Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: magnafuzz on December 19, 2011, 05:26:21 PM

Title: Speedball, Voltage Check at Headphone Jack
Post by: magnafuzz on December 19, 2011, 05:26:21 PM

I just did the upgrade and the headphone jack readings are a little high. It goes up to around 17-20V and drops back to 0V. I've read before that the speedball values might be higher than the stock crack (my stock crack measured around 7-8V before dropping) but measuring double the voltage seemed like i should check with someone first.

All of my other voltage checks are fine (largest deviation is 4%)

Title: Re: Speedball, Voltage Check at Headphone Jack
Post by: Grainger49 on December 20, 2011, 01:18:53 AM

Once it goes to zero you are safe to plug in your headphones.  Or just time it and then wait that long every time.

Title: Re: Speedball, Voltage Check at Headphone Jack
Post by: Laudanum on December 20, 2011, 02:07:20 AM

It's fine.  There are a couple other threads on this.  After Speedball and Film output caps mine went to 24V before dropping to 0.   

Title: Re: Speedball, Voltage Check at Headphone Jack
Post by: magnafuzz on December 20, 2011, 06:49:29 AM

Thanks, Ive been using it after waiting a while for the voltages to drop back to zero.

is it harmfull to the headphones if i were to leave them plugged in when i turn it on? or will it just produce a thud?

Title: Re: Speedball, Voltage Check at Headphone Jack
Post by: Doc B. on December 20, 2011, 06:54:30 AM

It's very difficult to give a general comment about any headphone. I have inadvertently left headphones in when starting a Crack and never had a problem, but I don't recommend doing so.

Title: Re: Speedball, Voltage Check at Headphone Jack
Post by: pro_crip on December 20, 2011, 07:09:34 AM

What happens if one were to leave the headphones plugged in while turning it on? My crack has died on me and I was wondering if that was a place to start trying to find a fault. Thanks for listening.

Rich

Title: Re: Speedball, Voltage Check at Headphone Jack
Post by: Grainger49 on December 20, 2011, 07:23:29 AM

Rich,

The headphones act as the resistor on the output does, they "shunt" the leaked DC to ground.  But... there's always a but, the headphones are probably a lower resistance, so the current divider between the headphones and the resistor allows a higher current through the headphones.  This could possibly damage the headphones but not the Crack.

I'll bet the manual says to unplug the headphones and plug them in 10s after turning it on.

Title: Re: Speedball, Voltage Check at Headphone Jack
Post by: Laudanum on December 20, 2011, 07:49:39 AM

Actually Grainger I dont think it says anything in the manual about that.  But I remember a thread here about leaving them plugged in and, if I recall, a few replies stated it was fine.  Measured voltage is much lower at the jack if heaphones are plugged in.    I dont do it and Im not saying it's OK, just pointing it out.  I always turn the amp on for a little while, 10 or 20 seconds,  before plugging them in. 

Title: Re: Speedball, Voltage Check at Headphone Jack
Post by: magnafuzz on December 20, 2011, 10:12:01 AM

Thanks for the input, i've started making it a habit to let it sit for a little while and then plug in the headphones but it's nice to hear that it might not be the end of the world if i forget.