View Full Version : AMP9 LP finished
so I've boxed it up,after buggerizing around for bit,
with different input and outputs and switching them, I decided it was all too complicated and went with normal RCA and binding posts,
and it does sound really great, I certainly can't pick between my NAD 214 poweramp and the AMP9 at low to medium volume.
I used a 50x200 RHS with 3mm walls, the front and back are made from the same section.
http://farm4.static.flickr.com/3327/3556474194_89976f50e2_o.jpg
http://farm4.static.flickr.com/3391/3555662483_79d8fc4c4f_o.jpg
http://farm4.static.flickr.com/3581/3555662427_df4ec49a4a_o.jpg
I've done some current measuring which was very interesting
with mute on, there is 70mA,
with amp on but no signal there is 192mA with two channels connected, and with all four channels 262mA
at 300mA it sounds great and volume is very good
at 500mA distortion is getting apparent and at about 1A distortion becomes unacceptable(I'm using a 12V battery and 8 ohm speakers)
Interestingly with two channels driven there is much more current draw for the same SPL.
I am very happy with the result, yet, I am wondering if there is more I can squeeze out of the amp, when I bought it I didn't know about the power limitation of 12V, so I chose the low profile version, In hindsight I would have been better off with the AMP9 basic, because I never intended to use a power supply, but I am wondering if I can put two 12V batteries together to supply the amp with 24V?
Hi,
Hmm, it's distorting at 500mA? That means you're only getting a few watts out of it ... it should be able to suck 3.6A into 4x8Ohm, at very low distortion:
http://www.google.com/search?q=%28%28%2860%25+of+%2812V%29^2+%2F+8+Ohms% 29+*+4%29+%2F+12+V
Source for calculation: http://41hz.com/Forums/topic.asp?TOPIC_ID=678
when you're using only two speakers, are you "zeroing" the input on the idle channels by jumpering signal to ground? And also "zeroing" the idle outputs with a resistor? (You need to. Not doing this could actually break the amp!) The amp might be wasting power unless you do this.
Also, make absolutely sure the amp isn't in AM mode. (It probably isn't, it would waste more power if it were, I guess?)
And yep, you can create 24V from two 12V batteries in series, easy.
Can you get more of these speakers? If you parallel them up to get 4 Ohms, and load such pairs on every channel, you'll be making the most of the available voltage. Might be too complicated though. Just a thought. If you'll stick with the 12V supply, try as you can to use 4 Ohm impedance per channel. Or use really high efficiency speakers, I guess above 93 or so dB/W. Higher than that is probably better.
quote:Originally posted by krilli
Hi,
Hmm, it's distorting at 500mA? That means you're only getting a few watts out of it ... it should be able to suck 3.6A into 4x8Ohm, at very low distortion:
http://www.google.com/search?q=%28%28%2860%25+of+%2812V%29^2+%2F+8+Ohms% 29+*+4%29+%2F+12+V
Source for calculation: http://41hz.com/Forums/topic.asp?TOPIC_ID=678
when you're using only two speakers, are you "zeroing" the input on the idle channels by jumpering signal to ground? And also "zeroing" the idle outputs with a resistor? (You need to. Not doing this could actually break the amp!) The amp might be wasting power unless you do this.
measuring the current draw has shown me that there is more efficiency with the speakers and inputs in parallel, so I'm not going to let channels go idle. So I have paralleled the outputs (and inputs) and using a pair of 8 ohm speakers.
quote:
Also, make absolutely sure the amp isn't in AM mode. (It probably isn't, it would waste more power if it were, I guess?)
to put the amp into AM mode I have to jumper pin 9 on J10 to ground? no didn't do that
quote:
And yep, you can create 24V from two 12V batteries in series, easy.
yes but can I then put 24Vinto the AMP9 LP?
quote:
Can you get more of these speakers? If you parallel them up to get 4 Ohms, and load such pairs on every channel, you'll be making the most of the available voltage. Might be too complicated though. Just a thought. If you'll stick with the 12V supply, try as you can to use 4 Ohm impedance per channel. Or use really high efficiency speakers, I guess above 93 or so dB/W. Higher than that is probably better.
Well these speakers have an average efficiency of 106dB and have useable output down to 80Hz which is why I am so happy with 6W or whatever input, the plan is to build more of these type of speakers and matching subs, but for the moment I'd just like to get a little more headroom.
