Tubelab SP-P: The lights are on.... - diyAudio
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Old 28th May 2010, 02:21 AM   #1
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Default Tubelab SP-P: The lights are on....

....and the music plays!

Sounding darn good too. On first listen, the bass has considerable authority. How many watts does this baby put out anyway?? Plenty of volume through the Vandersteen 2ci's in my 20' x 12' music room. No need for more watts here!

Another thing that impressed me at the outset, is the silence of this build. I mean, "hear-a-pin-drop" silence. The background between notes is pitch black. It adds a lot to the overall dynamics of the music being played.

While that (and the bass) really grabs your attention, I think this amp may not quite have the quality of timbre that either the Millett DCPP, or my reference system (PrimaLuna) has. Still, it's too early to determine that yet. BTW...I'm using Phillips 12AT7's and EH EL84's... nothing special.

With adequate (50-100 hrs) break-in time, this amp should make for an interesting comparison test with my (awesome) Millett DCPP. But for now, I'd say George has designed yet another winner!
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Old 28th May 2010, 02:59 AM   #2
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Nice looking Edcor CXPP you've got there. I have a set of 25 watt CXPP in an EL34 contraption. They're a little undersized for the power tubes, but otherwise nice transformers. I really like the chassis you've built. That's some attractive metal and woodwork.

One of the virtues of push/pull designs is the inherent cancellation. They tend to have low hum. They can also offer excellent bass authority due to the magnetic field cancellation and subsequent lack of core saturation. Without the need for an air gap, good transformers can provide far more inductance than would be possible with a comparable single ended design.

I take it you like your Vandersteen 2ci? I've got a well worn pair, but I was never able to get them to grow on me. The top end is too perfect, and I always felt they sounded sterile. They were never any fun unless played loud. Maybe I just got a dud set. They also seemed to like a lot of power, and were more at home with the Dynaco Mark III than the singled ended DHTs.
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Old 28th May 2010, 03:14 AM   #3
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Ty:

Thanks for the kind words and your comments.

Yeah...the silence of this build really surprised me. By comparison, my Tubelab SSE has a tiny bit of hum that cannot be heard from the listening chair. On the other hand, my Millett DCPP seems very quiet. I mean, I hear no hum or hiss from the speakers. However, there is this noticeable difference in background silence with the SP-P. I can't explain it, but it's very obvious to my ears.

As far as the Vandys go, I actually have 2 pair set up in my room. I have a 20 year-old pair of 2ci's that I bought new. And I also have a pair of newer 2ce Signatures. I have tried many other loudspeakers, but never sell the Vandys, because nothing ends up pleasing me like they do. While I have used SS amps with them, they do very well with many tube amps. At the shows, Richard Vandersteen often demos his 2c's with tube (Manley) gear.
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Old 2nd June 2010, 08:56 AM   #4
Ian444 is offline Ian444  Australia
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Nice build Neon! Looks great! Very tidy too. I see you are trying UL. I find the stereo separation of the SP-P to be extremely good, and I know what you mean by the black background/dynamics. Would you be able to share the P/N of the power tranny and the B+ you get from it? And the OPT's, I assume CXPP25? Are those a couple of inrush limiters I see?

Ian.
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Old 2nd June 2010, 04:16 PM   #5
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Hey Ian!

Your comments are appreciated! I'm enjoying this amp, and it's showing more of what it can do as break-in continues. I have around 30 hours on it now and it's opening up nicely. I'm surprised at the power (w=?) it is putting out. It is driving my greedy Vandersteen 2Ci's with volume to spare. The bass is nothing short of amazing.

You ask about the Edcor xfmrs...the PT is a XPWR008 and the OPT's are CXPP25-8-7.6K. Both are listed on the Edcor website. The Edcor stuff seems to be amazing for what you pay. I have them in my Millett DCPP, also a great sounding amp.

The Edcor OPT's are currently connected UL. Have not tried the pentode connection yet, but curious as to any differences in sound.

You've got sharp eyes, mate, seeing those CL-90 limiters; 1 in the hot leg of the 120v main and 1 in series with the HV CT. I did the same on my SSE, and along with the 5AR4, the power ramps up quite slowly.

I measured the B+ @ 340 with around 334 on the plates. I thought this was higher than I expected from the 600v (300-0-300) Edcor HV secondary.
I have 118 v at the wall.

The bottom line on this is the E-H EL84's I'm using have a very small display of the dreaded "red-plate". Same thing happened to beta-tester, Russ. He ended up using JJ's which he says are more tolerant of the high plate volts. The screens (what you can see of them) don't appear to be glowing / melting...yet. The amp sounds so good, I'm just content to leave it be and we'll see if it turns out to be a tube-eater.

One other thing I found out is this amp develops quite a bit of heat. The black anodized aluminum chassis I used got hot quickly! I first drilled a lot of 1/4" holes in the bottom plate, which helped a bit. I ended up mounting a small (7.7cfm) fan in the bottom plate, blowing upwards at the PCB. The amp is now very cool. You can't hear the fan from the listening chair.
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Last edited by neonthecat; 2nd June 2010 at 04:19 PM.
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Old 6th June 2010, 06:38 AM   #6
Ian444 is offline Ian444  Australia
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Hi Neon,

I too was surprised at the power and bass. I did try triode mode at one stage but that did nothing for the sound. Was going to try UL this weekend but got sidetracked with another project.

I'm surprised the EH EL84 are not comfortable at that voltage. I have similar B+ and have run the JJ's and some Russian 6P14P-EV without issues. Must be just a characteristic of the EH's. Something for future builders to be aware of I guess. I bought a nicely-matched quad of JJ EL84 from Jim McShane who sells them pretty cheap, around $10 each from memory.

I have found the East German NOS RFT brand 12AT7 to give nice detailed sound in a couple of amps now. The filament of one of them always lights up like a lamp briefly at switch-on so some people may not like that, but they sure sound good.

Ian.
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