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Unable to re-amp bass, w/ same settings as guitar re-amp

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Unable to re-amp bass, w/ same settings as guitar re-amp

Postby mhschmieder » Sun May 14, 2017 12:45 am

I encountered a bizarre problem tonight, but it's also the first time I've ever tried to re-amp a bass track vs. a guitar track.

Using the exact same setup as for guitar re-amping, and the same routing within Digital Performer, I get a 60 Hz hum in the bass head from the re-amper output, with a barely audible bass signal.

If I simply plug that same 1/4" cable into the guitar head, there are no issues -- nor are there any problems when re-amping the Guitar DI track.

Could this be an impedance issue? Mesa doesn't document the impedance of their amp inputs, but I wouldn't think it would be that different between the Bass Prodigy head and the Royal Atlantic head.

I am using the Radial Engineering passive JCR re-amper box. As I couldn't find TRS cables or a 1/4" to XLR of the right gender, I am connecting the third output channel of the RME Fireface UFX to the front of the re-amper using 1/4" TS -- the Radial box itself is balanced and appears to have the same functionality and specs when using the rear XLR input or the front 1/4" input.

From there, a 1/4" goes from the re-amper's output to the amp's input.

There is a ground lift on the re-amper, but it is currently inaccessible to me as it is not a button and I can't reach into my rack to change its setting without first removing the Radial boxes from the rack. Yet I can't see how it would make THAT big of a difference to engage the ground lift.

If I turn up the output level of the re-amper box, the 60 Hz hum gets louder, but the barely audible Bass DI signal does not increase at all (or at least it seems that way). This is another mystery.

Plugging a bass guitar into the amp head does not exhibit this problem; nor does the guitar head gets any mains hum even if the re-amper's output is maxed out.

I feel like I've isolated every possible variable, to no avail. Even switching the re-amper's low-cut filter to off (I use low-cut on guitar tor educe boom) has no impact. The hum doesn't go away if I flip the ground on the Mesa bass head either. And it's there even if DP isn't playing the track that is routed to the re-amper box.

My active monitors are turned off, and all but the necessary output is muted in RME TotalMix. I have verified that the sends in DP are all as expected, with no trim, and a single mono route to the third output channel of the RME Fireface UFX. Identical settings for Guitar DI and Bass DI in DP.
MacPro Quad-Core Intel Xeon (2.8 GHz, 16 GB), OSX 10.12.4, MOTU DP 9.13, iZotope RX 5.0.0
FireFace UFX, Audient ASP880, True Precision 8, AEA RPQ, Radial PZ-DI & Reamp JCR

Eugenio Upright, Dingwall ABI, BB-1025X, 60th P-Bass, Select J-Bass, Geddy Lee J-Bass, Hagstrom Viking Bari
57 Goldtop, Select Strat/Tele, Pro JMaster, RevStar RS502T, G5422-12, EXL-1, J-100 Xtra, E6D, OM-28VTS, E20P-SB, M-20, AC530-12, ABT60
Yamaha WX5, Hammond XK-1c, Minimoog Voyager, Prophet 12
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Re: Unable to re-amp bass, w/ same settings as guitar re-amp

Postby mhschmieder » Sun May 14, 2017 6:06 pm

I'm giving up on re-amping for now, as I can't figure out what's causing the problems -- I just spent several hours trying to narrow down the issues, which are separate for guitar and bass.

For guitar, even if I push up the gain on the Mesa head, and the treble and mids and lower the bass by just a bit, it sounds way different.

Going to an insane volume level with the master level knob on the Mesa head doesn’t change the timbre for the better — the original tracks were much warmer and articulate.

I am wondering if the guitarist had a boost pedal during the sessions, and I forgot to notate that, and it was between the DI and the amp vs. pre-DI?

It makes no sense. Even if I boost the DI track output to account for my giving a lot of headroom, and max the re-amp output, it sounds dark and muffled -- although less boomy due to the amp settings changing a tiny bit.

