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Old 5th April 2009, 02:27 PM   #1
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Join Date: Mar 2008
Default Need ideas for amp with 2A3, One Electron UBT-3

In the Aug 23, 2002, issue of Glass Audio, there's a neat little project for making a tube amp for a CD player, and then assembling the whole thing in a table-top radio type package ("A Hybrid Tube Radio," pp. 48-50). Long story short: I bought up all the parts, subbing in some premium pieces, and then my life got very busy. So, I have all the goodies on the shelf and may have some time to put an amp (actually, a pair of monoblocks) together.

But while I'm at it, I wondered if there's anyone out there who's used the 2A3 and the One Electron UBT-3 in a simple SE amp (I can solder and understand the basics of theory, but I'm no engineer)

Obviously schematics would be appreciated more than I could adequately thank for, but even just comments on the above-mentioned circuit and possible tweaks would also be appreciated. Note: the low power is fine, because when I still had a little "hobby time," I built a pair of horn-loaded speakers with single Fostex drivers. They sound good, although I think the current source-- an Acurus 150W amp-- is a serious mismatch.

In terms of acoustics, I have sort of a dilemma. I built a pair of active crossovers a while back (Steve Bench's design), so I had a wacky idea of the following:

[pre-amp]->[active x-over]\--->2A3 SET--->Fostex horns
\--->[Acurus amp?]--->subwoofers


[pre-amp] output 1-->[2A3 amp]-[passive xover]-->Fostex horns
output 2-->[Acurus amp?]-[passive xover]-- >subwoofer

To be honest, I'm trying to put the xovers (passive as well as active) where they seem to belong, but if I've the order ***-backwards, please let me know!

(FWIW, my pre-amp is a Melos MA111, perfect condition, with two amp outputs)


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Old 5th April 2009, 04:53 PM   #2
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azazello's Avatar
Join Date: Aug 2008
Location: Bulgaria
I can Email You schematic of my project 2A3 RCA & E180F Philips, that
sound with Fostex 206E in Hornes....if You interest ??
Output power is apr. 3 wts per channel.
One very good choice, better than my Hammonds....
Projects: OTL-OCL 6AS7 Gen. Electric, SEs 2A3 RCA, 300B JJ, 6S4S, 4P1L, EL11 Telefunken, 6AS7 RCA, 6S33S, 6S41S, 6S19P, E84L Siemens, E236L Telefunken, headphone ampl. OTL Loftin White 6AS7 RCA,... PPs 6005 Gen. Electric, EL34 Mullard, 6L6....
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Old 5th April 2009, 07:58 PM   #3
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Join Date: Mar 2008
Sure. I am new, so I can't email directly for a couple days, but you can reach me at (remove space): j a y l g o r d o n @ g m a i l . c o m

Thank you so much for your help!
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Old 5th April 2009, 08:42 PM   #4
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boywonder's Avatar
Join Date: Jan 2008
Location: So.Cal.
Here is a link to Tubelab's site discussing the One Electron output transformers as well as others, not a lot of discussion, but recommended for 2A3 use.

BTW, Tubelab George sells PCB's for a 45/2A3/300b etc based SE amp on his site as well. There is loads of SE amp info there that you may find relevant for your build.
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