Roskilde DIY - AMP6-B component fried

[jesperstald]

Hi,

Ive recently build my own portable AMP6-B powered "wagon" for this years Roskilde festival.
Playing atleast 10 hours pr day at medium to high volume throughout the festival without wearing my 60Ah car battery down, i am extremely pleased with the tripath amp.



The wagon is designed to serve as both boom-box and luggage transportation, so the speaker cabinet itself became rater compact. The drivers im using are high-efficiency 12' "Fane Classic" woofers. These and the tweeters are connected directly to the AMP without any crossover.

The sound is reasonable overall, with the biggest problem being the bass response (which i'm confident some tweaks to the speaker cabinet can fix). Taking into account that this is the first time I've ever messed with speaker building, i can live with the sound not being perfect right away.

A problem is though, that at the very last day at Roskilde (fortunately!), the sound in one channel became extremely faint (almost inaudible).
I've later discovered that the malfunction lies with the amp, and that the most probable cause to the amp malfunction lies with the C15-component.



When the amp is playing through the defect channel, the faint music turns in to loud noise upon touching the top of the C15.

I know from the AMP6-B assembly instructions that the C15 is the signal input capacitor for the right channel, but my question to you is: is it likely that the C15 is the cause of the defect, and if yes, where can i get a replacement?

Best regards,

Jesper

PS: Thoughts on cabinet design are also welcome

[V-bro]

Hi Jesper, I've got tons of those caps, just PM me your address and I'll send you one...

[gnome]

Hello Jesper, what in the bass response are you trying to fix? bearing in mind that you need a huge amount of power to get decent bass outdoors, and that driver being 'high efficiency' never had any pretensions to giving you any.

About the cap, if you can make it work by touching it maybe it would be worthwhile reheating the solder joints to see if it just cracked.

[mrath]

where can i get a replacement?

Are you from DK, Jesper? If you are, I know a couple of places, and V-Bro don't have to mail you the component from the NL

[jesperstald]

Are you from DK, Jesper?

Yes, i am i would love your recommendation!

Hi Jesper, I've got tons of those caps, just PM me your address and I'll send you one...

Thats extremely generous of you, but i don't want you to have the trouble if i can get it here in DK

About the cap, if you can make it work by touching it maybe it would be worthwhile reheating the solder joints to see if it just cracked.

Yeah i thought that was the problem first too, as that exact component took a hit during the construction phase, but reheating it didn't help.
Actually, the noise it made weren't upon pressing the component down, but merely touching the top surface.

Hello Jesper, what in the bass response are you trying to fix? bearing in mind that you need a huge amount of power to get decent bass outdoors, and that driver being 'high efficiency' never had any pretensions to giving you any.

Im not betting on huge bass, but the bass can (without bass boosting equalizers, atleast) be almost non-existing.
It feels like it produces a lot of bass, but it seems most of this is lost through the backwall of the cabinet. Because of this i'm planning on sound-insulating the inside of the cabinet.

Finally, i've made a bass-reflex cabinet, but that doesn't work to hot because the cabinet is far from airtight.

[mrath]

Sent you a PM Jesper, hope you find what you're looking for, else reply me and I'll try to help more. My experience only goes to Jutland, else you'll probably want to talk to Saturnus - he's the main electronics Don in the Copenhagen area

[V-bro]

I can send it as postcard, won't cost an arm and a leg....

[Saturnus]

Finally, i've made a bass-reflex cabinet, but that doesn't work to hot because the cabinet is far from airtight.

Fane Classic's are guitar speakers. They won't play bass no matter what you do. And they should actually be mounted in an open back cabinet (like a guitar cab) to get the best result.

Might I suggest that since you're changing the caps anyways, and you don't a flicker of hope ever getting bass out of those guitar speaker that you save a ton of power and change the caps for a much lower value.

[Sorenorr]

In the problemsolving section of the assembly instructions it says that if:
"the sound is weak from one channel.
Check if there is a 12V voltage offset on one output. In that case, an output
transistor is probably damaged and the chip needs to be replaced."

I'm same situation as yours but haven't checked for the 12V offset since i'm currantly not in possesion of a voltmeter.

However, a new chip goes for about 80 dkr on ebay.

Please post any progess

[jesperstald]

Thanks for the input Saturnus. I think youre right, i probably never will get any great amount of bass out of it. But if i want to do the best i can without replacing the drivers, what do you think i should do?

About the caps, a much lower value of what? and would changing this value only decrease bass, not total volume?
Btw, saving power is no concern for me, it already plays for days on a car battery.

Sorenorr, i've read the troubleshooting.. and my hope is that it is only the capacitor is fried, which would both mean lesser cost and less soldering work for me :P Have you tested if the dead channel makes static upon touching the cap, like in my case?
I'll make sure to post if a new cap works