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In Reply to: Re: I worship the DHT electric posted by Thomas Mayer on March 13, 2007 at 04:56:36:
Hi Thomas,You have some really interesting ccts in your collection. One thing that I've wondered for some time. There seems a trade off using the conventional series fed transformer vs conventional parafeed in that at some point a cap is involved. However the "theory" goes that the parafeed method can use a smaller cap (hence "better") and a more advanced core. OK you got rid of the cap but did you ever try say a decent cap (you might not think there is one :-) ) with a small amorphous core tx like Lundahl's 1544, 1676 etc?
What seems to you to be the attraction in the single ended EC8020 cct vs the differential one? Again, so many say how much better balanced is vs single ened. Your two ccts get about as close as you can to compare the two. What are your thoughts?
cheers,
Follow Ups:
Hi Stephen,I arrived at the differntial circuit by a different way than people usually do. In my quest to minimize the components in the signal loop I finally had gain stages with 3 elements in the output loop. These were the SE circuit in ultrapath, or parafeed in ultrapath. These basically had the tube, transformer primary and 1 cap in the loop.
I must admit I'm not a big fan of component comparisons. Once I identify a good component I tend to stick with it. I still use the same type 8uF cap which I got years ago. I did attend cap comparison tests but got bored of them. I find much bigger differences in circuit topologies.
So I never tried to optimize the cap size in a parafeed circuit. Can't comment on that.
When thinking about how to get rid of that last cap, I came up with two ways to substitute it. Replace it with a resistor or with another tube. The solution with a resistor burns a lot of power. The circuit with the second tube happens to be a differential scheme.
I always note biggest improvements when geting rid of a cap. The differential circuit brings an additional benefit by the large immunity to effects form the power supply. I can add some kiloohms of resistance in series to the power supply connection of the diff phono without noticing any degradation.
I like my current single ended EC8020 phono the best. It's as simple as it can get, just the tube and transformer in the ouput loop.
Best regards
Hi Thomas,I'm with you on the cap comparison thing. In fact, for most purposes, I don't compare components at all as much like you (maybe), I've found a set of ingredients that seem to work well enough and there are bigger things to muck about with. I tend to be moving in a direction where more coils seem advantageous :-)
I note what you say about the diff cct being more immune to psu artifacts. I've been thinking that many people use diff ccts for that very reason however if the psu is shall we say "super", then the benefit of differential starts to diminish over single ended due to complexity. All other things being equal of course. Is this your experience?
BTW, I'd be interestd in the type of cap you mention. Reason being, up till now, I've used high uF power supplies over lower C ones as I found, for my taste, Black Gates NH and WKZ to be more suitable than the metallised film type I was using in my phono unregulated supplies.
Hi Stephen,our preferences seem quite similar :-)
I agree on the differential circuit and PS quality. The purpose of the diff circuit should not be to get away with a poor PS.
As mentioned I did try to hear the influence of the PS by just adding a 2 kOhm series resistance (with adaption of the voltage to compensate IR drop. The PS was a pretty good one with very low ripple.
I didn't hear any significant degradation.The cap i use is a 8uF Matsushita MP. I guess that is metalized polyprop in oil. Bot I'm not sure.
I have a preference for low C values.
Best regards ... Thomas
P.S.; I'm currently building a new linestage with a different approach to volume control. Hope to report the results sonn...
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