Almost all. Any amplifier. Analog amplifier.
They can work in Class A.
First we need to understand. Class A states are not a certain number. It is only a working state for the load.
For example, NE5532. When it is used as a preamplifier. It is an amplifier working in Class A. Although it's not hot.
We need to determine the magnitude of the output current. When the static current is greater than the output current. It works in Class A. Maybe the current is not very high.
Of course. We often give specific values. For example, Class A amplifier of 30W 8 ohms.
Then the static current needs about 1.8A.
If lower voltage is used. For example, + - 25V. So the static current of 1.8A is not very hot.
In fact, my suggestion is. We don't need to pay too much attention to it. Category A. Or class B amplifier.
It's not the most important. Circuit structure is more important.
MX50SE and L12-2 have similar structures. But in some places they are not the same.
For example, their power transistor models are different. Or their input capacitance is different.
Yes, I understand the principles, but I'm not able to simulate if some component values should be changed when the supply voltage is lower?
I did some tests today with MX50x2, MX50SE, and L12-2. I had +-30VDC supply (I used the lowest voltage transformer I had) and a 8ohm load. I tried to vary the bias current, and measured distortion spectrum at different output levels. I measured both 1kHz and 13+14kHz input signals. I could see that on low bias (recommended), the CFP designs have a lot of high order harmonics. With higher bias, mainly the 2nd and 3rd were visible.
For some reason it seemed too, that at some level of bias, the distortion reduction did not follow the bias much. I guess it would be called 'point of diminishing return' for invested heat 🙂
I could see clear gains on varying output voltages, until they reached a 'roof' where only small gains could be seen on higher outputs. This 'knee' was different between amps, where the MX50x2 was highest around 0,8A (did not dare to go much higher, heat sink was getting a bit hot), and the MX50SE (with toshiba 2SC5242/2SA1962) around 0,4A.
It was not a very 'scientific' test, only the feeling I got when playing around a little bit. Maybe somebody has some explanation to this?
I did some tests today with MX50x2, MX50SE, and L12-2. I had +-30VDC supply (I used the lowest voltage transformer I had) and a 8ohm load. I tried to vary the bias current, and measured distortion spectrum at different output levels. I measured both 1kHz and 13+14kHz input signals. I could see that on low bias (recommended), the CFP designs have a lot of high order harmonics. With higher bias, mainly the 2nd and 3rd were visible.
For some reason it seemed too, that at some level of bias, the distortion reduction did not follow the bias much. I guess it would be called 'point of diminishing return' for invested heat 🙂
I could see clear gains on varying output voltages, until they reached a 'roof' where only small gains could be seen on higher outputs. This 'knee' was different between amps, where the MX50x2 was highest around 0,8A (did not dare to go much higher, heat sink was getting a bit hot), and the MX50SE (with toshiba 2SC5242/2SA1962) around 0,4A.
It was not a very 'scientific' test, only the feeling I got when playing around a little bit. Maybe somebody has some explanation to this?
I can add that the L12-2 measures very good on 0,6-0,8A with the +-30VDC supply. 'Optimum' current is depending on load, around 0,6A for 8ohm, and 0,8A for 4ohm. Very clean FFT at low power levels, and some improvement for high power too. The high Iq does a lot to improve the distortion around a few watts. IMD with 13+14kHz @1W is the cleanest I measured so far (better than my sound card can resolve). There is a lot of high order harmonics at low Iq and 1W.
When I listen to it, I find the sound 'bright' and detailed, but a bit lacking in 'depth', and I also get a bit tired from listening to it. I can't see any oscillations etc on the output.
When I listen to it, I find the sound 'bright' and detailed, but a bit lacking in 'depth', and I also get a bit tired from listening to it. I can't see any oscillations etc on the output.
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which toroidal transformer?
Hello, I have two toroidal transformers, one CLAIRTRONIC 625W PRIM 2X115V SEC. 2X45V and the other NORATEL MODEL PG 500/50 230V PRIMAR 50 / 60HZ / 500W SEC. 2X50V / 5A, and I do not know which would be better to put it on the L12-2 stereo modules, thanks for understanding
Hello, I have two toroidal transformers, one CLAIRTRONIC 625W PRIM 2X115V SEC. 2X45V and the other NORATEL MODEL PG 500/50 230V PRIMAR 50 / 60HZ / 500W SEC. 2X50V / 5A, and I do not know which would be better to put it on the L12-2 stereo modules, thanks for understanding
I it was me, I would stick with the lower voltage secondaries, it will still give quite a high rectified DC voltage.. not sure what the limit actually is for these amps.
