Aleph-x standby mode

[yup]

This is good discussion...

For people like myself who will be turning the amp on and off remotely (and frequently) the standby mode the production unit uses has some advantages, mainly low current swithcing.

I have attached a schematic showing a couple of ways of implementing this. What I would like to know is one of these better and why?

The schematic is here: Schematic

Option 1 is shown in red. The relay would swith A, B, & C while the capacitor C11 would be increased to balance the turn on / off thump. This method would allow more capacitance across the CS zenier diode helping to reduce noise.

Option 2 is shown in green. The releay would swith D, E, & F while an additional capacitor would be needed as shown to balance the turn on / off thump

Is one preferable? Did I overlook anything?

Thanks,
Jeff

[CheffDeGaar]

Hi,

I implemented a method that works quite nicely. I use relays to add a resistor in // to the bias setting network (pot between base of Q3 and R15/R14 node - and symmetrical parts). The lower the total resistor, the lower the bias.
More details on the attached file in http://www.diyaudio.com/forums/showt...687#post295687

Absolutely no problems since it was built. Keeps the heatsinks gently warm. Adjust the resistor to suit your needs.

[yup]

Cheff,
Great job on your amplifiers! Your method is definately beyond my capabilities... very elegant.

Is anyone using either of the methods I show in this Schematic?

I have my boards completed and running smoothly on the bench and just wanted to make sure I wasn't making an "obvious" mistake.



Thanks,
Jeff

[yup]

I have been informed that the PDF is not downloading correctly within a web browser...

right click the Link and select "Save Target as"

I will post it as a JPG when I get home tonight.

Jeff

[yup]

Here is the schematic in JPG format

Jeff
Look, I'm learnding...

[MEnsing]

Yup,

Have you already tried one of your options or did you use the option described by Cheff?

Maybe Patrick (EUVL) can describe within more detail his solution because I still don't understand what is the best way to implement this.

Marco

[yup]

I have been testing (and waiting on final custom transformers to arrive).

What I found worked fairly nice was this: Schematic


As you can see, I break the positve rail voltage to the active current source mosfet gates (D & F) to shut them off and I break the ground reference (E) to the current source mosfet gate to turn off the diff pair and the main output fets. All this is done with a single 4PDT relay.

As far as I can tell, the added capacitance (47uf) across the zenier is a good thing. The 630 Kohm resistor was added to bleed off the gate voltage of the current source mosfet at a similar rate as the active current source (220 uf) caps bleed down.

This setup makes zero noise on my test speaker on power down and only makes the slightest tick on power up. You must actually have your ear to the speaker to hear it.

the transient behavior of the two circuits are somewhat different. I guess because the current source circuit is fading from a different gate-source voltage potential than the active current source mosfets and also because the turn on/off voltage on the 9610’s and 044’s are different too. (please correct me if I am wrong)

In the end, when turned either on or off the absolute voltage (output to ground) smoothly swings towards the positive rail until it reaches about 5 volts and swings back to zero with no overshoot (4 seconds for turn off, 1.5 seconds for turn on). As always, the voltage across the speaker terminals is negligible (well matched mosfets). More capacitance or resistance across the zenier causes it to overshoot towards the negative rail after its initial move towards the positive rail and also increases the time it takes to reach steady state. The way it is now, the diff pair and main output mosfets turn on last and turn off first, so if signal is present, it won’t sound strange during turn on / off.

The circuit modified like this definaltely powers up quicker (1.5 seconds) than it powers down (4 seconds). It may be possible to modify the circuit to improve this performance, but I am fairly happy with this for now.

Please let me know if I any of you see any problems or have any questions...

Thanks,
Jeff