buffer ckt for overload LED?

[cjd]

recently finished my first amp6-basic. great kit, sounds terrific. I'd like to add some status LEDs. it looks like sleep/awake should require no buffer, and fault should just require something like a 2N7000. What about overload? I gather from reading the forum that other amps have this, but I don't seem to have access to the schematics. Having a 5V supply would make it easy; can I drive the LED from 5VGEN (pin 30) of the TA2020? it doesn't seem clear from the data sheet whether that's ok.

thanks!

[krilli]

Hi,
have you checked support.41hz.com ? I think you can download any 41hz schematics from there.

... re. the 5Vgen: my rule of thumb is to stay clear of the amps low power rails, dirt on those rails tends to go straight to the speakers, or so I've read. It's near to superstition on my part though.

[cjd]

hi krilli,

> have you checked support.41hz.com ? I think you can download any 41hz schematics from there.

yes, I checked. I can download assembly instructions and photos of just about everything, but schematics and BOMs only for the Amp6-Basic (the only amp I have purchased). I've looked through the assembly instructions but didn't find any schematics.

> ... re. the 5Vgen: my rule of thumb is to stay clear of the amps low power rails, dirt on those rails tends to go straight to the
> speakers, or so I've read. It's near to superstition on my part though.

It's a reasonable superstition. If the Tripath designers meant for you to draw current from that pin, the data sheet should have a max current spec. My rule of thumb is that without such a spec, or other knowledge of the chip internals, you probably risk disrupting the chip's behavior somehow. But I thought I would ask anyway, in case somebody knows something I don't.

thanks!

[krilli]

Ah ... there's a foggy memory of the "adult" Amp6 schematics somewhere in my mind. I think they exist.

Let's pray for their appearance ... V-bro? Any hints?

[V-bro]

Hi, yes 2N7000 you can use for all the status leds, I'll mail you some schematics...

------X-max. can be several meters on any driver, too bad it can be done only once...------

[V-bro]

Erh...can't.... you have no contact info specified in your profile.... can you update?

------X-max. can be several meters on any driver, too bad it can be done only once...------

[cjd]

oops - sorry. done. and thanks!

[cjd]

I think I found my answer in the assembly instructions for the AMP6:

"D16, the green diode, indicates normal operation. It actually uses
the OVRLDB output of the chip. This output is high when the amp is
un-muted but starts going low if the input signal is to high. This would
be synonymous to the amp output clipping, and indicates you should
probably decrease the volume"

If I read this right, the green LED goes *off* when the amp is clipping, so I can see how the 2N7000 is used for that. I was hoping to turn *on* an LED when the amp clips, and using a 2N7000 would require a different polarity signal (which I could readily get using a second 2N7000 as an inverter).

If anyone has alternative ideas or circuits I'd be happy to hear about them, but otherwise I consider my question answered. thanks all.