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Sub Octave (with headroom to handle a hot bass)?

_Some Dude

_Some Dude

Sep 14, 2016
2,380
5,963
#1
I'm looking for an OC-2 style octave that has more headroom to handle a hot bass. Need to do the Muse - Uprising thing.

I have an OC-2, but it clips from the input volume (I play a Spector). I've tried padding down the signal and it works, but that affects how everything else in the chain behaves.

Is there another option that'll get me in that ballpark that has more headroom?
 
#2
The MXR Vintage Bass Octave is essentially a modified modern OC-2 clone (recreated from one of Janek Gwizdala's personal OC-2s) that runs on 18V internally for increased headroom and has a few other useful modern updates (louder output, a clean mid-boost switch). I have 2 OC-2s and the the MXR sounds basically the same to me as a clean OC-2 but without the clipping that my OC-2s could experience (I usually use a compressor in front of my OC-2s set with some volume attenuation to deal with the headroom issues with hotter basses). I haven't owned a Spector and have heard in a few other effects threads that they can be particularly hot basses, so I can’t say for sure that it would handle your bass the same way it handles the hotter basses I have tried it with (I think my Godin A4 Ultra is probably the hottest bass I've used the MXR with, it can definitely distort my OC-2s but the MXR not at all).
 
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#6
The OC-2 can be safely operated on a 12V supply. If you know how to solder, you can also swap two e-caps for ones with higher voltage rating and operate it on 15 or even 18V. The other components can take that no problem, it's just the bulk caps on the supply and virtual ground line that are rated too low for that.

I did some testing and measuring with that pedal a while ago and operating it on 15V doubles the headroom compared to 9V operation so I highly recommend it.

I have also seen units where these caps are higher voltage right from the factory, so it might be worthwhile to check.

The caps in question:
1748582089825.png

On the PCB, these are two biggest caps, so they're relatively easy to spot.

The Behringer octave divider runs on 18V internally and has a lot of headroom on tap. The output at factory values is pretty low though, which is a shame. It can be modified to insane volume levels by changing one resistor, but it's SMD soldering so not for the inexperienced.

Distortion Measurements for the bypassed signal. Findings translate to active fx almost 1:1.
(bright/faint grey line is distortion only, the lower the better):

At 9V the signal audibly distorts (-40dBr) around 1.4Vrms input.

1748582573663.png


15V operation moves that point to about 2.5Vrms and increases overall dynamic range considerably:
1748582710917.png


Further increase to 18V results in yet another increase for distortion free dynamic range with about 3Vrms until audible clipping.
1748582765093.png
 
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#12
sunbeast said:
The MXR Vintage Bass Octave is essentially a modified modern OC-2 clone (recreated from one of Janek Gwizdala's personal OC-2s) that runs on 18V internally for increased headroom and has a few other useful modern updates (louder output, a clean mid-boost switch). I have 2 OC-2s and the the MXR sounds basically the same to me as a clean OC-2 but without the clipping that my OC-2s could experience (I usually use a compressor in front of my OC-2s set with some volume attenuation to deal with the headroom issues with hotter basses). I haven't owned a Spector and have heard in a few other effects threads that they can be particularly hot basses, so I can’t say for sure that it would handle your bass the same way it handles the hotter basses I have tried it with (I think my Godin A4 Ultra is probably the hottest bass I've used the MXR with, it can definitely distort my OC-2s but the MXR not at all).
Click to expand...

I started with the MXR and was clipping it, then switched to the OC-2 before adjusting any settings. I did all the bass/level adjustments with the OC-2. I'm going to go back and try the MXR again to see if I can just pad it down a bit and get it to work.
 
#13
Ratterbass_ said:
The OC-2 can be safely operated on a 12V supply. If you know how to solder, you can also swap two e-caps for ones with higher voltage rating and operate it on 15 or even 18V. The other components can take that no problem, it's just the bulk caps on the supply and virtual ground line that are rated too low for that.

I did some testing and measuring with that pedal a while ago and operating it on 15V doubles the headroom compared to 9V operation so I highly recommend it.

I have also seen units where these caps are higher voltage right from the factory, so it might be worthwhile to check.

The caps in question:
View attachment 7239580
On the PCB, these are two biggest caps, so they're relatively easy to spot.

The Behringer octave divider runs on 18V internally and has a lot of headroom on tap. The output at factory values is pretty low though, which is a shame. It can be modified to insane volume levels by changing one resistor, but it's SMD soldering so not for the inexperienced.

Distortion Measurements for the bypassed signal. Findings translate to active fx almost 1:1.
(bright/faint grey line is distortion only, the lower the better):

At 9V the signal audibly distorts (-40dBr) around 1.4Vrms input.

View attachment 7239583

15V operation moves that point to about 2.5Vrms and increases overall dynamic range considerably:
View attachment 7239584

Further increase to 18V results in yet another increase for distortion free dynamic range with about 3Vrms until audible clipping.
View attachment 7239585
Click to expand...

I took a look, but I can't see the values on the caps. It's a MIJ OC-2 (Octaver with the "r").

In all honesty, considering its age I'd rather leave it stock and pick up something that'll work without mods.
 
