Compact Power Amp

[Noisyjon]

Top stuff Alien, I'm well impressed with this project.

Rock on!

[Dood]

[quote name='Alien' post='216169' date='Jun 10 2008, 01:56 PM']It's not loud, but it is audible and would be very annoying, so I'll have a poke about in there with a 'scope later and try to find the source (my bet is that it's the power supply). Other than the whistle, it seems very quiet in operation, no buzzing or humming came through.

Andy[/quote]

lookin' good so far mate...

right, that high pitch noise you are hearing is the switching part of the amplifier, I am almost sure. The output of the poweramp should be filtered at a particular frequency to attenuate the high pitch noise getting out to the speakers. Interestingly though, the frequency should be much higher than 15K.. to get up passed the audio range. In the same way thatthe sample rate of CD encoding is 44.1Khz (in that case, double the highest frequency anyone can normally hear).

anyway, I digress.. the filtering can be as simple as an RC network on the output.. mebbe this either isnt working, or as I have seen in some modules, needs adding!!

I'll see if I can find some more information that will better describe what I am trying to say lol!!!

[Dood]

^^^^^ Actually, looking at some online information I am not 100% sure now.. as some amps switch up in the 450Khz region!!!!!!

[Alien]

It seems that most of the noise was coming in on the connections to the volume pot. Bypassing it with a jumper quieted things down a hell of a lot. Since it's actually audio going through the pot (rather than a control voltage), I'm going to rewire it with some screened cable, which should help things along nicely!

Andy

[Dood]

[quote name='Alien' post='216287' date='Jun 10 2008, 04:11 PM']It seems that most of the noise was coming in on the connections to the volume pot. Bypassing it with a jumper quieted things down a hell of a lot. Since it's actually audio going through the pot (rather than a control voltage), I'm going to rewire it with some screened cable, which should help things along nicely!

Andy[/quote]


Ah! i see!! I'm glad it wasnt serious!

[BigRedX]

Very impressive size and weight, hope you get the noise problems sorted.

Could be some digital clock signal being picked up by the unscreened wires to the volume control?

Also some of the Ashdown Superflys suffered from a high pitched whine breaking into the audio which was caused by a problem with the PSU I believe?

Edited June 10, 2008 by BigRedX

[Alien]

Well, it's been nearly a month since I last posted an update. This weekend, however, sees an uncharacteristic burst of energy and enthusiasm from me, so some progress is being made at last.

As I mentioned in my last post, a lot of the noise was coming in via the volume pot. I've replaced the twisted cables with a short length of screened twin core, which helped a lot. I also found that driving the Power LED from the +12V auxillary supply brought a noisy supply line into close proximity with the volume control. I decided to run the LED from the Fan supply instead and this, along with swapping the twisted pairs for coaxial cable and re-routing the LED cable so it's further from the volume pot, has quietened this amp down a lot.

OK, time for some pics.
[attachment=10459:PICT0415.JPG]
Initial load testing with the fan fitted. The holes at the front are to try and force air across the amp module. I've since added more to the other end of the amp to try and improve air flow. I'm not too happy about the holes being so open - I shall have to do something about that later. The fan is held in place with 2-part plastic rivets.

[attachment=10460:PICT0406.JPG]
My signal generator, built from a Maplins kit years ago, still going strong. I used a triangle wave set at about 200Hz for the load test - no real scientific reason why, it just seemed right.

[attachment=10461:PICT0403.JPG]
This is the dummy load I used for testing the amp. A dozen 25 Watt resistors and a 100 Watter give about 370 Watts of load at about 5 Ohms. The amp ran quite hot after 20 minutes on this load.

[attachment=10462:PICT0407.JPG]
The amp under load, with the clip LED lit. The more observant among you may have noticed that the blue Power LED has moved to the bottom position. This happened as part of the cable re-routing.

[attachment=10463:PICT0418.JPG]
I've stuck some coarse weave speaker cloth across the vent holes. Should keep most things out, but not reduce the airflow too much. It'll also act as a dust filter, but that's definitely not its main purpose.

[attachment=10465:PICT0419.JPG]
Here's the same thing from the other side - not quite as pretty, but no-one's going to see it but you lot. The cloth is glued to the case with epoxy.

[attachment=10467:PICT0420.JPG]
Before re-assembly. I deliberately left enough room for the fan as I had a suspicion it would be needed. Still a tight fit though. Also, I've coloured the amp and PSU black in the hope it improves heat sinking.

I performed a second load test, again using triangle wave set to approx 200Hz, at the very onset of clipping. (The LED indicator 'fades up' as clipping is approached, making this easier to set) The amp still ran pretty hot after 30 minutes of this, although not as hot as previously.

This is a pretty severe test for an amp, as real music has dynamic peaks and troughs, and would not normally be run flat out for 30 minutes like this. However, I would like to try and improve the cooling a little further, so I'm going to try to fit a small vaned heatsink inside the amp, where it will intercept some of the airflow through the case. That's for tomorrow though.

The last thing I've noticed is the fan noise. The fan runs fairly quiet, not noticeably louder than a PC fan in reality, but it seems hugely loud in a quiet room with a dummy load on the anp. I don't think it'll be a problem in the real world of a gig though.

Watch this space...

Andy

[s_u_y_*]

Looking good.

[Hamster]

Ummmmm - Alien Amps Ltd - Nice work.

