equalizer question

[superseadragon]

I am planning on building this Equalizer for a bass preamp. I was going to buy the parts but I am not sure what the wattage rating for the resistors and pots are. Anyone have an educated guess? Equalizers aren't affected by bass signals like amplifiers are right? I know most of the time bass amps have to be more robust to handle the bass signal. Does it matter with EQ's?

[superseadragon]

this is the EQ I was planning on building sorry forgot to put it in last post.

[radtech]

The signals in an equalizer are very low power, 1/4 watt resistors should work fine, you could probably even go with 1/8W, especially if you wanted to do surface mount.

The supply voltage is +-15V, and the smallest value resistor is 10K, wattage is E^2 / R, so the most DC power any of them could possibly see is (30*30)/10K or 0.09 watts.

[superseadragon]

radtech thanks a bunch. Do you think that there is any problem with exchanging the EQ from my previous post with the one in this preamp?

Preamp: http://www.albertkreuzer.com/pics/el...eamp_sch21.gif

Another question. Is there a standard pk to pk voltage max that preamps output? I am going to build one of quasi's amps
I just want to be sure that at max volume on the preamp i am not going to clip from the power amp and that I am not wasting too much wattage (too much head room)

[superseadragon]

can anyone explain what the purpose of the 2 inputs in this preamp?
It is the LOW and the High inputs. is it just putting a low and high freq channel together?

[radtech]

Those should be high and low level inputs, it's hard to tell what he's trying to do there though...
You'll notice the switched jack contact is grounded on the high jack, but connected to R2 on the low jack. When you pug into high it opens that gound contact and the signal goes through the two resistors in parallel , when you plug into the low jack it opens the contact to R2 and the signal goes through R1 and R2 in series to ground forming a voltage divider. Seems like the jacks should be labeled the other way around???

[AKN]

Hi,

Originally posted by superseadragon
can anyone explain what the purpose of the 2 inputs in this preamp?
It is the LOW and the High inputs. is it just putting a low and high freq channel together?

Two input jacks, only one of them to be used at the same time. Approx half sensitivity on low input jack.

Originally posted by radtech
Seems like the jacks should be labeled the other way around???

Maybe it means high and low sensitivity, then it's labeled correct.

Both jacks grounded when nothing is connected, good.

[superseadragon]

Ok so there should be no problem in leaving out the LOW input. also this preamp requires me to have BF245 fets. I can't find them anywhere. Can I replace them with any other model trasistor without huge changes to resistors/caps?


Oh one more question. With this preamp would there be any problem in leaving out the EQ cct he has and changing it with this EQ

[AKN]

Ok so there should be no problem in leaving out the LOW input. also this preamp requires me to have BF245 fets. I can't find them anywhere. Can I replace them with any other model trasistor without huge changes to resistors/caps?

A quick look around reveals that at least Farnell has BF245.
But someone may have experience with good substitutes.

Oh one more question. With this preamp would there be any problem in leaving out the EQ cct he has and changing it with this EQ

Yes there should be no problem exchange the EQ circuit, Just leave out R1 in the new EQ otherwise you will slightly upset the working point in T2.