My DIY Amp project

[Hdale85]

Well according to several people 30 watts of pure class A is a lot more then 30 watts class a/b and my speakers are like 100db. It's Klipsch speakers right now.

The problem with getting the caps from digikey is my order is under 25 bucks so they add on 5 dollars. Also I need to find caps for my PSU which mouser has these

http://www.mouser.com/search/ProductDetail.aspx?R=380LX223M050A052virtualkey59850000virtualkey5985-85-50V22000

Which is the same thing as what digikey has except not panasonic. I'm just not sure if these will work just as well or not?

[Amphiprion]

30W is 30W, whether it's class A or B or D. But with 100dB speakers, 'tis plenty. Plenty plenty. For me it would be, at least.

If there is an original BOM for the project, stick EXACTLY with that. Subbing parts is fine if you're experienced with the params that matter (ripple current for example). But with all the heat in a class A amplifier, I wouldn't go trying to substitute unproven electrolytics. Pay whatever it costs to get the right thing, maybe find some parts at Digikey like handy tools - a good pair of flush cuts, some tweezers, standoffs, things like that. I can recommend part numbers on stuff if you need suggestions.

What is the mica radial for? That's a small value. Is that part in the original BOM?

[Amphiprion]

ETA: there are lots of other capacitors that are just as good as the FC series (why does no one use the FK for example?) and other brands have products that would work too. But subbing parts on a design that I haven't analyzed isn't something I would do.

[Amphiprion]

There are some parts you can add to your digikey order to avoid the fee, stuff you will need/want anyway.

Tweezers: EROPAASA-ND at digikey ($3) Fantastic bargain, we used to use the Swiss versions for $15 a pop and they were worth it (these are Pakistani made by same company). We just got some of the Pakistani versions and they look just as good. Tweezers are invaluable for SMT work, and these are really cheap. SMT work is inevitable in the future.

No-Clean Solder Wick for Desoldering Parts: 60-4-10-ND at Digikey. MUST HAVE. $9

Flush cutters: get true flush cuts, not semi-flush cuts. No opinion on parts, but you get what you pay for. $15 should be plenty for a good tool.

Liquid flux pen: helps solder wick to the pad/lead and helps keep solder bridges from forming. We use Digikey part KE1803-ND($4) or you might try the no-clean version (KE1804-ND)

Allied has the good solder sucker pump that I like (DP-100). Mouser carries the DP-200, which looks quite similar and is made by the same mfg. It might be larger or smaller, I don't know. It's part number 801-DP-200. $25. This and the wick will be very worthwhile purchases in the long run.

[Hdale85]

That mica is an original part. The only thing I really changed was the resistors. I went with Vishay/Dale instead of the Panasonics. Also the Vishay/Dale are all over rated compared to the Panny's. The only caps I really have to change are the PSU caps because Digikey doesn't have them. But those ones I found at Mouser are identical to the Panasonic ones at Digikey.

[TacoD]

PSU caps, look for 105 degree types, I am using Kendeil. You can also look at BC, Mallory, Mundorf Mlytic etc.

[Martyn]

Martyn, You can build an Aikido rather inexpensively if you like tubes or you can take a look at twistedpair audio and they have some kits which look interesting.

Twisted Pear - got to love that name, but I think the designs are not fool-proof enough for my limited talents. The Aikido preamp that you and Dougie mention is interesting, but I'm not a "true believer" when it comes to tubes and I don't really want the extra complexity, and a phono stage would be useful too. I guess I'll keep looking - let me know if you think of any other possibilities.

[Hdale85]

Well that Aikido preamp is far from complex...I've seen SS preamps that are much much much more complex :B

[Martyn]

Well that Aikido preamp is far from complex...I've seen SS preamps that are much much much more complex :B

By "complexity", I meant the extra hassle of dealing with tubes - the fragility, replacement, etc. - rather than the complexity of the circuits or build. Sorry for the ambiguity.

[JoshK]

I am not going to argue for or against tubes, as that is a personal thing. I know plenty of those who prefer SS, but more that don't. I have some of JB's Aikido boards and have stuffed a few and I can say that they are very easy to build. If you followed JB's guidelines you will have your tubes last almost as long as electrolytics in your power supply (ss or tube).

The hassle/replacement issue is overdone IMO, many tubes can last a very long time if run conservatively (<60% of rated dissapation, which this design clearly does), especially in a preamp (different for amps, which often require re-biasing more often than SS amps). I think the real issue with this preamp design is potentially too much gain if your system has almost enough as is. And there is no help for a phono, although JB has shed light on how to do it, it would be a much more involved project.

