May or may not be an improvement driverless. The drivers do reduce the capacitive loading of the FETs on the VAS. An increase in driver current may even be helpful, as it will allow faster CGS discharge rates.
i looked at this earlier today as i thought it might be the issue, but when you look at this film cap, its not installed like this at all
C435 would be the cap
C435 would be the cap
Make sure the gates go only to the gate stoppers (R4 and R5) in the sim and nothing else.
We'll have to see if going driverless has an impact (its uncharted territory) but its always good to try and find what any issues might be.
We'll have to see if going driverless has an impact (its uncharted territory) but its always good to try and find what any issues might be.
That would depend on how well regulated the rails feeding the VAS are. If you just use a resistor bias, your output stage bias current will drop if the VAS rails do. Which can cause crossover distortion to appear at higher outputs as rail voltages drop. Keeping that gate bias pretty much regulated prevents that from happening. If your VAS was current source loaded (instead of boot strapped) it would be less of an issue.
The driverless version is what you are ultimately working towards I think. Uncharted territory but the technical basis is sound.
It should do. Remember the impedance selector switch disables the higher voltage rails when set to 4 ohms anyway. I think it would be fine in practice, those higher voltage rails are of very limited 'current vs time' ability, in other words their ability to deliver much current at that higher voltage is limited (by the PTC's in each high voltage rail).
Well I've still got 4 pairs of laterals spare so recon I might give that a go when this is done. Alot more of a challenge on that one though as they are vertical mounted, so it might mean a complete heatsink redesign
One thing I noticed last night was when adjusting the presets, measuring across the 1 ohm, the adjustment was very stable untill you got to about 45mv, then it suddenly jumps to 80,or 250, or even 400+mv. Now I checked both off the board and they adjust perfectly so nothing wrong with the presets, why would that be. You can't for example go from 0 to 400 in slow smooth increments.
One at a time methinks 🙂
It would be an interesting one to look at though. The 3240 has a totally different front end arrangement to all the other NAD's you've worked on.
It would be an interesting one to look at though. The 3240 has a totally different front end arrangement to all the other NAD's you've worked on.
That is a classic sign of instability or oscillation. Remember the reading across the 1 ohm is only valid if you have no load attached because anything going to the load will increase the current anyway.
Scope 😉 you need to get used to using that 🙂