Chip amp on the cheap *PIC*

[jaudio]

My 12.32 amp. This is the second cheapest amp I have built.

OPA549 4 Free samples
Case Free(Can buy for $1 goodwill)
Caps and Resistor $.60
Breadboard $1.50(MCM)
Screws $.99
Paint $3.00
RCA connectors $.80 (Jameco)
Binding Post $2.40(Partsexpress buyout)

[hongrn]

I thought mine was cheap. Just got this LM4780 from hifidiy.net for $40. Guess yours is ultracheap!

[robertcottiers]

> I thought mine was cheap. Just got this
> LM4780 from hifidiy.net for $40. Guess yours
> is ultracheap!

Hongrn:It looks like a nice kit,good luck with it.BTW If you attach the ChipAmp to the heatsink without an insulating washer,the heatsink will be at V- potential,most people are not aware of this.

***The following is from the LM4780 datasheet*****

Note 14: The TA27A is a non-isolated package. The package’s metal back, and any heat sink to which it is mounted are connected to the V- potential when using
only thermal compound. If a mica washer is used in addition to thermal compound, èCS (case to sink) is increased, but the heat sink will be electrically isolated from
V-.

Regards Bob Cottiers

[hongrn]

Thanks, Bob. Wow, I didn't even realize that they sold me the non-insulated chip. I read the datasheet on the LM4780 but didn't pay attention to note 14.

Hong

[cjd]

> Thanks, Bob. Wow, I didn't even realize that
> they sold me the non-insulated chip.

They don't *make* an insulated LM4780!

C

[jonpike]

> Note 14: The TA27A is a non-isolated
> package. The package’s metal back, and any
> heat sink to which it is mounted are
> connected to the V- potential when using
> only thermal compound. If a mica washer is
> used in addition to thermal compound, èCS
> (case to sink) is increased, but the heat
> sink will be electrically isolated from
> V-.

> Regards Bob Cottiers

Yes, nice kit, looks like good quality caps, as well! They've got a few other interesting ones on their site, too. Hmmm.. been thinking of putting together a chip amp, was going to check back with BrianGT's chipamp boards and kits effort, and here we are with another nice option...

A note on the heat sink situation... you do have to electricaly isolate your heat sinks, but the advantage of this package is you do have the lower thermal impedence to it, nothing but metal on metal. (and your high quality heat sink compound, of course) This will let you stay cooler/burn more watts, without problems.. I'd probably pick the non insulated type given the choice..

And, a question... how's the documentation? I tried to find any on their site, was wondering what transformer reccomendations they gave... voltage and wattage.

[cjd]

> A note on the heat sink situation... you do
> have to electricaly isolate your heat sinks,
> but the advantage of this package is you do
> have the lower thermal impedence to it,
> nothing but metal on metal.

This *is* a possibility, but it means your heat sink is at V- and that's bad news for *any* type of accident that may happen. You know, drop a screwdriver that connects the HS to chassis...

My choice would be to use a copper heat spreader bonded to the chip, and insulate the heat spreader with a thin mica or silpat or something similar.



Just be careful and make darn sure it's isolated properly.

C

[jaudio]

> I thought mine was cheap. Just got this
> LM4780 from hifidiy.net for $40. Guess yours
> is ultracheap!

It looks like a good set for the price. Is it $40 for a stereo pair? The filtering caps looks very intersting,I will have to look for more imformation.

[hongrn]

> It looks like a good set for the price. Is
> it $40 for a stereo pair? The filtering caps
> looks very intersting,I will have to look
> for more imformation.

Yes, for the pair. They say you have the option of building a 2-channel amp at 120W/ch, or a 4-channel amp at 60W/ch.

[robertcottiers]

> I thought mine was cheap. Just got this
> LM4780 from hifidiy.net for $40. Guess yours
> is ultracheap!

Hong:In case you have not purchased your transformer yet,PE has a buyout which would work well for your configuration.They are 25 volt CT,you will need two transformers,and you will not use the center tap wire.This will yield +/-35volts DC after capacitive filtering.PE does not spec a VA rating,but judging from the size of it it will power the chip amps....$5 apiece plus shipping = not bad.Just my 2 cents.

Regards Bob C.

heres the link:

<A HREF="http://www.partsexpress.com/pe/showd...number=129-084">http://www.partsexpress.com/pe/showd...number=129-084</A>

[trevorg]

> My 12.32 amp. This is the second cheapest
> amp I have built.

> OPA549 4 Free samples
> Case Free(Can buy for $1 goodwill)
> Caps and Resistor $.60
> Breadboard $1.50(MCM)
> Screws $.99
> Paint $3.00
> RCA connectors $.80 (Jameco)
> Binding Post $2.40(Partsexpress buyout)

Whats it do power wise?

[jaudio]

> Whats it do power wise?

about 80watts per channel

[trevorg]

> My 12.32 amp. This is the second cheapest
> amp I have built.

> OPA549 4 Free samples
> Case Free(Can buy for $1 goodwill)
> Caps and Resistor $.60
> Breadboard $1.50(MCM)
> Screws $.99
> Paint $3.00
> RCA connectors $.80 (Jameco)
> Binding Post $2.40(Partsexpress buyout)

Where could i start to build one of these? I like.

[jaudio]

> Where could i start to build one of these? I
> like.
First order samples froml <A HREF="http://www.ti.com">www.ti.com</A>

Then look for any alumimun modem or harddrive case(check goodwill,salvation amry or your job. It should cost about $1.) Be sure to get all the cables that come with case

You could salvage filtering capacitors(from broken stereo)or order from <A HREF="http://www.apexjr.com">www.apexjr.com</A>(12,000uf caps 2/$1) but shipping will burst you budget.

All other parts from partsexpress for about $4

LED from doller store keychain flashlights $2

[jaudio]

> First order samples froml <A HREF="http://www.ti.com">www.ti.com</A> Then
> look for any alumimun modem or harddrive
> case(check goodwill,salvation amry or your
> job. It should cost about $1.) Be sure to
> get all the cables that come with case

> You could salvage filtering capacitors(from
> broken stereo)or order from <A HREF="http://www.apexjr.com">www.apexjr.com</A>
> (12,000uf caps 2/$1) but shipping will burst
> you budget.

> All other parts from partsexpress for about
> $4

> LED from doller store keychain flashlights
> $2
I forgot want you order from order OPA549 or OPA541 four pieces and least three DRV134

[jaudio]

picture of the back of amp

[colby]

> My 12.32 amp. This is the second cheapest
> amp I have built.

> OPA549 4 Free samples
> Case Free(Can buy for $1 goodwill)
> Caps and Resistor $.60
> Breadboard $1.50(MCM)
> Screws $.99
> Paint $3.00
> RCA connectors $.80 (Jameco)
> Binding Post $2.40(Partsexpress buyout)

What about the power supply?

Am I the only one who can't see the pics?

[jaudio]

> What about the power supply?

> Am I the only one who can't see the pics?

Here is a picture.

[jaudio]

> What about the power supply?

> Am I the only one who can't see the pics?

Here a picture

[bill]