electronics question

shwashwa · #1 03-30-2006, 09:48 PM

would there be any harm in running my 2 pickups into 2 seperate preamps and then running them into a Y adapter and then into the input of my amp, effectively creating my own blender?

mje · #2 03-30-2006, 09:51 PM

Probably not. But to be on the safe side I'd use some sort of resistive mixer- just two resistors or a potentiaometer and the necessary hardware.

shwashwa · #3 03-30-2006, 10:00 PM

hmm, can you put that in english for me? and describe what function the resistors would serve? thanks

shwashwa · #4 03-30-2006, 10:08 PM

while we're speaking of resistors, how dificult would it be to make my own 2 channel blender with a 10m ohm input impedeance and only volume controls, nothing else??
also, for the origional question, the resistors in the individual preamps wouldnt suffice?
thanks

seamonkey · #5 03-30-2006, 10:28 PM

Little mini mixers are cheap
http://www.wwbw.com/Behringer-MICROM...-i156794.music

Rolls, Nady, also make them.

10M is pretty high. Did you mean 1M?

shwashwa · #6 03-30-2006, 10:38 PM

no, i meant 10, in case i wanted to plug my piezo directly into it. but if i'm preamping first, i guess i wouldnt need that high. is there a down side of having it that high if i'm preamping the signal first?

Quote:

Originally Posted by seamonkey

Little mini mixers are cheap
http://www.wwbw.com/Behringer-MICROM...-i156794.music

Rolls, Nady, also make them.

10M is pretty high. Did you mean 1M?

shwashwa · #7 03-31-2006, 06:50 AM

i actually have one of the ART mixers, but the quality is so low that i was considering using a Y cable. i guess there are resistors in the mixer, that's why there is an input impedance , right? the schematic has a squiggly line, that's the resistor, no? anyway, i guess i can use that until the jacks break, and they will, then i'll get them replaced or get another one.

new question, i'm interested in getting/making a buffer with 10m input impedance so that i can use my upright with any old electric bass preamp. there are some nice ones out there, but the impedances are not optimal. is this practical? do i need a volume control on it or can i just run the signal straight through? raven labs made a product like i'm describing, but you can't find them these days..

seamonkey · #8 03-31-2006, 11:40 AM

Quote:

Originally Posted by shwashwa

...

new question, i'm interested in getting/making a buffer with 10m input impedance so that i can use my upright with any old electric bass preamp. there are some nice ones out there, but the impedances are not optimal. is this practical? do i need a volume control on it or can i just run the signal straight through? raven labs made a product like i'm describing, but you can't find them these days..

Search around this board for "piezo" and fdeck
He has a preamp design that looks great.

I currently use a Behringer ADI21 V-tone preamp ($30 USD) with a realist (piezo). To let me plug into a balanced mic input on a PA. But it also has a line out. Works good for me.

drurb · #9 03-31-2006, 12:14 PM

Quote:

Originally Posted by shwashwa

would there be any harm in running my 2 pickups into 2 seperate preamps and then running them into a Y adapter and then into the input of my amp, effectively creating my own blender?

Harm no, crapshoot yes. Let us suppose that we are discussing two identical pickups and two identical pre-amps. What is to be gained (pun intended)?

I assume gain is not the issue if you are using active devices, such as pre-amps. You may be hoping for better coverage of the instrument's response by placing one pickup on the treble side and one on tha bass.

What is to be lost? Well, depending on the relative phases in which the pickups will be driven, perhaps a substantial amount!
I suspect this will be a great deal of inconvenience and tweaking for very little benefit.

mje · #10 03-31-2006, 12:17 PM

Quote:

Originally Posted by shwashwa

hmm, can you put that in english for me? and describe what function the resistors would serve? thanks

The resistors would isolate the output of the two preamps from each other.

shwashwa · #11 03-31-2006, 03:19 PM

2 different preamps and 2 different pickups in 2 completely diferent locations... only one will be on the bridge...i need to blend them and put them into one input on my amp... i dont want to buy a blender, because i have one, and i dont like it. i do however, have 2 other preamps that i like for each pickup, and i want to convert them into a blender cheaply by they use of a small mixer or a y adapter. as i stated, i have an ART mixer, and it's very flimsy. it's a matter of time before it breaks.

Quote:

Originally Posted by DRURB

Harm no, crapshoot yes. Let us suppose that we are discussing two identical pickups and two identical pre-amps. What is to be gained (pun intended)?

