Amp 9 - Works, but I need some advice

[dansolow]

I have an Amp 9 up and running, sounds good on all 4 channels, but there are a few strange things happening.

1. The Sleep switch does not work. I can open or close the jumper wires from pin 10 to pin 13 and the amp works either way. When open, pin 10 is @1.5 volts, pin 13 is at 5 volts. The amp does seem to sleep when I connect pin 10 to agnd, or touch the jumper wire with my hand. Is this normal. Note - the mute switch between pin 12 and pin 13 works correctly.

2. The chip seems to get hotter than is should. I have a 2" by 2" by 1/2" finned copper heatsink made for a pIII. I am using the same heatsink on an amp5 and it barely gets warm after hours of play.

On the amp 9, it gets noticably warmer than the amp 5 after a few minutes with 2 channels, 6-8 ohm speakers, running through moderate volume at 12 volts, and downright hot (heatsink uncomfortable to touch, let go after about 5 seconds) when fed with 20 volts. The variable test power supply only kicks out about 90 watts, and I have a 1 or 3 amp fuse (not sure which) so I'm not running that much power through it. Is it normal for this chip to run hotter than the Amp 5? Or is something wrong?

One thought is that given the strange behaviour of the sleep function, could the amp somehow be stuck in AM or A/B mode? But nothing I have never fed voltage through pin 9, and have tested it at 0 volts.

Please note, I checked the board and the solder joints and everything looks good. I did not install the eight zener protection diodes, or the led circuits (U4, U5, R14, or R15). Also, I am running DC directly to the board (no rectifier bridge).

[Kocsu]

I think the right way to sleep the Amp is connecting Pin 10 to AGND (open it is not enough), same for Mute pin

good advise from the forum was leaving the AMP awake all the time (pin 10 fixed to +5V) and play only with the MUTE pin, to avoid speaker thump, besides it is needed this way for the Auto DC-offset adjustment mechanism (awake the amp first then unmute triggers the auto dc-offset adjustmetn process according to.. manual?)

[dansolow]

Thanks,

I'm not concerned with turn-on thump. Can I just jumper the three (J10, J12, J13) together and leave it at that? Or will that prevent the DC Offset adjust when i connect power?

Any thoughts on the heat situation? How hot are other peoples chips/heatsinks getting?

I have seen alot of pic's with larger heatsinks than mine. Perhaps I need some more surface area?

[V-bro]

Hi,

at first I've been playing around with an audiodigit 4x100 amp (same chip) that I fed with 24V batteries (28.5V when fully charged...) the chip was just bolted to the case (die-cast alu...) and sometimes it felt pretty warm (especially in the car on a hot day, I series my two car batteries to get the 24V...).

My AMP9 is a low profile version, so the chip will never see the voltages capable of making it hot, it's really hard to 'feel' whether it is on or off (even after hours). Photo's can be seen somewhere on page 6 or 7 in the photo gallery, I bolted the chip to an aluminum L-profile and to the middle of the home-made alu case...

I keep my amp awake all the time, but do have a switch to the mute pin. Beware that a turn on thump can destroy speakers (speaking out of experience...)By switching mute the turn-on 'thump' is quite minimal (it's more like a soft turn-on 'click'). I did install the 'zeners' which are schottky diodes actually (according to Jan a typo in the instruction manual) and installed all
fets and diodes (because it's my first AMP9 I valued reliability more than for it to be 'audiophile'...)

[V-bro]

Have to add that even the warmest I felt from the amps I could always keep my hand on it. I guess it was about 50 degrees C max. But I think the PIII heatsink you use has poorer heat capacity than the case I used....can the heatsink really 'breathe' or did you place it inside something?

fixed typo...[:I]

[dansolow]

Thanks, I think I might install the protection diodes just to be safe.

I have permanently connected the sleep jumper, and continue to use Mute. The amp has only a few milliamps of dc offset, so that part is working.

My understanding is that the FET's only control the LED's (U4, U5, R14, or R15)and don't affect the actual operation of the amp at all. Is this correct?

The hot heatsink was with the top of the amp open so it did have room to breathe.

I'll post some photos. I might try a bigger heatsink, and just enjoy it.

