Hi guys, can anyone recommend feasible schemes to complete my amplification?
My amp is made up of two physically separate sections, an OPS with 0.9 gain and a VAS that has about 30x gain, forcing me to use a preamp to get 100w / 8 ohms. All stages are zero negative feedback. I would like to try other configurations of VAS always ZNF but they should necessarily have a gain from 80 to 120 times to eliminate the preamp and enter directly with the source in the VAS. With the tubes this is not a problem, but with the solid state it is difficult for me, do you have any already experienced circuits to suggest to me? It should work on a 15k ohm load and allow the OPS to deliver at least 100w into 8 ohm and be no negative feedback
My amp is made up of two physically separate sections, an OPS with 0.9 gain and a VAS that has about 30x gain, forcing me to use a preamp to get 100w / 8 ohms. All stages are zero negative feedback. I would like to try other configurations of VAS always ZNF but they should necessarily have a gain from 80 to 120 times to eliminate the preamp and enter directly with the source in the VAS. With the tubes this is not a problem, but with the solid state it is difficult for me, do you have any already experienced circuits to suggest to me? It should work on a 15k ohm load and allow the OPS to deliver at least 100w into 8 ohm and be no negative feedback
Most mp3 players and phones have very low output, if you want to work with them you will be very dissappointed with 2V sensitivity...
You may have NFB-phobia.
The problem would be much easier if you allowed some local NFB to set the gain.
The problem would be much easier if you allowed some local NFB to set the gain.
the input sensitivity that I said is necessary for me to be able to use all my sources, my amplification chain is without negative feedback due to the design philosophy, and the designer is not the latest arrival and I think it is difficult to question it especially after listening to his creations, Bartolomeo Aloia. Having said that, my request was to discuss possible substitute schemes for my current VAS, not to argue about why
If your VAS doesn’t have enough gain, you need to add another stage, period. It can be free of global NFB, but you will still need it.
Once again, we will clarify that there is always either a general NFB, or a local NFB, or a combination of both. There may also be positive feedbacks.
We understand what you want, and indeed that designer has earned his wings. But there is also the little thing that if you want one gain for both a 2V output CD player and a 30mV other source, you will have a very awkward volume control that maybe almost unusable. Maybe think about it some more.
Jan
this is the top of Aloia solid state production, now there is the updated version SE Jepun but it is too expensive for me, and I wanted to do something simpler, now as a VAS I have the entry version in the Aloia world, only 4 bjt in its simplicity I believe it has few competitors. In diyAudio posts I see mostly complex circuits with a lot of NFB
I think there are very few people designing with zero global negative feedback because it is quite difficult to achieve low distortion levels, especially in a simple circuit.
I colleague of mine and brilliant electronics engineer designed a scalable, single pole rolloff (unconditionally stable) mosfet output audio amplifier design with zero negative feedback that produced <0.002% THD at any power from 1 watt up to 2000 watt.
In a practical amplifier we built for a professional applications rated at 800 watts per channel into 4Ω, we implemented 20dB of NFB, not to reduce amplifier distortion, but to lower the output impedance and consequently reduce distortion in the loudspeakers being driven by the amplifier.
I colleague of mine and brilliant electronics engineer designed a scalable, single pole rolloff (unconditionally stable) mosfet output audio amplifier design with zero negative feedback that produced <0.002% THD at any power from 1 watt up to 2000 watt.
In a practical amplifier we built for a professional applications rated at 800 watts per channel into 4Ω, we implemented 20dB of NFB, not to reduce amplifier distortion, but to lower the output impedance and consequently reduce distortion in the loudspeakers being driven by the amplifier.
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