Integrated dual mono lm4780

[kuldeepsingh]

your metal working skill are very impressive

[SoIL4x4]

Originally Posted by kuldeepsingh

your metal working skill are very impressive

Thank you

[squalor]

Originally Posted by kuldeepsingh

your metal working skill are very impressive

I agree, nice work. Do you have any pictures of the chassis construction ?

If I were you, I would plan to use the Klipsch with the FE My_Ref and use two 22V secondary transformers.

[SoIL4x4]

Originally Posted by squalor

I agree, nice work. Do you have any pictures of the chassis construction ?

If I were you, I would plan to use the Klipsch with the FE My_Ref and use two 22V secondary transformers.

Thank you, and yes I do have some photos of the construction, I will post them here with some explanation of what I was doing.
As for the klipsch they are currently under the knife receiving a face lift and some up grades. New veneers and some crites titanium diaphragms are in the works. When they are done they will look kind of like heresys. Hey are halfway there I just need to order the veneer.
I think I am going to order two more an3222 transformers from antek for the MyRef fe. They should be a good match for either of my speakers, but the klipsch are going to be the main drivers for the MyRef.

[SoIL4x4]

As requested, I started with the bottom panel which is 1/8 inch aluminum with a perimeter of 3/4 angle. The angle gave the sides a place to attach to. the sides are thinner guage aluminum that already had the bends at the top(next time I will not use any recycled panels like this, they are a pain to work around). I then squared all the sides and measured for the other panels.

note: the front panel blank is made from a large "drop" of 2024 .250" aluminum that I dug out of the basement of shapiro metal supply in St. Louis. the rest of that peice will be the front panel to my lighter note build.

[SoIL4x4]

I started the front panel by drilling the eight holes that would be visible from the front. the outer four would mount the panel to the enclosure and the inner four will mount the volume assembly. I cut the inner three pieces to size and drilled the corners to mount to each of the other pieces as you can see from the picture. All of the holes were counter sunk. and all of the parts were cut from the original chunk of 2024.Once all the peices were aligned I drilled a single hole as an index for the volume section and the power switch.

[SoIL4x4]

Drilling the front panel, details to follow.

[SoIL4x4]

First off, sorry about the sideways picture above, I was in a hurry. Anyways I tested a couple different techniques for cutting the circles in the aluminum including using a circle cutting setup in the press but the hole saw won hands down. Making sure the saw was tight to the arbor was a key step as it makes for a cleaner initial cut. To do this I drove the saw into a block of 2x4 before making the cut in the aluminum.

I should also mention that the 2024 aluminum is considered soft and very easy to machine. This allowed for the use of several woodworking tools. I used a router to machine the rounded corners, but I will get to that later.

I very slowly fed the saw into the metal taking many breaks to clear the dust and let the saw cool. It takes a few minutes to get through the .250 stock. Once the hole is cut the edges of the hole are a little rough, too rough for display. To remedy this I wrapped the hole saw in sand paper and fed it into the hole, moving it up and down. Doing this a few times wrapping over the last layer with finer grit as you go will yield a hole that looks like it was laser cut and smooth as glass. Again I should mention that using a mask or respirator is a good idea because this creates very fine dust in the process. Using a small amount of water in a spray bottle to wet down the cutting area as you go will help encapsulate the dust.

Repeating this throughout the layers using the original index hole will make for a very accurate set of holes. I like how it turned out and plan on using this design element on a few other builds.

[SoIL4x4]

Well after several months of flawless operation I ran into a snag today. I turned on the amp and cd player like I always do (volume at minimum) but when I turned up the volume it took a second to come on and then it wasn't right. It was scratchy as it increased and then began to rise on its own! I quickly shut everything off and disconnected my speakers. I then connected my test speakers (three way infinitys with blown woofers) and the sound was terrible, the volume was very scratchy and then slowly tapered off to nothing. I connected my phone as a source and again no volume, nothing. When I move the volume pot though it does make a minute scratching sound at a few spots in its rotation, not loud though noticeable.

I then disconnected everything and checked the dc offset. At the lowest setting I measured 3mv on the left channel and 10mv on the right. At max volume both channels measured around 175mv. I am a little confused, there is no visible damage to the amp.

I have not checked the offset of the cd player. It is an ancient Sony so it may have given up? Would dc from the cd player cause this. Did it cook my input coupling caps, is that why im getting no sound?

Any ideas are welcome!

[AndrewT]

The input coupling caps (DC blockers) should be OK. They are probably rated for >>2Vac.

The vol pot may have gone faulty/dirty.

Attach a voltmeter to the output. Turn the vol pot down to about half volume (-20dB) and then apply a 1.5V battery to the input leads. Try reversing the battery.
You should see some reading on the voltmeter.
If the reading is very low, try turning vol pot up and repeat the experiment.