Greeting Javier!cgospsa wrote: ↑2021-02-26 17:16 Greetings from Spain.
From specs: Giella is a headphone amplifier built in dual mono. That means each side handles one channel only; left and right. ...
With this in mind:
Would it be possible to change the Jack for a 4 pin XLR (female), and put the output on the front?
I have several headphones with cables terminated in XLR-4 pin (Amp-end).
What do you think?
Thanks in advance.
Javier
You're asking two questions:
1. Would it be possible to change the 1/4" headphone jack to an XLR 4-pin?
2. Can you position that connector on the front?
My answers are:
1. I chose between having an XLR 4-pin female connector and the 1/4" jack and I chose the 1/4" jack because it's more common. There's room on the rear panel for one of them but not for both. Giella is a rather compact case. I have evaluated the sound of a lot of 1/4" jacks but not any of the rather few XLR 4-pin connectors out there.
2. None of them can go on the front, because behind the front panel, there's a transformer. So there's no room for it. The reason to put the connector to headphones on the rear is that it will become optimal: It can be soldered directly to the main circuit board. To route it to the front plate is very similar to getting an adapter (as Pierre just mentioned), because it would require the signal to travel through cables to the connector on the front plate.
Speaking of adapters, I did try a lot of 3.5 mm jacks (the small 3-pole headphone connector) and strangely enough, it was better to use an adapter from 3.5 mm to 1/4" and plug this into the best sounding 1/4" jack on Giella than using the best sounding 3.5 mm jack that I found. This was a rather odd finding, but it made me decide to not use any 3.5 mm jacks and only provide the optimal 1/4" mm one, directly soldered to the circuit board.
The XLR 4-way connector has a theoretical advantage in that it provides two different grounds, one for the left and one for the right channel. However, these two grounds are best directed directly to the ground Mecka (a term in electronics meaning the point where all the grounds come together as a "central ground point"). So there is no difference between an XLR 4-way connector and a 1/4" jack in how Giella is designed. They would both be connected directly to ground Mecka on the circuit board. Therefore an adaptor will work as well as exchanging the 1/4" jack to an XLR 4-pole. But I'd make that adaptor short as possible, one decimeter is probably reasonable.