IKEA Gainclone

[scigu63]

Hallo everybody, here is my IKEA LM3875 Gainclone.

Quick notes:

• Case: Ikea Lack shelf, cut and emptied of the inside cardboard ( please see my previous Densenclone [ http://www.diyaudio.com/forums/class-d/220995-densenclone.html ] experience and picture 1 ) and aluminum sheet to cool the IC’s ( quite enough for home listenings, after 3 hours of playing it’s only slightly warm )
• IC: LM3875
• Power supply: 2 x 24V – 200VA transformers
• PCB from Audiosector
• Star ground to avoid hum noise
• 2 single 12 position make-before-break rotary switches, connected to various resistances ( ground, 10, 22, 39, 82, 180, 330, 680, 1.5K, 3.3K, 4.7K, 8.2K ) to obtain the input 20 Kohm stepped attenuator

I’m quite satisfied of its sound ( and power … ) and my wife of its aesthetics.

Ciao.
Luca

 

[jacques antoine]

Northern design + southern inventivity = very nice!
Cheers,

Jacques

 

[jjrh88]

What is the tower speaker with it? I have been looking for something to pair with my chip amp

 

[scigu63]

They're 15 year old DIY TQWT with Audax full range speakers, covered with matt white vinyl adhesive sheets.

Let me search in my archive and I'll give you more information.

Thanks for appreciating.
Luca

 

[Bare]

Interesting build. There was a D (ta2020) amp build a few years back stuffed into an Ikea Lack shelf.
And you are NOT having Heat issues??
Those chips DO have a heatsink requirement.. Do they Not?

 

[scigu63]

TQWT speakers ( off topic ... )

Hi Jjrh,

here are the internal measures of the speakers. Use 19 mm MDF.

Any 17 - 18 cm ( or 6 - 7 in ) full range speaker will fit, from Tang Band to Fostex.

Since painting MDF with good results is not easy, I covered them with matt white vynil adhesive sheets.

Ciao.
Luca

 

[scigu63]

Heat issues

Hi Bare,

I know that TA2020 amp quite well: it was me who made it !! It's the Densenclone.

With 12 Vcc power supply there are no cooling problems at all, just like the famous Sonic Impact T-Amp.

The LM3875 needs more attention, as You said, and before choosing this case I made some tests in order to see if the aluminum plate was enough or some heatsinks were necessary.

After hours of playing ( at home volume, for stadium volumes I cannot tell ... ) I saw that the plate was only slightly warm, so no heatsinks. Anyway, for better cooling, I made 2 holes in the bottom plate and 2 holes in the backplate ( please see pictures ) to let the fresh air pass by.

Ciao.
Luca

 

[scigu63]

Power Supply rearrangement

Hi everybody,

here is an upgrade of the power supply wooden case: I had to screen it inside with kitchen aluminum sheets, as when it was very close to the amp I heard a little hissing coming from the speakers ( that’s why the original Gaincard uses metal boxes … ).

Now the noise is over and I can put them close. You can see them in the new arrangement ( with the speakers in rest position ).

Ciao.
Luca