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Hagerman Bugle turn-on pop

post #1 of 8
Thread Starter 


I have one of these preamps that I built in a cigar box. I turn it on with a regular DPDT toggle switch. When I turn it on, my stereo makes a big nasty POP sound, so I usually turn it on with the volume down. However, I want to make a circuit that automatically turns it on when my turntable tonearm un-docks. So I have to do something about the pop.

What causes the pop? Would an RC circuit on the power rails, so the voltage slowly builds up to the rail voltage, make it better, or is it something else?

post #2 of 8

The standard order for turning on and off components.


Turn ON:

1] High gain mic & phono pre-amps

2] Control & effects units.

3] Power amps & powered speakers & subs.


Turn OFF:

1] Power amps & powered speakers & subs.

2] Control & effects units.

3] High gain mic & phono pre-amps

post #3 of 8
Thread Starter 

The problem is, I keep leaving my Bugle on and running the battery down. I need some way to turn it off automatically when I'm done listening (most records are 45 minutes or less so a fixed 1-hour timer would be fine). I could use a timer, but I can't think of a cheap easy way to do that in my small Bugle case. I thought it would make more sense if I just had it turn on when I un-docked my turntable tonearm. It's just the pop that's a problem.

post #4 of 8

Get a regulated wall power supply and never turn it off. 

post #5 of 8
You're running this on the 9v's, not a power supply?

I have a Bugle with the old bipolar 15v supply and it has a slight thump, if I remember correctly (I turn down the volume on my amp before turning it off out of habit).
post #6 of 8
Thread Starter 
I'm running 12-volt sealed lead-acid batteries.

Would it work to put crossed zener diodes on the outputs? I could play a loud record and view the preamp output on a scope to determine the approximate peak voltage level, then use diodes with a breakdown voltage slightly higher than that so it doesn't affect the music, but clamps the turn-on pop or other large signals that might occur if I drop the tonearm or something. Bad idea?
Edited by trains are bad - 12/25/13 at 3:29pm
post #7 of 8

Hmm, this is an interesting potential project.  Not long ago, I was thinking about building my turntable and preamp into a single enclosure (with a single power switch).  A separate 'stand by' switch for the outputs would be a quick and dirty solution for the pop, but it doesn't solve the on/off battery drain issue.


What kind of turntable do you have and how is that switched?

post #8 of 8
Thread Starter 
It's a Technics 1700. It has auto-turnoff, which is part of the problem, because I let the record play to the en and it safely stops itself, but then I forget to turn the preamp off. The batteries last for over a year without charging if I don't forget to turn it off.

I can easily detect when to switch the preamp without modifying the turntable by either using a photo detector on the tonearm parking position, or with a photo sensor on the strobe lamp.

I really can't think of a reason the clamping diodes wouldn't work. I don't have an aesthetic objection to the pop I just need to turn it down so I don't abuse my speakers.
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