2. amps-preamps
  3. 191157-18279

DC Offset Issue in Don Sachs Preamp

I have a nice Don Sachs preamp.  It's making an incredibly loud popping sound on power off.  Obviously, it's always good to power preamps first then amps and reverse the order for power down. But, I'm still concerned about potential damage to my loudspeakers. 

Would this be do to a leaky coupling cap at the output stage?  Or not enough uF/capacitance to take out all the DC? 

I could email Don but I bought the amp used and I got the sense he may have retired. 

 

Any insight is very welcome. Thank you.

jbhiller

Showing 4 responses by jbhiller

jbhiller's avatar
jbhiller OP
1,446 posts
 

Amp is used (3-4 years old) but new to me.  

Today, I swapped out the CV181Zs for classic 6sn7s, and things may be better. Would that make sense? Doesn't the CV181Z have higher heater current value than 6SN7s?  

jbhiller's avatar
jbhiller OP
1,446 posts
 

Thank you! 
 

I’m running 100dB sensitive horns with larger woofers.  I’m currently playing the Sachs into a Marantz Ruby set to Power Amp mode.  This hybrid setup sounds sublime. 

jbhiller's avatar
jbhiller OP
1,446 posts
 

Thank you everyone!  Lynn, you are the man! 
 

don’t tempt me on those new models! 

jbhiller's avatar
jbhiller OP
1,446 posts
 

Thank you Ralph! 

The unit had some super microphonic tubes (CV181s) that sounded sublime but were so noisy that after several hours of low volume play, the tubes could pick up nearly any activity in the room and subtlety amplify it, which I've never experienced (outside of guitars, only 10 year of tube experience here). 

I've got a pair of run-of-the mill reissue Tung Sol and EH in there now and things are quiet. 

I'll open the unit up shortly to see if there's a bypass cap on the power switch.  I could always replace it for like uF/voltage to see if that helps. 

 

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