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Balanced to unbalanced board


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Guys, Dr. Gilmore has done a review of the Buffer's design.

Includes several improvements like two servos (one for the input and one for the output) resistance for the input impedance, trimpot for bias ...

diffinput5b - CADCAM.ZIP


All in the same size as the previous board. 

These improvements help solve the two problems that I have encountered:

A) Oscillation by impedance in the input
B.) Offset due to Fets

Thanks Dr. Gilmore  B) 


Edited by jose
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  • 4 weeks later...

Thanks Dr. Gilmore. 

It really is not that expensive either (an extra Opa and some more resistances). If it is as versatile as we want, what does it matter if something more expensive comes out?

In addition, the unbal/bal works perfectly so it would be normal to have the buffer at the same level.



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  • 2 months later...

digging up this thread ...

has anyone build smd version of ubal and buffer? 

I built mine ,when firing it up , leds did lit up and  smoked instantly

picture as attached .not quiet sure whats going on yet.



I use diffinput3smtd and  dbuf3 gerber files to make curcuit boards

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I only know one person so far that did the SMD version.

He says it gets pretty toasty and needs heatsinks. He also did a few mods. On my Dynalo Mini I mounted the LEDs backwards initially and it drove the temp really high.

Read his posts because he also changed a few things that you should probably implement. I plan on building it too but have some other projects in my queue I need to finish.

first thing i would ask is does it work without the buffers?

Edited by cspirou
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No, I was lucky I was able to find BC546CFA (Mouser) and BC556C (musical equipment and electronic store of my city) from "On Semi" but remember that I could only matched NPN with NPN and PNP with PNP.

If you are not sure, you can buy some and measure them. Maybe you're lucky.


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Thanks guys.

My idea is to have three normal inputs (1 XLR +2 SE) plus a MM preamp (in my case a VSPS) AND three different types of outputs (and a mute):

1º Un/bal + pot. (It´s like a "direct" output)
2º Un/bal + pot + KG Diamond buffer MKII
3º Un/bal + pot + KG Diamond buffer MKII + dc Caps.

So you can have three "different" types of sound. 

The appearance is not as good as I would like ? but it works (which is the important thing) although I still have some things to finish.

Edit: Did I say that I like blue LEDs? ?☺️?

Edited by jose
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That's looking good Jose!

I was able to find Diotec BC546CTA


And Diotec BC556CTA


They have them in stock for a decent price and sell to individuals like us.  I ordered yesterday and got a DHL tracking number early this morning.  It says I'll have them tomorrow.  They charged like $9.00 for overnight from Poland to the US!

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