VU BUFFER & PEAK LED KIT BUILD THREAD

[djmiggymigz]

Question about the 34mm VU meter y'all sell (looked around the forum and didn't see a specific place to ask this so just dropping it here). Does the 34mm VU have rectifiers internally? Specifically, can you run the VU meter without the buffer circuit and just use the series resistor? (Disregarding my specific need for the gain of the buffer circuit.)

I'm currently a little stuck between the JLM 34mm and the Sifam AL15 meter and trying to discern what the differences may be.

[Joe Malone]

Question about the 34mm VU meter y'all sell (looked around the forum and didn't see a specific place to ask this so just dropping it here). Does the 34mm VU have rectifiers internally? Specifically, can you run the VU meter without the buffer circuit and just use the series resistor? (Disregarding my specific need for the gain of the buffer circuit.)

I'm currently a little stuck between the JLM 34mm and the Sifam AL15 meter and trying to discern what the differences may be.

The 34mm meter is dc so needs VU buffer or diode bridge. Both 34mm and AL15 will need the buffer to makeup the 6dB from the single winding and to block the nasty THD from the meter damaging the output audio

[djmiggymigz]

Gotcha, thanks so much for the responses/advice!

[pelagos]

Gyraf / MNATS 1176 build and VU meter issues - using the JLM buffer kit

This may or may not be related to the VU buffer kit - but will ask here in case you have any ideas Joe

I have a couple of these diy 1176 builds just completed and trying to get the VU meters to work...

I am waiting on some of the JLM Large VU Meter to be in stock so bought some 'cheapies' to test in the meantime (tn-73-9213h) with the VU buffer kit

The meters seem to work fine when connected directly to the buffer kit - I can calibrate etc as per doco

But when i connect up to the VU output board of the 1176 I get basically nothing - I can see the VU meters move a tiny bit if i crank the input gain but only very slight....

Also trying to set the GR to 0VU using the trim pots on the 1176 also doesn't work

the meter board just has +/- out (no gnd) so have just used the +/- into the buffer - but I have also tried other combinations as well and no luck

The VU does move slightly when changing connections, turning on.off etc - so there is some life there, and if i measure the voltage across the VU outputs from the board - its increases / decreases when turning input gain up/down so also something is happening - just nothing on the VU...

I assume it is an issue with my build - but just wanted to throw it out there in case you had come across this issue or similar and can maybe advise anything to try???


Many thanks for any suggestions

pelagos

[ldarieut]

I have built the buffer and it works, somewhat.
my setup is the following:
- minidsp flex-8 with 8 unbalanced out
- 6 unbalanced goes to 6 balanced hypex amplifier to power my 3-way speakers
- 2 unbalanced goes to the vu buffer, and then to nissei p-134 https://meterexpert.com/products/vu-meter/p-134/

My volume output is on the minidsp, so my meter will not move at acceptable noise level (-40dB on the minidsp volume)

I put a -20dB out on the 6 unbalanced to the power amplifier, and a +10dB gain on the 2 channels going to the vubuffer. So, there is a 30dB gain difference on the meter vs the actual sound output.
Now the meter will barely move when the volume is at -20dB on the minidsp.

Can I change some values on the buffer to have maybe more gain?

[Joe Malone]

I have built the buffer and it works, somewhat.
my setup is the following:
- minidsp flex-8 with 8 unbalanced out
- 6 unbalanced goes to 6 balanced hypex amplifier to power my 3-way speakers
- 2 unbalanced goes to the vu buffer, and then to nissei p-134 https://meterexpert.com/products/vu-meter/p-134/

My volume output is on the minidsp, so my meter will not move at acceptable noise level (-40dB on the minidsp volume)

I put a -20dB out on the 6 unbalanced to the power amplifier, and a +10dB gain on the 2 channels going to the vubuffer. So, there is a 30dB gain difference on the meter vs the actual sound output.
Now the meter will barely move when the volume is at -20dB on the minidsp.

Can I change some values on the buffer to have maybe more gain?

First make sure -in to connected to 0v as this will give you some extra gain.

The best way to increase gain will be to make the R1 & R2 47k smaller in value down to as small as 3k3

Remember a VU should be before any volume control as they only show 23dB range.

[ldarieut]

Thank you!
Adding a cheap drv134 to convert signal to balance seems to give already very satisfactory result.
I will do further testing by soldering resistors in parallel of R1 and R2 to lower the value without butchering the pcb