The bass guitar amp hum remains, and even if I boost the bass DI track by +24dB, the hum greatly overpowers the bass. Ground lift does nothing to alleviate this!

Even stranger, it MUST be at the amp end, because I can cut/paste the bass track to the guitar track to eliminate DAW internal issues/mistakes. And of course sending it to the guitar amp works fine in terms of signal level being high and hum barely existing.

So why does plugging the bass in directly to the amp, or from the regular DI box, not cause this problem? Can a mismatched impedance between re-amp box and amp head make this big a difference? I don't know either impedance as neither is documented.

I am even now using a balanced signal from the audio interface to the re-amp box, and this had only minimal impact on the bass and guitar results.

Perhaps the last time I re-amped, I wasn’t comparing to previously amped tracks and was only dealing with DI-only, so didn’t notice the difference?

Yet one is supposed to be able to get the same results via re-amping as through original amping, correct? My mic changes are NOT the reason -- I only changed the room mic, and yet the close dynamic mic and the mid ribbon mic sound WAY different from before, on the guitar tracks!
MacPro Quad-Core Intel Xeon (2.8 GHz, 16 GB), OSX 10.12.4, MOTU DP 9.13, iZotope RX 5.0.0
FireFace UFX, Audient ASP880, True Precision 8, AEA RPQ, Radial PZ-DI & Reamp JCR

Eugenio Upright, Dingwall ABI, BB-1025X, 60th P-Bass, Select J-Bass, Geddy Lee J-Bass, Hagstrom Viking Bari
57 Goldtop, Select Strat/Tele, Pro JMaster, RevStar RS502T, G5422-12, EXL-1, J-100 Xtra, E6D, OM-28VTS, E20P-SB, M-20, AC530-12, ABT60
Yamaha WX5, Hammond XK-1c, Minimoog Voyager, Prophet 12
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Re: Unable to re-amp bass, w/ same settings as guitar re-amp

Postby mhschmieder » Sun May 14, 2017 6:22 pm

Obviously, I can isolate the guitar timbre difference by recording a fresh guitar DI track on my own, along with miked tracks, and then compare to the re-amped tracks. That will eliminate any mystery about whether the guitarist had intermediate pedals in the signal path that I forgot about.

The bass amp hum is of bigger concern, as it blocks me from re-amping bass entirely, and is a complete mystery that I can't find an explanation for, as everything has already been isolated as a cause other than an impedance mismatch, and/or maybe a problem with the ground lift feature on the Mesa bass amp head.
MacPro Quad-Core Intel Xeon (2.8 GHz, 16 GB), OSX 10.12.4, MOTU DP 9.13, iZotope RX 5.0.0
FireFace UFX, Audient ASP880, True Precision 8, AEA RPQ, Radial PZ-DI & Reamp JCR

Eugenio Upright, Dingwall ABI, BB-1025X, 60th P-Bass, Select J-Bass, Geddy Lee J-Bass, Hagstrom Viking Bari
57 Goldtop, Select Strat/Tele, Pro JMaster, RevStar RS502T, G5422-12, EXL-1, J-100 Xtra, E6D, OM-28VTS, E20P-SB, M-20, AC530-12, ABT60
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Re: Unable to re-amp bass, w/ same settings as guitar re-amp

Postby mhschmieder » Sun May 14, 2017 6:23 pm

Obviously, I can isolate the guitar timbre difference by recording a fresh guitar DI track on my own, along with miked tracks, and then compare to the re-amped tracks. That will eliminate any mystery about whether the guitarist had intermediate pedals in the signal path that I forgot about.

The bass amp hum is of bigger concern, as it blocks me from re-amping bass entirely, and is a complete mystery that I can't find an explanation for, as everything has already been isolated as a cause other than an impedance mismatch, and/or maybe a problem with the ground lift feature on the Mesa bass amp head.

