[Emon]

I know that, I meant aluminum is aluminum when all you need is a chunk of metal with fins to absorb heat. The most you should be getting is what, 15 or 30 watts of heat? Or was it 60? All I'm saying is that I don't think you should need some super fine quality heatsink meant for military grade applications where the life of a pilot is relying on the heat dissipation of a certain circuit otherwise his guidance systems will fail. Especially if you use a little active cooling, you shouldn't have any problems at all. Besides if I were to use some cheap heatsinks, I'd be sure to carefully monitor temperature when I first turned it on. If it got out of control I'd probably junk it and buy something better. But to me the amount of money you can save is worth the risk/effort.

Anywho, that's not important. I'm researching the Dynahi right now basically to see what it would cost and how difficult it would be to build a high end amp. I'm an awfully frugle guy, I don't see the point in building several lower end amps to work up to a higher end amp and then never use the old ones. Sans making a little profit from selling the old ones perhaps. The Dynahi looked pretty simple (still does, I mean all the chassis work is no issue for me). The main thing that concerns me is the parts matching and the electronics troubleshooting. I have a lot of electronics experience, but it's mostly practical stuff, not much theory. And especially not in the more niche audio application, but I do pickup fast. Since I'm such a cheap guy I'm not planning on having a lot of upgraditis (oh, if only you could plan that :/ ) and a Dynahi might just be overkill in terms of quality anyway, when I'll be using an EMU 1212m and HD600. I don't see myself buying a $900 DAC like, ever. Anyway I think you get the idea...

 

[rsaavedra]

Quote:

Originally Posted by gsferrari but at the end of it you will have a silly grin on your face when you get the low down with your favorite music, cans and beer...

Yes very much, the building process was enjoyable and a great learning experience, but the end result, the sound, is (was, b/c the rig is in storage thousands of miles away) even more enjoyable. I miss my Tosh->Dynahi->Zu->650's so bad...

 

[Emon]

Quote:

Originally Posted by rsaavedra Yes very much, the building process was enjoyable and a great learning experience, but the end result, the sound, is even more enjoyable.

You basically just said my reasons for wanting to shoot high in amp building. I already enjoy my music so much with my semi crappy setup, I'd probably **** my pants with something much nicer. I remember a time when I barely cared about audio, it was all about spending 200-300 dollars every few years on a new video card for gaming. Now I'm more about stretching my 200 dollar card over a 2-3 year period and using my superior audio equipment to locate and smite my foes in multiplayer.

I know very few people that can understand spending so much money on audio equipment. My brother and my dad are a little familiar with it, but just don't care that much. Funnily enough I get criticized by gamers for spending $50 on my HD497 but they spend $400 every year or two on a new video card. My purchases last many, many years. Theirs don't.

Aaaand with that I'll end another rant of mine...

 

[gsferrari]

I say go for it step by step...tackle each problem as you go...doing too much reading now will stop you from getting off the block.

Begin

YGPM

 

[Emon]

Well actually, I don't have a choice to just read right now, because I don't have anywhere near the money to build anything short of a MINT. Two months of a summer job will get me enough at minimum wage, but I don't plan to be making minimum wage this summer...

 

[Edwood]

Dynahi not hard to build?

Are you kidding me?

Just take a look at the ratio of the Dynahi group buy participants and number of actual, fully functional Dynahi's built.

Oh, you're having a hard time finding posts of people showing off their newly built Dynahi's?

Oh, and don't forget to add in the cost of the Power Supply (with a decent toroid) and a Decent Case. Unless you want to house your Dynahi in a lunchbox. Not that there's anything wrong with lunchbox amps, or little Timmy getting 3rd degree burns.......

-Ed

 

[Pars]

Quote:

Originally Posted by Edwood Dynahi not hard to build? Are you kidding me? Just take a look at the ratio of the Dynahi group buy participants and number of actual, fully functional Dynahi's built. Oh, you're having a hard time finding posts of people showing off their newly built Dynahi's? Oh, and don't forget to add in the cost of the Power Supply (with a decent toroid) and a Decent Case. Unless you want to house your Dynahi in a lunchbox. Not that there's anything wrong with lunchbox amps, or little Timmy getting 3rd degree burns....... -Ed

I don't think the reason that there aren't more from the PCB group buys built yet is entirely due to difficulty... cost and time are two issues that I know have at least caused me to not even start one yet... that and finishing up 2 Dynalos.

The casing in particular can get expensive for a really nice case.

To the OP... there is an entire thread on transistor and FET matching... the place to start is to get your transistors (a bunch of them, as in at least 2x what you will need other than maybe the FETs), and get them measured and matched. Then the resistors and other passives. If you don't have a +/- 30V bench supply that can handle the Dynahi, you will then need to first build the PSU and get it debugged. You will of course need some sort of bench power supply for the transistor matching, especially the output trannies at 85mA apiece. And so on...

