Correct on the first part, not so correct on the second part. For an 8 ohm output of 100W, you would want about +/- 50V supplies on the output. I like to run the VGS a few volts higher. In the schematic I posted, the VGS has +/- 42V supplies. That means it could probably put out close to 40V peak. The actual power the amp delivers is determined by the +/- 34V supplies on the output. If you leave generous room for loses in the output stage, the amp will put out 29 to 30 V peak. That is just over the 20VRMS required for 50W at 8 ohms. 50 watts is a target number. If the amp does 55W, no one will complain. If it does 45W, they will.
Thanks for the response Steve ,
The PSU that i use puts out 28 V with 800 VA trannies/ch . Will this be 2 low for the Krill? I'm mostly interested in output @ 4/2/1 ohm , with 300-400 @ 1 ohm is more my target . 30-50 watts @ 8 ohm is OK by me (8 ohm speakers will never be in this system) and a 100 watts @ 8 ohm will not interest me if it's going to current limit @ 1 .
Regards,
The PSU that i use puts out 28 V with 800 VA trannies/ch . Will this be 2 low for the Krill? I'm mostly interested in output @ 4/2/1 ohm , with 300-400 @ 1 ohm is more my target . 30-50 watts @ 8 ohm is OK by me (8 ohm speakers will never be in this system) and a 100 watts @ 8 ohm will not interest me if it's going to current limit @ 1 .
Regards,
Your transformer is perfect for this. That should give you 400W at 1 ohm, no problem. Keep us informed on your build if you decide to do this.
One really fast way to make a simple circuit complicated is to add protection. For pro amps, non clipping is helpful. Here is the same circuit I posted last with the addition of soft clipping/compressor circuit and a fault detect and shut down circuit that protects everything except the fuse. Look it over and ask questions if you have any.
Here is the next step in the Krill evolution. This is a 200W balanced amp. These were built by combining two of the 50W amps in a single case and configuring one of them as an inverting amp. This has an input impedance of only 1K, so some preamps won't like it. Any modern solid state design should have no problems. I have shown it with an unbalanced input, but if you have a balanced source, you can disconnect the common input connection.
R37 has been added to the input of the inverting amp so the gain of the two amps can be matched exactly. You would do this by placing two 1K resistors in series between the outputs and adjusting R37 for a null at the center point of the two resistors.
R37 has been added to the input of the inverting amp so the gain of the two amps can be matched exactly. You would do this by placing two 1K resistors in series between the outputs and adjusting R37 for a null at the center point of the two resistors.
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hi, hugh
You did notice it ?..
So rare that one just don t expect it to the point
that we don t even care about it when looking at a schematic..
Some distorsion measurements would be insightfull, as this kind
of OS scheme yield at least 0.5% Thd at high level...
Hi Hugh,
Everything I have posted so far is with the output stage open loop.
wahab,
I have posted distortion results for the 100W and 50W in earlier Krill threads. I don't plan to get into that in this thread, but THD is well below o.5%.
Steve,
In listening tests, and contrary to the higher THD readings, I too have found that open loop output stages sound better. Given that the signal compression of most output stages, particularly at high output, creates a spray of odd order harmonics (along with crossover issues), it tends to indicate that taking feedback from the speaker output introduces some sort of even worse sonic effect, doubtless due to phase shift and back emf. It's curious, but there it is.....
Hugh
In listening tests, and contrary to the higher THD readings, I too have found that open loop output stages sound better. Given that the signal compression of most output stages, particularly at high output, creates a spray of odd order harmonics (along with crossover issues), it tends to indicate that taking feedback from the speaker output introduces some sort of even worse sonic effect, doubtless due to phase shift and back emf. It's curious, but there it is.....
Hugh
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