I'll try my EBTech Hum Eliminator between the power cable and the wall, after dinner, as that will probably tell us whether the Mesa Prodigy amp head's ground lift feature is at issue. Sometimes new gear can have problems you don't know about, in features you don't use at all, or rarely use.
MacPro Quad-Core Intel Xeon (2.8 GHz, 16 GB), OSX 10.12.4, MOTU DP 9.13, iZotope RX 5.0.0
FireFace UFX, Audient ASP880, True Precision 8, AEA RPQ, Radial PZ-DI & Reamp JCR

Eugenio Upright, Dingwall ABI, BB-1025X, 60th P-Bass, Select J-Bass, Geddy Lee J-Bass, Hagstrom Viking Bari
57 Goldtop, Select Strat/Tele, Pro JMaster, RevStar RS502T, G5422-12, EXL-1, J-100 Xtra, E6D, OM-28VTS, E20P-SB, M-20, AC530-12, ABT60
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Re: Unable to re-amp bass, w/ same settings as guitar re-amp

Postby mhschmieder » Sun May 14, 2017 8:26 pm

Using the EBTech Hum Eliminator between the bass head and the wall circuit greatly diminishes the hum, but neither eliminates it nor results in a usable S/N ratio for the main audio signal to come through and not still be dominated a bit by the hum.
MacPro Quad-Core Intel Xeon (2.8 GHz, 16 GB), OSX 10.12.4, MOTU DP 9.13, iZotope RX 5.0.0
FireFace UFX, Audient ASP880, True Precision 8, AEA RPQ, Radial PZ-DI & Reamp JCR

Eugenio Upright, Dingwall ABI, BB-1025X, 60th P-Bass, Select J-Bass, Geddy Lee J-Bass, Hagstrom Viking Bari
57 Goldtop, Select Strat/Tele, Pro JMaster, RevStar RS502T, G5422-12, EXL-1, J-100 Xtra, E6D, OM-28VTS, E20P-SB, M-20, AC530-12, ABT60
Yamaha WX5, Hammond XK-1c, Minimoog Voyager, Prophet 12
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Re: Unable to re-amp bass, w/ same settings as guitar re-amp

Postby mhschmieder » Sun May 14, 2017 8:59 pm

I was able to get near-identical results before and after re-amping, on a fresh track I had full control over, with no pedals but using the high gain channel of the Mesa Royal Atlantic head (at 50w vs. 100w) and removing the 15 dB pad from the Radial PZ-DI direct box.

I used my new Eastman T486RB thinline semi-hollow guitar, as it overdrives the easiest of any guitar in my collection, and in a very musical way right from the outset. Lollar low-wound pickups.

The guitarist from the earlier sessions probably had a boost or overdrive/distortion pedal that I forgot to notate in my usually fully-detailed project notes.

At any rate, I don’t feel the re-amped tracks sound as organic, even though timbrally they are now almost identical. The reason is that there are subtle differences in the harmonic structure of the distortion from the overdriven pre-amp, and the rhythmic pulse of these harmonics is different with just the slightest change in levels.

So it seems like too much “fix it in the mix” work is required for really getting inspired and musical results from re-amping vs. original amping. Perhaps re-amping is best used just for doubling with a different amp, than for serving as the main (and/or only) amp tracks.

Perhaps if I had recorded the DI track at near to zero dB peak vs. my usual -12 dB down, the subtle "organic differences" between original miked amp tracks and miked re-amp tracks would diminish, but now it's 9pm and I need to move on to an hour of working on bass parts for one of my bands.

I remain disturbed and perturbed by the hum issue with the bass re-amp attempts, however. I have run out of ideas as to the cause and a potential solution. I only need to re-amp the bassist because he insisted on having his headphones up full blast, and also a few songs had drum bleed in the room mic (but not the ribbon mic 22" from the grille or the MD421 3" from the grille).