As Ed points out, it isn't just stuffing a couple of boards and firing it up... hehe.

 

[Edwood]

Quote:

Originally Posted by Pars I don't think the reason that there aren't more from the PCB group buys built yet is entirely due to difficulty... cost and time are two issues that I know have at least caused me to not even start one yet... that and finishing up 2 Dynalos.

If it cost less and took less time, it would be easier, no?

Time is always the limiter, eh?

Oh, yeah. There's that pesky budget thing too.........

-Ed

 

[Emon]

Too bad school's out already, even the lowliest electronics lab has all the stuff I'd need. I'll have to look around at home and see what I have...my dad as a lot of stuff leftover from the 70s. There's also the option of buying transistors already matched at a premium, which could be a deal considering how much you might have to spend buying extra transistors. Just gotta find a place that sells the right ones though. As for resistors I stumbled across some place not too long ago that had, I think, 0.1% or 0.01% metal film transistors at some fair prices.

 

[aerius]

How the heck did you run up $365 for the parts? When I built one channel on a protoboard a couple weeks after the plans first came out, it cost me about $40 for the parts and $30 for a suitable power supply.

Quote:

Originally Posted by gsferrari I dont want to get into an argument but not all aluminum is aluminum...that should suffice to say the least. there are different varieties...densities...alloys...manufacturing methods (extruding vs moulding vs machining), surface treatments, impregnation...

It's a heatsink, it's not rocket science. Fatigue limits, S/N curves, grain structure, and all that other fun stuff isn't really important. For the purposes of a heatsink, they're all effectively the same except for some 8000 series aluminum-lithium alloys which have a significantly lower density.

 

[blip]

If you're still interested in using a fan (personally I'd just go with a bigger sink which your right can be had for nothing if you know where to look... and have better luck than me at scrounging) I'd recommend some sort of a temperature control circuit so that it isn't running full-bore all the time. (Unless of course you really skimped on the heatsink and need it at all times during operation... Personally I think it is better to think of fans in amplifiers as exhausting built up heat, not providing crucial cooling)

Anyway, building a control circuit can be as simple as a single thermistor or as complex as a PIC (or PICAXE or Basic STAMP or AVR etc.) powering multiple fans through PWM.

Edit: Also here is some more info on matching transistors: http://sound.westhost.com/transistor-matching.htm

 

[gsferrari]

Quote:

Originally Posted by aerius How the heck did you run up $365 for the parts? When I built one channel on a protoboard a couple weeks after the plans first came out, it cost me about $40 for the parts and $30 for a suitable power supply

pics please

Quote:

It's a heatsink, it's not rocket science. Fatigue limits, S/N curves, grain structure, and all that other fun stuff isn't really important. For the purposes of a heatsink, they're all effectively the same except for some 8000 series aluminum-lithium alloys which have a significantly lower density.

All is fair in theory - try putting your "simplistic" approach to practice.

I want to see your $100.00 Dynahi...maybe I need to head back to school and re-educate myself

 

[Nisbeth]

Quote:

Originally Posted by blip I'd recommend some sort of a temperature control circuit so that it isn't running full-bore all the time.

Probably not worth the trouble. The amp is running class A so dissipation is pretty much constant

/U.

 

[blip]

Quote:

Originally Posted by Nisbeth Probably not worth the trouble. The amp is running class A so dissipation is pretty much constant /U.

Good catch Nisbeth... Guess I wasn't thinking this morning. Yeah, Class A will more or less require a constant fan or a bigger heatsink. (Unless you wanted to have one turn on just to exhaust some case temp from time to time... In which case you probably should ventilate the case better to begin with.)

 

[aerius]

Quote:

Originally Posted by gsferrari All is fair in theory - try putting your "simplistic" approach to practice.

Been there, done that. I used to work in the industry. Thermo conductivity of various aluminum alloys can differ by about 15-20% from best to worst, in practice this translates to about a 1°C temp difference at most. Unless the design is marginal it's not going to make or break the design.

Quote:

I want to see your $100.00 Dynahi...maybe I need to head back to school and re-educate myself

Remind me in about 3 months when I start taking photos of my bike trips. I'm still using a film camera and that's just how long it'll be before I start shooting pictures and taking in my film for developing.

Thing is we have a bunch of shops in my area where I can buy the transistors for a bit over a couple bucks each, the FETs were 3 bucks and the resistors were pennies each. Same way I built a complete Dynalo for $30 including the Alps Blue pot. And transformers are cheap since I can get slightly used surplus ones for $5 a pop.