Amp Camp Amp

[MrBoat]

These boards are different than the ad pics. These contain the additional spot (R15) for the 2.21kohm resistor.

 

[MrBoat]

Off the wall or not, I think you'll like it. The genuine class A single ended approach definitely has it's charms. Many of the OCD audio nuts feel it's the holy grail of amplification, and hey, you get to smell what they're stepping in first hand, and on the cheap thanks to the diy aspect.

One thing you may want to consider is upgrading from the cheapie SMPS that was part of the kits to a linear supply. Yes, this will push up the total cost a bit, but you don't want to hamstring the little bugger. For example, THIS would work perfectly for a stereo pair of amp camp amps, and ensure you were getting everything they have to offer.

Would this power both of them as well. I already have it from another 2 channel amp board. The upgrades allow this ACA to be run with 24V with some minor adjustment for more power.

ETA: I found out that I can indeed use this power supply.

 

[MrBoat]

Got the boards built today. Was just tiny for these old welder eyes.

I managed to get the scale of the solder joints/heat down after a few. I had to use the solder sucker on a couple that BB'd a bit on the front side of the board. It would have been ok but I cleaned them up anyway. I think if I was to do this again, I would clean all the sockets first with some alcohol, just because.

I haven't added the power mosfets yet or the wires. Figure to do that when I get the heat sinks situated. I was done with these two boards in just over an hr, and that with ohm'ng out all the resistors first. At any rate, the tedious part is somewhat over, or, the procrastinative part.

Still dreaming up a chassis for it. I have a good feeling about this amp.

 

[MrBoat]

Managed to get one of the sinks drilled, tapped and the board fitted. It's a little tedious and I only have one 3mm tap for the m3 hardware. The standoffs I bought for the boards are very shallow threads so I had to make custom length screws. Basically, spinning a nut on the screw and grinding it off and using the nut to chase the burr that is left. I used a benchtop drill press for the holes and tapped the threads very carefully with my cordless drill. I did not make through holes. They stop just shy of going through.

I used a very sharp scratch awl for my layout marks and a center punch divot to locate the 2.5mm drill bit. At any rate, they were right on the money.

I set the mosfets up unsoldered, marked the holes instead this time with my center punch which centered in the hole in the fets perfectly. I ended up using a board spacer to keep it level with the rest of the assembly when soldering the fets in.

I ended up using the mica and thermal plaster route. My EE buddy says it probably transfers heat a bit better than the pads do.

I was going to do the other one but I'll wait until tomorrow, I think.

 

[highfigh]

These boards are different than the ad pics. These contain the additional spot (R15) for the 2.21kohm resistor.

Plated feed-throughs- nice! You won't have to deal with pads that lift off from the PCB from heat and the solder joints will be stronger.

 

[MrBoat]

I did end up finishing both last night. Something about when the flow is already good, take advantage of it. If I did this every day, it'd be different but, as it was and being still fresh on the first board, the second went much faster.

Still have to come up with a chassis. I'm thinking something elegant by way of simplicity and neatness. Nothing too fancy. A good utility appearance, perhaps.

 

[ski2xblack]

Well fire 'em up!

 

[MrBoat]

Well fire 'em up!

I reckon I could!

 

[slipperybidness]

I reckon I could!

No need to wait for a chasis!

At the very least, I would be powering them up and testing them at this point. Personally, I would connect a dummy load on the outputs, a function generator on the inputs, and a dual channel O-scope on the inputs and outputs.

It would not be an exhaustive test, but it would give me a chance to spot any obvious problems before connecting speakers, check out my heat dissipation (IR thermometer), and check that the gain is set properly and that the channels are balanced.

Seems unlikely that you own an O-scope and a function generator though.

So......at least hook it up to your cheapest/crappiest speakers first!

 

[MrBoat]

No need to wait for a chasis!

At the very least, I would be powering them up and testing them at this point. Personally, I would connect a dummy load on the outputs, a function generator on the inputs, and a dual channel O-scope on the inputs and outputs.

It would not be an exhaustive test, but it would give me a chance to spot any obvious problems before connecting speakers, check out my heat dissipation (IR thermometer), and check that the gain is set properly and that the channels are balanced.

Seems unlikely that you own an O-scope and a function generator though.

So......at least hook it up to your cheapest/crappiest speakers first!

I did ohm out all the resistors first, did not experience any real issues soldering and I don't have any parts leftover. Anything that can be checked will have to be with a V/O meter and my sense of smell!

I could not find any wire. I had a bag full of the stuff and it has seemingly grown legs. I will have to get some more from work.

 

[ski2xblack]

So what's happening? Get some wire? Are you lost in the proverbial 'chocolatey' midrange, peeling apart layers in the mix? Did you accidentally let the magic smoke out? (Hopefully not this!) Somewhere in between?

 

[MrBoat]

So what's happening? Get some wire? Are you lost in the proverbial 'chocolatey' midrange, peeling apart layers in the mix? Did you accidentally let the magic smoke out? (Hopefully not this!) Somewhere in between?

None of the above. I forgot to look for wire at work for being in a Friday hurry to get out of there (was after 8 pm) and knew I was forgetting something other than my phone. Looked at home depot and all they seem to have is Romex and THHN.

If I ever offer up such fluffy explanations of audio, food or anything else I might have a hand on, just shoot me and feed me to the fishes. That's half of why I can't get through product reviews or half the topics on internet forums.

 

[MrBoat]

I fired them both up, let them warm up for 30 mins, checked volts against different ground points etc and did the bias procedure with the little blue pot. That is a touchy little thing. As was setting 24V at the power supply which has a similar tuner.

No smoke and no bites!