OK, I see I've been telling you some things you already know :) Everything is Looking rather good - I misunderstood how you were using the channels.
My hunch is that you can indeed get some more power out of there. Bear with me as I try to understand: When you parallel the amp outputs into an 8 Ohm speaker, does each amp output see 4 Ohm or 16 Ohm?
Hi, nice nice nice box!!![8D][8D][8D]
On the AMP9 you have it works in class D mode by default. On the BASIC you need to place a jumper to make it operate in class D mode...
The distortion is definitely due to the combination 12V/8ohms... You could swap some caps for higher voltage ones and make it work on 24V. Make sure you get very low ESR caps like the Panasonic THA that it uses right now...
I'm afraid the AMP4 would rock your boat better...
------X-max. can be several meters on any driver, too bad it can be done only once...------
I can see you have not used isolated RCA sockets. This will work, but introduces more noise.
My experience is best as follows:
-Isolate RCAs from the box.
-Isolate the chip from the box by using mica and paste or silicone pads.
-Connect the power ground* to the chassis AT ONE POINT.
* Power ground is the negative pole from the bulk caps with single supply amps. With dual supply amps this point can be VNN so watch out! Some amps (like the AMP4) have a ground point on the power screw terminal...
------X-max. can be several meters on any driver, too bad it can be done only once...------
OK, according to this: http://en.wikipedia.org/wiki/Bridged_and_paralleled_amplifiers#Paralleled_ampli fier
... when you parallel two channels to drive a 8 Ohm load, each output sees 16 Ohms! This is why you're seeing so little current draw - you really want as lower impedance as possible, especially with this rail voltage.
Right now, you're being current (and thus wattage) limited because each channel is driving 16 Ohms. You'll get more power if each channel drives 8 Ohms, and you'll get the most power AFAIK if you manage to have each channel drive 4 Ohms, and use all channels.
With the same speakers there's nothing much else you can do than go for higher voltage. Still the impedance match is quite off with the AMP9. It is also being pretty low gain by nature.
The AMP9 can really ROCK, but it is a current driving monster....so in need of a heavy load...
------X-max. can be several meters on any driver, too bad it can be done only once...------
quote:Originally posted by V-bro
With the same speakers there's nothing much else you can do than go for higher voltage.
... after dropping the paralleling, yes. :D
The speakers are high enough efficiency for the whole combo to work OK IMO.
quote:Originally posted by V-bro
Hi, nice nice nice box!!![8D][8D][8D]
On the AMP9 you have it works in class D mode by default. On the BASIC you need to place a jumper to make it operate in class D mode...
The distortion is definitely due to the combination 12V/8ohms... You could swap some caps for higher voltage ones and make it work on 24V. Make sure you get very low ESR caps like the Panasonic THA that it uses right now...
which particular caps?
quote:
I'm afraid the AMP4 would rock your boat better...
yeah I think you're right, if I knew three weeks ago what I know now then that is the one I would have bought, but at the same time, reading other people's experiences I realise that I may have been really lucky that it worked pretty much straight away, and it really sounds amazing, I'm very happy how this has turned out..
quote:Originally posted by krilli
OK, according to this: http://en.wikipedia.org/wiki/Bridged_and_paralleled_amplifiers#Paralleled_ampli fier
... when you parallel two channels to drive a 8 Ohm load, each output sees 16 Ohms! This is why you're seeing so little current draw - you really want as lower impedance as possible, especially with this rail voltage.
Right now, you're being current (and thus wattage) limited because each channel is driving 16 Ohms. You'll get more power if each channel drives 8 Ohms, and you'll get the most power AFAIK if you manage to have each channel drive 4 Ohms, and use all channels.
curiously I'm getting better results with one speaker on two outputs rather than one speaker on one output
quote:Originally posted by V-bro
I can see you have not used isolated RCA sockets. This will work, but introduces more noise.
no way! I was thinking that it is already very very quiet, I think I might try this
thanks V-bro
quote:
My experience is best as follows:
-Isolate RCAs from the box.
-Isolate the chip from the box by using mica and paste or silicone pads.
-Connect the power ground* to the chassis AT ONE POINT.
