Honey, I shrunk the Gainclone.. (a sequel of sorts)

[WWWJD]

Got back into gear on this project after a long pause and a re-think of how I wanted this thing to look. After two attempts at a case for the amp, and two failures (it was too freakin' complicated), I decided that a do-over was in order. Here's what the old amp looked like:



Not too shabby for the first time around. Less the knobs and connectors, the footprint was small; 8" x 9", and it worked. The case I had in mind just wore me out though. So I tore it apart.

Now... It's REALLY small.

A total redo of the layout, compressing the boards to the smallest footprint possible with the Brian GT's boards (chipamp.com). Same 250VA transformer, Same DAC, different heat sinks courtesy Digikey, and I got rid of those bulky speaker terminals. Now I'm using PE's little RCA jacks for speaker terminals. Mucho Spaco Savo!!



New footprint is 8"W x 5-1/2"D. Now truly a desktop amplifier, complete with original trippy spacey HK knock-off volume knob!!




Front and rear panels are attached to 3/8" aluminum angle with JB Weld epoxy after a surface rough up, then attached to the baseplate with 6-32 button head fasteners.


Also moved the USB socket off of the DAC board and remote wired it with an Amphenol bulkhead connector.. the DAC is now mounted below the socket with 3M RP45 structural tape (the most wicked mounting tape ever spawned). I also retained the selectable inputs, DAC or Line Level.


The volume knob is backlit by a six pack of ultra white LEDs. Left side knob LEDs are fed from the left channel PSU, right side LEDs from the right channel. Volume knob is basically acrylic tube, edge lit. The interior is a machined steel slug fit to the tube and potentiometer shaft. The front of the knob is dressed with a round piece of the same black anodized aluminum used for the front and rear panels.


and the new rear panel layout. Still need to touch up the heat sinks where I machined the mounting flanges off. They're now mounted through the back from the interior. Flanges were taking up space.


I'm pretty confident that this is as small as the chipamp dual mono kit can get while still using the boards (point to point amps are looking mighty tempting). The proximity of the toroid to.. well.. everything.. had me worried. Auditioning it tonight on the Ushers revealed that my worries were over. The amp is still quiet as a dead mouse.



Amp / Power module prior to install:



Bill of Materials (all the major stuff)
Dual Mono LM3886 Amp kit $90
Avel 250VA 18+18V transformer $54
IEC Power jack with fuse holder $2
RCA Jacks (2 pair) $13
SPST Rocker Switch $2
Alps Blue Velvet Stereo 50kohm Pot $18
Wakefield heat sinks (2) $11
Amphenol USB Receptacle $9
NKK 3PDT Source Selector $9
Bantam DAC, Glassjar Audio $47
2-1/2" acrylic tubing $18
Various fasteners n' junk $15

Total damage: $288 Not bad at all.

All of the signal wiring is basically an old set of RCA cables I butchered.. one of about 15 sets that came with various satellite receivers, cd players, etc. I've got a box full. Power wiring all came out of the scrap pile in the panel shop at the office. Not sure how much I spent on fasteners, angle, standoffs.. probably about $15. LEDs were all leftovers. I spend a lot more than $288 just messing around with this one and the first version, but if I had to build another one, then yea.. $300 give or take.

The knob slug, a friend of a friend did this in a couple minutes on the lathe.. cost me a 6 pack of beer. The slug is press fit into the acrylic tubing:


The inside ONLY of the acrylic was wet sanded with a Dremel 512E abrasive disk... until it looked like this when edge lit with a flashlight, then cut to length with a miter saw:

After wet sanding all the edges with 400 grit, it was masked off and I spray painted the exterior of the knob with matte black rustoleum. Beyond that it was a simple matter of aiming some leftover ultra white LEDs at the rear of the acrylic edge, mounting them in the volume knob's mounting plate.

VOILA!!

[Mgboy]

How much did it cost, and where did you get that knob?

[WWWJD]

How much did it cost, and where did you get that knob?

I choose not to remember how much I've spent. If I had to build it again tomorrow... $300'ish? ..and I made the knob.

[arlis_1957@yahoo.com]

wow mark. thats as small as my dta3 amp. nice job.

[philiparcario]

I have a few small ones but they have a 90va trans not a 250va!

[kornphlake]

That looks pretty nice. Even if the knob is a knock off of the HK knob, I like it because you did it without a bazillion dollar budget. Do you have another picture of the amp next to an object of known size to give a sense of scale?

Do you notice any noise having the amp board so close to the power supply? I know some people go to great lengths to shield the amp from the power supply, but I've been a little skeptical that it makes much difference.