 

[MrBoat]

Waiting on jacks, switches, LED's etc. While I am at it, I am trying out some different chassis ideas. I notice that all amps pretty much look the same. I like the idea more of the basic prototypical appearance. I am just holding these up here to give me a starting point of ideas.

What I have here is, some polished anodized flat stock along with some mill finish in the same dimension for the rear. I can round and polish the edges to the same semi-mirror finish. I also have some 11 gage I can use for the rest of the sides, perhaps with vent holes drilled with a slight chamfer. Was just going to add a toggle switch to the front and the LED.

Still going with the monoblocks for now. Would be nothing to join these into one being I am building the chassis, if monoblocks don't agree with me for whatever reason.

 

[slipperybidness]

Waiting on jacks, switches, LED's etc. While I am at it, I am trying out some different chassis ideas. I notice that all amps pretty much look the same. I like the idea more of the basic prototypical appearance. I am just holding these up here to give me a starting point of ideas.

What I have here is, some polished anodized flat stock along with some mill finish in the same dimension for the rear. I can round and polish the edges to the same semi-mirror finish. I also have some 11 gage I can use for the rest of the sides, perhaps with vent holes drilled with a slight chamfer. Was just going to add a toggle switch to the front and the LED.

Still going with the monoblocks for now. Would be nothing to join these into one being I am building the chassis, if monoblocks don't agree with me for whatever reason.

Looking good!

I'm not quite clear.....what will be the power supply for these? You are just using that bench supply for testing?

As far as trying to exactly dial in that 24V on the supply, it likely isn't necessary to be exact. A review of some data sheets for the solid state devices will likely show a range of supply voltages that will work fine.

Personally, I'm a fan of Steampunk-inspired designs!

And, hard-core industrial designs!

 

[slipperybidness]

@MrBoat
https://forums.audioholics.com/forums/threads/new-chipamp-project-thread.92513/page-2

Have a gander at my ChipAmp project. Some good pics start on post#24.

That P/S that I built is way over-kill for a chipamp like this. Eventually, I plan to build a discrete amp and use that P/S on it, and then add an in-chassis P/S for this chip amp.

I kind of put amp-building on hold once I had more amps than speakers

 

[highfigh]

Just in case-

 

[MrBoat]

Looking good!

I'm not quite clear.....what will be the power supply for these? You are just using that bench supply for testing?

As far as trying to exactly dial in that 24V on the supply, it likely isn't necessary to be exact. A review of some data sheets for the solid state devices will likely show a range of supply voltages that will work fine.

Personally, I'm a fan of Steampunk-inspired designs!


And, hard-core industrial designs!

If the bench supply works, maybe I make it's own case and use it until. . . . What's that saying about nothing being as permanent as a good, temporary repair?

The 24v setting I was not as concerned with as I was just able to dial it in with a little patience so, why not, right?

I like the examples/themes you showed too. In this case, something perhaps unassuming, that does not look like it should sound quite as good as it does? I get all the metal for free for small projects, plus we have a large amount of scrap and quite a selection of extrusions both in anodized and plain finish.

 

[MrBoat]

@MrBoat
https://forums.audioholics.com/forums/threads/new-chipamp-project-thread.92513/page-2

Have a gander at my ChipAmp project. Some good pics start on post#24.

That P/S that I built is way over-kill for a chipamp like this. Eventually, I plan to build a discrete amp and use that P/S on it, and then add an in-chassis P/S for this chip amp.

I kind of put amp-building on hold once I had more amps than speakers

Well that is a well done project so thank you for the inspiration!

I do own a lot of speakers (mostly DIY) and am always eyeing more. I do use most of what I own in rotation which is easy to do as much as I manage to listen to music every day.

This amp thing has a bit more attraction to me just for being tired of reading about Yam, Denon, Marantz, Mac, etc. etc. The Nelson Pass stuff is easy to appreciate once following what amount of effort he puts towards the DIY community. That's pretty darn nice of him, I think, and I like his approach. Not to mention the build quality of the Pass Labs amps!

 

[slipperybidness]

Well that is a well done project so thank you for the inspiration!

I do own a lot of speakers (mostly DIY) and am always eyeing more. I do use most of what I own in rotation which is easy to do as much as I manage to listen to music every day.

This amp thing has a bit more attraction to me just for being tired of reading about Yam, Denon, Marantz, Mac, etc. etc. The Nelson Pass stuff is easy to appreciate once following what amount of effort he puts towards the DIY community. That's pretty darn nice of him, I think, and I like his approach. Not to mention the build quality of the Pass Labs amps!

Yeah, Pass is an odd duck. He has his fair share of great electronics, and his fair share of quack-job electronics too. And, he still contributes heavily to the DIY community!

We do have some other guys that contribute heavily to the commercial offerings and the DIY community too (though they don't have the odd-ball designs like Pass). But, I'm thinking of Dennis Murphy, Jeff Bagby, and Douglas Self.

If you ever think about moving towards some true reference DIY designs on the amps and electronics, Douglas Self has written several books, and his DIY products are available (but not cheap).
http://www.signaltransfer.freeuk.com/

I'm looking at eventually doing my own PCB etching, taking it down to that level!

Once you start the DIY path, you start to understand the limitations on the commercial designs, most specifically how commercial designs make design decisions and trade offs in performance in order to meet a price point. For DIY, you are not held to those same constraints.

Then, you also start to see how silly all these snake oil and magic cable believers really are! Clearly, these people don't have a clue when it comes to science, data, technology, etc, so they fall back onto voodoo science, fancy terms, and "trust your ears"

Yeah, I rotate gear and speakers too, but in practice I tend to be lazy so I stick with a particular setup for quite a while before making a swap.