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Double Bass fdeck preamp techie question...

#43
jonphilpott said:
With a battery reading 9.25v, i read ~3.8v on the source of each fet and 6.35v just before the blocking cap, seems right?
Click to expand...

That is not too far outside the bounds of what I would expect. One thing you can also try is to see what kind of output you get directly from the first stage, to divide and conquer.
 
#46
jonphilpott said:
Another question,

Could I take the first stage verbatim and use it as a general purpose phase inverter for use with other instruments, etc?
Click to expand...

Yes. But notice that in my circuit, the output of the phase inverter uses one of the capacitors in the filter as a DC blocking capacitor as well. So, you would want to go from the switch to the output jack through something like a 10 uF capacitor, positive side towards the switch. And then for good measure, I now include a 100k resistor across the final output terminal, which drains charge buildup on the output cable, but I forgot to update my article to reflect that.
 
#47
Just found this thread, and have a couple of questions. I'm using the fdeck pre in the FX loop of my Phil Jones Flightcase 300 amp (it's velcroed to the back of the amp so that the knob is accessible from the top), and it works beautifully. Recently, I'd noticed the volume of the amp starting to fall off, and was wondering if there was something wrong with the amp. Like a dumb hillwilliam from KY, I never thought that the answer might be the battery in the fdeck pre, since the HPF still worked perfectly even as the volume was falling off. After last night's gig, the sound was getting really weird, so (in spite of the fact that I'm a Kentuckian) I got smart and checked the battery anyway. It was dead as a post.

My questions:

1) Which plug on the pre activates the battery - input, or output? I'm guessing input, but once I find out for sure I can know to keep the other one connected at all times.

2) As the battery starts to go, what are the likely sonic repercussions? I'm going to be carrying spare batteries from now on, but if I knew what to listen for, it would be easier to know when to change the battery.

3) Is there an easy way to test 9v batteries, and if so, at what level should one be replaced before a gig in order to keep the sound intact?
 
#48
Chris Fitzgerald said:
Just found this thread, and have a couple of questions. I'm using the fdeck pre in the FX loop of my Phil Jones Flightcase 300 amp (it's velcroed to the back of the amp so that the knob is accessible from the top), and it works beautifully. Recently, I'd noticed the volume of the amp starting to fall off, and was wondering if there was something wrong with the amp. Like a dumb hillwilliam from KY, I never thought that the answer might be the battery in the fdeck pre, since the HPF still worked perfectly even as the volume was falling off. After last night's gig, the sound was getting really weird, so (in spite of the fact that I'm a Kentuckian) I got smart and checked the battery anyway. It was dead as a post.

My questions:

1) Which plug on the pre activates the battery - input, or output? I'm guessing input, but once I find out for sure I can know to keep the other one connected at all times.

2) As the battery starts to go, what are the likely sonic repercussions? I'm going to be carrying spare batteries from now on, but if I knew what to listen for, it would be easier to know when to change the battery.

3) Is there an easy way to test 9v batteries, and if so, at what level should one be replaced before a gig in order to keep the sound intact?
Click to expand...

1. The output activates the battery.

2. As the battery goes down, I would expect noticeable harmonic distortion.

3. You can get a cheap digital voltmeter at a place like Home Depot. In fact, you could drill a couple tiny holes in the battery cover to let you insert the probes. You should be able to let batteries go down to at least 8.5 Volts. If you pickup doesn't have a particularly "hot" output, you may be able to go lower.
 
#49
Since the output activates the batt, me thinks this would be just the thing the Dr. ordered for an onboard device on my Underwood equipped EUB.

Xmas time:hiding:, or at least Thanksgiving is 'a coming!:)
 
#60
Holy carp, the HPF-Pre is a wonder box! I played it for a few hours this morning with a fairly loud band, using my old German bass with Full Circle pickup through a GK 800RB and Bag End Russian Birch cabs with EVM 12L and 15L speakers. I've never had this good of a bowed tone from any amp/pickup/mic/PA/etc. I was using a Lava Cable Retro Coil (disclaimer-I'm a dealer), which rolls off just a touch of highs and the amp set with all of the controls at noon except the boost off. The HPF cleans up the low end beautifully, the slight boost is nice, but it's mostly about matching the pickup to the amp.

No wonder drurb calls it a wonder-box. My drummer loves how we can interact without fighting for sonic space. He's got an active and intricate right foot, and I've been basically forced into playing electric bass with him for the past 15 years. The combination of my new old bass, the Full Circle, and now the HPF-Pre has brought much joy and inspiration to my playing.

Thank you fdeck (and TB for guiding me to you!!
 

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