You might get a smaller voltage drop for a 5AR4 vs a 5U4, but does that translate into anything meaningful seen by the driver tube/01A? Perhaps it might potentially protect against voltage sag in the power supply, but I've never heard any of Dennis' builds have this problem, especially in a pre amp, which shouldn't be a current hog. The 01A is only going to draw 2-3 mA of plate current anyway, not even close to the 40mA limitation of a VR75.

The Decware is likely a totally different circuit.

+1 I'll try an 80 and post my subjective opinion.

Does Dennis use high-end power cables on his amps and preamps in his home?

I have sometimes upgraded stock power cables with modestly-priced Belden 14/3 shielded cables. Don't hear any difference but figure the better shielding can't hurt. Tried a few higher priced cables but also didn't hear a difference.

Lew Johnson, of Conrad-Johnson, once told me that under normal household conditions he couldn't imagine how a power cable could make a difference in any of his products. He said that his power supplies would filter any noise picked up by a power cable in a home environment.

I don't hear much difference with tube gear, but do with digital components.

Has anyone actually used a USAF 596 rectifier in one of Dennis's amps? I happen to have one and can't find out much about it. I have read in another forum that it's equivalent to a 5U4, but that's not confirmed. My curiosity is peaked.

I’ve had significant improvements with Oyaide power cords on both Inspire and Cary tube preamps/amps. The price range of the cords is in the $300 to $800 range. Seems like Oyaide 004 ends go well. Add an Oyaide Black Mamba to the preamp and the focus and soundstage will become more clear and depth will open up. On the amp an Airsine with 004 ends will crank up the resolution and hugely increase the slam. You won’t hear much of this though if you’re using contractor grade outlet. Here Oyaide comes through again. For a warm lush sound the SWO-GX outlet works good. Use the R-1 outlet mor a more neutral sound. Currently the preamp plugs into GX and the amp into the R1. These upgrades are well worth it IMO.

I have and it's sonic signature in my amp is similar to a 5U4. Although it has a steampunk look

Awesome, thanks - I'll give it a go. It does have a very interesting look "steampunk" is a good description.

Hey Straitwire, how difficult would it be to rewire the input tube of the KT88 firebottle to 12v? Or better yet, to put in a switch to choose between 6v and 12v? Is it the kind of thing that a competent tech could do?

I've emailed Dennis about the possibility of buying a new amp with that capability but have not heard anything back. I assume he is too busy with new toys to worry about redesigning a boring part of an existing amp lol.