Best DIY TDA2050/ or other guitar amp

[Crontox102098]

Hi guys, i'm very undecided... just i want to know your opinion...

Cheers and thanks. 

[mth5044]

Tiny Giant.

[R.G.]

You're making the classical mistake - an amplifier is a small wart on top of a power supply and heat sink.

To a first approximation, for how hard something is to build, the amplifier doesn't matter, only the power supply and heat sink.

That being said, the LM3886 is a remarkably good and reliable chip amp if the power supply and heat sinking is right for it.

I personally think that a clever thing to do is to make modular amplifier/speakers so that you can use as many as you need.

Imagine one 50W amplifier (the LM3886 does this nicely) with its own power supply and heat sink inside a speaker cabinet with one 50W speaker. (You can make this lower than 50W by simply lowering the power supply voltages and currents by design)

Then make another one. Now you have a 100W amplifier, but you also have
- smaller loads to carry into/out of a gig
- two speakers that can be individually aimed, and which will produce higher SPL over more of the audience than one single 100W/two speaker box
- no disaster if only one dies; you'll just be playing not quite as loud instead of air guitar
- the option to make two more and have a 50/100/150/200W guitar amplifier; this can get remarkably loud, but even more it's flexible, as you can use one "channel" as a monitor on your own
- great freedom in making/choosing a preamp setup to get the sound you want.
- much - MUCH - simpler construction than one bigger amp

[Crontox102098]

You're making the classical mistake - an amplifier is a small wart on top of a power supply and heat sink.

To a first approximation, for how hard something is to build, the amplifier doesn't matter, only the power supply and heat sink.

That being said, the LM3886 is a remarkably good and reliable chip amp if the power supply and heat sinking is right for it.

I personally think that a clever thing to do is to make modular amplifier/speakers so that you can use as many as you need.

Imagine one 50W amplifier (the LM3886 does this nicely) with its own power supply and heat sink inside a speaker cabinet with one 50W speaker. (You can make this lower than 50W by simply lowering the power supply voltages and currents by design)

Then make another one. Now you have a 100W amplifier, but you also have
- smaller loads to carry into/out of a gig
- two speakers that can be individually aimed, and which will produce higher SPL over more of the audience than one single 100W/two speaker box
- no disaster if only one dies; you'll just be playing not quite as loud instead of air guitar
- the option to make two more and have a 50/100/150/200W guitar amplifier; this can get remarkably loud, but even more it's flexible, as you can use one "channel" as a monitor on your own
- great freedom in making/choosing a preamp setup to get the sound you want.
- much - MUCH - simpler construction than one bigger amp

Thanks for your answer, R.G.
Really i didn't understand what do you mean with modular amps... You're talking about something like this:
https://www.kickstarter.com/projects/1335354839/banana-jack-amps-no-solder-all-tube-guitar-amp-kit

Or something like the power supply in a box, amp in other...

I'm spanish, sorry and i really don't understand very well.
Thanks.
Carlos.

[R.G.]

No apologies. Your English is far, far better than my Spanish, which is purely rudimentary.

What I was suggesting was to separate the preamp of a guitar amp from the power amp. The preamp typically does all variable gain, tone controls and other fancy stuff. The power amp does nothing much (*) except make it louder for the speakers.

The second suggestion is to make it louder not by making one very loud power amp, but several power amps, each having their own speaker. Then drive one, two, or more modular power amp/speaker combinations to get as much audio power as needed.

It's a fundamental rethinking of what a power amp is. It's much more like the modern practice on public address systems.

So you would make (or use a pre-existing) preamp which is made for a guitar to get your favorite guitar sound, and then make several output jacks to go to power amplifier/speaker combinations.

This has several advantages, not the least of which is that it's far, far easier to get a 30W to 50W amplifier to work than it is a 100W, 200W, 500W amplifier to work. And it's far easier to get a SECOND, THIRD, FOURTH.. power amp/speaker to work, because you've worked out the problems on the first one. And it's easier to find parts for a moderate sized amplifier than a gigantic one. This list of advantages just goes on.

The TDA2050 is a 32Wrms power amplifier that works from +/-18V power supplies. The LM3886 is a 50-60Wrms power amplifier that works from power supplies up to +/-32Vdc or so. They are roughly equal on the same power supply voltages. I happen to like the self-protection qualities of the LM3886, but that is a personal preference.

