NV500 Mic pre BUILD THREAD

[ballo333]

Hey Joe

So sorted all out pre is all working sounding sweet
New red 48 LED is fine but the blue DI still nothing
So i checked inside the chasis and the blue led was working but very dim
So i checked my other NV500 pre built one and realised it has a FLAT blue LED like it says on BOM lol
So yeah the one suppled was a round blue one and the one i replaced a clear round blue one is faint still
Also ill show in pictures my other NV500 has what looks like foil on the back of DI? The one i built has nothing there not sure if that makes a difference?

IMG_0323.jpeg

IMG_0324.jpeg

My local Jaycar had no flat blue LEDS

Thanks Sean

[hasanova]

Hi,

I'd like to use my JLM pre-amps for LINE-IN (24 channel mixing - 500 series) by using an inline U-PAD on the inputs.

I'm a bit concerned about phantom power.
Some of the mic/line pre's I have defeat +48V on the inputs when switched to LINE-IN, but the JLM ones don't have LINE IN. For some other micpre's it's just a matter of removing the cap on the switch and it becomes impossible to depress it with a finger (!).

I know it's a lot discussed topic, but I' don't need it at the moment and I have external phantom boxes for mic's that need it. I'm not looking for or interested in phantom-blockers.

Instead of removing the switch completely, is there an easier way like by removing some resistors, and replace by holders. So it becomes easy to reverse later.
I ask for the NV500 (and if possible also TG500)?

Thanx!

[Joe Malone]

Hi,

I'd like to use my JLM pre-amps for LINE-IN (24 channel mixing - 500 series) by using an inline U-PAD on the inputs.

I'm a bit concerned about phantom power.
Some of the mic/line pre's I have defeat +48V on the inputs when switched to LINE-IN, but the JLM ones don't have LINE IN. For some other micpre's it's just a matter of removing the cap on the switch and it becomes impossible to depress it with a finger (!).

I know it's a lot discussed topic, but I' don't need it at the moment and I have external phantom boxes for mic's that need it. I'm not looking for or interested in phantom-blockers.

Instead of removing the switch completely, is there an easier way like by removing some resistors, and replace by holders. So it becomes easy to reverse later.
I ask for the NV500 (and if possible also TG500)?

Thanx!

All of our mic pres can handle +24dBu line input when the pad is switched on the front panel. Leave 48v switched off on the front panel.

If you want to disable 48v phantom power on NV500, TG500, Dual99v500 just remove or lift one end of the 48v 10R resistor next to the 48v rear edge connector pin 15.

You can add a external U pad using 2 x 470R with 51R to 100R depending on the amount of attenuation you need. Then the internal pad can be turned off.

[hasanova]

Thnx Joe!

[hasanova]

I have 2 units. #2 is working fine, but #1 has no output signal from GAIN setting 60dB and up.

FYI: I have have disabled phantom power by lifting one leg of 48V resistor (10R).

Schermafbeelding 2025-08-28 om 10.30.39.png

Schermafbeelding 2025-08-28 om 10.31.00.png

[hasanova]

I've removed parts to get an as clear as possible view for the pictures.

Schermafbeelding 2025-08-28 om 10.29.26.png

Schermafbeelding 2025-08-28 om 10.30.02.png

[Joe Malone]

I've removed parts to get an as clear as possible view for the pictures.

Schermafbeelding 2025-08-28 om 10.29.26.pngSchermafbeelding 2025-08-28 om 10.30.02.png

Ok first if you swap the 2 BA283AV cards does the gain work the same to 60dB or does the problem change ?

If the problem stays the same then the problem will be to do with the 5v reed relay and the 5v1 and 1N914 diode. So Check both diodes are correct way around. You should have 5v across the 5v1 diode ? and above 60dB you should have 5v across the 1N914 ? on the other side of the reed relay. Let me know what you find

[hasanova]

Yes, it was D3 (1N914 or 1N4148) that was wrong way around. Now #1 can go max gain also.
Thank you!

[Joe Malone]

Yes, it was D3 (1N914 or 1N4148) that was wrong way around. Now #1 can go max gain also.
Thank you!

Cool great to hear it was a simple one. Enjoy