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nl wrote:

I have used Russian high-gm tubes like 6C45 in amps before, including single-stage designs very much like Romy's single-stage Milq. These have many attractions. However, in my experience it just didn't have the tone. Jim de Kort of VT52.com came to the same conclusion, regarding his WE437 spud using amorphous output transformers, on his 107db horn speakers. He went back to his 26-10-45 combo, three stages instead of one.

Jim de Kort's wrote:

Even a single tube performing all the tasks can't come close to my three tubes per channel DHT amp system. There is no getting around the immense difference in sound. Yes, the 437A and 6S45P sound incredible and perform a unique task, but compared to a DHT it really can't hold water. I was doubtful about the comparisson before, but now I am fully convinced. Even three stages of (good) DHT's can't be beaten by a circuit using only one IHT.

Romy the Cat wrote:

Meanwhile the upper range of PP2000 is back completely and oh boy – I do not like my MF channel now. I clearly would like it to be loaded to 2-3 time higher impedance; I mean much higher, the way how I use to have it 2 years back. If you remember my progress with S2 driver then you will see how I fought with it “liveliness” by loading the stage that drives S2 harder and harder. The first Melquiades was driving S2 with 1700R that is VERY high impedance for 6C33C.  The best load I go at the time was at 1350R, it was very high as well. Then I started to cure (as I presume now) the electricity problems with damping of my MF driver. I was driving with 1000R, 650R and in the end with 550R. When I circulated my MF transformer for single-stage 6E6P I made it 15:1 or relatively heavy loaded. Now I can go for much-much higher loading – the electricity from PP2000 shell be able to care it.

In a light of my recent electricity-inspired dissatisfaction with my MF driver I begin to think about return to the two stages Milq and as it might be understood from this thread I am contemplating to use DHT in the Milq’s output stage. Still, the single-tube quandary is extremely lucrative. Jim de Kort (and I do not know who he is) said that a single tube is performing all the tasks but something he did not like in it. However, we under impression that a single stage high gain IDT and DHT shell be identically loaded in respect to own plate impedance.

Let me to prose another alternative. How about if we load the high-gain single-stage IDT against very high impedance, much higher than a common wisdom would suggest? Sure it will eat a lot of power and the small IDT do not have a lot of it but I drive only HF and near 110dB sensitivity then ever 0.5W would be enough and I might do away with it. The 5E5P load to 30/40:1 transformer might be a ridiculously lucid way to experiment.

Sure, the DHT shell be tried and it highly highly-possible that just two-stage DHT will do just fine. Still, the single stage IDT with completely idle anode might have own undiscovered kink that shell be also considered.

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