Aric Audio Systems Unlimited Preamp

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 :-)

Aric,thanks again! I just ordered a Sylvania 5U4GB and a GE 0C3. Both should be here by Tuesday.

Awesome! You're very welcome and please do let us know how it works out! Best regards, Aric

I’m also very curious to hear how the 5U4GB and 0C3/0D3 combo will sound as compared to the 5AR4 and 0D3/0D3 arrangement. Please report back. I’m currently running a Tung-Sol 5AR4 (vs. the stock Sovtek) and a pair of NOS GE 0D3s. Couldn’t really tell much of a difference is sound quality. I just thought the GE tubes' Coke bottle shape looked a bit cooler. For me, trying different brand(s) of the driver tubes by far made the most difference in the sound signature of the preamp.
Aric, out of curiosity, what would be the effect of running a pair of 0C3s with the 5U4GB?