Tascam M520 - Have a second meter bridge - How to use

Starliner

Member
Hello all,

I found a second meter bridge for my Tascam M-520. I was wondering if anyone else had piggybacked a second one onto their unit? I was thinking it would allow better meter monitoring and avoid switching.
Thanks!
Starliner
 

skywaveTDR

Active member
Well if the unit is hooked up with RCA cables then yes but if it is hard wires into the mixer I don't see how it can be used without some engineering involved.
 

Starliner

Member
Hi,

Thanks for your reply!

The meter bridge is hardwired into the mixer through a cable. There are also RCA jacks on the back of it. Haven't been inside the mixer, but assume the cable connections are soldered without connectors.

I don't have a problem doing the electronics modifications, but was wondering if anyone else had either done this, or considered this and maybe abandoned the idea. I do have the manuals for the unit.

My worst problem is... too many projects! Between trying to build a studio, repairing vintage gear, and researching / sourcing a lot of stuff... very time-consuming!
 

skywaveTDR

Active member
Well even if a connector is inside which I would think there is you would want different sources for the meters. So the connector inside is not something to work with and besides that the power supply would not want to deal with all that extra amperage going into those lamps. You would be able to get a external power supply and feed the lamps from that and then use line level signals to feed the meters depending on what the RCA connectors go to. If there is a tape input option this would work but then also the power supply for the meter drive circuits would also need to be provided not from the mixer.
I just looked at a M50 mixer schematic I have on computer- the M50 is the same as a M512 with the exception of a stereo Aux Fader. This connector went to meter off motherboard and had 11Vac for lamps- probably in a series (2) parallel combination and then it has Plus/ Minus 15Vdc.
The highest current is probably the lamps and the Plus/Minus 15Vdc can come from a small switcher. If the DA513 type lamps are used in series (2) then parallel after that the the 11Vac draw would be about 300mA. This is calculated with 10 meters- 8 buss and 2 2 track if there were more then add another 55mA so say a 400mA supply would do.
Do you see how this will make things more complicated? The mixer can not have another meter bridge just added to it. It was not designed for that power wise.
 

Starliner

Member
Yes, I see your point. I am relatively sure the power supplies were not designed with more than a 20% -25% overload limit. I do have the complete manual for the M-520... looked at it last night, but my eyes were tired and not focusing well.
I don't know if the supplies in the PSU could be altered to provide the correct current, or whether it would be possible to install a separate, wired supply within the mixer / meter bridge itself.
And, I need to ask myself, is it worth the effort? I am sure other questions / issues would pop up along the way.
 

skywaveTDR

Active member
I would not try and upset the power supply in the mixer as the transformer and all the way down is designed for what is in the mixer only. I would apply a separate power supply with Molex connectors and then kind of use the meter bridge in a stand alone configuration with external RCA signals feeding it. This would be the wise way to do it. I do make mods on equipment like tape deck when there is a need but it is all withing the normal operation of the deck . It is just that I refine what they should have put in the deck in the first place and my mods work wonderfully as I designed them. I did a X1000R last night with one.
 
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