I think I have found the End Game Amp


For the past couple of years I have been searching for a power amp that plays well with the highly resolving nature of the Esoteric K-01XDSE source and the Rockport Atria II speakers.

How do I get a mid-range to captivate without losing the sense of air and space?

The K-01 and the Atrias deserved something great in between but I could not bring myself to spend $25k - $50k if I went all out on both pre and power.  Building an amp is surely easier than building transducers?

The closest I came was with a Cary SLP-98 pre - with NOS RCA 6SN7s and the Elekit 8900 running Black Plate 2A3s.  There was not quite enough power, slight sounds of strain at fff and not quite the warmth in the mids.

I was enamored of the 2A3 sound and wondered if there exists a PP or PSET 2A3 amp, so I discovered and contacted Frank Ng at Triode Labs.  He had recently found a pair of Tamura OPTs and Tango chokes and had built a pair of the PP 2A3 GT-C amps that I could have immediately!  Working with Frank was an absolute joy, getting a story of his constant search for the Tamura OPTs, and seeing his views on various tubes.

He gave me great price (he supplied only the 6SQ7s) and I was able to pay through PayPal - I rounded up (dividing by .96) to cover the fees.  I got him to autograph the base plates!

The shipping boxes were superbly protective but easy to unpack.

Even cold out of the box I could hear something special; there is just a natural quality to the sound.  The amps now have about 30 hours and Frank expects break in to be about 200.

Everything I play sounds - I am not sure of the word - but "right" seems to fit.  I have played everything, from Angela Hewitt's Goldbergs - you can clearly her management of tone from her Fazioli piano - to Simon Rattle's Mahler 7 (Bavarian Rundfunk).  Also the Borodin recording of Shostakovitch quartet 9, the Beethoven op.132, the Sveshnikov Rachmaninov Vespers with Klara Korkan's haunting mezzo, Hilary Hahn playing Bach.  AMAZING!

There will be some tube rolling to fine tune (!) everything but at this time the SLP 98 has coin base a 6SN7 gain stage, Tung Sol buffers.  The GT-C has Motorola branded 6SQ7s, Smoked glass RCA 6SN7s, JAN Black Plate 2A3s and Sophia 274B rectifiers in the main amp..

 

 

 

retiredaudioguy

Retired audio guy,

 I recently read an article concerning dynamic range and calculating amplifier power necessary to drive speakers. It was written by Tom Martin 7/9/2026 for The Absolute Sound. If I could figure out how to link it here I would. You should be able to find it easily. It is titled “Dynamic Range and choosing Amplifier Power”. Regardless of whether your amp can drive those speakers, if you enjoy them and they are not doing any damage by clipping, that’s all that matters. Enjoy.

Everything I play sounds - I am not sure of the word - but "right" seems to fit.  I have played everything, from Angela Hewitt's Goldbergs - you can clearly her management of tone from her Fazioli piano - to Simon Rattle's Mahler 7 (Bavarian Rundfunk).  Also the Borodin recording of Shostakovitch quartet 9, the Beethoven op.132, the Sveshnikov Rachmaninov Vespers with Klara Korkan's haunting mezzo, Hilary Hahn playing Bach.  AMAZING!

Yeah, I should really start listening to more classical. Been mainly jazz 70% of the time, but there is whole world of recordings to listen to, all at my fingertips, and I gravitate to the same 1000 albums. 

2A3 not the best pair up with those inefficient Rockports

There is a misconception that all amplifiers given a tube spec are the same, and that makes as much sense as saying all 50 wpc solid state amplifiers are the same. The quality of the power supply makes more of a difference. Similar to when someone comments that all 300b amps have poor wooly bass, they obviously have not heard a good 300b amp. 

I fondly recall giggling like a small child the first time I felt my walls shaking from my 4.2 wpc 2a3 amp (98db efficient 4 ohm speakers). I am pretty sure my 100 class A watts per channel Coda 15.5+ does not shake them any harder. 

I have tried a variety of pre amp & power amp combinations over the last two years and the current setup, though perhaps unconventional, is yielding the best sound, based on my desired qualities and music preferences.  I realize that the setup is "at the margin", SE 2A3s and 300Bs did not quite handle orchestral works.  Solid State was not beautiful, powerful PP tubes (KT 120s) sounded good (indeed the C-J amp was very good) but did not quite have the magic of superbly executed PP 2A3; yes, Mahler’s timpani had more slam but the beauty of the human voice, and the sense of space, in liturgical works, was not quite there.

Proof is in the pudding. You know when you know. 

@posbwp55 Thanks for the article.  I read it through and it seems to (just) validate what I hear on theoretical grounds.

I mentioned that I measured the SPL at my listening position at 84dB with 2 watts (2.83v).  14 watts yields an additional 8.45 watts (theory) and in practice 92 dB is about my comfortable peak for orchestral stuff.

At the bottom end pp passages are at 65db, do a dynamic range of 27dB - in line with the article's 26 dB range.

So, yes, the power is marginal at the upper limit but the SQ in the middle is sublime.

@mclinnguy No, I cannot shake the walls at 92 dB, but I live in a log home and it would take a bulldozer to move them anyway!

Most of the time I am listening in the mid 70dB range - .5 watts.

Regarding "wooly bass" and 300B amps, for many years I had a VAC Ren 70/70, driving Audio Physic Virgo IIIs.  Than could do excellent bass!

 

 

As long as you don't require head banging volume, a pushpull 2a3 amp can be used with somewhat inefficient speakers.  I think most people greatly overestimate how much power they need or put too much emphasis on the ability to play at extremely high volume even though such demand requires a lot of compromise in the ability to play beautifully for the vast majority of the time.  I am a big fan of low-powered tube amps.  I own a parallel SET 2a3 amp and a pushpull 349 amp (5 watts per channel).