GoodShowSir Posted July 29, 2023 Share Posted July 29, 2023 Right stupid question, and probably something I should have figured out a while ago. Why do some active basses need two 9v batteries? I think I get it for something like a dual humbucker, but there seems to be others that have it and only single coil? Quote Link to comment Share on other sites More sharing options...
Newfoundfreedom Posted July 29, 2023 Share Posted July 29, 2023 Because they run an 18 volt preamp system instead of 9 volt. 2 Quote Link to comment Share on other sites More sharing options...
Ed_S Posted July 29, 2023 Share Posted July 29, 2023 I've seen some with two where there's a built-in effect or fret marker LEDs etc. as well, so one is for the preamp and the other is for the accessories. Don't think I've ever seen a production bass with two wired for 9v just to extend the runtime, but I believe EMG used to suggest it as an option in their wiring guide alongside the 18v system for increased headroom. 2 Quote Link to comment Share on other sites More sharing options...
fretmeister Posted July 29, 2023 Share Posted July 29, 2023 18V operation is the main reason for increased headroom Quite a few basses with that now. The new Stingray Specials are 18V with 2 batteries for example. 3 Quote Link to comment Share on other sites More sharing options...
TheGreek Posted July 29, 2023 Share Posted July 29, 2023 My Spector 6er has two 9v. I think the only other bass I can recall having two was my Overwater 1 Quote Link to comment Share on other sites More sharing options...
Hellzero Posted July 29, 2023 Share Posted July 29, 2023 Fodera, Sire, Warwick, MTD, Ibanez, Ken Smith, Status (the Hellborg model was even running on 4 batteries, so 36 Volts...), loads of luthiers basses, ... have an 18 Volts preamp installed. 1 Quote Link to comment Share on other sites More sharing options...
itu Posted July 29, 2023 Share Posted July 29, 2023 (edited) Simplified background: Operational amplifiers (opamps) need double sided power. Positive (+), negative (-), and the zero point. A preamp can be built with one sided (with a single 9 V battery), or two sided power (2 x 9 V). Two sided is easier to build, because it is simpler and requires less components (the first battery is the lower side from -9 V to 0 V, and the second from 0 V to +9 V). If a preamp is functional with both options, the circuitry is based on a one sided power, and "an artificial zero point". +9 V 0 V -9 V The preamp sees the lower side (- connected to negative, + connected to 0 V) as negative voltage, and the higher side (- connected together with the first battery to 0 V, + connected to +9 V) as the positive. Opamp is happy with this arrangement. If there's just one battery, the voltage has to be divided with components to positive, negative, and 0 V. More voltage equals more headroom (Status has a preamp running at 4 x 9 V = 36 V, like @Hellzero mentioned), but the output of an ordinary bass is in the ballpark of 1 V (peak to peak). Even a single 3 V battery could be enough to drive a pre. True: depending on the pickups, some transients could reach few volts (peak). [Sometimes it would be wiser to have two batteries in parallel. Then the last drops of the batteries would be used till the very end.] Edited July 29, 2023 by itu additions 3 1 Quote Link to comment Share on other sites More sharing options...
Newfoundfreedom Posted July 29, 2023 Share Posted July 29, 2023 9 minutes ago, itu said: Simplified background: Operational amplifiers (opamps) need double sided power. Positive (+), negative (-), and the zero point. A preamp can be built with one sided, or two sided power. Two sided is easier to build, because it is simpler and requires less components. If a preamp is functional with both options, the circuitry is based on a one sided power, and "an artificial zero point". More voltage equals more headroom (Status has a preamp running at 4 x 9 V = 36 V, like @Hellzero mentioned), but the output of an ordinary bass is in the ballpark of 1 V (peak to peak). Even a single 3 V battery could be enough to drive a pre. True: depending on the pickups, some transients could reach few volts (peak). [Sometimes it would be wiser to have two batteries in parallel. Then the last drops of the batteries would be used till the very end.] I'm glad you made that simple. 🤔 17 Quote Link to comment Share on other sites More sharing options...
fergs40 Posted July 29, 2023 Share Posted July 29, 2023 My Westone Thunder 1A (the later one with the big - Magnabass? - pickup) has two 9v batteries - and that dates from 1986… 1 Quote Link to comment Share on other sites More sharing options...
pineweasel Posted July 29, 2023 Share Posted July 29, 2023 24 minutes ago, fergs40 said: My Westone Thunder 1A (the later one with the big - Magnabass? - pickup) has two 9v batteries - and that dates from 1986… My 1983 Thunder 1A does too, they all had an 18v preamp 1 Quote Link to comment Share on other sites More sharing options...
Hellzero Posted July 29, 2023 Share Posted July 29, 2023 I think Alembic started the "18 Volts" preamps way back in the 70's... In fact they started active basses. Quote Link to comment Share on other sites More sharing options...
theyellowcar Posted July 29, 2023 Share Posted July 29, 2023 I had a Fender Deluxe P/J with an 18v preamp - believe the equivalent models these days (Player Plus) still do as well. Quote Link to comment Share on other sites More sharing options...
GoodShowSir Posted July 29, 2023 Author Share Posted July 29, 2023 Amazing! Thank you everyone! Quote Link to comment Share on other sites More sharing options...
