Yes homemodder I agree, this one is maybe even older than that.
Do I smell jealousy here?
I think I smell some sort of jealousy all across the board, especially when going by certain posts that do not actually contribute to the amp, it's design and or the discussion
Edit: Instead' let's just put your / our energies to good use and enrich each other's knowledge rather than try to demean others
Edit: Instead' let's just put your / our energies to good use and enrich each other's knowledge rather than try to demean others
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Yes homemodder I agree, this one is maybe even older than that.
Do I smell jealousy here?
Older ?? Im sorry to say but you really should look into modern circuit techniques.
Jealousy, you must be kidding, I had that JLH circuit topology you use figured out even before I entered varsity.
As you are so knowledgeable, please go ahead and explain to everyone here how exactly this vas combination operates and show examples of how it was used and in what amps. I kinda have my hands tied but please free to do so.
I think I smell some sort of jealousy all across the board, especially when going by certain posts that do not actually contribute to the amp, it's design and or the discussion
Sorry MagicBox, not from my part, a certain member just didnt like me mentioning his circuit circulates around since 1968 and that the older original version actually performs even better than his with its mods and proved by another member. I dont know why they had to bring that matter here, maybe the moderators should intervene.
OT; but when these oracles found their way into the Corinthian congregation, they were babblings; they needed intelligible interpretation.
I've seen problems with convergence with high gain circuits - MOSFETs can give "infinite" DC gain
and ideal current sources can drive nodes to kV when things go wrong
sometimes explicit power supply ramping helps - define the PS Vsources as PWL with ms ramp time from 0
limit any ideal source with series R, clamp diodes - a quick limited, "passive" ccs can be made with high Vsource and high value series R
and ideal current sources can drive nodes to kV when things go wrong
sometimes explicit power supply ramping helps - define the PS Vsources as PWL with ms ramp time from 0
limit any ideal source with series R, clamp diodes - a quick limited, "passive" ccs can be made with high Vsource and high value series R
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An update will be pending soon I made a few more changes to the schematic. The VAS is now using a fixed reference cascode - I needed the bandwidth more than the reduction in phase shift at its Fc which was the benefit of the topology I initially described. The double cascode in the IPS is gone too - now it's just one cascode; zeners will take care of the additional voltage drop. All ideal current sources are gone and have been filled in by discretes; the IPS CCS is adjustable to optimize JFET bias currents. Output power is now rated 500W RMS into 4Ohms.
I made a few more changes to the schematic. The VAS is now using a fixed reference cascode - I needed the bandwidth more than the reduction in phase shift at its Fc which was the benefit of the topology I initially described. The double cascode in the IPS is gone too - now it's just one cascode; zeners will take care of the additional voltage drop. All ideal current sources are gone and have been filled in by discretes; the IPS CCS is adjustable to optimize JFET bias currents. Output power is now rated 500W RMS into 4Ohms.
After reading another thread I found a short piece taken from " an interview with Charles Hansen" describing the circuit he uses in voltage gain stages in his latest amps.
Key to Ayre's development is what they call EquiLock circuitry for the MX-R monoblock. "In a conventional circuit, the gain transistor has a load, usually either a resistor or a current source," Hansen said. "When the current through the gain transistor changes, then the voltage across the load also changes, which, in turn, means that the voltage across the gain transistor is changing. In fact, all of the parameters (transconductance, capacitance, etc.) vary when the voltage across the transistor varies.
"The EquiLock circuit adds another transistor between the gain transistor and the load. (In our case, the load is actually a current mirror.) This extra transistor holds the voltage of the gain transistor at a fixed level while still transmitting the changes in current to the load (the current mirror). By stabilizing the voltage across the gain transistor, all of the parameters of the gain transistor are also stabilized. The circuit is very similar to a cascode circuit, which has been used by other manufacturers, but EquiLock is an improvement over a conventional cascode circuit."
MagicBox, looking forward to see what you come up with next.
Key to Ayre's development is what they call EquiLock circuitry for the MX-R monoblock. "In a conventional circuit, the gain transistor has a load, usually either a resistor or a current source," Hansen said. "When the current through the gain transistor changes, then the voltage across the load also changes, which, in turn, means that the voltage across the gain transistor is changing. In fact, all of the parameters (transconductance, capacitance, etc.) vary when the voltage across the transistor varies.
"The EquiLock circuit adds another transistor between the gain transistor and the load. (In our case, the load is actually a current mirror.) This extra transistor holds the voltage of the gain transistor at a fixed level while still transmitting the changes in current to the load (the current mirror). By stabilizing the voltage across the gain transistor, all of the parameters of the gain transistor are also stabilized. The circuit is very similar to a cascode circuit, which has been used by other manufacturers, but EquiLock is an improvement over a conventional cascode circuit."
MagicBox, looking forward to see what you come up with next.
Thanks, I'm still in the process of optimizing It's not just THD, but also making the schematic power-, thermal- and component- tolerant without too much compromizing.
I also dug up a link to my build log of the 80W symmetrical MOSFET amp I was talking about Somewhere at page 4 and on there are various pictures. It's in Dutch however, but pictures should be understandable regardless. Say hello to CircuitsOnline.net when you stop by It's one of Hollands most educational electronics forums.
It's not just THD, but also making the schematic power-, thermal- and component- tolerant without too much compromizing. I also dug up a link to my build log of the 80W symmetrical MOSFET amp I was talking about
Somewhere at page 4 and on there are various pictures. It's in Dutch however, but pictures should be understandable regardless. Say hello to CircuitsOnline.net when you stop by It's one of Hollands most educational electronics forums.
Thanks, I'm still in the process of optimizing
I also dug up a link to my build log of the 80W symmetrical MOSFET amp I was talking about
Thanks I ll have a look at the site. I am versed in a couple of languages, Dutch is one of them so it wouldnt be a problem.
Well. I wasn't completely satisfied with the circuit's performance. It was hard to get into sub PPM numbers. In a way I didn't like the VAS as it was a non-symmetrical VAS, its control input having an exponential slope, making the control signal imbalanced. It needed a decent VAS current to obtain my target slewrate.
So I set out to think.. I want a symmetrical push-pull VAS. But the thing is, I "only" have a single-ended input. But in essence, that's the perc of the circuit, as with the Cdom feedback cap, output stage inclusive, THD numbers were low to begin with. But at this power level, I knew I needed a symmetrical drive from a single ended input. And this, I got to work
It now does sub ppm numbers consistently, no matter minor tweaks. Full power output THD20 is 0.34ppm, 1.3W THD20 is 56ppb! It's amazing I think, the circuit has improved leaps over the previous version. FETs are great.
So I set out to think.. I want a symmetrical push-pull VAS. But the thing is, I "only" have a single-ended input. But in essence, that's the perc of the circuit, as with the Cdom feedback cap, output stage inclusive, THD numbers were low to begin with. But at this power level, I knew I needed a symmetrical drive from a single ended input. And this, I got to work
It now does sub ppm numbers consistently, no matter minor tweaks. Full power output THD20 is 0.34ppm, 1.3W THD20 is 56ppb! It's amazing I think, the circuit has improved leaps over the previous version. FETs are great.
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