Elektor PA300

[ADMicroNov]

Hello everyone.
This several months that we walk in the threads of discussions. To see and understand.
We work for a French humanitarian work. Emmaus.
I mainly deal with recycling. So we have access to a hellish amount of material.
Just for the introduction.
We have been repairing all equipment for over 20 years.
I do not claim to know everything, far from it. But we are a whole team to tinker and build a whole bunch of things.
In short, we have fun.
Elektor circuits have been updated for some time.
Normal, Elektor in France is quite a poem.
As we can no longer get out with once again, confinement.
We decided to make a sound system in the village.
The PA.300 Elektor is still buildable, parts available. So we started. We re-route the circuit board.
PA.300_400-600
For the 600, we started from the Elrad magazine, but the circuit was so equivalent to that of Elektor we directly modified the PA.300. PA.600 = 8 pairs. We have therefore modified the circuit ion feed resistances. We draw everything on Autocad, sorry. But Kikad and c ° it takes a bit of our head.
Okay, I'm attaching some of our work to give an idea.
See you everyone.
Jacky

[ADMicroNov]

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[Kay Pirinha]

Beautiful! Mind to share your PCB layouts? And where do you plan to source these panel meters from?
Best regards!

[jamesfeline]

Hello .... good luck with your project
Regards

[Guerilla]

I accidentally? just bought an Elektor PA300 unseen... I really want to know if it has ballansed inputs If not I would be gratefull if someone has links to a good kit for adding ballanced input.

Cheers!

[Kay Pirinha]

The PA 300 has got a NE5534 as the input amplifier. Perhaps it is possible to add a NE5532 and arrange an instrumentation amplifier?
Best regards!

[Guerilla]

@kay Does that mean it only has rca or other unbalanced input?
Cheers!

[Guerilla]

I only want ballanced output cause my crossover DBX 234 doesnt have unbalanced out

Cheers!

[Kay Pirinha]

The Elektor PA 300 amplifier, as it was published originally, neither has a balanced input nor a balanced output.
Best regards!

[JMFahey]

Originally Posted by Guerilla

I accidentally? just bought an Elektor PA300 unseen... I really want to know if it has ballansed inputs If not I would be gratefull if someone has links to a good kit for adding ballanced input.

I only want ballanced output cause my crossover DBX 234 doesnt have unbalanced out

1) Elektor PA300 does NOT have balanced input (attaching schematic below)
Good news is you do not need one

2) DBX 234 XL does have unbalanced outputs built-in, hidden in plain sight

It has "electronically balanced" outputs, actually two conventional unbalanced outputs, each referred to ground, only fed exact same signal level but out of phase, each connected to pins 2 or 3 of XLR output.
You can use them individually as what they are, unbalanced outs.

Make an adapter cable: one end connected to male XLR pins 2 (signal) and 1 (ground/shield), at the other end male RCA (or 1/4" plug if amp was built for PA use and has an 1/4" jack instead).

Presto, your problem is solved.
Clearly suggested in DBX user manual, by the way:

Specifications
Input Connectors XLR
Input Type Electronically balanced/unbalanced, RF filtered
Input Impedance Balanced >50k ohm, unbalanced >25k ohm
Max Input >+21dBu balanced or unbalanced
CMRR >40dB, typically >50dB at 1kHz
Output Connectors XLR
Output Type Impedance-balanaced/unbalanced, RF filtered
Output Impedance Balanced 200 ohm, unbalanced 100 ohm
Max Output >+21dBu balanced/unbalanced into 2k or greater

As you see, both input and output can be used balanced/unbalanced.