sorry? you mean heatsinks from surplus stores? why wouldn't it? we just mean a standalone amp-speaker type guitar amp here, don't we? i'm afraid i don't follow you greg.
i do like aluminum angles, though. one builder did handsome minimalist monoblocks by putting each amp inside two angles placed upright as a post. (can't find the photo. i thought it was on scott nixon's site.)
ofb said:
Sorry to confuse you, I meant that the aluminum angle probably won't be sufficient for a guitar amp.
You're right, I thought I'd come up with the idea of using al angle myself but I now remember seeing it first on a Scott Nixon gainclone many years ago. His current site doesn't have the pictures anymore.
Thanks
Hi Nuuk,
I don't really know anything about guitar amps but imagined that they need to be as compact as possible and portable, so weight would be an issue. Also, I thought they would be played at full volume, so I would guess you needed a compact efficient heatsink. A piece of angle doesn't really meet this criteria.
See ya
I don't really know anything about guitar amps but imagined that they need to be as compact as possible and portable, so weight would be an issue. Also, I thought they would be played at full volume, so I would guess you needed a compact efficient heatsink. A piece of angle doesn't really meet this criteria.
See ya
Me neither Greg but the piece that I used would not make the amp very big or heavy and should afford adequate cooling. I was really just making the point that aluminium angle is not confined to the spindly sizes we find in home DIY stores.
I like using the angle for P2P construction as it lays the chip flat and makes connections much easier than when it is vertical.
"portable" with guitar amps usually just means you have a handle on it. i don't know what sybex23 is aiming for, but i'm sure you can do a gc style g-amp with an aluminum angle sink. the amp case has to be a good size to hold the speaker, and most of the weight is in the durable carcase anyway. you could probably do something about the size of the classic little pignose.
http://members.aol.com/Rogthurman/bassov.jpg
http://www.ishibashi.co.jp/machida/amp/kogata/gif/pignose.jpg
another source of aluminum heatsinks would be offcuts from windows and door frames. there's a lot of existing extruded aluminum shapes that would provide good material for gc's. door sills are particularly thick.
i don't know what sybex23 is aiming for, but i'm sure you can do a gc style g-amp with an aluminum angle sink. the amp case has to be a good size to hold the speaker, and most of the weight is in the durable carcase anyway. you could probably do something about the size of the classic little pignose.http://members.aol.com/Rogthurman/bassov.jpg
http://www.ishibashi.co.jp/machida/amp/kogata/gif/pignose.jpg
another source of aluminum heatsinks would be offcuts from windows and door frames. there's a lot of existing extruded aluminum shapes that would provide good material for gc's. door sills are particularly thick.
hot chips
Just a thought:
You say that the power supply is well separated from the amplifier. This is not generally good practice, as the filter/reservoir capacitors should, ideally, be as close as possible to the amplifier supply pins, or at least, there should be very local decoupling. Also, the actual supply routing is quite critical in many aspects.
Is it possible that the amplifier is oscillating at RF? Even a tiny amount would make the chip very hot, compared with a typical signal at audio frequencies. You wouldn't hear it, and all would sound OK.
Try by-passing the supply pins - very close to the chip - with, say, a 100uF elco and 100nF ceramic in parallel from each supply pin to ground. I assume you have the usual Bucherot/Zobell network (a few ohms in series with about 100-220nF from the outputs to ground, also close to the chip). Do you have a well damped series inductor after this? This is often necessary to reduce the effect of reactive loads such as crossover filters.
BTW, the LM3886 is excellent. Very stable, sounds very good too. Just watch the layout, and be careful how the supplies come up with respect to the un-muting current, to avoid switch on thumps.
Hope this is useful.
Let us know how you get on!
Just a thought:
You say that the power supply is well separated from the amplifier. This is not generally good practice, as the filter/reservoir capacitors should, ideally, be as close as possible to the amplifier supply pins, or at least, there should be very local decoupling. Also, the actual supply routing is quite critical in many aspects.
Is it possible that the amplifier is oscillating at RF? Even a tiny amount would make the chip very hot, compared with a typical signal at audio frequencies. You wouldn't hear it, and all would sound OK.
Try by-passing the supply pins - very close to the chip - with, say, a 100uF elco and 100nF ceramic in parallel from each supply pin to ground. I assume you have the usual Bucherot/Zobell network (a few ohms in series with about 100-220nF from the outputs to ground, also close to the chip). Do you have a well damped series inductor after this? This is often necessary to reduce the effect of reactive loads such as crossover filters.
BTW, the LM3886 is excellent. Very stable, sounds very good too. Just watch the layout, and be careful how the supplies come up with respect to the un-muting current, to avoid switch on thumps.
Hope this is useful.
Let us know how you get on!
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