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The Multi Amp aka Dynalo Mk2


spritzer

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2 hours ago, rumina said:

Not a Mini Dynalo but a small one. Finished my Dynalo today, thanks to this forum and the members the build was easy and free of trouble, thanks everyone. Was fun to put it in a small case and solve this puzzle. Also a big thanks to Kevin Gilmore for this design and sharing it with us.

http://www.diyaudio.com/forums/gallery/showgallery.php/cat/2231

Thanks to sbelyo for the group buy of the pcbs.

 

dynalo1small.jpg

man..same thoughts here, but I failed squeezing GRLV in it,lol

DSC_6537-800x532.jpg

 

DSC_6526-800x532.jpg

 

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@pars thanks for the info, was puzzeld about the 3th rectifier and didn't take much time thinking of it, a bit of wiggling and it's out now. Something new learned about the grlv, used it the first time. That's a part i love about head-case, helpful people and always something new to learn.

@ang728 look nice your amp, building this in a small case is like a 3d puzzel, part of the fun for me.

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  • 2 weeks later...

Hi everyone! I also finished my build of Susy Dynalo! Still doing run-in of the amp but it already sounds really great even driving a HD800!

Since the layout from Mr.Gilmore is a little bit too large and cannot fit into a 10cmx10cm pcb, I have to redraw the layout. But good thing is that an extra inductor was added to the power rail of input stage as well as the VAS to prevent distortion from output stage. Also the rails are surrounded by "guard rings", aimed to avoid EMI problems.....

image2-min.JPG

image4-min.JPG

Sorry for the crude casing... just carved it out from kinda plastic flowerpot...

Some detailed specs: 

Quiescent Current of Input: 1.2mA

Output stage bias: 6.7mA per transistor

rail voltage: 18.5V, tried 20V but it's too hot.

Gain: Approx 3.

Also some interesting results. The THAT340 was then replaced by hand-matched ksc1815/ksa992, beta deviation within 0.1% - Huge improvement in transparency and details!

 

The power supply based on Jung's regulator, but an extra transistor was added after the error amplifier to lower the load seen by the Op-Amp, works well.:D

 

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  • 2 weeks later...
23 hours ago, Pars said:

AOT is a resistor (R62) spot in parallel with R54 (10K), feeding the sense line on U3 (TPS7A3301RGWR?) to ground. Maybe used to tune V- to match V+? No value listed in the BOM for it.

Yes.  AOT means Adjust On Test.  It's not required but can be used to finesse the output voltage on the negative rail.

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Thanks Kerry, for the clarification and providing us the board design.

Any advice on the best way to solder the TI 7A4700?  That thing's tiny, I ruined one board doing this already.  I'm thinking melt some solder first on the pins and then put the chip on.  I got a rework air gun, not sure it's the best way though. 

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20 minutes ago, Skooby said:

solder the TI 7A4700

watch Louis Rossmann - YouTube

I used a candle warmer to preheat the area.

clean the pads

 liquid flux

 tin the pads

clean

reflux

use hot air station

solder with silver content helps with gold plating.

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On 1/31/2017 at 11:30 AM, congo5 said:

watch Louis Rossmann - YouTube

I used a candle warmer to preheat the area.

clean the pads

 liquid flux

 tin the pads

clean

reflux

use hot air station

solder with silver content helps with gold plating.

I watched part of Rossmann's video soldering a chip on a Mac or the like...damn.  Soldering free for all.  That man doesn't play.  LOL

HS

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under video description click "show more"


✖ TOOLS USED:
● Flux: http://bit.ly/2cYIx7t
● Solder paste: http://bit.ly/2epK1JE
● Soldering Iron: http://amzn.to/2cKkMyO
● Preferred tip: http://amzn.to/2d5MgPn
● Micro Soldering Pencil: http://amzn.to/2d5MWUP
● Micro soldering tip: http://amzn.to/2eYrF4a
● Hot Air station: http://amzn.to/2d5M7Lw
● Hot Air EXPENSIVE: http://amzn.to/2cYI6tY
● Tweezers: http://amzn.to/2d5NBpi
● Multimeter: http://amzn.to/2cYJY5T
● Multimeter Probes: http://amzn.to/2cKkvMh
● Fume Extractor: http://amzn.to/2d5MGoD
● Microscope: http://amzn.to/2iLrE16
● Microscope LED light: http://amzn.to/2d5Mh5T
● Solder: http://amzn.to/2cKkxUp
● Crest CP500HT Ultrasonic cleaner: http://bit.ly/2iv3aci
● Branson EC cleaning fluid: http://amzn.to/2cKlBrp
● Jumper wire THIN: http://amzn.to/2eqF5T7
● Jumper wire THICK: http://amzn.to/2eAJ5AU
● Nitrile gloves: http://amzn.to/2iUfumS
Bench PSU: Agilent 6542

I'm using Kester.

turn down the blow.

hold with twezers

mask off  blow zone with aluminum foil?

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8 minutes ago, HemiSam said:

 Might have to spoil myself with one of those.

Yes, want! don't have small pencil

on Flux: its a big deal, what he has is way better, the kester boils off quick and leave's more residue but works

I got the positive regulator on the first try, but took three times on the negative   Had too much solder under and some side pins would not make contact.

flux dries> solder won't stick> start over

going slow and careful as I only have one board, that took half a day ;-)

Really want the microscope + camera.

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