The Multi Amp aka Dynalo Mk2

[UFN]

Correct. IIRC Kevin made the SMD-layout when On-semi announced that they were discontinuing the MPSW-devices and only keep the surface-mount PZTAs. As it's the same transistors I don't believe there are any difference in performance.

 

//UFN

[cspirou]

I made a list on mouser.com for parts of the amp boards alone. I included both the 240 ohm and 255 ohm resistors but you could easily remove one. The only thing I don't have are the terminal blocks. Anyone know which blocks I should use?
kgssdynalobal9 - 2 channels

I noticed that most amps that are class A have a lot of heatsinks but this one doesn't seem to really need them. It is because the current is distributed among several transistors which spreads out the heat more efficiently without the need for heatsinking?

[UFN]

Partly. From memory, the Dynalo runs app. 300mA at +/- 15-20V, i.e. an idle dissipation of around 10-12W per channel. This is not much by class A standards (a 20W/ch speaker amp like the Pass F5 or similar dissipates from 60W/channel and up).

Distributing the heat across many transistors means the Dynalo can use smaller output transistors - the MPSW/PZTA-ones are only rated for 1W dissipation each.

//UFN

[Kerry]

Here's an update on the mini.

I've got the external regs running now.  This thing does throw off quite a bit of heat.  I've some sinks on the output transformers now, but I'd like to make them a bit larger.  The regulators heatsinks are going to about 140 deg F at their peak and I'm ok with that.

I was testing at +/-14V before I put the heatsinks on.  The bump up to +/-20V seemed to smooth things out a bit on the top and bottom ends.  I'm very happy with this so far

 

Edited August 7, 2016 by Kerry

[nopants]

nice job, is the heat going to change how you case the thing?

[kevin gilmore]

"output transformers"   ??

needs a wood knob. I can help with that.

[luvdunhill]

"output transformers"   ??

needs a wood knob. I can help with that.

Transistors. Check out the picture

[Kerry]

Yeah, I'd like to blame that on my swipe typing, but that's a bit of stretch.

Should be transistors

[HemiSam]

 

Woot!!!

HS

[sorenb]

35 minutes ago, HemiSam said:

 

Woot!!!

HS

is that Dan Clark after inventing plastic with holes in?

[JoaMat]

20V and 0.46A, twice. About the same power as T2 output stage. In the palm of your hand.

[nopants]

I take it there's no need for heat sinks over the output stage then? how's the sound

[JoaMat]

Running the Mini Dynalo as I did above need heat sinks. Measured 250 deg. Fahrenheit.

I believe Kerry and Kevin have some modification in mind.

[Kerry]

Just looking to get the bias back in line with original specs.  That plus the heatsinks I was testing should put us around 110 deg F on the output sinks.  The regulator sinks should also come down to 105 deg F.

Need some parts to test.

[RudeWolf]

What's the usual procedure for heatsinking smd devices? Sprinkling vias around or screwing on a small heatsink?

[Kerry]

Yes, but because we were saving space, we'll be mounting the heatsinks directly to the output transistors.

You can see them mounted in my post above.

[luvdunhill]

What's the usual procedure for heatsinking smd devices? Sprinkling vias around or screwing on a small heatsink?

There are a few ways to do it. If you attach the heatsink to the transistor case, you pay a pretty large thermal penalty. I think the best way is a large land with an attached heatsink.

[Kerry]

On Kevin and Birgir's latest SS Dynalo board the collectors of the transistors are mounted to a large copper pad and a heat stink is mounted to the pad.

[Mister X]

I was half awake and imagining a single sided plug in amplifier board with the whole bottom being an exposed mounting pad for a BGA heat sink this morning.

Dunno how practical that would be in the light of day.

[luvdunhill]

I think if your bottom became a top, that might just work.

[kevin gilmore]

where is steve when you need him?

one man's floor is another man's ceiling

 

 

[Mister X]

Yep. Component side down, with a cutout section in the "main board" under where the amp board ends up.

Add some case vents and almost sounds like a plan until trying to route a PCB for it.

 

 

Edited August 11, 2016 by Mister X

[RudeWolf]

What about solder-on sinks? Like here - 

[wink]

And, you could always bolt another sink on the top.

[joehpj]

How a about using the whole case as heatsink?

It's rather easy to calculate the distance between case and PCB. Customized aluminum block can do this job.

Or, hollow the case to expose the heat sink. My concern is if the whole PCB is cased and heat dissipation will be a problem after hours of running.