fleabag Posted December 30, 2019 Share Posted December 30, 2019 (edited) This is about both amps and bass, so stuffed it in GD Both my gigging basses are passive, and at rehearsals, where i use our guitarist's business warehouse, he has a Trace combo which i plug into, to save dragging my rig there. The Trace has active / passive inputs, and naturally, i used the passive one. He asked why i used passive and i said because i have a passive bass, but his argument was because i go through a Zoom B3 first, the Trace no longer sees a passive signal as the zoom changes the impedance. I wasnt sure what he was talking about, being a bit technically deficient in that area, so is he right ..should i be using the active input ? By the way, he's a clever electronics engineer, and builds upto 48 channel mixing desks for businesses here and Europe. He purchased all ex SSL stock after they closed down ( he was an engineer there ) and builds the desks from scratch. Edited December 30, 2019 by fleabag Quote Link to comment Share on other sites More sharing options...
FinnDave Posted December 30, 2019 Share Posted December 30, 2019 My Jazz bass with a John East pre amp built in works better plugged into the passive input of my Rootmaster head. I was told to use whichever input matches the output level. 3 Quote Link to comment Share on other sites More sharing options...
Jus Lukin Posted December 30, 2019 Share Posted December 30, 2019 (edited) - Edited March 4, 2022 by Jus Lukin 5 Quote Link to comment Share on other sites More sharing options...
Hellzero Posted December 30, 2019 Share Posted December 30, 2019 1 hour ago, fleabag said: The Trace has active / passive inputs, and naturally, i used the passive one. He asked why i used passive and i said because i have a passive bass, but his argument was because i go through a Zoom B3 first, the Trace no longer sees a passive signal as the zoom changes the impedance. I wasnt sure what he was talking about, being a bit technically deficient in that area, so is he right ..should i be using the active input ? He is (technically) right, your passive bass has a high impedance output matching the impedance of the passive input. When going through a preamp or a pedal, this signal becomes a low impedance, so has to go to the active input to have input and output impedances matching. You should have trusted him, because of his background. It's like not trusting the surgeon saying he has to put back that finger that you stupidly cut with your very sharp new knife. That said, you can live with one finger missing as you can live with the wrong input, it doesn't make a great difference... Quote Link to comment Share on other sites More sharing options...
itu Posted December 30, 2019 Share Posted December 30, 2019 (edited) 36 minutes ago, Hellzero said: He is (technically) right, your passive bass has a high impedance output matching the impedance of the passive input. If that amp has a FET-based input, it certainly matches any bass or pedal output. @Jus Lukin wrote wise words: active input is just a pad + that passive input. Many amps have good gain adjustments that cover practically all bass or effects outputs. Some hard loads (usually piezos) are hard for the preamps but most of these FET inputs can eat nearly anything. Edited December 30, 2019 by itu Andphone... Quote Link to comment Share on other sites More sharing options...
BlueMoon Posted December 30, 2019 Share Posted December 30, 2019 59 minutes ago, Hellzero said: That said, you can live with one finger missing as you can live with the wrong input, it doesn't make a great difference... As long as it's not "the finger" that Cuzzie extols as being the only thing that makes gear sound different. 👆 Quote Link to comment Share on other sites More sharing options...
mrtcat Posted December 30, 2019 Share Posted December 30, 2019 Yeah on a trace amp the active / passive switch is nothing more than a pad. His theory is correct but he is assuming that the switch is something different. As long as you have set the gain correctly so the red light isn't on too often then it'll make no difference which way you have the switch pushed. 2 Quote Link to comment Share on other sites More sharing options...
chris_b Posted December 30, 2019 Share Posted December 30, 2019 You want as much signal going into the amp as possible. When there is an active/passive or padded option, I always choose the loudest. If you get clipping either adjust the volume on the bass and amp to get the right level. 2 Quote Link to comment Share on other sites More sharing options...
drTStingray Posted December 30, 2019 Share Posted December 30, 2019 I have found with most active basses that using the passive input is best - however an 18 volt active may well start clipping if you play hard - even a 9 volt might when playing hard. This was something I found when I used an Ashdown. However I always tried to use the passive input as it sounded better somehow, and controlled it from the input volume on the amp and controls on the bass. However, my Mark Bass doesn't have a choice so you just adjust the input gain control accordingly. The original Stingray manual from the 70s refers to the bass having a hotter output than many passive basses and thus needing potentially amp control adjustment to compensate - as people often play a two band Stingray with the tone controls cranked this is possibly true. Outboard powered pedals and preamps do indeed convert the signal to active. Quote Link to comment Share on other sites More sharing options...
fleabag Posted December 30, 2019 Author Share Posted December 30, 2019 Good answers folks As stated, i use the passive input and just boost the gain on the Trace to find the clip point and then back it off so its not lighting up. If i used the active input, i simply have to up the gain to achieve the same clip point and then back it off, so i see no advantage to using the active input Quote Link to comment Share on other sites More sharing options...
TheGreek Posted December 30, 2019 Share Posted December 30, 2019 7 hours ago, fleabag said: he has a Trace combo which i plug into, I can't hear it properly....can you turn it up just a bit... 1 Quote Link to comment Share on other sites More sharing options...
itu Posted December 30, 2019 Share Posted December 30, 2019 4 hours ago, drTStingray said: Outboard powered pedals and preamps do indeed convert the signal to active. The right terms would be that they turn high impedance signals to lo-Z. "Active" is not so accurate word here. 1 Quote Link to comment Share on other sites More sharing options...
