Equalizer with only 3V supply voltage

bassyes · #1 01-09-2011, 01:15 PM

In my Ibanez SR5006e bass, a 6 string Wenge/Bubinga neck on Mahogany, the equalizer is not properly working. The midrange Q (bandwidth) shows no and the treble Boost/Cut knobs shows only a small effect. The corresponding electronics is a Power Curve III EQ with only 3V (2*1.5V) supply voltage. The electronics has been replaced. However the effect/improvement was only small. In the previous version the Mid Boost was weaker. Switching off electronics leads to a brighter, more direct sound. Batteries are ok. Does it make sense to increase the supply voltage? The included ICs of the circuit are specified for higher voltages.

darkstorm · #2 01-09-2011, 02:47 PM

Never heard of a onboard or other preamp that only nuses 3 volts. 9 volts and 18 volts is the standard for such. Sounds like the replacement eq is bad. What kind of batteries does it use? Then expensive button batteries are only ones I know of that are 3 volt.

bassyes · #3 01-09-2011, 03:35 PM

Yes, these are two normal AA= 2* 1.5=3V. I used alkaline, just as delivered.

darkstorm · #4 01-09-2011, 07:41 PM

O, ok, 2 AA size baterries. Much better choice then them silly expensive little button batteries. Still, thats first Ive heard of 3volt preamp. Are you sure someone didnt use the design from a pocket radio that uses 2AA b atteries for its power? Thats only source of 3volt versions I can think of offhand. Still, that could work fine if battery life is long enough (4 months or more).

**line6man** · #5 01-09-2011, 08:42 PM

3V!?
I can't imagine there would be any headroom with the transistors running a 3V supply.

fdeck · #6 01-09-2011, 08:58 PM

Quote:

Originally Posted by bassyes

In my Ibanez SR5006e bass, a 6 string Wenge/Bubinga neck on Mahogany, the equalizer is not properly working. The midrange Q (bandwidth) shows no and the treble Boost/Cut knobs shows only a small effect. The corresponding electronics is a Power Curve III EQ with only 3V (2*1.5V) supply voltage. The electronics has been replaced. However the effect/improvement was only small. In the previous version the Mid Boost was weaker. Switching off electronics leads to a brighter, more direct sound. Batteries are ok. Does it make sense to increase the supply voltage? The included ICs of the circuit are specified for higher voltages.

Do you know the types of IC's used?

**line6man** · #7 01-09-2011, 09:01 PM

Quote:

Originally Posted by fdeck

Do you know the types of IC's used?

That's what I'm wondering.
Someone send me a spec sheet!

fdeck · #8 01-09-2011, 09:36 PM

It seems odd to me because there are relatively few op amp types that can operate on voltages as low as 3 V.

**line6man** · #9 01-09-2011, 09:50 PM

Quote:

Originally Posted by fdeck

It seems odd to me because there are relatively few op amp types that can operate on voltages as low as 3 V.

Exactly.

bassyes · #10 01-10-2011, 03:38 PM

The larger chip is a 76E884T TLC 2260C with 14 legs. However this name makes no sense. So most probably its a TLC 2264C, a double advanced TI LinCmos opamp, specified for battery operations with supply plus/minus 2.2 to maximum plus/minus 8V. Does this mean that I can safely use a single 9V supply? A second, smaller one has the imprint 503A with 6 legs. This one I cannot find on the net.

ZolkoW · #11 01-11-2011, 12:58 AM

Quote:

Originally Posted by bassyes

The larger chip is a 76E884T TLC 2260C with 14 legs. However this name makes no sense. So most probably its a TLC 2264C, a double advanced TI LinCmos opamp, specified for battery operations with supply plus/minus 2.2 to maximum plus/minus 8V. Does this mean that I can safely use a single 9V supply? A second, smaller one has the imprint 503A with 6 legs. This one I cannot find on the net.