The TDA2050 is not recommended for new designs. The LM3886 and TDA2050 are about the same price, the TDA about US$1.00 to US$1.50 cheaper. But there are many PCBs and power supplies/transformers available for the LM3886 on ebay. Here is one link: http://www.ebay.com/itm/60W-LM3886TF-Sound-Audio-Amplifier-Mono-Digital-Power-AMP-DIY-Kit-/371198412910?pt=LH_DefaultDomain_0&hash=item566d26486e I do not know if this is the best, just an example.

The power supply, consisting of a chassis (!!), heat sink (!!!), power transformer, rectifiers and filter caps will all cost you far more than the whole amplifier setup.  Probably so will a good speaker.

* Some tubes-are-everything people will say that the power amp is a magic tone block all by itself. Well, maybe that's true. But if so, how do we hear good guitar sound from the small amplifiers on stage at concerts which are sending their sound directly into microphones for the Public Address system to make louder?

[Crontox102098]

No apologies. Your English is far, far better than my Spanish, which is purely rudimentary.

What I was suggesting was to separate the preamp of a guitar amp from the power amp. The preamp typically does all variable gain, tone controls and other fancy stuff. The power amp does nothing much (*) except make it louder for the speakers.

The second suggestion is to make it louder not by making one very loud power amp, but several power amps, each having their own speaker. Then drive one, two, or more modular power amp/speaker combinations to get as much audio power as needed.

It's a fundamental rethinking of what a power amp is. It's much more like the modern practice on public address systems.

So you would make (or use a pre-existing) preamp which is made for a guitar to get your favorite guitar sound, and then make several output jacks to go to power amplifier/speaker combinations.

This has several advantages, not the least of which is that it's far, far easier to get a 30W to 50W amplifier to work than it is a 100W, 200W, 500W amplifier to work. And it's far easier to get a SECOND, THIRD, FOURTH.. power amp/speaker to work, because you've worked out the problems on the first one. And it's easier to find parts for a moderate sized amplifier than a gigantic one. This list of advantages just goes on.

The TDA2050 is a 32Wrms power amplifier that works from +/-18V power supplies. The LM3886 is a 50-60Wrms power amplifier that works from power supplies up to +/-32Vdc or so. They are roughly equal on the same power supply voltages. I happen to like the self-protection qualities of the LM3886, but that is a personal preference.

The TDA2050 is not recommended for new designs. The LM3886 and TDA2050 are about the same price, the TDA about US$1.00 to US$1.50 cheaper. But there are many PCBs and power supplies/transformers available for the LM3886 on ebay. Here is one link: http://www.ebay.com/itm/60W-LM3886TF-Sound-Audio-Amplifier-Mono-Digital-Power-AMP-DIY-Kit-/371198412910?pt=LH_DefaultDomain_0&hash=item566d26486e I do not know if this is the best, just an example.

The power supply, consisting of a chassis (!!), heat sink (!!!), power transformer, rectifiers and filter caps will all cost you far more than the whole amplifier setup.  Probably so will a good speaker.

* Some tubes-are-everything people will say that the power amp is a magic tone block all by itself. Well, maybe that's true. But if so, how do we hear good guitar sound from the small amplifiers on stage at concerts which are sending their sound directly into microphones for the Public Address system to make louder?

Now i understand, i cannot make nothing with tubes because buy it here in Colombia are really expensive. Thanks for your help, now i've got some ideas for the "modular thing"

Again, thanks R.G.

- Carlos.

[bluebunny]

The power amp does nothing much . . .

After a couple of years of reading R.G.'s wise words, I now think of a power amp as an "audio-modulated power supply".

[monksanto]

Thanks for that R.G., that was interesting to read!

[Crontox102098]

The power amp does nothing much . . .

After a couple of years of reading R.G.'s wise words, I now think of a power amp as an "audio-modulated power supply".

"Audio-modulated power supply"
Really i think that is, too. If you look good the power amp there's doing nothing compared to the power supply.

[sajy_ho]

Hey man, I've recently build a nice practice amp using TDA2040. I'm using this chip because it can work on wide range of supply voltage. I'm using my laptop supply(20V) to power it and in this range it has a warm tube-ish clean sound and at high Gains you'll get a sweet overdrive! Originally I used Fairchild 2N5457s for my amp, but there was a bad clicking noise when overdriven, then I switched to 2N3819 and the problem solved. The only thing you must know is 'How to bias a Fetzer Valve stage', and then you'll be surprised about the sound!
Here is the project file:https://www.dropbox.com/s/gry98nzod6gs93d/The%20Practice%20Box.pdf?dl=0
And a picture of my build:https://www.dropbox.com/s/r9c7ntcz9x1gp3l/20141114_193840.jpg?dl=0
Wish it comes handy for you!


