ZEN amp question

[till]

The Zen Lite should be used with the High / Low Pass http://www.diyaudio.com/forums/showt...394#post155394
driving TAD2001 with my horns http://www.diyaudio.com/forums/showt...6329#post96329

I´m still not sure about the schematic. I don´t want to build it exactly like the original Zen Lite. I don´t have a large 4mH inductor, i don´t want a turn on thump protection circuit. I don´t need low frequency from the amp as the TD2001 should be used above something between 500 and 1000Hz. So i think some capacitors could be smaller -- what means i can use higher quality (film instead of elko) I don´t have ZVP3310 so i have to use IRFP9610. The amp will have no powersupply - only a connector for an external powersupply 2m away. Mr. Pass, could you please critically comment this schematic?

[till]

Box is ready, but still not sure about values in the circuit. (see above)

[till]

I have it running, but without the 9610 yet.

One more question:
from the article

The circuit of Figure 5 has a substantial turn-on thump as the voltage across the MOSFET goes from 0 to 15 volts, and some of your more sensitive speakers might take offense. Figure 14 shows a simple turn-on delay circuit which will short the output of the amp to ground for a few seconds.

What are more sensitive speakers? TL1601a and TD2001 are more sensitive or not? i have no turn on delay circuit now. Would a powers supply that turns on very slowly be an alternative? a regulator powersupply with a delay?

[joensd]

Hi Till,
what about the regulator in the ZenV3 variations?
Take Fig2 and make C1 bigger and you should have a delay you can modify to your needs.
I once used this as slow turn on PSU for headphone amp.
It just won´t help you with turn-off-thumps.

Regards
Jens

[till]

Yes, this was what i thought of. But turn off thumb? if i turn off it goes slowly silent and distorted but no thumb.

[joensd]

Yes, this was what i thought of. But turn off thumb? if i turn off it goes slowly silent and distorted but no thumb.

I don´t know how the Zen Lite behaves switching it off just though I mention this.
Marcello who scaled the Zen amp for the use with headphones experienced a turn off thump and recommended a circuit that shorts the ouput during startup and switch off as well to avoid that.
In that case the regulator of the ZenV3 wouldn´t be sufficient.
But I think I´ll try anyway ;-)

Cheers
Jens

[Nelson Pass]

You are going to have some difficulty with this circuit with R1
looking at the top of the light bulb. R1 and R2 are there to
set the DC operating point for the Mosfet, but to do this they
need to see the Drain voltage of the Mosfet, and your circuit
only gives the supply. At the very least, make R2 a
potentiometer.

Note that the impedance of R1 and R2 are quite high compared
to the source impedance. As such, they don't contribute much
in the way of feedback at AC frequencies - they simply set the
bias point.

[till]

Thank You very much. If i connect R1 to drain, shall i make R2 a potentiometer too? Should it be adjusted to 1/2 V+ at drain or to 15V?

Is the circuit diagram right so?

Would values for C1 and C2 be ok in case the amp is used as high frequency amp for TD2001 and driven by the coming High / Low Pass Xover or do they need to be larger?

V+ is only 35V at the moment because my bench supply don´t delivers more. I think a final PS will be 45 - 50 V so.

[till]

hopefully corrected:

[till]

with 32V i have 2,3 A for both channels. So a larger powersupply with 45V may be better. Unfortunaly after 48 hours dissicipating heat with the bulbs the wood under the bulbs got a crack. I think it was not dry enough. I have to replace it.