Actually they work pretty well near the wall. at least as far as we've tried them. They seem to work especially well near corners where the open woofers have the rear walls for reflection of the rear facing sound waves. The tweeters aren't open in the rear, so they aren't part of this equation. I might ask Hoosier Hi Fi to comment on positioning as he is actively working with his set, and I am out of town without access to the Ziracote veneered pair...

Thanks Ivan!

Hi, the models of Odeon Audio could also be an alternative.
Tweeter horn and bass with down fire port.
high efficiency and only need a little distance to the rear wall
I don't know if there is a dealer in the USA, canada definitely

Took the 5AR4 out. Couldn’t take the PT Hum anymore after 5-6 days of usage and messing around with cable routing and even connecting it to a different power socket. Put the 5U4G back in and normalcy restored. I plan to send the offending rectifier to a tube dealer to get it tested. The Had amp is designed to accept the 5AR4 so it has to be a fault with the tube. Perhaps I should get a new production equivalent to compare. Any recs?

Also, was looking at the back of the amp and couldn’t recall the function of the black knob right next to the power input?

That black knob is the fuse holder. I’ve become acquainted with that recently. Had 2 different 5ar4 arc and die. One Sovtek, the other an older Russian. I’ve gone back to 5u4g, a current production EH. I’m a little gun shy when it comes to 5ar4, I’m certainly not going spend big money on one now! Luckily, as I’ve posted in the past, I’m not a big believer in spending a lot of money on diodes anyway.

@khashmi did you ever get to listen to speakers from Decware?

Thanks, I need to learn when and how to use that fuse holder when needed. Wondering if there any instructions on it that came with the amp—will need to look it up. A YouTube tutorial would be even lovelier.

I’ll be in Peoria on the 7th of October and will listen to multiple speakers during the weekend. Will report back afterwards.

Heh, that's why the Mullard 5AR4s go for such big money. They tend to be lifetime tubes.

I can check my stock and if I have a spare, perhaps we can make a deal. And of course, I always guarantee my tubes for 30 days or so....

I appreciate the offer but I think I'll stick with the 5u4gt. I don't notice any difference in sound quality. Don't think the little bit extra power was noticeable anyway. If I did want to reach for the extra watt or two I might try one of the solid state rectifier replacements.

I have another idea. What if, instead of sending the tube to a dealer to get tested, I send it to you to check on your Had amp and compare with your other 5AR4s? Trying to gauge if the same buzz happens on your end as well, using the same equipment? Just thinking out loud…