Can TDA2040 amplifier be used as a power amp for bass or guitar?

[JebemMajke]

I was wondering if this tda2040 circuit could be used as a power amplifier for guitar and/or bass?

I would use fet version of alembic f-2b as a preamp. Or even better ROG's ginger.

[therecordingart]

Peavey seems to think so. The Vypyr 15 has a TDA2040 chip and that little amp sounds great!

[JebemMajke]

So in theory i could place that preamp directly in front of that poweramp and it would work on 8 ohm speaker?

[Mark Hammer]

Yes.  In fact a quick survey of all the solid-state amps in the 50W-or-less range (especially the 20W-or-less range) shows many make use of the TDA2030/2040/2050 chips, along with many other chips in similar form factor from other manufacturers.

Just make sure you have suitable heat-sinking, because they can't manage all that current alone.

And, as always, I'll add the consideration that good cab design, and efficient speakers, can make every watt stretch further.  When it comes to low-budget amps, manufacturers look for ways to shave off production costs.  And when you're down that low, things like cab depth/size/weight, and transformer weight, start to become considerations, because they impact on required space for inventory, as well as packaging and shipping costs.  Just because a manufacturer who wants to turn a profit on an amp with a $149 retail price feels that an open-back cab 6" deep with 5/8" chipboard, and a power transformer that delivers 50VA but weighs half as much as one that would get every last watt out of the power chip, is "good enough", doesn't mean YOU have to think of that as good enough.

[Gurner]

Just make sure you have suitable heat-sinking, because they can't manage all that current alone.

JebemMajke didn't state what voltage the rails would be for his cicruit - the TDA2040 can work as low as 9V ...in which, I'm fairly sure it wouldn't need an heatsinking....but yeah, increasing the rail voltage up to the 40V absolute max is gonna make that puppy cook at full drive, so heatsinking is the order of the day.

[JebemMajke]

It's not going to be portable so it doesn't have to be a 9v amp. I just want it to be as clean as possible and to be FET preamp friendly. And ofc stompbox friendly
So it needs big heat sink for 40 volts. How big? Any suggestions? Should I put "send-return" jacks between preamp and poweramp?
Do i need some cab simulator or something else between preamp and poweramp?
Edit
I've just looked at the page I;ve nicked that schematic from. It says 16v +/- and 30W. Neat.
So in order to run it on 40 volts do i need to make some adjustments? Or will bigger heat sink suffice?

[R.G.]

Good points. To this, I would add that if the power supply voltage is 30 to 60V total (i.e. most negative to most positive) it is quite difficult to beat the cost (about US$5.00), self protection and performance of the LM3886.

@JM: It's not commonly appreciated, but the power supply and heat sink are a much, much bigger issue for any power amp than the actual power amp circuit itself. To a first approximation, the power amp itself doesn't matter. It's only at the second level of consideration that you worry about the insides of the power amp. If you have not already bought 2040 chips, I suggest you spend some time thinking about the power supply for the amp and the heat sinking.  Two LM3886's will give you 100W - from a suitable power supply, with suitable heat sinking.

[Seljer]

The rule of thumb on heatsinks seems to be that you can never have too much. I built a TDA2030 amp (30watts of output power) and used the heatsink from a $12 computer CPU sans the fan and in the most vigrouous testing I gave it (an hour of full volume fuzzed out power chords) it barely got warm

Send/return jacks are a good idea.

You don't need any cab simulator, unless you plan on hooking this up to fuill range speakers. Using a real 10 or 12" guitar speaker will be real thing

There should be a graph somewhere on the datasheet that shows output power vs supply voltage (and have multiple lines drawn for different loads), that'll answer your last question. (and check the "maximum ratings" section at the start for the maximum supply voltage!)

[Gurner]

Just as a throwaway input....just because a chip might be 30W capable, it needn't get hot.

