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KG Balanced Dynahi build discussion thread


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What could possibly go wrong :)

Seriously; great idea though! Things could potentially get toasty on a 2U heatsink, so being able to choose current would be welcome flexibility.    

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Just want to add that the bias control is not my invention. You find similar on Uberamp and AMB’s beta22.

My view on Copyright is - my right, as DIY:er, to “copy and paste” as I wish. :)


Edited by JoaMat
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On 3/21/2022 at 1:42 PM, JoaMat said:

So here is my first attempt

Hi, JoaMat!

Very nice PCB routing concept.

Something similar:

Let's go ahead, it's time to provide DIYers with the next features:

1. A simple swapping JFET/BJT input stage on the mezzonine with standartized fitting place/connector.
2. Really smaller dimensions with easier through-pcb-screwing.
3. Integrated onboard fitting connector for corresponding voltage regulator.
4. Check transistors availability and, of course, create different versions of the output stage, one for TO-126, other for TO-220 devices and maybe one for TO-3P/TO-247/TO-264.
5. Since you have provided bias control it's time to make output stage 2-stage emitter follower, vertical mosfet source follower or lateral mosfet source follower for those who want to experiment.
6. Input JFET transistors have cascodes, so aren't we ready to provide cascodes for VAS devices?
7. VAS devices on the main heatsink and also an option of the TO-126/220 cases.
8. Really higher dedicated IPS/VAS supply rails, up to +-150 volts.
9. An option to use modern low-ESR solid polymer capacitors for the power stage.
10. Dedicated input stage before volume regulator for common mode error rejection.
11. Second order integration filter for output nulling.


So, the concept.

Mezzonine construction. One PCB for JFET/BJT input stage and corresponding cascode devices, second PCB for one OPS shoulder and third PCB for the voltage regulator. All for as-LEGO-construction as possible.

Edited by Bespav
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Joamat's build reminded me of some problems with balance and setoff on my own Dynahi. I adjusted the amp a couple a months ago, a bit tricky with DC fluctuating, but got numbers down to 3-15 mV with servo in, depending on volume pot position. However, with headphones connected, DC between hot and cold is 50-80 mV. Anyone got theories why this is?

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Here is picture of the amplifier in work. Mono version. AMB sigma 22 PSU.


It has four trimmers. Lower middle controls the offset. Middle upper controls the balance. The two outer controls respectively channels bias. Input stage current source/sink approximately 1.7 mA. Output bias 35 mA.

Setup procedure I used:
•    Let heats sink get warmed up to working temperature
•    Trim offset to zero
•    Trim balance to zero
•    Set desired bias of both channels to desired bias

Redo previous procedures if needed.

I find the setup easily done. 

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  • 3 weeks later...
  • 1 month later...


I could get now DynaMight 4pcs boards version 2004. Does anybody know is there any difference for balance amplifier between: DynaMight and Susy Dynahi v 1.43?

Edited by bbest
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  • 4 months later...

A slightly reworked “Dynahi smd” board. Balance and offset trimmers removed. Now servo on each side that bring the offsets to ground potential.  Bias trimmers moved to north for easier accessibility “in flight”.

This is a "solder and play" board. No set up procedures required, except to turn bias trimmers to desired bias. At least that’s the idea.

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You have to think Joachim style, i.e., smd-small and vertical :). I believe the board is stereo and it mounts flat (vertical if seen from above) to a 2U heatsink. In the pic four posts above you can see how the previous edition boards are mounted through the grille.   

Edited by MLA
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It’s a balanced board.

Inputs in center. Outputs at far right and far left. Positive rail at top edge and negative rail at bottom.


Dynahi boards mounted to 80 mm x 300 mm heat sinks. Here I’ve removed upper screws holding front and back plates to heat sinks and then “unfolded” for maintenance. To make it possible to unfold the wires are made “to long” when folded and then it looks like a snake nest. This is an Only DIY version, not to be sold...

 I hope this makes it a bit clearer.

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