Sajad

[Crontox102098]

Hey man, I've recently build a nice practice amp using TDA2040. I'm using this chip because it can work on wide range of supply voltage. I'm using my laptop supply(20V) to power it and in this range it has a warm tube-ish clean sound and at high Gains you'll get a sweet overdrive! Originally I used Fairchild 2N5457s for my amp, but there was a bad clicking noise when overdriven, then I switched to 2N3819 and the problem solved. The only thing you must know is 'How to bias a Fetzer Valve stage', and then you'll be surprised about the sound!
Here is the project file:https://www.dropbox.com/s/gry98nzod6gs93d/The%20Practice%20Box.pdf?dl=0
And a picture of my build:https://www.dropbox.com/s/r9c7ntcz9x1gp3l/20141114_193840.jpg?dl=0
Wish it comes handy for you!


Sajad

Thanks a lot! think i can use the "preamp" with the Fretzer Valve and use it with the LM3886. Need something warm and loud, and soft when i need to. Know LM3886 can do this very well.

Cheers.

[Crontox102098]

Guys, for example,a TDA2050 do the same thing in single power supply than dual power supply? 

Thanks.

[R.G.]

Thanks a lot! think i can use the "preamp" with the Fretzer Valve and use it with the LM3886. Need something warm and loud, and soft when i need to. Know LM3886 can do this very well.

The LM3886 (and TDA2050 and other chip amps) are *accurate*. They reproduce what you send them. So if you send them warm, they put out warm. If you send them harsh, they'll accurately do that out too.

Guys, for example,a TDA2050 do the same thing in single power supply than dual power supply?

The difference between a dual power supply amp and a single power supply amp is that the single power supply amp, just like opamps on single supplies, have to be biased to half the total single power supply, and have to have a **BIG** capacitor on the output to couple the AC power out to the speaker while blocking the DC level. A dual power supply amplifier needs two big filter caps in the power supply, but no coupling cap on the output of the amp. So they both need two big electrolytic capacitors, just on slightly different places.

I recommend that if you go to all the trouble to build an amp like this, you do the power supply to match modern amplifier practice: use a dual power supply, and don't try to save a little on using some compromise power supply. Single power-supply amplifiers can get tricky, and there's no need to add another layer of complexity.

In fact, I recommend finding and buying a used or dead existing amplifier. I found a Guitar Center "Rogue" amplifier for USA$40 in the local classified ads. This was a combo cabinet, with two 12" speakers, a chassis, and a 100W power amplifier and power supply already in it. It even worked, but that was not a consideration. $40 is very cheap for an existing cabinet and chassis and two disposable speakers in it just as a test rig. It would have been worth the money for only the cabinet, chassis, power supply and heat sink. It saved me a LOT of time. It is possible some guitar tech near you has some truly dead amplfiers left by disappointed owners that you could buy for cheap, then strip the insides out. Truly, the cabinet, chassis, power supply and heat sink are where 90% of the work is.

[caspercody]

What about one of these kits:

http://chipamp.com/product-category/chipamp-kits/lm3886kits/

I also am interested in finding a small amp to use with my Line 6 HD300. This does not sound to great going through a amp, even just into the send (or return I forget) input of the effects loop. Just going into headphones sounds great.

Thanks
Rob

[PRR]

> I now think of a power amp as an "audio-modulated power supply".

A BIG modulated power supply.

Much bigger than most folks here have ever worked with.

HIGH current. HIGH heat. Voltages that you don't put your tongue on (not even a sweaty finger).

Things go wrong very quickly, and expensively.

In most lands, by-far the better path is to find a "dead" commercial amp and fix it. Amps don't go 100% dead. Often only one (maybe a few) parts are shot. The case and heatsinks are usually fine. Often the power transformer is fine. Fairly often a not-old amp has good main filter caps. So that's 80% of the cost right there, already professionally selected to play well together and assembled, at a discount. 

__________________________________________

IMHO, the TDA2050 is a fine _small_ amp (20 Watts or so). Tens of thousands of small practice amps have shown that it holds-up under abuse just fine. The LM3886 has a very glorious protection system, and super well documented, but that does not make the '2050 series a bad choice. And '2050 has the right number of pins (5), while the LM3886 has a long row of pins to figure out. OTOH there are (as R.G. and Rob say) easy-use kits for the LM3886, and it will handle nearly any TDA2050 job without strain. So it may come down to what's available locally, or if eBay from China is affordable. (I know that Brazil slaps a heavy tax on some imported electronics, so Columbia might also; but small eBay deals sometimes sneak past the tax-man.)

