2a3

[mickm]

Hi,Steve,
The 2A3' you sent me are doing great...
Mick.

[The Shadow]

Hi Mick

Those Sovteks are very nice valves. I'd still be using 2A3s if my speakers had been efficient enough. But at only 90dB the Metronomes caused the 2A3 monos to run out of steam a bit too early, which squashed dynamics too much for my liking. Compressed rock and 60s soul was fine. Big band jazz and big classical stuff was right out.

The PSE Rocky has plenty of power to get the best out of the speakers, but EL34s don't have that magic that DHT triodes give. OTOH they do have a richness and a big tone that 2A3s lack. It's horses for courses as usual.

PT15s with pentode drive and DC heaters still pull at the edges of my reason. That big wiring experimental chassis with the tall cage would be just the ticket. One day Steve one day.

Steve

[IslandPink]

Steve, Have you run PT15s and 2A3s in a close time-frame so you can offer any good comparisons ? Still thinking about trying them out against 300Bs , particularly relevant if I can get more efficient speakers .

Mark

[The Shadow]

Hi Mark

The PT15 stereo chassis was a direct replacement for the pair of 2A3 monoblocks I had at the time so they were run one after the other.

However the output transformers used were different to the 2A3s so how valid the following comparison will be I don't know.

The 2A3s used Hammond 1627SEs with 2.5K primaries.
PT15s first used a pair of Hammond 125FSEs and finally Sowter SE04s with fixed 6R secondaries, 3000R Primary and a 43H primary inductance.

From the start the PT15s sounded much bigger than the 2A3s with a highly detailed treble that was extended and clean. Midrange was powerful and detailed with a fat bottom end that again was highly articulate but seemed to cut off quite steeply below about 70Hz. Very deep bass was noticeable by its absence in the first configuration, probably due to the cheap output transformers.

With the 125FSEs the PT15s gave, for want of a better description, a Naim type sound. Tight fast and rhythmic with a curtailed deep bass that increased the illusion of forward momentum and dynamics. In short they kicked ass, but because of the mid-forwardness caused by the lack of deep bass the sound was missing subtlety and delicacy. They were the polar opposite of the 2A3.

After splashing out on a pair of Sowter SE04s which were of obviously higher quality than the cheap Hammonds, we started to get somewhere.
The higher primary inductance gave far deeper bass which had the effect of pulling back the midrange to a more natural perspective. Thunderous would be an apt description for the bass I was getting now. It was deep, controlled and articulate. In the all-important mid range, subtleties were no longer being swamped by the forwardness and all sorts of little details became evident, no longer being glossed over.

Treble was extended and clean with plenty of air. The soundstage thrown by these valves in conjunction with the Sowter output TXs was quite simply huge.

I would say that with the proper conditions of high primary inductance and a nice big output TX, these transmitting pentodes are in a different league to the 2A3. Properly applied they have all the subtlety and delicacy of the 2A3 coupled with much of the heart-stopping dynamics and clarity of the bigger transmitter triodes.

They need careful tuning or they can become a bit in-your-face for my liking. But get them right and they are a gutsy, clean, detailed and powerful musical experience.

I will without doubt return to them sometime, but on the speaker front I will need bigger drivers. I would cite the Fostex FE167 as an absolute minimum standard.

My poor little FE108EZs with their 0.28mm Xmax fairly wilted under the low end onslaught once I had put the Sowters in circuit; so much so that I had to band-limit the main speaker outputs with 3n3 capacitors. These did not do much for the sound at all.

As a result I have ended up shelving them until the day I build some bigger Metronomes..........They'll be back.


Steve