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Message started by BradC81 on 12/20/24 at 21:42:29

Title: Greetings and Happy Holidays - new SE84UFO25 owner
Post by BradC81 on 12/20/24 at 21:42:29

Hello and Greetings everyone!

New SE84UFO25 owner here – about 20hrs in. This is my first foray into tube gear, having come from an Exposure 2010S2 integrated. The amp and tubes arrived last week, so I donned a pair of white cotton gloves and started to gently wiggle everything into its respective seat. The amp is paired with Klipsch Forte IIIs. At first, I ran my phono pre directly into the UFO, but I’m also trying out my 2010S2’s preamp output to the UFO, as it allows multiple inputs, and I can connect my REL Q108 via the high-level speaker outputs on the integrated.

For this go, I used the tubes as specified on the amp body. I believe the two “voicing” selections were the OD3 regulator and 7DJ8 input. I was surprised the OD3 was printed, as having read the manual this is the -75V from stock option. Do most people start with the OA3, or OD3 as I did?

Second observation re: the OA3. Can someone explain, the OA3s at the rear of the amp look different than the OA3 input tube option. In the case, they’re both labeled OA3/VR75, yet they’re obviously different?

I generally listen at ~60-75db, but I did crank things up a bit and noticed the meters moving ever so slightly when the music would peak in the high 80s. I don’t intend to regularly play loud, but I did read that dimming of the OA3s in indicative of clipping. Is the idea that the meters should never move at all, or is a slight wiggle ok?

Lastly, I’d just like to say, I’m absolutely loving the amp so far and every indication is that it’s only going to get better over the next 100hrs.

Happy Holidays everyone!

-Brad

Title: Re: Greetings and Happy Holidays - new SE84UFO25 owner
Post by CAJames on 12/20/24 at 23:11:30

Welcome to the club Brad! And happy holidays to you and yours as well.

Let me see if I can help with a few of your questions.

Quote:

For this go, I used the tubes as specified on the amp body. I believe the two “voicing” selections were the OD3 regulator and 7DJ8 input. I was surprised the OD3 was printed, as having read the manual this is the -75V from stock option...

Here's the deal with the voltage regulator, aka VR, tubes. The tubes have an actual voltage drop as follows:

0A3 -> -75V
0B3 -> -90V
0C3 -> -105V
0D3 -> -150V

It's been a while since I looked at the manual and I don't think the 0B3 is mentioned, but they are a thing. Regardless, using a 0A3 would drop the B+ voltage 75V, which is stock, and by stock I think what Steve means is what is hardwired into all the other UFO type amps. Using a 0D3 would drop it 150V, or 75V below stock. Using a 0B3 or 0C3 would drop it in between.

Quote:

Do most people start with the OA3, or OD3 as I did?

Firstly, everyone is different. Different tastes, different systems, different rooms blah blah blah. So rule #1 is do what sounds good to you, not what "most people" do. One of the joys of owning tube gear is experimenting as much (or as little) as you want. For me, I typically like the 0C3 tube in front but the only way you're going to know is to try them all. And don't forget the bias switch at the front of the amp, it also affects the sound. It kinda splits the difference between adjacent VR tubes. But it also affects the volume so make sure you adjust it, otherwise the louder setting with usually sound "better."

Quote:

Second observation re: the OA3. Can someone explain, the OA3s at the rear of the amp look different than the OA3 input tube option.

Different tube manufacturers (or the same manufacturer at different times) made tubes that look different but have the same electrical properties. Vacuum tubes were the "high tech" of the mid-20th century and tube companies were constantly trying to find ways of making the same (or equivalent) tube cheaper.

Quote:

...I don’t intend to regularly play loud, but I did read that dimming of the OA3s in indicative of clipping. Is the idea that the meters should never move at all, or is a slight wiggle ok?

It's up to you. Tube clipping is a gradual thing and a slight wiggle means you are just getting there. If you don't hear anything wrong with the sound then there is nothing wrong.

Quote:

Lastly, I’d just like to say, I’m absolutely loving the amp so far and every indication is that it’s only going to get better over the next 100hrs.

Indeed. It is a remarkable piece of gear and I expect you will enjoy the heck out of it. If you haven't already I'd encourage you to spend some time reading the various fora, probably starting with the UFO25 and Replacement Tube fora to get a glimpse of other's experience. There is a great deal of wisdom on this site.