[caspercody]

On that same link I posted, they have a kit for the LM1875. Anybody work with this chip?

[caspercody]

Also, here is a link to a TDA2050 project:

http://diyaudioprojects.com/Chip/DIY-TDA2050-Hi-Fi-Chip-Amplifier/

I built his tube headphone amp using a 12AU7 / IRF510 and it sounds great.

I also see Velleman has a kit using a TDA2616, any thoughts on this kit?

Thanks
Rob

[R.G.]

On that same link I posted, they have a kit for the LM1875. Anybody work with this chip?

I have. It works well within its limitations, but think of it as a 20Wrms amplifier max. It does very high quality sound within its power rating. I put a 20W amp into a Hammond 1590BB for a friend one time. A quarter-brick heat sink is a nice fit on this package, and just gets warm at full RMS power with a sine wave. He's still using it.

For all chip amps, keeping them from going into thermal shut down requires some really good heat sinking. They don't have enough nano-acres of heat transfer area to get heat out as well as discrete power transistors. But if you can content yourself with keeping them in a modest power supply and not pushing the thermal ratings, they work great.

The Lm3886 is marketed as a 50-68W power amp. That requires immaculate thermal design and probably regulated power supplies.  I really like the LM3886 as a 30-40W power amp, where the thermal issues are not so severe (largely because it's running from a lower total power supply voltage) and it starts being really reliable.

A single LM3886 with a power supply of +/-32V minimum, rising to +/-40V under high line/low load will drive one 8 ohm speaker to 30-35W very reliably. If you use +/-28V you can get 40W into 4 ohms, but you start running into thermal issues.

It is possible to electrically parallel N power amplifiers, and I have toyed for a long time with re-powering a Vox Beatle with four LM3886's in parallel to run the 2-ohm load to 120Wrms. Someday I'll try it.

[bool]

A sturdy chip to build an amp is a TDA7924.

TDA2040 and TDA2030A (A!) are both fine and good and forgiving up to cca. 10W output. It's also possible to run them from +/- 15V supply - if you have a good enough PSU to handle that.

One rule with these chip-amps is to never let them swing close enough to rails to engage their protection circuits. Otherwise, the result is no-good (in multiple areas) and prone to smoke.

If you want a trusty amp that will be nice to your speaker (yes speaker), use a single-supply schematic and connect the speaker through a big cap (simple math shows that a +/- supply will need two big caps - and a single supply will also need two big caps, one as a reservoir and the second as a coupling cap). This generally removes the need for speaker-protection circuits etc.

A single smaller value elco and two additional biasing resistors are the price for that (according to TDA datasheet application circuits).

Added benefit is the ability to mount the chip directly to a grounded heatsink, which is double-plus-good for a throw-around circuit and it's a bit sturdier as well.

The negative? There will be some losses in the output cap, so a bit less headroom. Do you care?

I suspect that added capacitor distortion will be of no concern in the guitar world. There are ways to minimize that, however.

[Crontox102098]

A sturdy chip to build an amp is a TDA7924.

TDA2040 and TDA2030A (A!) are both fine and good and forgiving up to cca. 10W output. It's also possible to run them from +/- 15V supply - if you have a good enough PSU to handle that.

One rule with these chip-amps is to never let them swing close enough to rails to engage their protection circuits. Otherwise, the result is no-good (in multiple areas) and prone to smoke.

If you want a trusty amp that will be nice to your speaker (yes speaker), use a single-supply schematic and connect the speaker through a big cap (simple math shows that a +/- supply will need two big caps - and a single supply will also need two big caps, one as a reservoir and the second as a coupling cap). This generally removes the need for speaker-protection circuits etc.

A single smaller value elco and two additional biasing resistors are the price for that (according to TDA datasheet application circuits).

Added benefit is the ability to mount the chip directly to a grounded heatsink, which is double-plus-good for a throw-around circuit and it's a bit sturdier as well.

The negative? There will be some losses in the output cap, so a bit less headroom. Do you care?

I suspect that added capacitor distortion will be of no concern in the guitar world. There are ways to minimize that, however.

R.G.'s says dual, you says single power supply... Don't know, i want a clean and CLEAR sound, loud, warm... (i know i must to have got a preamp) but, really don't know what to do...