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In Reply to: RE: My 3 years to the goal of the non-compromise SET and still learning.. posted by aknaydenov on September 13, 2015 at 12:53:04
Wonderful build quality, and some deep thought behind construction.
I have different priorities.
1. Only use DHTs
2. Use higher gain DHTs (4P1L PSE) so you only have 2 stages.
3. Use DHTs in filament bias so there are no cathode bypass caps.
4. Avoid all coupling caps - use transformers.
5. Only polypropylene caps in the PSU.
Basically just DHTs and transformers for the ultimate in clarity. I avoid capacitors like the plague except where they are unavoidable, and I haven't used an indirectly heated tube for years.
Follow Ups:
Andy, my next dream amplifier will be a 100% DHT tube and 4P1L is a wonderful magic tube.
I've heard the magic that a DHT delivers. Although there are IDHT tubes that are better than some DHTs. In my case, I liked the 6P45S better than 6B4G.
Another tube that is a IDHT and is magically sounding is the EL36 and it's the poor's man 2A3.
About paragraph 5 you mentioned ; in my experience, not all polypropylenes are better. For example these RIFAs PEH169 destroy the myth that electrolytics are slow and veiled - these are very fast and transparent and for me, the sound better than cheap polyprops.
I have had a SE 4P1L breadboard under development for the last five years . Currently I'm running the HT from a Morgan Jones 'statistical' shunt regulator bypassed by a 50uF film cap . Driver again uses stacked statistical regulators and is 7N7 with DC coupled 7N7 cathode follower to the 4P1L . I am soon to implement 3A/108A DHT input stage . Avoid cap coupling . Compared to direct coupling or an interstage transformer , it's heaven and hell with 4P1LNo matter what IDHT you try triode strapped , it comes no-where near a directly heated tube
Al
Edits: 09/17/15
I'm not going into this kind of debate, I've done so enough times to come to the conclusion that it's pointless.
"Alternate current" is just a technical term that tries to simplify phenomenons that are too complicated and have to be seen from a different point of view, not just from a basic electronics book view.
Al, I am already dreaming about a 4P1L and a GM70 amplifier SETs. One day, I will build them.
Regards,
Alexander
My suggestion if you go that route is stick with 2 stage and use a high quality amorphous input step up transformer. I don't know why more people don't use this option, it is way better than 3 stage and good (but expensive) input transformers are pretty much transparent.
amorphous iron
amorphous nickel
amorphous cobalt
Builder of MagneQuest & Peerless transformers since 1989
Sorry I am not sure the answer to that. My SET amps use Lundahl input transformers, with and without not much difference besides more gain.
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