+/- 2.2V is 4.4V minimum > 3V ...
The TLC 2264 is a good choice IMO, eats the same as a TL064, but less noisy. only that 16V max power supply bothers me.

SGD Lutherie · #12 01-11-2011, 10:41 AM

Is this a preamp made for an instrument? The dull tone would imply its input impedance is too low. This would also affect the tone controls since it's limiting the high end.

chucko58 · #13 01-11-2011, 11:19 AM

Quote:

Originally Posted by fdeck

It seems odd to me because there are relatively few op amp types that can operate on voltages as low as 3 V.

Not true any more. The trend in new op amp releases is a MAX supply voltage of 5.5V. Some "high voltage" types go as high as 12V.

The days when op amps were routinely spec'd to at least +/-15V are gone.

ZolkoW · #14 01-11-2011, 01:35 PM

Quote:

Originally Posted by chucko58

Not true any more. The trend in new op amp releases is a MAX supply voltage of 5.5V. Some "high voltage" types go as high as 12V.

The days when op amps were routinely spec'd to at least +/-15V are gone.

...there are many <5V op-amps, but for audio, I don't think, they will ever replace the higher voltage, higher performance ones. and many times you need more than 9V for the headroom, so you can't use these "single-supply" ICs

chucko58 · #15 01-11-2011, 03:14 PM

Quote:

Originally Posted by ZolkoW

...there are many <5V op-amps, but for audio, I don't think, they will ever replace the higher voltage, higher performance ones. and many times you need more than 9V for the headroom, so you can't use these "single-supply" ICs

Agreed. (Though I think 9V gives enough headroom for an on-board preamp.)

Back on topic... A 3V pre would only be useful for low impedance pickups. Most high impedance pickups can easily generate that much peak-to-peak voltage into a typical amp input.

ex-tension · #16 01-11-2011, 03:56 PM

Maybe there is a charge pump type circuit. Probably that 503A IC is a DC/DC converter. Are there inductors around that IC?

This video talks about that 3V preamp:
http://www.youtube.com/watch?v=USTEd-l9Vdc

THIAGO Ibanez · #17 01-11-2011, 04:50 PM

Hi Guys. I also have the same bass IBANEZ SR 5005 EOL. The pre on my bass worked just fine. Ireplaced it bcause i thougt the AGUILAR OBP3 woul trasform my sound but it didnt.
This is the picture of the pre amp that i just replaced for an AGUILAR OBP 3 and i regret it to death. I dint notice any sound improvemet accept the mid EQ frequency switch. Now i Know tha the problem is the PUs not the 3v EQ. When I tap the PUs with a screw driver there is sound just on the left side of the PU (when holding the intrument)
Thats why i think they are not humbackers but single coil.
I cant wait to replace them whith DELANO MC 5 HE/S-L
or DELANO SBC 5 HE/S
What do you guys recomend for a modern sound with scooped mids.

Thanks

THIAGO Ibanez · #18 01-11-2011, 04:51 PM

Thats a great pre amp battery lasts ferever

THIAGO Ibanez · #19 01-11-2011, 07:13 PM

oops that was the wrong one.

bassyes · #20 01-22-2011, 12:35 PM

Quote:

Originally Posted by ex-tension

Maybe there is a charge pump type circuit. Probably that 503A IC is a DC/DC converter. Are there inductors around that IC?

This video talks about that 3V preamp:
http://www.youtube.com/watch?v=USTEd-l9Vdc

Here comes an update on the Ibanez Bass SR5006 with weak equalizer Power Curve III. At the IC that contains the OPs there is really a larger voltage, around two-three times what is supplied by the batteries. Attaching an external power supply I noticed a current of about 35mA at 3V. The circuit sounds better with 4-5V external. Using a 9V block, however, it oscillates and kills the battery in an hour. Fortunately nothing broke. Presently I will continue to use fresh 1.5V batteries and later replace the circuite, may be by Glockenklang. Thanks for the help and info from all of you.