Making a pedal out of practice amp effects??

Mad_Phingers · #1 03-24-2010, 07:27 PM

I have this Crate GX-15R practice amp with a little 8 inch speaker that I use for noodling and practicing when I don't want to disturb anyone.

It is a faithful little amp, and it has the absolute BEST distortion channel for bass. I can dial in anything from subtle Jack Bruce to face-ripping Cliff Burton. And the little 3 band eq allows me to grab any color I like.

To all you electrical engineers out there. Is there anyway I can turn all of this into an effects pedal? Somehow keep all the knobs working like they do, but remove the power amp and just allow the rest to do its job?

I am gonna try to post some sound clips to see if any of you agree that this thing sounds badazz.

MooseLumps · #2 03-24-2010, 07:29 PM

Probably a large part of the sound is the speaker/box design/amplifier. Just bear that in mind.

Mad_Phingers · #3 03-24-2010, 07:41 PM

I thought about that, although, I have run the speaker ext into my Ampeg 410 and it still sounded great, so that at least rules out the speaker/box design. Leaves the amp tho...hmm

Frettage · #4 03-24-2010, 07:45 PM

Interesting thought. The Roland Bass Micro Cube also has a lot of effects in it (Flanger, Chorus, T-Wah, Delay, Reverb, EQ, plus COSM). Could make very a very nice multi-pedal.

ajota_di · #5 03-24-2010, 07:57 PM

Ghetto rig it up, just go out the headphone out... nothing wrong with that right?

gumtownbassman · #6 03-24-2010, 07:58 PM

something like this..

Sound Chaser · #7 03-24-2010, 08:05 PM

I would love to have the chorus from my Ampeg BA-210SP in a stompbox.

Mad_Phingers · #8 03-24-2010, 08:59 PM

hahaha, Gumtown, that is it!

Mad_Phingers · #9 03-24-2010, 09:14 PM

here are a couple shoddy clips i took with my phone. my strings are also very dead, but try to imagine these pumping through an 810!

Light gain, Ric4003 neck pickup, fingers
http://ia331234.us.archive.org/0/ite...lips/light.wav

Full gain, neck pu first, then bridge pu, fingers
http://ia331234.us.archive.org/0/ite...lips/heavy.wav

dune2k · #10 03-24-2010, 09:17 PM

Quote:

Originally Posted by Mad_Phingers

To all you electrical engineers out there. Is there anyway I can turn all of this into an effects pedal? Somehow keep all the knobs working like they do, but remove the power amp and just allow the rest to do its job?

I'm not an electrical engineer but I can tell you it is in theory possible but It's not going to be cheap neither easy.
You'd have to trace the board (otherwise you'd have to destry the amp), design a pcb layout and then find all the right parts and build it. Whole lot of effort and since you can't do it yourself I guess it's going to be quite expensive...

Easier way would be to write crate what they modled it after and get that effect (or ask them for a schematic).

Mad_Phingers · #11 03-25-2010, 06:43 PM

Quote:

Originally Posted by dune2k

You'd have to trace the board (otherwise you'd have to destry the amp), design a pcb layout and then find all the right parts and build it

Would it be any easier if I don't mind destroying the amp? Honestly, its a $30 practice amp and if I had the effects, I would have no need for the amp...

Is there any way to take the power amp out and just re-route the output signal?

gumtownbassman · #12 03-25-2010, 10:21 PM

The power amp section will be a part of the main board, most likely a power chip.
If you removed the power amp, your sound might not be the same, since the headphones usually run from the power amp section via some attenuation resistors.
I see no problem leaving it as is, or you could remove the internal speaker and cut down the case (as pictured above), the power amp (well 30 watts, lets just call it an amp) won't draw much if it's not driving a speaker, and running from the headphone jack seems to give you 'your sound'.

Mad_Phingers · #13 03-26-2010, 12:04 AM

Actually, the headphone out does not work into an extension cab, there is a separate ext. out for that. If I were to just use the ext. speaker out I would have (have had) some bad output issues and tons of feedback.

I know this sounds kind of silly, but i think its a worthwhile experiment, there's not a lot to lose.

gumtownbassman · #14 03-26-2010, 12:09 AM

i would not worry about the ext speaker output, only use the headphone out into your amp input. And use the Crate only as a preamp/drive pedal.

blastjv · #15 03-26-2010, 04:10 AM

It's funny, I have thought about the same thing. Crate's distortion sounds sick on bass. I have a Crate VTX665B Guitar amp that I really think is the ultimate practice/small gig amp. It sounds better as a bass practice amp than any bass practice amp I've tried. The distortion on that is amazing for bass. I was wondering about how to do this.

Maybe you could run the amp in a bypass loop and switch it on and off that way. Interested to hear if the headphone thing works. Mine does not have a headphone jack, but it has a preamp out...

-JV

Mad_Phingers · #16 03-26-2010, 04:05 PM

i will experiment this weekend.... I could just pull the amp out and stick in my rack.... and i think i have an extra a-b switch lyin around somewheres...

M0ses · #17 03-26-2010, 04:19 PM

That's what I would do. Disconnect and remove the power amp, then put it in a switchable loop.

ajota_di · #18 03-26-2010, 06:14 PM

Why on earth would you bother to remove the poweramp? What's the problem with going from the external cab hookup to your current effects loop? or even from the headphone out? Take the speaker out (as the picture suggests), move the little Crate logo, stick some metal wings on it and throw that bad boy in your rack.

LowWay · #19 03-26-2010, 06:51 PM

I'm no EE, but my guess is that a voltage divider would work:

http://www.epanorama.net/circuits/speaker_to_line.html

Taylor Livingston · #20 03-26-2010, 07:38 PM

Quote:

Originally Posted by LowWay

I'm no EE, but my guess is that a voltage divider would work:

http://www.epanorama.net/circuits/speaker_to_line.html

Not a good idea. That sort of circuit needs power resistors, not just plain 1/4w resistors you get at Radio Shack. You also need to be careful about heat sinking or things will start to melt/blow.

There's no reason to take the output from the speaker out unless the OP likes the sound of overdriving an amplifier chip, which is extremely unlikely.

The preamp/effects are going to be on the same board as the amp section, so removing it is, for the purposes of someone unfamiliar with working on electronics, not possible. And it's not necessary. As some have said, the simple way to do it is tap from the headphone jack. That's not an ideal solution, but the next step up is for you to trace the circuit and find the output from the pre/effects, and solder an output from there. If you don't know how to do that, you'd have some serious reading ahead of you to make it work. The next step up from there is to pay somebody to trace the circuit and copy it, or rehouse it in a huge stompbox enclosure with a jack from the preamp out, and you'd probably be offended at how much someone would charge for that.