amplification power amps seems like someone is just putting pre-bought modules into a cheap box and selling them from home, I could be wrong but I would not buy one unless they have been fully certified for public use like that.

If you want and need a really powerful amp then it is best to buy a good quality made one as it will be certified with all the various agencies required nowadays.
I don't think that it would be worth the effort to build an amp from scratch if you want to truly be able to gig with it, I believe some venues might not allow non-certified gear to be used due to insurance reasons.
If an arena was to burn down because of a musos homemade amp caught fire there could be serious problems with the insurance companies as well as with the legal implications if someone got hurt or worse.

If you want your own sound then build a preamp in a stomp-box and run that into the return jack on a commercial amplifier, proper Class-D Bass amps are not that expensive and deliver a lot of power. Certification  can cost $20,000-$50,000 to get through for a single amplifier model and that has to be included in the final cost of a proper amp you can buy in the shop.

If you just want it for home use then get/make whatever you want and go for it.
Have you read Teemu Kyttälä's Book about solid-state guitar amplifiers ?
There is more in it then most people will ever need.

https://www.ssguitar.com/index.php?topic=711.0

Thanks for the input.  I hadn't considered all of those factors.

I do understand getting what you pay for and I would definitely rather buy something legit than risk blowing myself up. 

I am wondering something- you mentioned issues with combining a power supply board with an amp board:
I have some TPA3118 boards and I have been looking at some AC to DC power supply boards to use with them. 
The ones I have looked at are minimum 110vac to 24vdc 2-5A. The specs call for minimum 48 watts so I have been looking at ones rated above that.

Would it be a bad idea to use one of those? 

I would prefer a proper power cable instead of a laptop power pack supply.

Thanks for the book link, I have saved it and I will definitely be reading it!

I have looked at those ICEPower modules and they do look nice.
They are a little pricey though.

I think it's a little strange that there aren't more DIY high wattage Class D PCBs or kits available.

I recently read a thread on another forum about Straight Ahead Amplification power amps. I got his email from Facebook and reached out to him.

He said that he offers a standard and a bass model. The Bass model handles lower frequencies better.
He mentioned modifying modules.

Does anyone know what would be modified?


The truth is, I don't really want "change this resistor and capacitor" but more so I would like the ability to test/breadboard/socket components on a PCB so that I could see what sounds best.

I would also really like to learn more about the general operation compared to a tube amp.

For instance, the ability to adjust negative feedback and response.

Does Class D work like that? I think I've seen Class AB solid state amps that do but maybe it was just simulating that.