BTW - I like the diamond plate cases. Nice touch.

quote:Originally posted by V-bro
[br]Have to add that even the warmest I felt from the amps I could always keep my hand on it. I guess it was about 50 degrees C max. But I think the PIII heatsink you use has poorer heat capacity than the case I used....can the heatsink really 'breathe' or did you place it inside something?

fixed typo...[:I]

[V-bro]

quote:Originally posted by dansolow
[br]Thanks, I think I might install the protection diodes just to be safe.

The inputs are rather sensitive, so good choice...

quote:Originally posted by dansolow
[br]
My understanding is that the FET's only control the LED's (U4, U5, R14, or R15)and don't affect the actual operation of the amp at all. Is this correct?

That is correct...

quote:Originally posted by dansolow
[br]
The hot heatsink was with the top of the amp open so it did have room to breathe.

Still really strange...make sure you use paste...and make sure the chip legs don't suffer mechanical stress from the heatsink. Anchor the heatsink well to the case....(or use a case as heatsink lik I did...)

quote:Originally posted by dansolow
[br]
I'll post some photos.

Nice, if gallery access is a problem, use this link:
http://www.41hz.com/forums/photo_gallery.asp

quote:Originally posted by dansolow
[br]
BTW - I like the diamond plate cases. Nice touch.

Thanks, I can make you one if you like...

Here's what I use for paste:

quote:Originally posted by V-bro
[br]Here:http://prisguide.hardware.no/product...roductId=21288

[dansolow]

I'll post some photo's but right now the upload to gallery does not seem to be working.

I did use paste, but the heatsink is not yet secured to the case, so there might be some static stress on the legs. How did you feel this would result in more heat?

As mentioned, I'm going to try a bigger heatsink, I think mine is too small for the 9, but this does still seem like alot of heat, particularly when compared to the Amp 5 with the same heatsink. Voltages of @18 vdc make the 9 get fairly hot after some time, even when playing at low volumes out of only 2 channels.

Dan





The heat

quote:Originally posted by V-bro
[br]

quote:Originally posted by dansolow
[br]Thanks, I think I might install the protection diodes just to be safe.

The inputs are rather sensitive, so good choice...

quote:Originally posted by dansolow
[br]
My understanding is that the FET's only control the LED's (U4, U5, R14, or R15)and don't affect the actual operation of the amp at all. Is this correct?

That is correct...

quote:Originally posted by dansolow
[br]
The hot heatsink was with the top of the amp open so it did have room to breathe.

Still really strange...make sure you use paste...and make sure the chip legs don't suffer mechanical stress from the heatsink. Anchor the heatsink well to the case....(or use a case as heatsink lik I did...)

quote:Originally posted by dansolow
[br]
I'll post some photos.

Nice, if gallery access is a problem, use this link:
http://www.41hz.com/forums/photo_gallery.asp

quote:Originally posted by dansolow
[br]
BTW - I like the diamond plate cases. Nice touch.

Thanks, I can make you one if you like...

Here's what I use for paste:

quote:Originally posted by V-bro
[br]Here:http://prisguide.hardware.no/product...roductId=21288

[Kocsu]

Hi
my Amp9 runs "warmer" than AMP5 or AMP6, as there are double the channels on it I didn't worry too much (I paralleled inputs/outputs in pairs and connected to 24VDC)

I'm not using real heatsink but aluminum profiles, sorry I don't have exact measures but I'm using 4 pieces, "U" thin profiles, 8cm.x 16cms exposed area each, composing an squared metallic pipe with sides open

I can touch the aluminum just behind the Tripath chip, it gets hot but I can touch it with no skin damage, after some time playing music three sides of aluminum faces get warm, with a very slow fan the aluminum get cold very easy

it called my attention but haven't tested again, that playing music at moderate volume or with no signal (awake and unmute), the amp gets warm the same

I know there's no much objective/useful information here, but I concur with dansolow about the weird temperature behavior of amp9, conclusion: take good care of temperature dissipation on amp9, remember the same chip is doing 4 channels amp and 5Volts regulation

the amp is playing music very good, very very quiet
only suspicious thing so far is: one channel (pair in parallel) has 0 milivolts DC offset but the other one has about 100milivolts, after the mute-unmute action and no signal

[longitude]

I think it is not a good idea to put a fan (even a slow quite fan) inside the amp.
It emits much noise...both real noise and EM noise (more serious problem).