I found a very simple 200W audio amplifier schematic:
http://www.mif.pg.gda.pl/homepages/tom/files/simp200W.gif
I actually happen to have a few TDA2030s in a box, hence the interest in this particular schematic. As far as I can tell it's a reasonably solid design. Can anyone spot any immediate problems with this design, or any simple and cheap improvements?
http://www.mif.pg.gda.pl/homepages/tom/files/simp200W.gif
I actually happen to have a few TDA2030s in a box, hence the interest in this particular schematic. As far as I can tell it's a reasonably solid design. Can anyone spot any immediate problems with this design, or any simple and cheap improvements?
The transistors are probably BD707 and BD708, not KD.
According to the datasheet the TDA2030 is limited to 36 V supply voltage, not 44 V.
According to the datasheet the TDA2030 is limited to 36 V supply voltage, not 44 V.
I actually spotted that last night whilst I was looking at the datasheet. I'll use a 30V supply.
As regards the power supply shown, would it not be a bit too noisy for audio purposes? I'd have expected to see an SMPS driving a circuit with this kind of amplification.
As regards the power supply shown, would it not be a bit too noisy for audio purposes? I'd have expected to see an SMPS driving a circuit with this kind of amplification.
I know I'll need heatsinks for the transistors, but what about the opamps? Not sure what kind of thermal output I should be expecting.
200w is perhaps a little optimistic...
Perhaps the 200w is peak, not rms
The power transistors mentioned will pop if you use more than a +/- 30v supply, they are rated 60v...
Most other parameters of the transistors are too small to get 200W from this arrangement, you will simply make nasty smelling smoke.
Fortunately the BD70x transistors are slow, so there is a good chance substituting other slow transistors that are appropriately rugged will get you closer to your goal...Adcom made the GFA1 that was a 'real' 200w RMS BTL amp, it used ~50v rails and 2SB554/2SD424 outputs. I have successfully substituted mj15003/4 to get a little more margin in current and power, seems like you could use them here.
The tda2030 will need to drive the base current of the outputs, to pretty much the full rail voltage, worst case maybe an amp or two. With 30v rails, at half power into 8 ohms, depending on the gain of the transistors the chip will be dissipating 5-10w. It will definitely need a heatsink for even short term operation.
HTH
Stuart
Perhaps the 200w is peak, not rms
The power transistors mentioned will pop if you use more than a +/- 30v supply, they are rated 60v...
Most other parameters of the transistors are too small to get 200W from this arrangement, you will simply make nasty smelling smoke.
Fortunately the BD70x transistors are slow, so there is a good chance substituting other slow transistors that are appropriately rugged will get you closer to your goal...Adcom made the GFA1 that was a 'real' 200w RMS BTL amp, it used ~50v rails and 2SB554/2SD424 outputs. I have successfully substituted mj15003/4 to get a little more margin in current and power, seems like you could use them here.
The tda2030 will need to drive the base current of the outputs, to pretty much the full rail voltage, worst case maybe an amp or two. With 30v rails, at half power into 8 ohms, depending on the gain of the transistors the chip will be dissipating 5-10w. It will definitely need a heatsink for even short term operation.
HTH
Stuart
I'll swap the transistors for MJ15003/4s. Turns out the chips I have are indeed the TDA2030A's. A lucky break for me 😀
As regards the power supply I'll see if I can knock up one that puts out around 40V. I'm actually waiting on delivery of a 75VA 230V primary, 2x 50V secondary transformer that was on sale for only £7.50 because one of the screw holes didn't get punched through when it was manufactured. The normal price is around £20. Bargain!
As regards the power supply I'll see if I can knock up one that puts out around 40V. I'm actually waiting on delivery of a 75VA 230V primary, 2x 50V secondary transformer that was on sale for only £7.50 because one of the screw holes didn't get punched through when it was manufactured. The normal price is around £20. Bargain!