If you already have enough gain and can get away with unity gain then you might take a look at tranformer volume control based "preamps". They can sound absolutely wonderful IMO. I've only heard one SS preamp that I ever really was all that thrilled with so take this with two scoops of salt. That SS preamp was the IRD purist, which used opamps and was remarkeably neutral sounding. I owned it for a while and was quite happy with it. It replaced my $2k+ Cary tube preamp and bested it IMO. I've owned, borrowed and heard many others but the IRD is not shamed.

[cjd]

Twisted Pear - got to love that name, but I think the designs are not fool-proof enough for my limited talents.

They're about as foolproof as I've found. Parts are so clearly marked I find it annoying, actually.

C

[Martyn]

Thanks, Josh. I'm not really sure where to go from here, other than to take this question to AudioCircle or DIYAudio - I didn't intend to usurp Dougie's bandwidth.

I need minimal gain, maybe only 6 dB. JB's Aikido design is certainly attractive and affordable in terms of the kit and attenuator, although I wouldn't know what to do about a power supply and he doesn't seem to offer one. I get the impression that IRD has gone through some hard times recently, so I might be wary of laying out cash up front. I'll do some more searching...

[Hdale85]

Well he has a schematic for a PSU not sure if you can follow a schematic though? As far as output though....the Aikido has tons of output. It was an option I was thinking about for the F4. Although you can use different tubes to change the amount of output.

[Martyn]

Couldn't find a PS schematic directly, but did find one via a Google/Tubecad search. Without a BOM, preferably with suppliers' part numbers, I'd regard it as being too risky. I'd really prefer something that comes as a kit with instructions, like his Aikido boards. Thanks anyway...

[Hdale85]

Yeah I understand that

[JoshK]

A friend of mine just built the Aikido using the Lite Audio regulator boards. This basically takes care of all the power supply and heater supply issues for the Aikido, making it much more kit like. So that is an option, if you really wanted to go the Aikido route. However, if you only need 6db then the Aikido might not be the best option as it typically provides more than 15db, mine is 20db. I then will lower the gain in the amps as I prefer to do it this way around.

[Hdale85]

I just placed an order for a lot of parts. Got the soldering station and a bunch of stuff. All the parts for the PSU and the amp boards minus the big caps for the PSU and the fets for the amp boards. I'll start posting some pics when I start soldering! Maybe when I'm off next thursday if stuff arrives by then. We'll see.

[Finleyville]

When this is all said and done I wouldn't mind seeing and listening to this project of yours. I bet it turns out great!

[Hdale85]

Oh you should all be able to listen to it when we get together again.

[Hdale85]

Ok well got the soldering station, the digikey order, my multimeter (which if anyone wants a good cheap multimeter go to digikey this thing is very solid and was only 19.95) and the heatsinks just arrived. Here is a pic of the heatsinks!



They are much larger and heavier then I had imagined. VERY NICE! Probably worth more then I paid. For reference thats a 22" LCD behind them. The 3 in a row like that shows how long the sides of the chassis will be.

[TacoD]

nice heatsinks, the thick base will help you spread the heat. So your idea to mounting the devices on the side of each sink should not cause any problems.

My solder station died ... (after 2.5 years, the digital station is still oke, but now I need a new sensor for my iron, brand = Antex).

[Hdale85]

Yeah also planning on using a piece of copper between the fets and the sinks. So it'll spread the heat more evenly between the 3 heatsinks. Should work really well.

[TacoD]

Do not use copper, only if you can attach this copper very good with the alu base of the heatsink. Otherwise the heat transfer will be suboptimal (burned a output stage this way, copper was much hotter than the heatsink itself).

[Hdale85]

Yeah I'm going to look into it and if I can't seat them right together I probably won't do it. Right now I'm trying to decide if its worthwhile.

[Hdale85]

Stupid question I'm sure but what lead is positive on a cap? It's the long one correct? It's been a little while so I'm second guessing my self.

[Amphiprion]

Stripe is negative. IIRC that is the shorter lead. I honestly can't recall very well though, I always use the stripe. When I make boards I always make the stripes go the same direction, so that upon inspection of the board I can always know if I got one backwards before it goes pop. The techs like it when I do simple things like this on my boards.

[cjd]

Tech sheets *always* provide this information. Long lead or marked lead or what, is usually positive. But CHECK. I don't trust the shrink-wrap any more...

[itsparks]

WOW! really, those are bigger than mine, totally. Mine are 5.5" wide those look a little like 7-8" wide, i'm going to have to pickup a set now.