Hellzero Posted December 30, 2019 Share Posted December 30, 2019 Exactly what I wrote above. You must be in the wrong thread 😁 : Quote Link to comment Share on other sites More sharing options...
Woodinblack Posted December 30, 2019 Share Posted December 30, 2019 3 hours ago, fleabag said: If i used the active input, i simply have to up the gain to achieve the same clip point and then back it off, so i see no advantage to using the active input The advantage of using the active input, in fact the whole original point of having an active bass is that an active input is lower impedance than a passive input, which means that any injected noise down the length of your cable is reduced. So in my book it is more you should use active unless you have a reason to use passive, which is with a passive instrument you load the pickups too much and reduce your treble. 1 Quote Link to comment Share on other sites More sharing options...
Crawford13 Posted December 30, 2019 Share Posted December 30, 2019 10 hours ago, Jus Lukin said: It's really just a pad, as you might have on a mixing desk, so that if a signal is so hot you can't avoid clipping you can drop the sensitivity of the inout (often by 15 or 20db) so that it can be kept clean. +1 on this. Quote Link to comment Share on other sites More sharing options...
Lozz196 Posted December 30, 2019 Share Posted December 30, 2019 11 hours ago, Hellzero said: He is (technically) right, your passive bass has a high impedance output matching the impedance of the passive input. When going through a preamp or a pedal, this signal becomes a low impedance, so has to go to the active input to have input and output impedances matching. You should have trusted him, because of his background. It's like not trusting the surgeon saying he has to put back that finger that you stupidly cut with your very sharp new knife. That said, you can live with one finger missing as you can live with the wrong input, it doesn't make a great difference... Wowzers, you learn something new every day, this is why I love this forum. As I use a preamp pedal to get my eq this applies to me - just typical that I learn this on the day of my last gig for the conceivable future, Quote Link to comment Share on other sites More sharing options...
fleabag Posted December 30, 2019 Author Share Posted December 30, 2019 2 hours ago, Woodinblack said: The advantage of using the active input, in fact the whole original point of having an active bass is that an active input is lower impedance than a passive input, which means that any injected noise down the length of your cable is reduced. So in my book it is more you should use active unless you have a reason to use passive, which is with a passive instrument you load the pickups too much and reduce your treble. I can try this next rehearsal Quote Link to comment Share on other sites More sharing options...
itu Posted December 30, 2019 Share Posted December 30, 2019 (edited) 6 hours ago, Woodinblack said: The advantage of using the active input, in fact the whole original point of having an active bass is that an active input is lower impedance than a passive input, which means that any injected noise down the length of your cable is reduced... Is it really? The text above mixes stuff quite some. The input is a modern opamp (which are usually FET-based) with very high input impedance. They do not load the source. In a signal line the source has to be lower impedance than the input, or the input will load the source. These opamps have so high input impedance, that they are practically invisible to any modern coil-magnet pickup, hi-Z or lo-Z. Even piezos. "Matching" is used in a funny way here. Bassist @Woodinblack uses lo-Z output to reduce noise and to ignore the load of the cable. High input impedance has nothing to do with that. Only if the input Z would be in close range with the source, there would be reduction of the frequency response. A modern opamp has an input impedance in the GOhm range. Your source, i.e. bass output impedance is probably ten to hundreds of kilos. Come on fellow players, this is basic electronics. Easy test of this is to bypass all hi-Z bass adjustments. This means those cheapo carbon track pots. What happens? Well, there will be more treble, as the pots load the pickups. Easy as that. Lo-Z electronics tackle this issue by using the pots only to affect amplification. The pots do not have to be in the direct signal route. Check John East's creations. Edited December 30, 2019 by itu Andphone issues. Quote Link to comment Share on other sites More sharing options...
Woodinblack Posted December 30, 2019 Share Posted December 30, 2019 (edited) 17 minutes ago, itu said: The input is a modern opamp (which are usually FET-based) with very high input impedance. They do not load the source. Interesting, which amplifiers have preamps with inputs go directly to a modern opamp without a resistor divider then? Certainly nothing I have. I don't have any amplifiers with input anything like a GΩ Edited December 30, 2019 by Woodinblack Quote Link to comment Share on other sites More sharing options...
itu Posted December 30, 2019 Share Posted December 30, 2019 Non-inverting opamp, anyone? If the first stage is inverting, the input Z of the amp can be designed to nearly anything up to around 100 MOhm. By the way, how do you measure your amps' input Z and how much are they? Quote Link to comment Share on other sites More sharing options...
Woodinblack Posted December 30, 2019 Share Posted December 30, 2019 (edited) Apart from the TC (which I havre no idea what is in there), my amps are ashdown which means I can just look at the circuit diagram (although also to be fair, there are no input opamps, just fets or valves but same sh*t, different package). So either 20k or 2m for one, and I don't have the CTM diagram to hand on this machine. eta - I don't think the high and low on the CTM is anything to do with impedance (although I am sure it is different), I suspect it is specifically so that you can overload the input on high and not on low. Edited December 30, 2019 by Woodinblack Quote Link to comment Share on other sites More sharing options...
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