Have I missed something? I was planning on building a simple power supply to run it off using that transformer. I don't see the issue.
Edit: Hmm... I think I calculated something incorrectly somewhere. For some reason my calculations say I can pull 15A from the primary without the transformer dying. Er, that's very wrong! I'm off out for a bit, then I'll fix my numbers.
Edit: Hmm... I think I calculated something incorrectly somewhere. For some reason my calculations say I can pull 15A from the primary without the transformer dying. Er, that's very wrong! I'm off out for a bit, then I'll fix my numbers.
Well let's see. 50V transformer (which will make approx 69V DC) with 44V absolute max chip. I can see the flames from here.
Hi,
each half of that bridged amp must deliver 100W into 2ohms to achieve that 200W into 4ohms specification.
This needs 20Vpk from each half and expect a peak current from a transient pulse to be approaching 29Apk.
MJ15003/4 will easily achieve that with Vce=30V, if you keep them cool to warm but not hot.
But, I can't see how you can get 20Vpk from a supply that MUST be <=44V from +ve to -ve, i.e.+-22Vdc max.
75VA for a 200W amp? Is this ambitious?
each half of that bridged amp must deliver 100W into 2ohms to achieve that 200W into 4ohms specification.
This needs 20Vpk from each half and expect a peak current from a transient pulse to be approaching 29Apk.
MJ15003/4 will easily achieve that with Vce=30V, if you keep them cool to warm but not hot.
But, I can't see how you can get 20Vpk from a supply that MUST be <=44V from +ve to -ve, i.e.+-22Vdc max.
75VA for a 200W amp? Is this ambitious?
I wasn't planning on hooking it right up, I was going to build a regulated power supply. I'm not a complete idiot - it's pretty obvious that a 50V transformer would hit +/-69V peaks and blow the chips.
Sorry if I sound a little harsh, I just don't like it when people assume I don't know what I'm talking about.
Anyhoo, back to the project - I'll probably build a small SMPS to run this thing.
EDIT: Strike that. SMPS is too complicated for this kind of setup. I'll use that transformer for something else. I found a cheap toroidal that should do the job with a pair of 30V secondaries. Specs:
# TRANSFORMER, 330VA 2X 30V
# Voltages, primary:0-120, 0-120
# Voltages, secondary:0-30, 0-30
# Power, per secondary winding:165VA
I need the primaries to take a UK 230V supply. However, my brain ceases functioning when it comes to wiring up primaries for different voltages. If my memory serves me correctly, I just wire the primaries in series, right?
Sorry if I sound a little harsh, I just don't like it when people assume I don't know what I'm talking about.
Anyhoo, back to the project - I'll probably build a small SMPS to run this thing.
EDIT: Strike that. SMPS is too complicated for this kind of setup. I'll use that transformer for something else. I found a cheap toroidal that should do the job with a pair of 30V secondaries. Specs:
# TRANSFORMER, 330VA 2X 30V
# Voltages, primary:0-120, 0-120
# Voltages, secondary:0-30, 0-30
# Power, per secondary winding:165VA
I need the primaries to take a UK 230V supply. However, my brain ceases functioning when it comes to wiring up primaries for different voltages. If my memory serves me correctly, I just wire the primaries in series, right?
Well you did say a simple power supply was what you wanted. Even with an SMPS that's still a lot of voltage to shed. Not to mention that you will need another transformer again for the SMPS.
Is it worth all this hassle for what is going to end up a pretty crappy 50W amp? Why not seek out a more suitable transformer and you will get more performance and the cost and complexity will be far less.
edit: your new transformer looks ideal. Yes the primaries go in series.
Is it worth all this hassle for what is going to end up a pretty crappy 50W amp? Why not seek out a more suitable transformer and you will get more performance and the cost and complexity will be far less.
edit: your new transformer looks ideal. Yes the primaries go in series.
I disagree.