Jase

[Hdale85]

They aren't 7-8" wide...only about idk..little less then 5.5" wide. They just look big for some reason I set them all up on my desk in the layout and spacing they will be fore the amp and this thing is looking bigger then I had imagined. And I decided to go with a 16" width as well. Might up it slightly to the standard receiver width but we will see.

[Hdale85]

Messing around more.





this is with the heatsinks spaced about where they will be in the chassis. So 16" wide.

[Johnloudb]

Yeah I'm going to look into it and if I can't seat them right together I probably won't do it. Right now I'm trying to decide if its worthwhile.

Use a Thermalloy's Thermalcote, thermal joint compound between the two metal pieces. And also on transistors too.

You could get a 2 thick strips of aluminum to connect heatsinks together from a local metal fabrication shop, pretty cheap also.

Get it all anodized. Copper will oxidize, and may hurt thermal conductivity in time, possibly?

[Amphiprion]

Don't stick anything between anything. The biggest problem with heatsinking is at junctions. Stick the thermal pad of the package directly to the biggest heatsink you can find, and use the right amount of joint compound/insulator. The back plate of your sink is plenty thick, adding anything will invariably make it worse. Biggest problem in heatsinking is package->sink. Work on that first. Also don't waste time 'lapping' heatsinks with sandpaper or whatnot. If you don't have a flat surface it's not going to do any good. I lap small extrusions here on this 4" thick piece of stone we have that's certified flat within some ridiculous tolerance. It's amazing how non-flat the common small aluminum extrusions are for packages like TO-220s or TO-247/TO-3Ps that really need the heatsinking. I never knew til I started fixing them with some fine grit paper and that 4" thick piece of stone.

But anyway, just go package->heatsink. No copper spreader. Rod Elliot has a good article on heatsinking IIRC. It's really one of the more neglected areas in power electronics by non-specialists (myself included - I'm so lazy I'll use Sil-Pad's frequently).

[TacoD]

I second that :agree:

[Hdale85]

I'm done populating the parts I have so far. Still need to get the Fets and some how i got the wrong caps for one of the parts. Gotta order those. Then its all the PSU and what not.



BTW I think I'm just going to P2P wire the fets on the heatsinks. I think this is going to work best. These heatsinks are huge and I don't see a need for the copper anyways.

[cjd]

P2P is the way to go, FET directly on those sinks.

Is the solder penetrating all the way through the holes? Looks like it may be slightly cold on those joints. Hard to tell for sure.

Manufactured sheet glass is generally appropriately flat for lapping heatsink material. If you wet-sand (as you should) with a good emery paper, you soak it and it'll stick to the glass nicely.

C

[Amphiprion]

Ooh, hadn't thought about glass as an option. I guess it does some self-leveling as it cools?

[Hdale85]

Yes the solder is going almost all the way through. There was one spot on the PSU board where i messed up one of the pads and had to solder from the top. I think its ok though. I think I got pretty good solder contact. But I was also trying to make sure not to heat the components up too much.

[Hdale85]

Ok I realized what you meant and went over all my solder joints again.



This is about the best I could do. A few spots just would not soak up the solder.

[cjd]

get some flux if you continue to have issues. Works wonders.

Check the temp ratings on the components - you do have a variable temp iron, right?

A good iron makes SO much difference it's not even funny.

[Hdale85]

I have a Weller EC2002M. Does 350-850 degrees. And yeah it works fine I just wasn't leaving the iron there long enough.

[TacoD]

with double sided pcb's with through hole plating you have to check that in the case of a broken solder pad you solder on both sides (using the component lead) otherwise the top/ bottom traces are not connected anymore.

Check that you don't apply to much solder and you get shiny joints.

[Hdale85]

They aren't supposed to be shiny? The solder goes all the way through the holes to the other side where it is soaked up by the pad on both top and bottom. Although the top pad is not socking it up quite as much as the bottom it still looks like a very good connection.

[wkhanna]

They aren't supposed to be shiny?

Yes, what TacoD is saying is you want nice shiny joints. The solder should 'wick' or travel through the hole and up the lead toward the component, as you hold the iron to the pad and lead, as you feed in your solder.

If you are having trouble with some joints, make sure you are 'tinning' your iron. Wipe it clean on the wet sponge, then melt a small amoount of solder on the tip. Make sure there is no black crap on the iron tip. Tinning helps to x-fer the heat form the iron to the components fast.

Get in - flow the solder - get out......quickly.
It's a learned skill, and once you see it work, it is obvious, and you will know you are doing it right.

[Hdale85]

Yeah I've soldered lots before. Just haven't done it in a while. Honestly in person my joints look very good to me.

[Johnloudb]

Progess

Hey Dougie,

How's your amp comming along? What's your next step?