Ampeg BA500 Input Characteristics (and some signal stuff too) PLEASE HELP!!!

[general lee]

Howdy y'all! I'm new here, but I was hoping that you guys could give me some good advice/info!

(I would also like to apologize in advance...I am an electrical engineer in a time crunch, so sorry if I don't make much sense).

I'm currently designing a pedal that is similar to a switch box (amp selector), but with a few more tricks, and I had some quick questions.

One of the amps I'll be utilizing for this project is a BA500 (the other is a Fender Deluxe 90, but that's a guitar amp, so I don't blame you if you don't give me any info on that).

Anywho, in the pedal, I'm going to set up an op amp as a simple voltage follower to keep the input impedance high (and not lower the quality of the bass signal), but I need to know how much current I need to feed the BA500 and the Fender Deluxe 90.

The specs for either one of those will be good enough (seeing as how one will give me a good approximation of the other).


Thanks!

 

[general lee]

Bump!!!

Gotta order parts by Tomorrow...well...today...

 

[asad137]

Pretty much ANY op amp will have lower output impedance (i.e. more output current capability) than a passive bass. If I were to make a WAG, I'd say that instrument inputs on an amp should have an input impedance of somewhere around 100K or higher.

Asad

 

[general lee]

Pretty much ANY op amp will have lower output impedance (i.e. more output current capability) than a passive bass. If I were to make a WAG, I'd say that instrument inputs on an amp should have an input impedance of somewhere around 100K or higher.

Asad

Yeah...my new set-up involves two voltage follower op amps to supply a high input impedance.

I also included two buffering capacitors to isolate the input signal from a copy of the input signal that I float up 4.5v (so I can keep the op amp's supply voltage in the positive range.

I then dump the output of the op amp (low impedance) through another buffering capacitor (which is also part of a filter for the guitar amp half) and into the amp.

Life is good.

Thank you for your help!



(For reference, I'm using an OP275. Not sure how it will work as a voltage follower...hopefully it will perform well...)

 

[general lee]

For those interested, here is the basic circuit I used:

The input wave is the same as the output (for this setting) and that's the one centered around zero. The wave around the 4.5v mark is the signal present in the DC isolated region between the capacitors:

The following graph shows the filtering capabilities I have with a couple of different input capacitors:

I'm going to accomplish the filtering with the output caps though (I only want to filter one of the channels).

Looks good so far.

Parts ordered.

 

[Emergancy Exit]

ampeg.com for specs on the BA500 go to the BA series.


RMS Power Output: 350-Watts with Internal Speakers
RMS Power Output: 500-Watts with Extension Speakers
LF Driver: 2 x 10" Speakers
HF Driver: 1" Compression Driver with Level
Preamp: Solid-State
Power Amp: Solid-State
Tone Controls: 3-Band EQ
Mid Tone Control: Ultra Mid
Balanced Line Out: Yes, Pre/Post Send, -20dB Pad
Preamp Out/Power Amp In: Yes
Effects Loop: Yes
Dimensions (W x H x D inches): 24 x 23.5 x 17.25
Weight: 86 Pounds


there ya go this is all i can help you with