In with the new plate chokes ... and out with the signal bypass caps?

[Deke609]

As I mentioned elsewhere, I've installed some new plate chokes on my Kaiju headphone amp rebuild - more inductance and a different core material, nano-crystalline stuff (Hitachi's "Finemet", some kind of specially treated amorphous metal). What do I hear compared to before? More detail and tighter, punchier bass.  I believe the better bass was to be expected given the increase in inductance. I believe the stock Kaiju is 40H. Prior the newest chokes, I had been using some Lundahl 53H plate chokes. The new ones are 69H. Is the change big?  Nope, but I'm fairly confident it is there. I got actual shivers listening to a few tracks with which I am familiar - certain passages sounded "more immediate" and surprised me. 

BUT ... the perceived increase in detail was weird. To use a visual metaphor, I got the impression that one or more faint identical images were superimposed slightly askew on the dominant image.  It's hard to describe. It's like the additional clarity brought the "blur" into focus - I could hear it fairly distinctly, particularly on tracks that exhibited the most new detail. 

I wondered whether what I was hearing was an artifact of the chokes potentially being miswired - e.g., one having more parasitic capacitance than the other b/c of mistakenly swapped anode and B+ connections.  But, nope, I checked the wiring, it was correct. 

So then I wondered whether it might have something to with my use of bypass signal caps: 0.1uF VCap CuTF caps across the 10uF output cap in the BP1 and across the 10uF parafeed cap (both of which are VCap ODAM caps). Doc B. has commented in various threads that he hears "smear" when using bypass caps, and others have shared similar impressions.  While others have had positive experiences. So I thought I'd see for myself, but knowing that I now had expectation bias: I wanted the askew superimposition to go away. And sure enough it did! On some tracks/albums the change was was really noticeable and positive - example, "The Chain" by Fleetwood Mac.

BUT -- and here is what makes me think the change was at least partly real -- some things got a bit worse. Focus was better, but some tracks/albums lost a bit of "magic".  Paul Simon's "Graceland" album is one example. It became less "ethereal", more "just here".

I have no solid sense of how bypass signal caps might change the sound, if in fact they do. Some have speculated that it is a function of mismatched time constants. I wonder whether it might also have something to do with different dielectric constants resulting in different tangents of loss - sort of a phase mismatch problem?  But at this point, I'm basically talking out of my @$$ b/c I don't understand enough about these things to make educated guesses (so I make lots of uneducated ones). I'm unlikely ever to know and am ok with that. I'll just go with my ears, without ever being 100% confident that some or all of it isn't just in my head.

What I am confident about is my preference for VCap CuTF caps (teflon and copper foil) over the small selection of other caps I've heard. I was bypassing a metalized polypro cap (VCap ODAM) with a teflon copper foil cap (CuTF). My fantasy is to have 10uF CuTF caps - but they don't exist, and even if they did they would be too big and too expensive. So I'm wondering whether I can keep the detail/clarity but get a bit of the lost "magic" back by using copper foil caps (sans teflon dielectric).  I already have a couple of Miflex 600V 10uF copper foil caps that were originally purchased for the Kaiju but were too big and ended up in the prototype rebuild of the BP1. I liked them and only replaced them with the ODAMs w/ CuTF bypass caps b/c the latter were so much smaller and consequently easier to install - and in the end, I thought they sounded different but equally good.

My plan is to try some slightly smaller 250V Miflex 10uF copper foil caps in the BP1. And if I like what I hear, I will make the future Kaiju monoblocks extra large to accommodate the 600V versions.

I will also try some 0.01 uF CuTF bypass caps with the presently installed ODAMS - but if there's anything to the "time constant" theory of bypass cap "smear", then this 10X lower capacitance should make things even worse than before.

I'm way down the rabbit hole now... but happily so.

Some final thoughts on the new plate chokes: Unfortunately, I have no idea whether the nan0-c cores contribute anything to the perceived new detail I'm hearing. The only reasonable way to test that would be to have a winder make two pairs of plate chokes with identical specs, using the same winding techniques, but using different core materials. That would be an expensive experiment. If I win the lottery I will try it.

cheers, Derek

[johnsonad]

Holy smokes. Thanks for posting your experiences.  Small changes make a difference to the listener and you really are fine tuning to your ear at this point. I feel bad for your wallet!

[Deke609]

I feel bad for your wallet!

Yeah, my way of engaging with this hobby hasn't been cheap. (Nor yours, Aaron, IIRC!). That said, I'm getting to the point where my slowly accumulated parts collection isn't just expensive clutter anymore and is now a half decent parts library.  I think I have enough stuff to build 3-4 very nice parafeed amps. All I'd need are some power transformers and maybe a few resistor values. And for the next capacitor experiments in my BP1 and Kaiju rebuild, I only had to buy the 250V Miflex caps - and I found that they're a lot cheaper if you buy direct from Poland (and would have been even cheaper still had I succeeded in convincing the seller that exports outside the EU are VAT exempt - but even with the erroneously charged VAT, buying direct was way less expensive than the usual UK/Canada/USA online retailers).

Plus, I need something to do during lockdown here in Toronto, besides spending way too much time looking at the BH forum and a couple of other audio online forums.  Speaking of which, prior to the past year I really didn't appreciate the "addictiveness" of new technologies. I have no interest in social media, and mostly use my phone as, well, a phone.  I can go a week without even looking at it (only to find it out of power). But I've caught myself more than a few times these past few months having spent the majority of the day doing nothing but look at audio stuff, and compulsively checking for anything new to read on the forums. And I've noticed most recently that I have trouble pulling myself away. Eesh.  Not good. Anyone experiencing something similar?

And on that note, I will close the computer and go ride on my indoor trainer.

cheers, Derek

[Deke609]

... I only had to buy the 250V Miflex caps - and I found that they're a lot cheaper if you buy direct from Poland (and would have been even cheaper still had I succeeded in convincing the seller that exports outside the EU are VAT exempt - but even with the erroneously charged VAT, buying direct was way less expensive than the usual UK/Canada/USA online retailers).

Scratch that. I just heard from the seller/manufacturer that he needs to charge an additional 90 Euros above the quoted shipping price.  That's on top of more than 60 Euros in improperly levied VAT. So I am canceling the order.  I'll have to wait for the caps to go on sale at one of the usual online vendors.  Oh well.