Like I say if you run it at 9V, it'll barely get warm ...many moons ago (when starting out in all of this), I used to think that by using a 3W, 5W 10 IC, it actually gave me that output just by using a circuit with one in - it doesn't (the "aha" moment  was a big one for me!) ....you only get higher output power by either increasing the voltage swing (increasing the rails or using btl) or lowering the actual impedance of the load (speaker).

So dropping in a '30W' IC that's pin compatible into a circuit that previously had a '10W' IC (and keeping everything else the same), you haven't gained anything power wise.

[Perrow]

General guitar gadgets has a schematic for a 20X0 amp.

http://generalguitargadgets.com/projects/13-amps/59-tda20x0-amp

I've built the Marshall 8010, guess some values would benefit from being tweaked if you're going to play bass through it.

http://dl.dropbox.com/u/20165528/8010_pdf.pdf

I have a smaller (verified) layout with pots, switches and jacks offboard, I can post it if you'd like.

[Mark Hammer]

Just as a throwaway input....just because a chip might be 30W capable, it needn't get hot.

Like I say if you run it at 9V, it'll barely get warm ...many moons ago (when starting out in all of this), I used to think that by using a 3W, 5W 10 IC, it actually gave me that output just by using a circuit with one in - it doesn't (the "aha" moment  was a big one for me!) ....you only get higher output power by either increasing the voltage swing (increasing the rails or using btl) or lowering the actual impedance of the load (speaker).

So dropping in a '30W' IC that's pin compatible into a circuit that previously had a '10W' IC (and keeping everything else the same), you haven't gained anything power wise.

Which is pretty much why I shine the spotlight on cab design and speaker choice.  Unless we're talking about substantial differences in wattage, the need for output levels is more easily addressed by simply having something that makes more efficient use of the power available.  Many of the audio books I used to read in the early 70's would comment that 4W would provide "room-filling sound" if using a properly designed enclosure with reasonably efficient speakers.  More wattage, suitably powered, will afford greater headroom for peaks, but you can do an awful lot of audio damage with a mere 10W.  I think most folks would be surprised to see how little wattage is being supplied by their various audio amplilfiers in their car, or home, or band practice, when they hear levels that they find "loud enough". 

In the case of bass amps, there is usually a need for much greater wattage, even though the typically larger speakers and cabinet produce greater loudness levels.  The reason is that bass is generally played clean, and the instrument itself generates some serious peaks, so the extra wattage is principally for headroom to accommodate the peaks.

[soundclone]

I've built the Marshall 8010, guess some values would benefit from being tweaked if you're going to play bass through it.

http://dl.dropbox.com/u/20165528/8010_pdf.pdf

I have a smaller (verified) layout with pots, switches and jacks offboard, I can post it if you'd like.
[/quote]
Post it ,Please..

[Perrow]

Post it ,Please..

For the first time in a long while I'll be without my computer for the weekend. I'll see if I can post it Sunday evening (GMT+1).

[Nasse]

http://www.jabel.com.pl/files/instrukcje/J-057.pdf another way to skin the cat, if you have suitable power transformer

[JebemMajke]

General guitar gadgets has a schematic for a 20X0 amp.

http://generalguitargadgets.com/projects/13-amps/59-tda20x0-amp

I've built the Marshall 8010, guess some values would benefit from being tweaked if you're going to play bass through it.

http://dl.dropbox.com/u/20165528/8010_pdf.pdf

I have a smaller (verified) layout with pots, switches and jacks offboard, I can post it if you'd like.

How about schematic?

@Nasse
Cool one, thanks.

[Earthscum]

In the case of bass amps, there is usually a need for much greater wattage, even though the typically larger speakers and cabinet produce greater loudness levels.  The reason is that bass is generally played clean, and the instrument itself generates some serious peaks, so the extra wattage is principally for headroom to accommodate the peaks.

I'd like to point out that many newer bass amps (my TNT is supposed to have it) have compression built in for this reason. I have troubles leveling effects when I run direct, but through my amp I don't have as many problems. Direct, I have to level a distortion to sound somewhere between the attack and the sustain, and it's never in a happy place, so direct recording gets split into clean runs and distortion run after. With my amp, the attacks are compressed down (partly due to the speaker, of course) and I can swap between distortions and cleans all night without running into the problem.

