10.08.13

Preamp for a bass amplifier.

As with the microphone comparison, we're going to split this up between the sound out of the high frequency cabinet and the low frequency cabinet.

HI FREQUENCY CABINET

[ Last time I did this ] I settled on a "stock" channel of the Sytek MPX-4A preamp for the bass rig's 4 x 10 cabinet. (The Sytek has the option of having a different internal component for a particular channel - an operational amplifier made by the Burr-Brown company. Sytek says it gives a warmer sound; I find it tends to be preferable to the "stock" channels when handling bass-ier sounds. My unit is stock on channels 1-2, Burr-Brown on channels 3-4.)

Since then, I've acquired the dbx 786 preamp. Seems like it might work well on a bass cabinet, right? It's very blue, and that begins with b, just like bass.

1. A Sytek MPX-4A (stock)

2. A dbx 786

The low frequency cabinet is also blended in; it's using the e22s through one of the Sytek's Burr-Brown channels.

There is a slight more bit of detail on the second of these choices, the dbx 786. I don't think that this is entirely due to EPI. This comes through in two ways - you get a little bit more of a sense of the percussive attack as the pick hits the strings and the difference between the two notes in this riff (D and D#) is a little bit clearer. The Sytek would be just fine, but unless it's sorely needed elsewhere, one channel of the 786 will handle the high frequency of the bass cabinet.

LOW FREQUENCY CABINET

This is a similar comparison to what's above with the HF cabinet. In this case, it's the BB channels of the Sytek vs the 786. The HF part here is the RE-20 run through the Sytek's stock channel.

1. A Sytek MPX-4A (Burr-Brown)

2. A dbx 786

Hi end mic on both of these is the RE-20. Both of these mics are run through the Burr Brown channels of that Sytek MPX-4Aii.

This is the kind of thing that makes me wonder if I'm just deaf or what. I really hear almost zero difference between these things. Now, I do notice that differences between things like mics and preamps are usually more evident when listening to high frequency sources than low frequency ones. I even have a theory about why this is so that I'll tell you if you buy me a drink. Still, we are in near-dartboard-toss as far as having a reason to pick one over the other.

I dunno, maybe it's just how very, very blue the face of it is, but something makes me think I can hear a little bit more distinction between the notes using the 786. Again, either would be suited for the job, but we'll just take up the whole bass preamp business using this dbx.

DECISION TIME

- The bass high frequency cabinet will be the EV RE-20 through one channel of the dbx 786 preamp.

- The bass low frequency cabinet will be the Josephson e22s through the other channel of the dbx 786.

- Placement on the RE-20 will be 6cm off-center from the speaker cone. The mic's grill will be 4.5cm back from the cabinet's grill. The LF rolloff switch is on.

- Placement on the e22s will be 6cm off-center from the speaker cone. The mic's grill will be 5 cm back from the cabinet's grill. The mic's polarity is flipped.

The dbx has tone control options like a "Super Low Z" button and a high frequency EQ. I'm not messing with any of that; the unit is being used "flat".

Last on the bass will be relative blend between the HF and LF cabinets, but that's gotta wait until all the rest of the instruments are done.

Next up: mics for the guitar cabinets.

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See how I made the gear not being used look all old-timey sepia? Pretty neat, huh?