I assume gain is not the issue if you are using active devices, such as pre-amps. You may be hoping for better coverage of the instrument's response by placing one pickup on the treble side and one on tha bass.

What is to be lost? Well, depending on the relative phases in which the pickups will be driven, perhaps a substantial amount!
I suspect this will be a great deal of inconvenience and tweaking for very little benefit.

shwashwa · #12 03-31-2006, 05:48 PM

here's another question. is there any disadvantage to having a preamp or blender with a 10m ohm input, even with magnetic pickups? in the raven labs manual, they recommend using the 10m ohm input if you're only using one channel, regardless of what type of pickup it is...i guess what i'm looking for now, is a way to run my piezo or any other pickup i want, blended, into the input of any bass guitar preamp that i want, without too many gain stages and eq stages. i just want a buffer, and i want to do all the eq in the actual preamp. maybe what i'm looking for is a 2 into one DI with hi impedance inputs? if i'm completely lost, please enlighten me...

shwashwa · #13 03-31-2006, 06:06 PM

here i am again... is this what i'm looking for?
http://www.lnrmusic.com/demeter.html
2 piezos into 2 of these into my little ART mixer into the preamp of a bass guitar amp ? would this allow me to use the piezo with an amp origionally intended for bass guitar?

mje · #14 03-31-2006, 06:50 PM

Quote:

Originally Posted by shwashwa

here's another question. is there any disadvantage to having a preamp or blender with a 10m ohm input, even with magnetic pickups?..

Yes, often magnetic pickups are really designed to work into around 1M or less. You don't need 10Mohm except for piezos, and then it should be mounted as close as possible to the piezo. Too high an input impedance will also result in higher cable noise.

fdeck · #15 03-31-2006, 07:40 PM

Quote:

Originally Posted by seamonkey

Search around this board for "piezo" and fdeck
He has a preamp design that looks great.

I currently use a Behringer ADI21 V-tone preamp ($30 USD) with a realist (piezo). To let me plug into a balanced mic input on a PA. But it also has a line out. Works good for me.

Thanks for the kind words. I have moved and updated my web page:

http://personalpages.tds.net/~fdeck/bass

You could try a "Y" cable with a resistor in series with each leg. Use 10k if driving the signal input of your amp, or 1k if feeding the effects return. The preamps should be able to handle either load, and the low resistance will minimize adverse effects from the entirely passive circuit. You will lose 6 dB in each channel, which you can easily recover with your gain knobs.

shwashwa · #16 04-01-2006, 07:09 AM

gadzuks i think that preamp is what i've been looking for! just for my info, would a DI box with a high impedance input like the demeter be appropriate for sending to the normal input on he front of the amp?

Quote:

Originally Posted by fdeck

Thanks for the kind words. I have moved and updated my web page:

http://personalpages.tds.net/~fdeck/bass

You could try a "Y" cable with a resistor in series with each leg. Use 10k if driving the signal input of your amp, or 1k if feeding the effects return. The preamps should be able to handle either load, and the low resistance will minimize adverse effects from the entirely passive circuit. You will lose 6 dB in each channel, which you can easily recover with your gain knobs.

fdeck · #17 04-01-2006, 09:24 AM

Quote:

Originally Posted by shwashwa

gadzuks i think that preamp is what i've been looking for! just for my info, would a DI box with a high impedance input like the demeter be appropriate for sending to the normal input on he front of the amp?

So long as the input impedance is a Megohm or higher, you should be OK.

shwashwa · #18 04-01-2006, 11:08 AM

the input impedance on the bass amp or the DI? the demeter is something like 20M ohm... i guess what i'm asking is will the di buffer the signal enough to run it into the normal bass amp with a 1/4" jack, not an xlr?...

Quote:

Originally Posted by fdeck

So long as the input impedance is a Megohm or higher, you should be OK.

fdeck · #19 04-01-2006, 11:23 AM

Quote:

Originally Posted by shwashwa

the input impedance on the bass amp or the DI? the demeter is something like 20M ohm... i guess what i'm asking is will the di buffer the signal enough to run it into the normal bass amp with a 1/4" jack, not an xlr?...

Yes, it will be fine. The only real difference between running 1/4" or XLR is that XLR will cut down on noise in situations where you have really long cable runs or extreme electromagnetic interference. But it's seldom an issue for the typical bass rig situation.

Driven by the preamp, the input impedance of the bass amp will not matter.