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Rocktron VooDu Valve On-Line Guitar Multi Effects Processor

Sound Quality

I consider this a good practice device, as it can get decent approximations to good tube sounds. Don't let the fancy effects & gazillion parameters fool you. There are a few serious shortcomings that prevent the VV from being a true "pro" preamp... 1. Digital convertor noise & distortion is very dominant in the tone. Rocktron uses cheap phillips 18-bit analog to digital & digital to analog convertors (16-bit on the original VV). These low cost convertors add undesireable distortion & noise to the signal. It's not so obvious on very clean settings, but add a bit of gain & you'll hear it. (Gain amplifies the convertor noise & nasty distortion.) Sure you can turn on the hush effect so you don't hear this noise when you stop playing, but you can certainly hear it as your signal level decays. Try turning off the hush on your favorite medium to high gain preset. You'll hear the nastiness that is mixed into your tone. It's true that high gain amps/preamps are inherently noisy, and a nice even hiss is normal. But the VV has a very high level of nasty digital noise. Sure you can turn the hush back on to mask it when your not playing, but the VV's hush adds its own zipper noise artifacts as the signal level crosses the hush threshold. SO WHY DOESN'T ROCKTRON USE GOOD 24-BIT PRO AUDIO CONVERTORS IN THE VOODU VALVE? Perhaps it cuts into PROFIT! It's too bad because good 24-bit convertors will provide 10dB to 20dB reduction in noise & THD, and that's HUGE! Rocktron, if you're listening, check out AKM's AK5392 & AK4396, which are excellent sounding, moderate cost convertors. 2. Real presence is lacking in the VV. There is a very steep roll-off of high frequencies in the VV, even when the speaker simulator is turned off. The result is a dullness in the high end. Compare the VV to any decent tube or solid state amp & you'll hear what I'm talking about. You can turn up the high EQ to try to fake some presence out of it, but you'll end up getting a peaky upper mid sound. The abrupt roll-off is most-likely an attempt to reduce digital noise, or to cover up some nasty dither technique. Again, better quality convertors run at a higher sample-rate (like 48kHz) would help, by eliminating the need to roll-off the audible highs. 3. The tube is run in starvation mode causing an abrupt overdrive transition. The 12AX7 is under-biased for the given plate voltage. This causes a relatively harsh overdrive characteristic, which is one of the reasons why it is difficult to get a good in-between sound out of the VV. So, the tone retains an aggressive edge regardless of gain setting. There are two ways Rocktron can address this: run the tube at a hotter plate voltage, or set the bias current correctly at the current plate voltage (ie: change plate & cathode resistor values).


The VV seems to be quite reliable, though I have seen data retention problems on the earlier version (with the witch doctor icon).

General Comments

The VV is a great idea, but it's in serious need of an update. As it is, it's okay to use when guitar is in the background of the mix. There are plenty of nice effects that may help mask its shortcomings.


Dear Rocktron:

PLEASE, PLEASE, PLEASE update the Voodu Valve...

- Use good 24-bit convertors run at 48kHz

- Bias the tube properly

- Don't roll-off the upper harmonics

- Ditch the u-chassis design, it's terrible for service & tube changes!!!


Also, please try to add a tuner. You can mute the output during tuner mode to conserve DSP resources. The tuner display may be as follows:

"TUNER: C# 0" (C# in tune)

"TUNER: G +1" (G a little sharp)

"TUNER: D -3" (D quite flat)


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