Stub Mandrel Posted July 29, 2023 Share Posted July 29, 2023 Being cynical, it's to provide sufficient headroom for the excessive gain of some active basses. I'd love to know what benefits are gained by the higher output level of active basses beyond generating the requirement for lower gain input stages on amps to compensate. I hardly think it's justified as improving signal to noise ratio or microphones would be boosted to similar levels. Quote Link to comment Share on other sites More sharing options...
itu Posted July 29, 2023 Share Posted July 29, 2023 59 minutes ago, Stub Mandrel said: Being cynical, it's to provide sufficient headroom for the excessive gain of some active basses. I'd love to know what benefits are gained by the higher output level of active basses beyond generating the requirement for lower gain input stages on amps to compensate. This is not that simple. The output level doesn't have to be super high, not at all. Some hi-Z ("passive") basses may even have higher output level. A 9 V battery is an easy option, because it contains enough energy to drive a tiny preamp (usually the tone stack only) for a year or so. The voltage is suitable for an opamp or few. The low output impedance (Z) requires some energy. If the Z is lower, more energy is needed. An NE5534 consumes pretty much energy compared to say, TL07x family, or much newer (and better) opamps. But it is also a very lo-Z output opamp. Alembic used the NE 553x family, and chose an external PSU to drive the high current consumption circuitry. I am not sure, but the PSU could be two sided, someone could maybe verify this? Once more: battery voltage is not directly connected to the output level. Battery powered lo-Z preamp does not have to have higher output than its hi-Z sibling. With all settings maxed out (treble, bass etc.) it is possible, but not a must. 1 Quote Link to comment Share on other sites More sharing options...
Woodinblack Posted July 29, 2023 Share Posted July 29, 2023 Just easy to make an amp with a proper centre zero voltage, rather than one made by making a half 4.5 rail on a 9v system. Doesn't have to be 18v, the original ibanez actives are 2 1.5V but 9v are convenient battery size. 1 Quote Link to comment Share on other sites More sharing options...
Hellzero Posted July 29, 2023 Share Posted July 29, 2023 @itu The Alembic DS5 is a two sided power supply and the bass can also be powered (not that long) with two 9 Volts batteries. 1 Quote Link to comment Share on other sites More sharing options...
Newfoundfreedom Posted July 29, 2023 Share Posted July 29, 2023 14 minutes ago, Hellzero said: @itu The Alembic DS5 is a two sided power supply and the bass can also be powered (not that long) with two 9 Volts batteries. Thanks. That's much clearer. 🙄 4 Quote Link to comment Share on other sites More sharing options...
Stub Mandrel Posted July 29, 2023 Share Posted July 29, 2023 3 hours ago, itu said: This is not that simple. The output level doesn't have to be super high, not at all. Some hi-Z ("passive") basses may even have higher output level. A 9 V battery is an easy option, because it contains enough energy to drive a tiny preamp (usually the tone stack only) for a year or so. The voltage is suitable for an opamp or few. The low output impedance (Z) requires some energy. If the Z is lower, more energy is needed. An NE5534 consumes pretty much energy compared to say, TL07x family, or much newer (and better) opamps. But it is also a very lo-Z output opamp. Alembic used the NE 553x family, and chose an external PSU to drive the high current consumption circuitry. I am not sure, but the PSU could be two sided, someone could maybe verify this? Once more: battery voltage is not directly connected to the output level. Battery powered lo-Z preamp does not have to have higher output than its hi-Z sibling. With all settings maxed out (treble, bass etc.) it is possible, but not a must. I'm not convinced. The majority of pedal effects run happily on 9V. I'm not sure why you should need super low output impedance (unless you want to run old 40R headphones dirct from your bass). Even the venerable 741 is 75 ohms, nothing compared to any amp input. Mic level is usually 2k and line 10k. Quote Link to comment Share on other sites More sharing options...
itu Posted July 29, 2023 Share Posted July 29, 2023 True. But a 741 is a noise machine compared to the low noise NE5534. There are several parametres that require energy. Long ago had a Washburn (a copy of Status) which preamp had a single opamp. It was filed blank, so the actual type was unknown. I decided to try several types, because it was easy, and such ICs were (and are still) pretty cheap. TL071 was just fine, the sound was quite close to the original. Power consumption was just slightly larger. The last in line was this NE. Superb sound, deeper bass, wider response, everything was better. Except it was power hungry (OP series wasn't available at that time). Battery (batteries, to be honest) cried, and I had to change batteries pretty often. Later I studied electronics, and started to understand the details. No, I haven't been very active with designing circuitry, although some time ago I fell in love with the designs of our own @Passinwind. His work is very interesting. I wish at least one preamp will find its way to the basses I work with. Quote Link to comment Share on other sites More sharing options...
kodiakblair Posted July 29, 2023 Share Posted July 29, 2023 Several of my Peaveys needed 2 x 9v, suspect it was the pairing of active pickups with internal preamps . Quote Link to comment Share on other sites More sharing options...
White Cloud Posted July 30, 2023 Share Posted July 30, 2023 On 29/07/2023 at 11:13, GoodShowSir said: Right stupid question, and probably something I should have figured out a while ago. For what it's worth I don't think this was a stupid question at all. 1 1 Quote Link to comment Share on other sites More sharing options...
Gasman Posted July 31, 2023 Share Posted July 31, 2023 MM Bongo runs 18v... Quote Link to comment Share on other sites More sharing options...
ahpook Posted July 31, 2023 Share Posted July 31, 2023 I've converted my Spector basses to run at 18v rather than the stock 9v. Any excuse to switch on the soldering iron 2 Quote Link to comment Share on other sites More sharing options...
kodiakblair Posted July 31, 2023 Share Posted July 31, 2023 1 hour ago, ahpook said: Any excuse to switch on the soldering iron What did you solder ? 1 1 Quote Link to comment Share on other sites More sharing options...
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