[WWWJD]

Do you have another picture of the amp next to an object of known size to give a sense of scale?

Do you notice any noise having the amp board so close to the power supply? I know some people go to great lengths to shield the amp from the power supply, but I've been a little skeptical that it makes much difference.

It's noiseless with open inputs (both USB and line) at max volume. Not going to have to worry about shielding.

[kornphlake]

That's freaking awesome, one of the best looking gainclones I've seen. If someone made a mass produced version and could bring the cost down it would certainly give the diminutive T-amp a run for its money.

[philiparcario]

That's freaking awesome, one of the best looking gainclones I've seen. If someone made a mass produced version and could bring the cost down it would certainly give the diminutive T-amp a run for its money.

If that amp sold mass production at the right price it could change stereo listening, for the better. Gainclones are really nice amps for a computer. Mcm electronics puts out a nice small usb amp for 100 bucks this amp looks far better. I don't remember which chip he is using but if it is the 3886 he has over 40 watts per channel.

http://www.mcmelectronics.com/product/50-4606

it is bigger does not look as good and has less power

[WWWJD]

I don't remember which chip he is using but if it is the 3886 he has over 40 watts per channel.

It is the LM3886; running 18VAC secondaries / 25VDC rails. 4 ohm operation was the goal. According to the data sheet this lands me in the 60W x 2 neighborhood.

[philiparcario]

Yeah 35 for 8ohm and 60 for 4ohm. It really is a nice amp you built. I have 4 or 5 diy ones around the house none are as small as yours. They are nice sounding amps.

[tomzarbo]

That's really beautiful.

It's amazing what a person can do when they really sit down and try to think of every detail. That's a small package and it looks fantastic! That's nicer than I would expect a piece of retail gear to look. Way nicer.

Good work!

TomZ

[philiparcario]

For a diy amp it looks really good. when first gainclone came outit was hi-end. the first unit was getting thousands of dollars. then some one copied the design and released it to diy crowd. That amp with its looks small size and good sq would sell for a premium with the right marketing.

[tevirs]

Impressively simple design! I had an interesting idea for you... You could stand that thing up, put the feet on the small side panel. The make some real nice hardwood panels for the sides (what is now the top and bottom). Maybe do a nice chamfer on the wood and polish it up real nice. The transformer would be low in the box for stability, and the volume knob would be placed at the top and it is already centered side to side. That would be real nice small footprint for a desktop amp.

[philiparcario]

Impressively simple design! I had an interesting idea for you... You could stand that thing up, put the feet on the small side panel. The make some real nice hardwood panels for the sides (what is now the top and bottom). Maybe do a nice chamfer on the wood and polish it up real nice. The transformer would be low in the box for stability, and the volume knob would be placed at the top and it is already centered side to side. That would be real nice small footprint for a desktop amp.

that is a nice twist to an impressive design.

[WWWJD]

I almost did that, no joke... one thought was to do that but with the transformer mounted horizontal.. front view would have been trapezoid'ish. Maybe the next one.

[aarond]

That is pretty cool. I have shoehorned a lot of components into a small space before but never that well and it definitly didn't look that good. Nice use of the standoffs, I'll keep that in mind. Questions:

1) You have 2 RCA line ins and a USB input selected by a 2 pole 3 position switch, correct?

2) Why not mount the input switch on the front(power switch as well for that matter) ? I know you could have I'm just wondering why you chose what you did. Front looks clean though.

3) Would a regulated switching supply have worked too? A cheaper option if so, no?

4) Would you mind listing/linking the sources of the major components in this? I'm particularly interested in the DAC.

Finally, I think some of us would be interested in seeing some details of the construction of the volume knob.

Once again, nice work.

[WWWJD]

OP updated with a BOM.. wound up being less than I thought. $300. I did prefer the clean front look; too many switches and the like gets distracting.

I suppose a switching supply could work.. but the amp design would have to change a bit to support single ended supplies.. and cheaper? I don't think so... maybe. Besides, nothing feeds an amp better than a nice heavy chunk of copper. Ask anyone older than 40.

[Mark65]

Dude, you're a freak! In a good way, of course...

That is....extremely....cool!

I once again stand in helpless awe of your talents!

That is so freaking sweet!

Mark

[aarond]

Good stuff. Thanks for the extra info. Was than knob really machined to 1/10,000th of an inch tolerances? Just kidding of course...

Re the power supply, I didn't realize the amp boards only required direct input from a transformer. Pretty simple and much more classy than a switching supply. I like torroids too, and I'm not 40 yet (closer than I would like to admit, you have no idea...).