Marks comment about generating "serious peaks" made me think of that, so I figured I'd throw it out there for consideration.

My TNT is supposed to be D-Class output, which I've come to understand makes it really easy to implement compression at the power section. A while back I was starting to look into the TDA7294 to make a head unit for my blown TKO (the original head blew, and ended up in the garbage during one of my many moves. Stupid me).

[Mark Hammer]

And in fact, if you look at some of the 2040/2050-powered amps for bass and/or keyboard (from CRate, in particular), you'll see a limiting circuit built around the power section; likely because the chip has sufficient power to be able to handle the average signal level, but not the peaks.

[R.G.]

I was starting to look into the TDA7294 to make a head unit for my blown TKO

The 7294 has the reputation for some serious reliability problems and built-in application circuit traps. Not that it can't work, just that it requires some serious technical work and not a few blown chips to get it there. The LM3886 has a reputation among amateur builders for just working as long as you don't give it a task that's just impossible to do.

The 7294 will - theoretically - work at higher powers than the LM3886 because it can withstand a higher power supply voltage. This is somewhat diffused by the fact that you have to use multiple units to get more output power dissipation because a single unit at the higher power supply voltages can't get enough heat out of the package to survive. So you use multiples anyway.

Having been a power amp nut for at least 50 years (!) I'm coming back to discretes as the way to go, based on cost and power arguments. The chassis, power supply, and heat sinks are the majority of the costs for a power amp over a couple of watts; this gets even more so as power goes up. At over about 20W, you can neglect the power amp electronics itself as a cost factor. At over 100W, buying whatever power transistors you need and building a small-signal front end for them is a trivial task compared to the chassis, power supply, and heat sink, even including the self-protection circuits.

[Perrow]

How about schematic?

Schematic: http://dl.dropbox.com/u/20165528/8010%20schematic.pdf

Layout and transfer as pdf: http://dl.dropbox.com/u/20165528/Marshall8010.pdf

Layout and transfer as png: http://dl.dropbox.com/u/20165528/Marshall8010.png

Square pad denotes pin 1 of IC and pots and positive of caps. The order of the pots is the same as in the previously posted layout.

Just left of the diodes (D5, D6) is the 2PDT clean/overdrive switch. Originally one of those diodes were a 3mm red led, and there's holes for easier/more beautiful mounting of such under both D5 and D6.

Connections for output jack (lower right corner) reduced to four cables instead of six. Line out connection is still untested.

The 0.1R resistor has the room to be higher wattage if you have trouble finding a 1/4W one, I initially had but bought a bunch of 1/4W ones from ebay (50pcs for $1.98 shipped).

The layout follows the "original" posted earlier quite well, albeit compressed (less so the further right you get in the layout).

[soundclone]

How about schematic?

Schematic: http://dl.dropbox.com/u/20165528/8010%20schematic.pdf

Layout and transfer as pdf: http://dl.dropbox.com/u/20165528/Marshall8010.pdf

Layout and transfer as png: http://dl.dropbox.com/u/20165528/Marshall8010.png

Square pad denotes pin 1 of IC and pots and positive of caps. The order of the pots is the same as in the previously posted layout.

Just left of the diodes (D5, D6) is the 2PDT clean/overdrive switch. Originally one of those diodes were a 3mm red led, and there's holes for easier/more beautiful mounting of such under both D5 and D6.

Connections for output jack (lower right corner) reduced to four cables instead of six. Line out connection is still untested.

The 0.1R resistor has the room to be higher wattage if you have trouble finding a 1/4W one, I initially had but bought a bunch of 1/4W ones from ebay (50pcs for $1.98 shipped).

The layout follows the "original" posted earlier quite well, albeit compressed (less so the further right you get in the layout).

Tanks Pelle..i'll built it soon.