No eq in passive mode...

[BrunoBass]

I have a RMI Boomerang Jive, which is wonderful bass. I always play it with the active circuitry engaged, but at the weekend I removed the battery to fit a replacement. Whilst the battery was out I decided to see how it sounded in passive mode. It sounded great, just like the active tone only with a lower output. However none of the eq controls worked. I inserted a fresh battery and switched back into active mode - the eq works. Back into passive mode with the battery still inserted and none of the eq works. By this I mean the bass, mid and treble controls have no effect on the signal in passive mode. This isn’t a big problem as I only really use the bass in active mode, but I wonder if this is a fault? I assume it must be, as the eq controls work on every other (passive) bass I own.......!

What’s causing this and is it easily rectifiable?

Thanks.

[jrixn1]

7 minutes ago, BrunoBass said:

Back into passive mode with the battery still inserted and none of the eq works. By this I mean the bass, mid and treble controls have no effect on the signal in passive mode. This isn’t a big problem as I only really use the bass in active mode, but I wonder if this is a fault? I assume it must be, as the eq controls work on every other (passive) bass I own.......!

EQ is generally an active control (offering both cut and boost) and so no I wouldn't expect it to work in passive mode.

What are your other basses which have EQ in passive mode?  Are they a G&L by any chance? (Which is the only bass I can think of right now which has passive high and low EQ i.e. cut only, no boost.)

On the other hand a tone control (like on a P bass) is a purely passive control - but most people wouldn't refer to  it as "EQ"  (even though I suppose it technically is EQ i.e. it's affecting the response at certain frequencies).

[itu]

@jrixn1 answered this, but once more.

If the preamp module was active from start to beginning (vol, blend, bass, treble...), the bass would be muted without an energy source (battery). I am pretty sure that your bass has only active tone control, so vol and blend are passive (high impedance), that is simple potentiometers without electronic buffers.

Active tone equals amplification of the signal, as the tone shaping would otherwise mean only reduction of certain frequencies. Active tone can amplify AND attenuate the signal. This is why preamps need an energy source (usually a 9 V battery).

Passive tone can only reduce the signal level.

If the bass has a true active preamp (practically a mixer), it should cover all adjustments: blend, vol, tone controls. These are somewhat rare, but there are few from EMG, and John East.

Edited November 20, 2019 by itu

[EBS_freak]

4 hours ago, itu said:

If the bass has a true active preamp (practically a mixer), it should cover all adjustments: blend, vol, tone controls. These are somewhat rare, but there are few from EMG, and John East.

Somewhat rare? Umm. I think I'd disagree with that one!

[Hellzero]

I think @itu means full active circuitry including volume and blend, which is rarer, but not that rare. EBS, Audere, some Bartolini's, EMG, John East and some others have these features.

Otherwise volume and blend are passive in most of the preamps.

[lemmywinks]

Would probably be a simple job to add a passive tone rolloff before the bass signal goes to the preamp. All basses with an active/passive switch should have this IMO but it's not something you see too often, mind you an active/passive switch itself seems to be uncommon too.

[itu]

Thank you @Hellzero

There are few fully active, but a complete list might be good.

John East & EMG BTS.

bartolini has only AG2BP & MPB1 that I know of and have two channels.

Kubicki, WAL, Zon?

[Hellzero]

John East

EMG BTS and BQS

EBS-PRE

Leduc EL-5 and EL-10

Audere

Wal

Schack BC3P

Marleaux ProgramAble

Vigier Nautilus

Bartolini AG2P and MPB1

...

 

Edited November 20, 2019 by Hellzero