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Double Bass External power supply for fdeck HPF pre?

Pings Bass

Pings Bass

bassist, arranger, aelurophile, ਵਿਦਿਆਰਥੀ
Supporting Member
Apr 11, 2018
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Portland, OR
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#1
I keep leaving my HPF plugged in and burning batteries. I can't see any reason an external 9v power supply wouldn't work. Does anybody do this? Any downsides, besides extra cabling to schlepp and rig?

(Searched, but could not find. Feel free to point me to previous discussions if this has already been hashed out.)
 
#4
Pings Bass said:
I keep leaving my HPF plugged in and burning batteries. I can't see any reason an external 9v power supply wouldn't work. Does anybody do this? Any downsides, besides extra cabling to schlepp and rig?

(Searched, but could not find. Feel free to point me to previous discussions if this has already been hashed out.)
Click to expand...

Esteban,
Most of the FDeck's do not have a connector for the 9v Power Supply only the Series 3 Does. I too have dealt with this issue so I simply train myself to disconnect the jack
that switches the power on.
 
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#5
Ric Vice said:
Esteban,
Most of the FDeck's do not have a connector for the 9v Power Supply only the Series 3 Does. I too have dealt with this issue so I simply train myself to disconnect the jack
that switches the power on.
Click to expand...

Training myself to unplug is a problem. Lack of a jack is not a problem.:)
718JAxGlJYL._SL1500_.jpg
 
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#9
CosmicRay said:
Yes, sorry I forgot there are various series. I've the series 3
However I see some good suggestions for your issue......or sell yours and get a series 3....LOL!!!
Click to expand...

Man, I just got that thing! And after seeing my visa bill from last month, I need to seriously take my foot off the GAS!! :laugh:
 
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#11
A very good point, I too prefer having an AC cord for preamps so I have a Grace Designs Felix and the Headway EDB-2 which has a decent AC adaptor.
I can empathize with players who like their current amplifiers that don’t have HPF’s, Phase Reverse, or proper impedance loading. Sometimes if a room is really small, using the Headway with batteries just makes things easier. So there are s few exceptions. :)
 
#12
Batteries have zero AC, so they are very good for low noise audio applications. Good AC driver power supplies with low/no AC part on their DC output are more expensive than the cheap ones that almost always are not useable to replace a battery designed circuit.
Since the current drawn by the HPFpre 1 and 2 is very small it makes sense to design the circuit for a battery to make it cheap and still useable over long time period if used correctly.

If you don't like it that way, find a power supply that was designed to replace a battery in an audio circuit like a stomp box, since that should deliver a clean DC signal.

As far as I remember the version 3 of the HPFpre is more complicated (and therefor a bit more expensive) and draws more current than the previous versions, so therefor Francis might have included a power supply input for this one.
 
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#15
teopatl said:
Sorry to revive an old thread, but the google machine isn't working for me on this (probably user error): anyone know the current draw of the series 3?
Click to expand...
I estimate that the Series 3 should draw about 8 mA, based on the specs for the op amp chip that I use. That's well below the rated output current of practically any wall wart.

There's a tradeoff between operating current and noise for most audio circuits using FETs, and I chose to go with low noise rather than super low operating current.

Just to review the rest of the thread, the Series 1, 2, and 2M all use the same basic preamp circuit, which doesn't play well with external power supplies. The reason is that any amount of power supply noise is coupled into the audio signal. The Series 3 circuit has a property called "power supply rejection" which allows it to operate cleanly on a wall wart.
 
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#17
Hi all, hope it's ok to ask here, can I confirm the 9V switching on the Series 3 is through the Output jack? I.e., it is only if you leave a cable plugged into the output jack the battery will drain, but it's ok to leave one plugged into the input side? Asking because I have mine velcroed to my DB, with a short cable permanently from the pup to the FDeck input side, then I just plug into amp when needed. Thanks!
 

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