[erix]

Boy, this one was like giving birth. Or not.

This one started last October as an experiment into adding the enhanced bass Mier crossfeed to Jung's multi-loop amp as presented by ppl. Turns out the only way to do it was add a buffer stage before it. I know, I read it in the archives, but I had to learn it myself, right?

Anyway, someone asked me if I could build an amp in an aluminum box they had. My goal was to make this as hurky as possible and still look good.

Some details:
(2) BUF634T per channel in wide bandwidth mode
(1) BUF634T virtual ground driver
(2) AD823 opamps (1 is a buffer before the x-feed)
Wima MKP10 caps through out the x-feed
(4) 2200uF/16V Cerafine resevoir/filter caps
(4) 1uF/63V local bypasses
(1) 4-pole, 3-throw rotary switch for the crossfeed. I used the leftover pole to throw the power indicator supply to one of the three blue LEDs on the front panel.

How does it sound? Quite well, thank you. I don't like the crossfeed anymore than I did on the portable amp I built or the various Cmoy/Hansen boards, but hey, to each their own.

This is a very strong amp. Not brittle sounding at all and, like the 440 CID engine in the Bluesmobile, this thing will snap your head back if you aren't careful with the "Louder" knob. The thing has some huevos, comprende?

That's a 12" Emminence musical instrument speaker being manhandled by this amp. Musical instrument speakers gennerally have a good SPL rating and this one, despite being rated at 8 ohms, was uncomfortably loud powered by this amp.

I'm sad to see it go..

ok,
erix

 

[KR...]

That one killer looking amp, totally professional looking.

 

[zoboomofo]

Ouch, do you think you can get a thicker enclosure?

btw, you've got the most unDIY looking amps. Is that another Timesaver job? Looks great!

 

[Serow]

Quote:

Originally posted by erix That's a 12" Emminence musical instrument speaker being manhandled by this amp. Musical instrument speakers gennerally have a good SPL rating and this one, despite being rated at 8 ohms, was uncomfortably loud powered by this amp.

Funny that you should say that... I built a set of two-way Alnico magnet speakers, about 95 dB/w efficient. My Millett hybrid with parallel BUF634 drives these more than loud enough for my bedroom listening.

Nice amp! I like the switched LEDs.

Eric

 

[dokebi]

drool...

 

[kevin gilmore]

You have gone 99% of the way, now finish it.

All the wires have to be at right angles, and tied together
with silk thread.

 

[Voodoochile]

Not just tied, either. A nice smooth seamless weave covering the full harness would be good. Maybe you could contract some silkworms to handle it for you.

Seriously, that's a hard-core study in industrialist design, IMO. Bang and Olufsen meets Rosey Greer, perhaps.

 

[jamont]

That looks like it might be fun to build, do you have a schematic?

 

[antomas]

Absolutely delicious!
How thick are the aluminium panels?

Massimo

 

[erix]

Some folks have wanted to know a little bit more about the box.

The box was built by the owner - I just dressed it up. The top and bottom panels (actually side panels as it stands upright) are made of .125" aluminum plate. The rest of the panels are made of .25"x1.5" aluminum bar stock. The plates are held to the bars by (12)4-40 phillips-head screws in countersunk holes.

I used a 1.125" drill bit in a vertical mill at work to punch the holes through the front and back. I then made a pair of brushed aluminum panels out of .090" aluminum and adhered them to the bars with automotive panel adhesive. This is nasty stuff - stronger than any epoxy I've worked with and designed for metal-to-metal.

After it was drilled, I put it together and ran it through the "Timesaver" which is like a belt sander with 4' wide rolls. It has an 80 grit brushed finish which was then covered in flat clear acrylic laquer.

The knobs are made from 1" aluminum rod and have the same finish.

Quote:

That looks like it might be fun to build, do you have a schematic?

Not really but it is pretty simple. Just take the multi-loop circuit from tangent's site and replace the single output buffer to two BUF634's in parallel. Next, take the crossfeed portion of the Cmoy/Hansen PCB and plop it in front of the multi-loop amp. In front of THAT place a non-inverting unity gain buffer.

Quote:

All the wires have to be at right angles, and tied together with silk thread.

I've seen some guitar amps built that way (well, maybe not silk..) talk about ****...

ok,
erix

 

[jamont]

Quote:

Originally posted by erix Not really but it is pretty simple. Just take the multi-loop circuit from tangent's site and replace the single output buffer to two BUF634's in parallel. Next, take the crossfeed portion of the Cmoy/Hansen PCB and plop it in front of the multi-loop amp. In front of THAT place a non-inverting unity gain buffer.

I would probably omit the crossfeed, so in that case what's left is the multi-loop circuit from tangent's site, using parallel BUF634's. Would there be any reason to keep the other buffer (the one before the crossfeed)?

Looks like the BUF634's are TO-220 without heatsinks? Do they get hot?

 

[CaptBubba]

Quote:

Originally posted by jamont Looks like the BUF634's are TO-220 without heatsinks? Do they get hot?

Warm, but not too hot, I use some buf643T's in a similar way.

 

[Wodgy]

Gorgeous work!

 

[XXWoodmanXX]

Eric,


Well, after much anticipation (and LOTS of begging, on my behalf LOL), it looks as if this has turned out nothing-short of astounding, sir.

It seems as if your craftsmanship has superceded you, acording to your "progress" pics that you've sent me in the past.

You've done a magnificant job, and I will be MORE than happy to provide more 'eye-candy' pics as soon as I get this baby in-hand. Hell, I want something to take pictures of with my new Sony DSC-F717 digicam anyway

*shivers at the thought of how well this sucker will sound on the Grado 325's*

 

[XXWoodmanXX]

Just wanted to show this little beauty in-action.....

....surely, a thing of beauty.

THANX, ERIC!