The major difference looks like the boost switch is gone. Other than that I would expect the two to perform in a similar fashion.
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Circuit alteration for preamp
- Thread starter Skywalker83
- Start date
Shouldn't the input opamps + go to Vref through a resistor? I think you are going to mis-bias the opamp.
You are also going to have to be careful with the trim pot. Why not just run the trim pot from input to ground?
Forgot i had that one! your right it is what i'm looking for.
Off to do some changes to the schematic i go
Ok, i started from scratch.
Had a look at another few circuits, and i think i may have a winner!!
I haven't added that component values yet , just thought i'd let you folks have a look at it whilst i go back and do that.
As always comments and crits please!!
Had a look at another few circuits, and i think i may have a winner!!
I haven't added that component values yet , just thought i'd let you folks have a look at it whilst i go back and do that.
As always comments and crits please!!
This seems pretty close to the original with the addition of the mid sweep pots. Is there still a blend pot? Not sure about the switching yet either if you still want passive/active.
The "Input From the DP/PT" on the schematic is the input from the Passive/Active switch.
The blend pot isn't shown in this schematic, this is purely just the active circuit.
Once i get this active circuit finalized i'll post up the passive circuit.
I've decided to go for 2 seperate volume pots , one for the active and one for the passive.
I also may stack the Treble and Bass onto one pot , just to keep the numbers down and free up a bit of space.
The blend pot isn't shown in this schematic, this is purely just the active circuit.
Once i get this active circuit finalized i'll post up the passive circuit.
I've decided to go for 2 seperate volume pots , one for the active and one for the passive.
I also may stack the Treble and Bass onto one pot , just to keep the numbers down and free up a bit of space.
You're going to have a very low input impedance. If you are not careful with the "not shown" part, you are going to seriously load the pickups.
Just a quick question, and you guys seem to REALLY know your stuff. It is a little off topic, but I have a hot soldering iron, and a trip to Radio Shack coming up.
My question is, is it possible to run a Bartolini BD5C in passive? If so what kind of pots should I get(value) and would the above passive schematic minus the active switch work with the Bart.
Like I said, a little off topic, yet not. Thanks guys
My question is, is it possible to run a Bartolini BD5C in passive? If so what kind of pots should I get(value) and would the above passive schematic minus the active switch work with the Bart.
Like I said, a little off topic, yet not. Thanks guys
Oi! Get yer own thread !! lol, kidding.
If the bartolini pickups are passive then, yes it would be possible. if they are active, you could have a similar set up but it would need some electronics in it to feed the active pickups the right volatge.
It also depends on what set up you want. 2 volumes and a tone, 1 volume and tone with blend pot (what i have above). There are several options.
P.S. im not an expert, just learning as i go along.
If the bartolini pickups are passive then, yes it would be possible. if they are active, you could have a similar set up but it would need some electronics in it to feed the active pickups the right volatge.
It also depends on what set up you want. 2 volumes and a tone, 1 volume and tone with blend pot (what i have above). There are several options.
P.S. im not an expert, just learning as i go along.
Thanks for the reply, next time I will start my own thread. lol. I just love the thought of starting a conversation that nobody else is listening to. lol.
Well, It will be a single p/u installation. The Bart preamp died about two years ago, been playing my other basses since. Problem is I can't get any info on the passive/active nature of this p/u. It is a simple two wire p/u, and is sealed all but the bottom. It has a large copper plate across the bottom that the ground/shield wire is soldered to, and an insulated pole not far from there that the hot lead is soldered to.
It has a wire joining the two halves of the bucker together, from two other insulated poles. And finally the last insulated pole has a solder joint to the copper plate. Each of the poles are on the p/u corners.
I do know the p/u is magnetic sans power.
Anything?
Well, It will be a single p/u installation. The Bart preamp died about two years ago, been playing my other basses since. Problem is I can't get any info on the passive/active nature of this p/u. It is a simple two wire p/u, and is sealed all but the bottom. It has a large copper plate across the bottom that the ground/shield wire is soldered to, and an insulated pole not far from there that the hot lead is soldered to.
It has a wire joining the two halves of the bucker together, from two other insulated poles. And finally the last insulated pole has a solder joint to the copper plate. Each of the poles are on the p/u corners.
I do know the p/u is magnetic sans power.
Anything?
Just wire the two wires straight to the jack and see if that works. If it does, it is passive
I believe you are playing very loose with your grounds. The circuit that fdeck pointed out assumes a +/- power supply, so the grounds are really Vref. You seem to be using Vref and ground interchangeably. You might understand which is which but it makes the circuit hard to follow.
I also don't understand the input stage. You are using Vref, but also seem to have added a voltage divider? It also, like I mentioned, is very low impedance and should only be used with an active pickup.
Ok, i've changed the input stage ( i realise now it was set up as an inverting op amp , when the circuit needs a non inverting)
it's basically the same as the guitar preamp circuit input in my very first post. So if you look at it you can get the resistor and cap values
it's basically the same as the guitar preamp circuit input in my very first post. So if you look at it you can get the resistor and cap values
Ok, (Sigh) here's another version. The input stage before the EQ section was taken from a mini preamp circuit i found for a guitar, but i switched a fixed resistor for a trim pot.
Down at the passive section i've added another switch. One that switches between the active volume and the passive volume. If anyone knows of a better way for this to work, without a switch let me know.
Cheers
Down at the passive section i've added another switch. One that switches between the active volume and the passive volume. If anyone knows of a better way for this to work, without a switch let me know.
Cheers
Well you are hanging that high impedance tone pot off the active volume control - not sure how that will work out. I wouldn't think well. I'm assuming the active switch is a DPDT?
Was that the intent - to have the passive tone control in the circuit when you are running active? Seems odd to me. But that's just me
That's really the only thing that jumps out at me from this circuit.
Was that the intent - to have the passive tone control in the circuit when you are running active? Seems odd to me. But that's just me
That's really the only thing that jumps out at me from this circuit.
Another revision., hopefully a step closer to completion.
Yes the passive/active switch is DPDT.
i got a comment from someone on another forum saying
ive done an alteration which i think is based on what he said, but not 100%
Yes the passive/active switch is DPDT.
i got a comment from someone on another forum saying
ive done an alteration which i think is based on what he said, but not 100%
I can't see the picture, but from the previous diagram:
He's correct. Looks like the + and - are reversed on the 3rd. Also, I assume you have dual op amps (1 and 2 on the same chip), so 3 and 4 should be on the same chip. But the pins are reused.
He's correct. Looks like the + and - are reversed on the 3rd. Also, I assume you have dual op amps (1 and 2 on the same chip), so 3 and 4 should be on the same chip. But the pins are reused.