For live all-at-once band recordings, I am using a cardioid pattern on the room mic, but prefer the sound and frequency balance of figure-8 overall. Omni gets too boomy, in the room I record in.
MacPro Quad-Core Intel Xeon (2.8 GHz, 16 GB), OSX 10.12.4, MOTU DP 9.13, iZotope RX 5.0.0
FireFace UFX, Audient ASP880, True Precision 8, AEA RPQ, Radial PZ-DI & Reamp JCR

Eugenio Upright, Dingwall ABI, BB-1025X, 60th P-Bass, Select J-Bass, Geddy Lee J-Bass, Hagstrom Viking Bari
57 Goldtop, Select Strat/Tele, Pro JMaster, RevStar RS502T, G5422-12, EXL-1, J-100 Xtra, E6D, OM-28VTS, E20P-SB, M-20, AC530-12, ABT60
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Re: Unable to re-amp bass, w/ same settings as guitar re-amp

Postby daniel.sneed » Mon May 15, 2017 6:06 am

I've made many re-amped guitar tracks with *in-the-box* amps.
Got satisfying results with stock DP amps and cabinets.
BTW, I used both bass and guitar cabinets.
Sometimes I doubled tracks and fed a *guitar channel strip* and *bass channel strip*, starting with hard high / low pass.
In these projects, I ended with none of the original miked amp tracks at all in the mix.
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Re: Unable to re-amp bass, w/ same settings as guitar re-amp

Postby mhschmieder » Wed May 17, 2017 11:33 pm

The guitarist has confirmed that he did not have a boost, overdrive, or distortion pedal at the sessions, but his super-hot EMG pickups may have produced a signal that doesn't re-amp so well?
MacPro Quad-Core Intel Xeon (2.8 GHz, 16 GB), OSX 10.12.4, MOTU DP 9.13, iZotope RX 5.0.0
FireFace UFX, Audient ASP880, True Precision 8, AEA RPQ, Radial PZ-DI & Reamp JCR

Eugenio Upright, Dingwall ABI, BB-1025X, 60th P-Bass, Select J-Bass, Geddy Lee J-Bass, Hagstrom Viking Bari
57 Goldtop, Select Strat/Tele, Pro JMaster, RevStar RS502T, G5422-12, EXL-1, J-100 Xtra, E6D, OM-28VTS, E20P-SB, M-20, AC530-12, ABT60
Yamaha WX5, Hammond XK-1c, Minimoog Voyager, Prophet 12
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Re: Unable to re-amp bass, w/ same settings as guitar re-amp

Postby mhschmieder » Sat May 20, 2017 9:30 pm

I reviewed the signal flow within RME TotalMix a bit more carefully today, and noticed that Analog 3-4 were stereo-bound both for the software outputs and the hardware outputs, so I split those to mono instead, pulling down channel 4 to minus infinity in the software outputs, and also bringing channel 3 back up to zero in the hardware outputs, to eliminate unintentional mono-summing, gain-followed-by-trim, or "open circuit" situations.

Eliminating the unintentional stereo output from the DI track, and the mistake in trimming that output by -28 dB, did not get rid of the hum problem when trying to re-amp to the bass head, but it did significantly improve the S/N from before, so every little bit is helping (along with using the hum eliminator at the power plug end), but it still isn’t enough to result in a usable signal level sans hum for recording purposes (even if I filter for the hum later, given that it is too close to the range of the bass guitar).

This remains an unsolved mystery overall, except that the remaining issue may indicate a flaw in Mesa’s design of the Prodigy bass head (or a flaw in my specific unit), since it doesn’t happen in the Mesa Royal Atlantic guitar head.
MacPro Quad-Core Intel Xeon (2.8 GHz, 16 GB), OSX 10.12.4, MOTU DP 9.13, iZotope RX 5.0.0
FireFace UFX, Audient ASP880, True Precision 8, AEA RPQ, Radial PZ-DI & Reamp JCR

Eugenio Upright, Dingwall ABI, BB-1025X, 60th P-Bass, Select J-Bass, Geddy Lee J-Bass, Hagstrom Viking Bari
57 Goldtop, Select Strat/Tele, Pro JMaster, RevStar RS502T, G5422-12, EXL-1, J-100 Xtra, E6D, OM-28VTS, E20P-SB, M-20, AC530-12, ABT60
Yamaha WX5, Hammond XK-1c, Minimoog Voyager, Prophet 12
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