The Multi Amp aka Dynalo Mk2

[Whitigir]

4 minutes ago, Pars said:

Yep, when I tried the onboard regs, I had problems getting the jumpers to bridge properly as well. They do go to ground, and anything going to ground on the 3oz boards was a problem, particularly if you were trying to use a sane tip size for the application.

The tab on O23 looks a bit light on solder... looks like you used hot air and paste on most of the SMD?

Yes, I did exactly that :).  So, when cranked up first time, what I encountered is alright and common ? Ok, I will warm it up and see if adjusting pot will do anything 

[Pars]

Don't adjust the pots with the servo 0R jumpers in; normally this is done without. And yes, those look like good results. What does the other channel look like?

[Whitigir]

46 minutes ago, Pars said:

Don't adjust the pots with the servo 0R jumpers in; normally this is done without. And yes, those look like good results. What does the other channel look like?

L+, L-,  R+ Instantly saw offset of +/-3mV without turning any pot. (Swinging back and forth)

only R- was instantly -12mV, but comes down to +/-3mV in like 30 seconds or so, without touching any pot.

Yes, 0-Ohms is not installed yet.  That was why it seems weird to me.  What did you encounter on your first cranked up about offset ?

Updates:

Great ! So I tuned into the pot, adjusting as @Pars listed out the channel and the Left is swinging +/-4mV and the Right is +/-5mV.  It swung upto +/-50mV but nothing extremely over that.  The things got Hot!

I think it is time to toss in the 0-ohms and try installing heatsink and listen 

Edited October 28, 2018 by Whitigir

[Whitigir]

Alright, after the adjustment on the pots.  I tossed in all the heat sink and 0 ohm resistors and had a test spinning.  The result is staggering ! HD800S sounds so wonderful and Excellent to take around ! Woaa

Finally, thank you first of all @Kerry for this amazingly portable design and awesome list of BOM and so on.  Thank you @kevin gilmore for the amazing cook!.  Thank you @cspirou for this beautiful chassis run (it was a perfect fit every where from even the screws itself).  Thank you @sbelyo for this amazing GroupBuy on the Boards and Pot which made this project a possible.  Then to the last but not least, all of you who contributed into this thread

still looking for the beautiful black volume knobs LoL.  Also, please don’t mind that LED, I didn’t think it was that bright X_X lol

Edited October 29, 2018 by Whitigir

[cspirou]

That is one blinding LED. Nice work! Where did you get the heatsinks for the THAT chips?

For knobs I was going to go with diyaudio or Parts Connexion

[Whitigir]

31 minutes ago, cspirou said:

That is one blinding LED. Nice work! Where did you get the heatsinks for the THAT chips?

For knobs I was going to go with diyaudio or Parts Connexion

Yeah, probably was meant to stay inside but I slot it into the front chassis and it is bright 

the THAT heatsink was bought from Amazon, but I cut them to fit.  Using double sided tapes as you recommended 

I will give you the exact parts tomorrow 

Amazon seller is no longer listing this parts.  I had to cut it anyways and since it was only 0.5mm thick, it was easy.  The brand was BNTechGo 20x20x0.5mm. This link shall bring you to the similar but thicker one, and you can cut it to fit as well ?

Edited October 29, 2018 by Whitigir

[Pars]

I used knobs from eBay seller AudioGD and liked them quite a bit, finding them to be nicely finished. 25mm is about as big as you can go on these; might get away with 30mm.



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[MASantos]

Could someone point me to the latest bom for the mini? I had one but cant find it.

[Pars]

There are a couple in posts 814/815 from 12/10/2016


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[Whitigir]

So, after installing THAT 340 and offset dialed in with 0 ohms on, there won’t be rolling those Trans right ? I asked because mine is a bit bright up top, and I want to try sc3381 and 1349 combo 

Edited October 29, 2018 by Whitigir

[Pars]

Why not? You might have to recheck the offset. If you feel this is bright, I would go with JFETs instead as I don’t think you will gain anything with the 3381s.


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[MASantos]

Parts ordered for a mini dynalo, should be here in a couple of weeks.

 

[Pars]

Listening to nopants amp tonight (Curve - Doppleganger). Sounds awesome! iphone -> Vox w/no eq -> amp -> modded T50RPs. I'm really enjoying this tonight...

Pics remind me I need to clean it as I've been abusing it in the basement for a bit. Also don't have the heatsinks installed yet. It seems the top, etc. don't get as hot... I'll have to shoot some temps with my IR gun tomorrow. I know @johnwmclean doesn't run heatsinks on his and felt it ran just as cool.

 

[RudeWolf]

Really need to get on building this.

As for knob fu, here's my favourite - https://www.ebay.com/itm/1x-hifi-36-20mm-Aluminum-6mm-Shaft-Volume-Control-KNOB-Potentiometer/291712398772?var=590738155026&hash=item43eb69f5b4:g:jyUAAOSw2ENW69SM

[Whitigir]

I can not even touch my Mini heatsink after 2 hours on.  It literally sits around 70C X_X

Anyways, I found the brightness spikes and sizzling top was due to THAT340, as I swapped in the 3381/1349 and I got an observable improve in performances.

I used Volume knob from Goldpoint which just came-in, the smallest knob, and she look awesome!

http://www.goldpt.com/knobs.html

 

Edited November 2, 2018 by Whitigir

[cspirou]

@Whitigir - Did you drill another hole?

[Whitigir]

Yes, I needed 4.4mm lol

[Pars]

You didn’t consider an adapter cable instead?


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[Whitigir]

4 minutes ago, Pars said:

You didn’t consider an adapter cable instead?


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Yes, I did, but have to unplug it and carry it where I want is a hassle.  My cables are all 4.4mm

it also look good :D, except that I do not have the digital printing, so I just touched it up with paint 

 

Edited November 2, 2018 by Whitigir

[MASantos]

Regarding the output transistors heatsinks, what size should I look for?

[Whitigir]

4 hours ago, MASantos said:

Regarding the output transistors heatsinks, what size should I look for?

45x35x18mm

https://www.ebay.com/itm/New-Aluminum-Heatsink-Cooling-Fin-Heat-Sink-Multi-Size-Choice-38mm-to-200mm-/263051780518?var=&hash=item3d3f1ba1a6

Edited November 3, 2018 by Whitigir

[Pars]

Yes, that is the same size I used.

As I noted above, I'm not sure these run cooler with the heatsinks. I'm going to do some more testing tonight.

[Whitigir]

It gotta help right ? The amp runs crazily hot

here is right on top of the lowest part of the heatsink, which is closest to the trans after 90 minutes mark or so, and seem to stay at it.  The IR-guns only show 70C though...strange

Edited November 3, 2018 by Whitigir

[cspirou]

13 minutes ago, Pars said:

Yes, that is the same size I used.

As I noted above, I'm not sure these run cooler with the heatsinks. I'm going to do some more testing tonight.

I think i share this observation as well. Heatsink temp is lower then the naked transistor for sure, but i am not so sure that the transistor itself is actually that much cooler. The vented PCBs like Headamp has on their newer amps would be the way to go, or some sort of PCB mounted heatsink like this.

[MASantos]

Have you measured the top.of the transistors without the sinks?