Relay on AMP5 ??

[flitgus]

Hi all!

I've just finish yesterday to assemble 2 AMP5 modules for my active speaker project.

They work nice, that's great, but there's something i don't understand about the logic for the relay.

On AMP5, the relay is open if the TA2022 is asserting the MUTE signal, and the relay is closing when the Tripath is de-asserting the MUTE pin.

What's the benefit of having here a relay?

Shouldn't the relay logic be as follows (in a switch on/switch off procedure):

1. Switch on the AMP, MUTE is initially asserted while the rail voltages are below the minimum.

2. MUTE is de-asserted.

3. DELAY (to be added, not currently on amp5)

4. Relay closing after delay elapsed.

5. Enjoy your music

6. Turn off -> the relay is opening immediately!! (this is currently not performed)

7. MUTE is asserted when the tank capacitors have discharged

8. The amp is off

This way there wouldn't be any commutation 'plok' in the speakers when turning the amp on and off.

Or am i going nuts?

Regards,

Flitgus

[Scratchy]

Look at the bottom of this page:

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Someone has already modified an AMP5 to do exactly what you have described.
(The relay protects your speakers from DC voltages, as it only closes if everything is normal on the output from the TA2020).

[Haggis Basher]

Hi all!

This way there wouldn't be any commutation 'plok' in the speakers when turning the amp on and off.

Or am i going nuts?

Definitely no more so than the rest of us!

I would add that amp5 as it stands has been very well thought out, as the speaker protection afforded by the relays also serves to remove some weird semi-digital breakthrough noises from the chip. If you have not yet done so, I would recommend reading up on this matter under the Truepath threads and possibly read up on the modus operandi of your chip from any available data sheets, although they can be a bit tedious at times (sorry mentors).

As Scratchy has already advised, you could modify the amplifier to operate in the manner you so desire, the sort of project I would revel in, and then know that you have succeeded way beyond imagined kit-type boundaries! I am on my third generation of surface mount technology attenuators, and am currently modifying a Truepath, and Audiophool’s safe test procedure (for which I will probably have to eat dried bread for a while, if he finds out).

Your post is super, please re-post, when you have got the amp working to your specifications. If you have problems, the experts will jump in and help you, they really do mean well.

Ken.

P.S. for scratchy alone. You had me for a day or so, the word amp distracted me onto the Forum. I remembered his obsequious walk first, and the rest came flooding back, including the legal court case in the UK when an “e” was added to his name, to allow the garish red and white outlets to inflict their foul rendition of “fake” food on the general public. That was tricky, references to audio, the UK and cartoons. Now the gloves are off, no more nice guy: “Dagnammit Muskie, you done gone in my melon patch again”. Googling won’t help the youngsters suss this one!

[flitgus]

Hi and thanks for your answers to my post!

Someone has already modified an AMP5 to do exactly what you have described.
(The relay protects your speakers from DC voltages, as it only closes if everything is normal on the output from the TA2020).

Scratchy: i couldn't find the mod you mentioned. I had already searched the site before posting. Can you help me locating the thread of interest?

Also, as far as i remember from my reading of the TA2022 datasheet, when the amp is muting, all the outs are tristated with a DC 2.5V voltage, which is safe for loudspeakers. Tripath also included a section on how to avoid commutation 'ploks' by using a microcontroller asserting the Mute pin at start on/ switch off.

The relay is a good feature though, but not very useful as implemented originally on the board.

[Scratchy]

Sorry, for the delay (pun intended), I was on my way out the door to work this AM when I posted that.

I did a search for "unmute, delay" and found a few posts for the TA2022:
http://www.41hz.com/forums/showthrea...ng-mute-button

However, this was not the thread I was thinking of.
Here is the one that seems to be really slick, but it is for the AMP4.
http://www.41hz.com/forums/showthrea...te-pop-remover

I suspect the same logic could be applied to the AMP5

connect a 100uF capacitor between pin 19 (VPPSENSE) of the TC2000 and ground

One difference is the AMP4 is single ended and only has a VPPSense.
The AMP5 having a split supply, would also have to have this treatment applied to VNNSense.

This is all just conjecture on my part, so don't attempt this unless you are sure of what you are doing.

[V-bro]

Have look at Audiophool's T-brick kit, it has this logic sorted out just like one would desire. No turn on/off pops and excellent protection. It is actually usable with all the 41hz amplifiers, but for some there are features you won't need. Audiophool has posted the schematic on his site maedos.com and also here on the forum.. (I think in the optimising Truepath thread...)