Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: Stickman on July 11, 2016, 06:53:13 AM

Title: Voltage Sanity Check before Speedball Upgrade
Post by: Stickman on July 11, 2016, 06:53:13 AM

Hi all!
I've been enjoying my Crack with Sennheiser HD650s and recently purchased the Speedball upgrade.  Before I install it, I thought I would do a quick sanity check on resistances and voltages again before proceeding.  A couple voltage readings bothered me.  (One a little, one a lot)
1st:  Terminal Voltage Actual
1  75-90  77.9
2  170      164.1
4  170      163.9
5  75-90   72.7
So in the above readings, it looked like they should be the same for 1 and 5, I was surprised that 5 was that much lower than 1.  Anything to be concerned about?

Also, when measuring A1, A6, B1, B4, each of those should be 90 VDC.  However, I got the following:
A1  72.4
A6  77.7
B1  77.6
B4  72.4

Each lower than should be and consistently low.  These are the readings that bother me most.  Should I be concerned with any of these?   Does it signal some tube issue?  I am currently running the two tubes that came with the amp.

Thanks in advance for all your help!

Title: Re: Voltage Sanity Check before Speedball Upgrade
Post by: fullheadofnothing on July 11, 2016, 06:56:38 AM

These are all fine. They mean you have a strong tube.

Title: Re: Voltage Sanity Check before Speedball Upgrade
Post by: Stickman on July 12, 2016, 01:58:26 AM

Thanks so much for the quick reply. 

Once the Speedball upgrade is complete, I assume all the same recommended tubes apply.  In other words, what's a good replacement for a stock Crack will also be a good replacement for a Speedball, correct?

I've been compiling lists of tubes from the forums and may try that next.