The 30-0, 30-0 dual secondary will give about +-44Vdc, i.e. 88V from +ve to -ve.
The chipamp died as soon as it was switched on.
yes 120-0,120-0 primaries go in series to be powered by 220/240Vac mains.
But, if the phase of one of the primary windings is reversed the primary will look like a 10hm resistor and burn out within seconds, unless the distribution board shuts down to save you and your transformer.
Use a light bulb tester for all power ups of any and every project. Even one that has previously "passed" and had a tiny modification.
The 30-0, 30-0 dual secondary will give about +-44Vdc, i.e. 88V from +ve to -ve.
The chipamp died as soon as it was switched on.
yes 120-0,120-0 primaries go in series to be powered by 220/240Vac mains.
But, if the phase of one of the primary windings is reversed the primary will look like a 10hm resistor and burn out within seconds, unless the distribution board shuts down to save you and your transformer.
Use a light bulb tester for all power ups of any and every project. Even one that has previously "passed" and had a tiny modification.
Ideal was maybe not the best choice of word. 2x15 would be ideal. However, with 2x30 I had in mind him paralleling the secondaries and running a virtual earth, which just so happens is what is depicted in the schematic.
Right, as I've mentioned before that my brain falls apart when it comes to transformers.
I've found a whole bunch of transformers with a single 230V primary and two 15V secondaries, each with a different power rating. There are also loads of toroidal ones with dual 115V primaries. Am I looking for 15VA, 30VA, 200VA or what?
With the virtual earth idea, I assume you mean tying the grounds shown in the circuit to the center tap of the transformer.
I've found a whole bunch of transformers with a single 230V primary and two 15V secondaries, each with a different power rating. There are also loads of toroidal ones with dual 115V primaries. Am I looking for 15VA, 30VA, 200VA or what?
With the virtual earth idea, I assume you mean tying the grounds shown in the circuit to the center tap of the transformer.
The VA is the power rating, basically watts. Power out can only ever be equal to or less than power in. I'll leave it to you to figure.
Transformers
To answer a few of your questions:
Yes: two 115v primaries are wired in series to behave as a single 230v.
Transformer ratings:
If you expect to have a 200w amp when you are done you will need at least a 200va transformer. For long term reliability you would want a reasonable safety margin, so perhaps 300va or even 400va.
200w is not in itself a complete specification, the load has to be known, and this lets you choose voltage and current appropriately.
The final 'peak' voltage from the transformer will wind up being a little below 1.4 times the AC rating of each of the secondary voltages. So if you want +/- 30v DC at full output, and allowing for ~10% regulation, you will be looking for a 23v AC from each secondary. A 200VA device will have about a ~4A rating for each secondary, 300VA more like 6A etc.
Note that 30v rails are not appropriate for a bridged amp that is designed to drive 200Wrms into 4 ohm, you only need +/- 20v, plus a volt or two for saturating the transistors...using the right rails will lower heat output and give you more current from the same rated transformer.
HTH
Stuart
To answer a few of your questions:
Yes: two 115v primaries are wired in series to behave as a single 230v.
Transformer ratings:
If you expect to have a 200w amp when you are done you will need at least a 200va transformer. For long term reliability you would want a reasonable safety margin, so perhaps 300va or even 400va.
200w is not in itself a complete specification, the load has to be known, and this lets you choose voltage and current appropriately.
The final 'peak' voltage from the transformer will wind up being a little below 1.4 times the AC rating of each of the secondary voltages. So if you want +/- 30v DC at full output, and allowing for ~10% regulation, you will be looking for a 23v AC from each secondary. A 200VA device will have about a ~4A rating for each secondary, 300VA more like 6A etc.
Note that 30v rails are not appropriate for a bridged amp that is designed to drive 200Wrms into 4 ohm, you only need +/- 20v, plus a volt or two for saturating the transistors...using the right rails will lower heat output and give you more current from the same rated transformer.
HTH
Stuart
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