I don't know about the grid voltage in your country, or what impedance speakers you are planning to drive etc.. With 4ohm speakers, I would definitely have chosen an even lover voltage.
I don't know about the grid voltage in your country, or what impedance speakers you are planning to drive etc.. With 4ohm speakers, I would definitely have chosen an even lover voltage.
I am concerned that you plan to connect a transformer directly to the amp module. Don't do that! You need to build a power supply from it and connect the output of the power supply to the amp module.
As a rough estimate, the DC voltage of a linear power supply (transformer, bridge rectifier, and smoothing capacitors) will be about 1.4 times the AC secondary voltage of your transformer. Your Clairtronic transformer will result in 1.4*45V = 63V DC for each power supply rail by this formula. In reality the voltage will be a little bit lower due to voltage drop in the rectifier, but this is too far above the maximum recommended voltage for the L12-2 (I think that is +/-55V). You risk damaging components and generating excess heat.
What I have outlined above is rather basic audio electronics. I would try to study proper design, especially in terms of safety, before doing anything. Here are a couple of links to read:
YouTube
PassDiy
Power Supply Wiring Guidelines
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You're very likely going to overpower the amplifier modules. The suggested max. power supply for a straightforward, general purpose DIY build of L12-2, is a 2 x 30VAC secondary voltage transformer. That gives you DC rails of +/- 43V. This has been indicated as max. by the designer several times in the thread. If you use large toroids for a stiff supply with plenty of current, +/-40VDC would be a safer maximum limit for 4 ohm loads. I understand that 50V rails would only be safe with 8 ohm loads.
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I believe the max rail voltages are more like +/- 55V, not 43V... See:
LJM L12-2 Stereo Amplifier Ultra Low Noise HIFI Power Amplifier THD<0.0005% 120W | eBay
You can also find some related posts starting on this page of this thread, with the link to one of your own posts:
L12-2 CFP Output amp 120W*2 8R
Yes, CharlieLaub, my apologies to you and to all for not checking the notes I made back then, before posting 😱 I was about to amend the post again when I saw your reply. However, +/-55V still isn't so good with 4 ohm loads. I did blow one board, just clipping with a test tone and learnt that lesson. As the toroids run cool, perhaps a lower VA rating one might have sagged enough to run safely. My present builds in fact, use 1 X 300VA 2 X 30VAC toroids per channel for 43VDC rails which has proven OK with nominal 4 ohm speakers.
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Thank you very much for your help, I have homemade 4 ohm speakers made by me, I would like to make an amplifier from "0" as well as Diy for my 4 ohm 3 way speakers with scanspeak TWEETER D2904 / 7100-03 speakers - 4 OHM, MIDWOOFER SATORI MW16P 4 OHM, WOOFER 22W / 8851T - 8 OHM 2 Pcs, but I think I'm going for this option, I have a defective Sony TA-5650 amplifier with the defective power amplifier, and I saw that the voltage that pulls it off Sony TA-5650 for amplifiers is +/- 47V 6.3 A, what do you say I put the L12-2 modules in the Sony TA-5650?
my speakers ,,,,,
my speakers ,,,,,
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Sony TA-5650 service manual
i would like to use the original speaker protection from your sony 5650, but i don't know how?
i would like to use the original speaker protection from your sony 5650, but i don't know how?
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Alternating between + and -? 😀
No, I was just making sure so there was no misunderstanding. I did not check in the schematics for the amp.
No, I was just making sure so there was no misunderstanding. I did not check in the schematics for the amp.
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a good approach for protection is in use at Linn power amp LK2-80 and Klout - check out the schematics here on diyaudio.
Can I use the transformer and DC power supply from here for L12-2?
I do not know from what Yamaha amplifier?please help
I do not know from what Yamaha amplifier?please help
Yes, that will work fine, as long as you connect it all correctly! Remove any redundant/unused wires from the Yamaha PS board, so you only have plus, minus and ground wires going out to L12-2 boards.
And please don't post any more schematics or pictures of loudspeakers only relevant to you in this thread - it is the wrong place for it. You should instead start a new thread for your amplifier project.
That schematic is wrong. The collector and base of Q12 and Q13 are swapped and the emitter of Q11 connects to R27 only. R27 should not be shorted.
A corrected schematic was posted (#12) but it was lost in the "photobucket".