You should start a thread to suggest names for the product range:

The Tribble
The Darth Vader
The Quark
The Predator
The Little Predator



Hamster

[Buzz]

What size is the fan? and if it's a standard style fan, you might be able to source a "quiet" fan off ebay in the pc parts section, although, finding a quite 40mm (yes?) might prove difficult.

Shame the actual chassis isn't about 15mm taller, as then you could wap a big hulking 80 or 120mm fan to the roof (or underside) which'll sort out cooling easily.

[Peaty]

[quote name='Hamster' post='233854' date='Jul 6 2008, 11:25 PM']Ummmmm - Alien Amps Ltd - Nice work.

You should start a thread to suggest names for the product range:

The Tribble
The Darth Vader
The Quark
The Predator
The Little Predator



Hamster[/quote]


A big +1 for the Tribble especially if it can with a fake fur covering (hmm probably wont help with the cooling though)

[Alien]

Gave the little fella a 'real world' test tonight. Ran it at a band rehearsal, using my Hartke HA7000 as a preamp. It's amazingly powerful - you'd never believe something that small could deliver that much wallop.

I ran it pretty well flat out, so the clip indicator lit occasionally. After the dummy load testing, I thought it might run hot with music, but I needn't have worried. It barely got warm - possibly a little cooler than my Hartke gets after the same sort of run.

I also mentioned the fan noise in an earlier post, but that too proved to be (marginally) quieter than the one in the HA7000, which has never been a problem, so I'm happy with that.

[attachment=10896:PICT0421.JPG]

This pic shows the extra heatsinks I fitted. Probably unnecessarily as it turns out, but it never hurts. As I said before, the load testing I did was a pretty severe test, as tonight proved.

Just need to put a couple of labels on it (ratings and the like) and stick it on the PAT tester at work and it'll be good to go.

Andy

[s_u_y_*]

Can´t wait to get my filthy mitts on this.

[Alien]

Final installment time. I've put on a few labels (rating plate, output/load info plus the standard 'arse covering' one about not using it in the bath etc.) and it's all ready to go.

Final pic before boxing it up:

[attachment=12677:PICT0512.JPG]

Nice snug fit in its shipping box, on the way to its new owner

[attachment=12678:PICT0516.JPG]

So, any requests for the next project?

Andy

[alexclaber]

Fantastic work!

Alex

[Kiwi]

[quote name='Alien' post='270697' date='Aug 27 2008, 12:55 AM']So, any requests for the next project?[/quote]
How about a Barefaced Alien active cab?

[Merton]

[quote name='Alien' post='270697' date='Aug 27 2008, 12:55 AM']Final installment time. I've put on a few labels (rating plate, output/load info plus the standard 'arse covering' one about not using it in the bath etc.) and it's all ready to go.

Final pic before boxing it up:

[attachment=12677:PICT0512.JPG]

Nice snug fit in its shipping box, on the way to its new owner

[attachment=12678:PICT0516.JPG]

So, any requests for the next project?

Andy[/quote]
Utterly brilliant. How much?

[Alien]

[quote name='Merton' post='270998' date='Aug 27 2008, 01:51 PM']Utterly brilliant. How much?[/quote]

If I could get enough interest to do a small production run (say 5 or so), it's looking like about £375 - £400.

Andy

[s_u_y_*]

Alien Audio... sounds cool! Cool logo too.

I hope you numbered it number "001". When you launch your successful amplification business empire, I wanna be able to retire on this baby. I'll be waiting patiently by the door (though I am away most of next week). Think I've got a gig next Saturday, perfect opportunity to test it out on the field.

Edited August 27, 2008 by s_u_y_*

[Alien]

[quote name='s_u_y_*' post='271428' date='Aug 27 2008, 11:35 PM']Alien Audio... sounds cool! Cool logo too.

I hope you numbered it number "001". When you launch your successful amplification business empire, I wanna be able to retire on this baby. I'll be waiting patiently by the door (though I am away most of next week). Think I've got a gig next Saturday, perfect opportunity to test it out on the field.[/quote]

Pre-production prototypes never get numbered

Hopefully it'll be with you tomorrow, possibly Friday. It went out this afternoon via Citylink.

Andy

[s_u_y_*]

[quote name='Alien' post='271439' date='Aug 27 2008, 11:52 PM']Pre-production prototypes never get numbered

Hopefully it'll be with you tomorrow, possibly Friday. It went out this afternoon via Citylink.

Andy[/quote]

Excellent mate... for some strange reason keep think today is Thursday. Wishful thinking I guess. Btw... just noticed how you packed it in the picture.

Edited August 27, 2008 by s_u_y_*

[s_u_y_*]

Here's my review of it here.

[url="http://basschat.co.uk/index.php?showtopic=28057"]http://basschat.co.uk/index.php?showtopic=28057[/url]

[phil_the_bassist]

a truely amazin bit of kit! moor oomph-per-lb than anything I've ever seen

[Merton]

Oh yeah, the sound of the EBS thru this thru OBBM's 6x10 berg was astonishing!

[EBS_freak]

[quote name='Merton' post='294396' date='Sep 29 2008, 10:51 AM']Oh yeah, the sound of the EBS thru this thru OBBM's 6x10 berg was astonishing![/quote]

Indeed - I liked. It makes perfect sense a rig like that. Bass in one hand, neo compact cab in the other and a backpack with microbass pre and alien power amp in (plus cables obviously!) - no problems - even on the Tube. It's certainly got me thinking!