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Double Bass Question on Pickup Impedance Matching
- Thread starter Ethan Eriksen
- Start date
That's the kind of thing us working schmucks have to deal with on a regular basis - even from experienced, well respect FOH engineers. I've had to fight with guys to even keep my PZ-Pre in the chain. They see a bass, and they want to go DI, and a Double Bass is no different to them. Good luck trying to suggest using a mic in those scenarios...I'd rather smile and let them do their thing rather than get into some weird cage-match over impedance loading and authentic acoustic tone
Of course the techs at the festival I did yesterday were extremely accommodating, even with a total of 5 minutes to get the entire band set up.
On the Realist not needing a pre....I posted in another thread recently that a few times I've gone straight into something like a small (16 channel) Soundcraft board and it sounded fine. And by fine I mean no weird piezo squawk that needs to be eq'd out, out other issues like that. Not something I'd do with the K&K (although that works straight into my recording interface, bit that has some kind if impedance switch on it). I put the Realist through my pre mostly for the volume boost (it's very quiet through pretty much all my amps) and for the tone shaping/feedback control.
That's interesting because the Soundcraft specs I found would put those input impedances at 10 kohms max.
It's an older board - It might be awhile til I rehearse with those guys again, but I'll try to find out the exact model. I'm curious about the specs myself.
My frustration with plugging piezo into a DI, a house 'snake' box, etc., is any luck one had without a piezo-oriented hi-impedance preamp is very likely lost...not only the lower input impedance, but the extended cable length....extra cable capacitance with a piezo can reduce the level as well, even if the frequency response remains adequate...and it depends on the characteristics of the pickup...all bets are off predicting what will happen other than probably being not what you want ;O(.
Have a good evening, or morning, whatever the case.
I don't play bass, but I went to a show the other day, and asked the bassist, 'Hey, is that a B-Band pickup? ...D-1? He said, Yeah, I upgraded from the older one...DO you play? 'No'...and he looked at me for a silent couple seconds and we talked about something else. I wondered a little what he thought ;O).
This is just cool stuff...to me, anyway. I don't adhere to artificial boundaries of knowledge. I try to be as aware of what I don't know as what I do. I bought some luthiery books to learn...because it interests me, but I started out certain I would never make anything but sawdust...
Have a good evening, or morning, whatever the case.
I don't play bass, but I went to a show the other day, and asked the bassist, 'Hey, is that a B-Band pickup? ...D-1? He said, Yeah, I upgraded from the older one...DO you play? 'No'...and he looked at me for a silent couple seconds and we talked about something else. I wondered a little what he thought ;O).
This is just cool stuff...to me, anyway. I don't adhere to artificial boundaries of knowledge. I try to be as aware of what I don't know as what I do. I bought some luthiery books to learn...because it interests me, but I started out certain I would never make anything but sawdust...
I find that my piezo (a Rev Solo II) can work well plugged straight into a DI box, provided the venue is using quality active DIs like BSS and I don't use a 20' cable. With cheaper boxes like the assorted Behringer, ART and unbranded ones found in the scruffier venues, I wouldn't like to chance it. I did meet a sound man recently who wanted to put a passive Radial DI in front of my amplifier, which would have been a disaster...
It also seems common now for the smaller PA mixers to have 1M "instrument" inputs on the first couple of channels. I wonder if this is what was going on with the Soundcraft desk mentioned?
Typically I will ask that a mic be placed in front of my bass rather than or in addition to a DI being taken out of my amp. If there isn't a (decent) mic available, I'll ask that the DI-out on my amplifier be used rather than a box in front of it in the signal chain. This way I know that impedance isn't an issue and I can send an EQed signal to the sound board. I know some people frown on this but I rarely touch my EQ during a show as I'm usually able to get it to sound good before-hand. Plus, my EQ typically consists of very small boosts and cuts so anything I do could easily be undone at the soundboard if it really didn't sound good through the PA.
A passive piezo should never be plugged directly into a DI. The DI goes between preamp and amp or into the amps DI out.
Even the few active DI boxes with 1 MOhm input impedance make the impedance load for the piezo higher because amps impedance and DI box impedance are connected in parallel. (But the 1 MOhm resistor usually could be replaced by a 10 MOhms resistor if it is your box, so it would not get critical unless you use a Fishman BP-100.)
Even the few active DI boxes with 1 MOhm input impedance make the impedance load for the piezo higher because amps impedance and DI box impedance are connected in parallel. (But the 1 MOhm resistor usually could be replaced by a 10 MOhms resistor if it is your box, so it would not get critical unless you use a Fishman BP-100.)
Not sure what circuit you're envisioning such that the parallel connection in an active box would be "seen" by the piezo back at the input. Could you explain?
surdopickups
Guest
The T(R)S-in and -out plugs for a DI-box are connected to each other and to the DI-box input stage. The DI-box input with its capacitor in series to the input resistor to ground will be connected in parallel to the capacitor and serial connected input resistor to ground of the amp if the DI box T(R)S-output is connected to the amp.
So for AC input to the DI-box T(R)S-input, the signal goes through both capacitors mostly unmodified and effectively the two input resistors (DI-Box and amp) will be connected in parallel from the signal input to ground.
Sorry for not posting a schematic, I'm really tired from the last week...
Thank you. Ah, so the impedance load, as you said, increases, meaning the impedance seen by the piezo drops.
I use my Fishman ProEQ Platinum as a DI but sometimes I think that it will be better for the sound to use my Fdeck's Series II preamp... is it compliant with the Fishman? what will be first in the chain?
I'm looking for a DI (I don't want to see more Behringer's!). What about the Radial ones? I suppose that an active will be better suitable for my Underwood...
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If you were going to gang the devices, I suggest you put the Fdeck first in the chain.
I completely agree with you...but preventing wrongdoing as far as wanton plugging-into-available jacks goes, one can't control what people will try to do other than yourself.
My daughter can't be bothered with her Baggs Para-Acoustic DI box, then uses the stage mic because she can't hear her pickup signal...then gets feedback, then backs off and isn't loud enough... :O)
- Jul 19, 2000
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- Disclosures
- Owner/President, Gollihur Music LLC
FYI - Radial does now make a couple of direct boxes that are specifically designed for plugging piezo pickups directly into - the PZ-DI and the Stagebug SB-4 Ultra-Compact Active DI for Piezo Pickups - so the "never" should be qualified with an "unless..."