#15
_Some Dude said:
I'm assuming it'll get close enough to the OC-2 thing or you wouldn't be recommending it. I'm curious what else I can do with it? It seems quite reasonably priced.
Click to expand...
Absolutely great pedal! Loved it when it came out. Had to sell it back then due to money reasons, but it's basically the only pedal I actually miss sometimes. It can get quite close to the OC-2 vibe but it's not an exact 1:1 type of thing. The other things it can do are mind boggling, especially when paired with an expression pedal.

The Helix/HX platform can also do some really nice OC-2 and beyond sounds. One of the recent updates even included an actual OC-2 model.

_Some Dude said:
I took a look, but I can't see the values on the caps. It's a MIJ OC-2 (Octaver with the "r").

In all honesty, considering its age I'd rather leave it stock and pick up something that'll work without mods.
Click to expand...
Are you powering it with 9V or 12V? The old MIJ pedals are made for 12V wallwarts. There is an internal -3V drop going on that brings the 12V down to battery level 9V. Powering an ACA type boss pedal with 9V will work but it will have less headroom, so maybe double check your power supply to make sure you're not missing out on anything.
 
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#16
_Some Dude said:
I started with the MXR and was clipping it, then switched to the OC-2 before adjusting any settings. I did all the bass/level adjustments with the OC-2. I'm going to go back and try the MXR again to see if I can just pad it down a bit and get it to work.
Click to expand...
I suspect your bass is likely to give issues with most of the analog options then, and I'd tend to agree with the C4 suggestion as it has a tweakable Input Gain setting that seems to have a pretty wide range in my experience (I also have one, but personally much prefer the feel/immediacy of analog pedals for octaves- the octaver tones are definitely killer and very tweakable in the C4 and the Spectrum though). I'm not sure why instruments are made with such uncontrollably hot outputs, as it limits their utility with a lot of effects and even some amplifiers (I've sold multiple basses in the past that had too much output for my FX chain, for me high output is a deal-killer unless I can turn it down internally).
 
#17
Ratterbass_ said:
Are you powering it with 9V or 12V? The old MIJ pedals are made for 12V wallwarts. There is an internal -3V drop going on that brings the 12V down to battery level 9V. Powering an ACA type boss pedal with 9V will work but it will have less headroom, so maybe double check your power supply to make sure you're not missing out on anything.
Click to expand...
9v, but my power supply has a 12v switch. I'll give that a try.
 
#18
#19
sunbeast said:
I suspect your bass is likely to give issues with most of the analog options then, and I'd tend to agree with the C4 suggestion as it has a tweakable Input Gain setting that seems to have a pretty wide range in my experience (I also have one, but personally much prefer the feel/immediacy of analog pedals for octaves- the octaver tones are definitely killer and very tweakable in the C4 and the Spectrum though). I'm not sure why instruments are made with such uncontrollably hot outputs, as it limits their utility with a lot of effects and even some amplifiers (I've sold multiple basses in the past that had too much output for my FX chain, for me high output is a deal-killer unless I can turn it down internally).
Click to expand...

The problem isn't so much that the bass is hot, per se, it's that bassists of yore thought it'd be a brilliant idea to put the equalizer on the bass. Left flat the level is fine, but someone figured out that if you crank the EQ on a Spector it overdrives the preamp.

I don't actually run my bass on 10, but it is up high enough (around 7 or 8) that it's killing my OC-2. I tried dropping it lower, but by the time the OC-2 cleans up it's lost the sound I'm looking for.

sunbeast said:
Here's a useful thread about potential mods to an OC-2 to increase headroom and output: https://www.talkbass.com/threads/oc-2-clipping.1027629/
I do suspect if you found clipping with the MXR VBO that you will probably still find clipping with a modded OC-2 short of swapping out the op-amps, a few capacitors, and providing 18V power
Click to expand...
Right now I'm leaning towards the Source Audio unit. I'd rather leave the OC-2 unmolested. I still use passive Ps and Js when called for, so it'll get set aside for that.
 
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#20
_Some Dude said:
I feel like you guys are trying to tell me something. :)

I'm assuming it'll get close enough to the OC-2 thing or you wouldn't be recommending it. I'm curious what else I can do with it? It seems quite reasonably priced.
Click to expand...
It is truly amazing considering all that is packed into either of the Source Audio pedals Spectrum and C4 Synth, in fact Source Audio is known for packing a treasure trove in every pedal they offer.

Source Audio Spectrum covers octaver and envelope filter needs both touch sensitive and LFO controlled or both plus a wide ranging distortion block that can be fully mixed with the original signal. I can cover octavers from the classic OC2 as well as access other octavers or create your very own concept with Neuro by mixing the 2 octaver engines. Plus it is a full featured envelope filter, two in fact that can be adapted for every bass, style of playing and need. Neuro is the control program that gives access to all the parameters on computer, tablet and phone where you can edit, store, share and access programs created by other players.

Source Audio C4 Synth can do everything that Spectrum but goes far beyond packing a 4 voice modular style synth into a pedal that includes a sequencer.

Neuro 3 gives access and control for every SA pedal, will play demo sounds and allow the user to edit and store sounds when your pedal is not connected, pretty amazing.
 
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