Jo Sharp
Pulls on doors marked push
Hi Ron,
By the way, how much do the chokes cost?
John
IIRC they were 30H...and around £300
Hi Ron,
By the way, how much do the chokes cost?
John
Just to piggy-back this question, how are tants used on Naim amps? As coupling caps, bypass caps or something else?A question on one of the above comments: why would a (tantalum) capacitor of a given rating have faster transients than a.n.other type?
Thanks, Martin.(James - both for coupling and bypass, i.e. decoupling).
Tant caps for all their folklore faults have one very, very nice feature: the ESR - often an ohm or so - dominates the response. This means that rails decoupled using tants will rarely 'ring' - the stable ESR provides very useful damping well above audio and into the HF (because the cap intrincially is pretty low-inductance). And nicely-damped things rarely display unwanted overshoot or 'ringing' as can easily be provoked for example by unthinking exchange for film caps (with very low-ESR)
I suggest if one wants something that might contribute to 'a sense of musical timing' it surely includes 'good time-domain response'...
I suspect not, as I once noticed a glitch when I measured DC going into my loudspeakers, and traced it back to the preamp output. That 'fault' could not be replicated since. By that measure, I also suspect that one of my amplifiers is DC coupled (otherwise, how would it have amplified DC) but the other pair probably has input caps.Does your pre amp have an output cap? If so the best input cap on the XO might be a piece of resistor offcut ? Carl seemed keen on this on input caps to power amps for example.
Since building my first active XO, I have little choice.I like how you are being dragged into the electronics more
Hi Ron,
I've been practicing with lower power chokes on preamps and done a few calculations on your design on the XPS2.
With a 40Henry choke with a 0.25 ohm resistance and 18800uF capacitors your looking at a very high Q filter Q = 188. Normally you would want to have the Q below 0.58 here to avoid ringing. Interestingly the ringing, if you can call it that, will be at a very low frequency of about 0.18Hz. Maybe that is OK as the pulses of feed current are of much higher frequency so the voltage never gets a chance to wander.
Perhaps a bit more worrying is the effect using the choke may be having on your voltage headroom for the regulators further on. The output voltage of the choke/capacitor filter will be 63% of the voltage you had with just the capacitor filter. That may be OK but my guess is that it is too low for the regulators that follow. They normally need 3 volts or so of headroom and it would be unusual for Naim to design with much much more voltage headroom than they need here.
If I were you I would check the voltages across the regulators in your XPS2.
By the way, how much do the chokes cost?
John