Is there any reason a rack EQ couldn't produce near identical results as the onboard EQ?

[erickompositör72]

Not trying to start an argument; would actually just prefer if some would offer insight purely from a standpoint of understanding circuits/electronics.

I understand that the onboard EQ is on 40v rails (whatever that means), as opposed to a 9v pedal- is that correct? Therefore, the pedal is easier to overdrive than the onboard?

In my personal experience, comparing the onboard EQ in a Studio Preamp to the pedal EQ produced quite a profound difference in lead tone: the crispness in the attack, and the envelope of the onset of the note was watered down substantially, making the lead sound less "liquid" and "juicy;" a slightly more muddled attack.

1. Couldn't one obtain a rack EQ that is just as capable as the onboard, due to higher voltage than 9v?

2. The other issue I've read is that there is some capacitor hooked up to the onboard (excuse my complete lack of electrical circuit understanding) which allows more low frequencies to pass through. However, some people prefer the sound of this circuit (all else equal) without the EQ and this capacitor in it. I know my Studio Preamp sounds way sweeter through the power section of my IIb S (no EQ) than it does through my IIb DRGX (of course, not apples to apples, but it's all I can go on now...). I've actually tried the StudPre using it's own EQ through both, and using the DRGX's EQ; my favorite (FOR LEAD! rhythm is best on the DRGX IMO) is StudPre (w/ EQ) through the IIb S (no onboard EQ).

3. Another issue I've read is that it's not in the same place in the circuit (fx loop vs onboard). Could a Mark II be mod'd to actually put the fx loop in the same spot in the circuit as the onboard EQ? Surely, this would only be a mod for the obsessive type....

 

[woodbutcher65]

Of course it can. But it can do so much more. The 5 band EQ is a coarse, crude tool, while a 1/3 octave 31 band EQ is a precision shaping tool that, if tweaked out control by control with care, can push your tone to absolute perfection.

I always favor having a 1/3 octave EQ in my effects loop. Every other effect can be taken out or turned off but the EQ is always there to make a good tone better.

 

[dtrax]

I understand that the onboard EQ is on 40v rails (whatever that means), as opposed to a 9v pedal- is that correct? Therefore, the pedal is easier to overdrive than the onboard?

Voltage rail just means supply voltage. More supply voltage = more gain (generally), which translates into more headroom.

In my personal experience, comparing the onboard EQ in a Studio Preamp to the pedal EQ produced quite a profound difference in lead tone: the crispness in the attack, and the envelope of the onset of the note was watered down substantially, making the lead sound less "liquid" and "juicy;" a slightly more muddled attack.

This could be anything from an inferior design (on the part of the pedal), an impedance mismatch, too long a cable, etc.

1. Couldn't one obtain a rack EQ that is just as capable as the onboard, due to higher voltage than 9v?

Sure. But said EQ will not have the same circuit as a Mesa GEQ, so expect some differences.

2. The other issue I've read is that there is some capacitor hooked up to the onboard (excuse my complete lack of electrical circuit understanding) which allows more low frequencies to pass through. However, some people prefer the sound of this circuit (all else equal) without the EQ and this capacitor in it. I know my Studio Preamp sounds way sweeter through the power section of my IIb S (no EQ) than it does through my IIb DRGX (of course, not apples to apples, but it's all I can go on now...). I've actually tried the StudPre using it's own EQ through both, and using the DRGX's EQ; my favorite (FOR LEAD! rhythm is best on the DRGX IMO) is StudPre (w/ EQ) through the IIb S (no onboard EQ).

I'm guessing you're referring to the blocking cap. That capacitor needs to be there for the amp to function. A side effect is that coupling caps form a HPF with the following stage. If they're large (IIRC a MkIIC+ uses a 47nF) then the LF loss isn't a big deal (and likely the amp was voiced to particular value cap). Either way, looking over the schematics, it seems as though the GEQ models always pass signal through the active circuitry, even when bypassed. So, I suppose people's ear steers them to a "purer" signal path.

3. Another issue I've read is that it's not in the same place in the circuit (fx loop vs onboard). Could a Mark II be mod'd to actually put the fx loop in the same spot in the circuit as the onboard EQ? Surely, this would only be a mod for the obsessive type....

Nope. The onboard EQ is fed directly from the FX return recovery stage, which then feeds the poweramp. At least that's how the IIC+ and IV are wired.

At the end of the day, there were SO MANY differences between models, revisions, etc of older Mark series Boogies. Everyone has their theories on why one is better than the other, and you'll drive yourself nuts trying to make sense of it all. Don't let me stop you though. Carry on. :mrgreen:

 

[erickompositör72]

....

At the end of the day, there were SO MANY differences between models, revisions, etc of older Mark series Boogies. Everyone has their theories on why one is better than the other, and you'll drive yourself nuts trying to make sense of it all. Don't let me stop you though. Carry on. :mrgreen:

Thank you for the thorough response! What I'm mostly hoping is that I can achieve some tone-sculpting, while still getting just as "pure" a signal going into the power amp section (as compared to an on-board EQ). I understand it may be slightly different- that doesn't bother me.

Luckily, I'm not trying to duplicate a particular tone, I'm just trying to get the best tone I possibly can (which my IIc+ HR with the 100 PT has already allowed me to achieve!).