Aric Audio Systems Unlimited Preamp

Hi Ray, I'm using a NOS Sylvania 5U4GB (Black Plates) which I have come to believe is a wonderful discovery as it transforms the whole presentation into something nearly magic. I don't know why. As far as the regulators go, truthfully, I haven't noticed a marked difference between any of the types I have tried. The rectifier tube seems to influence the delivery far more than do the regulators. My opinion only.

Thanks for the response tubepower. The Unlimited uses a 5AR4 rectifier. I'm wondering if that variation will yield similar results as the Sylvania 5U4??

Hey guys! @rocray , the 5U4GB (not 5U4 or 5U4G) can safely be used in the Unlimited as the first filter cap it requires can be no larger than 40uf, whereas the 5U4 is much lower (the Unlimited uses 33 uf). Using it will lower the B+ voltage just a bit, so just make sure the regulators light consistently. If you find they are going out, then use one OC3 and one OD3 when the 5U4GB is in place. I agree with Tube Power on his choice for a favorite 5U4GB. For 5AR4s I’ve only ever used new production- either the Sovtek, Tung Sol or Mullard reissues all sound really good! Best, Aric

Hi Aric. Thanks so much for the response and recommendations. It's awesome to have the manufacturer so easily accessible. What sonic differences can I expect by swapping in a 5U4GB?

You're very welcome Ray, and much appreciated on the kind words! When switching over to the 5U4GB, the presentation will be slightly more laid back due to the higher internal resistance of the 5U4GB versus the 5AR4, but you may find this is a good thing! The reason why an OC3 and OD3 regulator may need to be subbed when switching to the 5U4GB is there is an additional 20 volt drop in the power supply output when using the 5U4GB, and depending on your wall voltage, may be just enough of a drop for the dual OD3's to not stay lit reliably. In that case, when you go to the OC3 and OD3 pair, the B+ voltage will be dropped to around 275 volts instead of 300 volts which is still right in the range for the Unlimited to operate and sound its best :-)