* Power ground is the negative pole from the bulk caps with single supply amps. With dual supply amps this point can be VNN so watch out! Some amps (like the AMP4) have a ground point on the power screw terminal...
quote:Originally posted by gnome
quote:Originally posted by krilli
OK, according to this: http://en.wikipedia.org/wiki/Bridged_and_paralleled_amplifiers#Paralleled_ampli fier
... when you parallel two channels to drive a 8 Ohm load, each output sees 16 Ohms! This is why you're seeing so little current draw - you really want as lower impedance as possible, especially with this rail voltage.
Right now, you're being current (and thus wattage) limited because each channel is driving 16 Ohms. You'll get more power if each channel drives 8 Ohms, and you'll get the most power AFAIK if you manage to have each channel drive 4 Ohms, and use all channels.
curiously I'm getting better results with one speaker on two outputs rather than one speaker on one output
OK, interesting, then I must ask - are you then zeroing the inputs and dummyloading the outputs of the idle channels?
It doesn't make a difference at all to parallel or use two channels, it remains the same speaker pair at the same voltage. The extra current only results in somewhat more control, but sometime it sounds even over-controlled and a bit harsh... Depends on the speakers...
Indeed don't leave the outputs "open", you need to dummyload and short inputs. Otherwise you can get oscillation and extra current draw...
The caps you need to change to operate on 24V are only some electrolytic caps. the voltage rating is printed on them so it's easy to check. This is really the ONLY thing that is different with the 24V high profile version. Wouldn't be surprised if it's only the three large caps...
They need to be 35V rated at least...
When you decide to desolder them do pre-heat the board well around the pins. Snap in caps are a bugger to desolder and it would be a waste to damage the board...
I pre-heated them often with a small gas torch at some distance, a gas furnace can also be used. Just make sure you don't literally burn the board or melt any other parts. For as far as I know there's not much in this area of the board.... Don't be too afraid either...
------X-max. can be several meters on any driver, too bad it can be done only once...------
quote:Originally posted by krilli
quote:Originally posted by gnome
quote:Originally posted by krilli
OK, according to this: http://en.wikipedia.org/wiki/Bridged_and_paralleled_amplifiers#Paralleled_ampli fier
... when you parallel two channels to drive a 8 Ohm load, each output sees 16 Ohms! This is why you're seeing so little current draw - you really want as lower impedance as possible, especially with this rail voltage.
Right now, you're being current (and thus wattage) limited because each channel is driving 16 Ohms. You'll get more power if each channel drives 8 Ohms, and you'll get the most power AFAIK if you manage to have each channel drive 4 Ohms, and use all channels.
curiously I'm getting better results with one speaker on two outputs rather than one speaker on one output
OK, interesting, then I must ask - are you then zeroing the inputs and dummyloading the outputs of the idle channels?
let me clarify, I'm not running any channels idle
quote:Originally posted by V-bro
It doesn't make a difference at all to parallel or use two channels, it remains the same speaker pair at the same voltage. The extra current only results in somewhat more control, but sometime it sounds even over-controlled and a bit harsh... Depends on the speakers...
ahhh ok, I'm definitely getting more output all paralleled, but I wasn't quite sure if the sound became worse, quite marginal it is.
quote:
Indeed don't leave the outputs "open", you need to dummyload and short inputs. Otherwise you can get oscillation and extra current draw...
but out of intrest what is an appropriate load resistor?
quote:
The caps you need to change to operate on 24V are only some electrolytic caps. the voltage rating is printed on them so it's easy to check. This is really the ONLY thing that is different with the 24V high profile version. Wouldn't be surprised if it's only the three large caps...
ah damn that means they're not going to fit into the box
quote:
They need to be 35V rated at least...
When you decide to desolder them do pre-heat the board well around the pins. Snap in caps are a bugger to desolder and it would be a waste to damage the board...
I pre-heated them often with a small gas torch at some distance, a gas furnace can also be used. Just make sure you don't literally burn the board or melt any other parts. For as far as I know there's not much in this area of the board.... Don't be too afraid either...
could I put it in an oven at 100°C or would that kill some other components?
quote:Originally posted by V-bro
It doesn't make a difference at all to parallel or use two channels, it remains the same speaker pair at the same voltage. The extra current only results in somewhat more control, but sometime it sounds even over-controlled and a bit harsh... Depends on the speakers..
Yes, duh, thanks, I was in error. If you were to add more speakers though ... [:I]
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