Changing 48V Ramp Time on Go Betweens

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mcshimby
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Joined: Thu Oct 13, 2011 6:42 am

Changing 48V Ramp Time on Go Betweens

Post by mcshimby »

Hi Joe,

I have four of your Go Betweens and I would like to use them to provide phantom power to my V72's. Oliver Archut recommends a minimum of 5 seconds ramp time so as not to fry the sensitive input transformers.

Can you tell me what components I would need to trade out to make this happen? Ideally the ramp up and ramp down time could be altered.
Would you mind explaining the relationship between the resistance and capacitance values and the ultimate ramp time?
5s is good but I might as well do 10s. Apparently Vintage King's rack has a 20s ramp up.

Thanks!

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Joe Malone
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Re: Changing 48V Ramp Time on Go Betweens

Post by Joe Malone »

Can you tell me what components I would need to trade out to make this happen? Ideally the ramp up and ramp down time could be altered.
Easy change 10uF cap on GO between to larger value.
Would you mind explaining the relationship between the resistance and capacitance values and the ultimate ramp time?
5s is good but I might as well do 10s. Apparently Vintage King's rack has a 20s ramp up.
Time constant is resistance x uF = Seconds (eg 470 x 0.001 (1000uF) = 0.47 Seconds). So for 5 Seconds use 10000uF 50v cap which show how crazy this size of slow ramp is.

In reality on 0.47 second (1000uF) is heaps if there is a short unbalancing the input as the phantom is turned on or off.
Also the ramp does nothing to stop this happening if phantom is on while unplugging or plugging in a input lead causing the unbalancing.
In fact a long ramp time will make phantom power accidentally being on as a cable is plugged in our out more likely.
Joe :-)
JLM Audio
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