New plate chokes: initial impressions and some speculations

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Deke609

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As I mentioned elsewhere, I have added new plate chokes to my Kaiju rebuild. The purpose of the rebuild was to convert the amp to a dedicated headphone amp for planar magnetics -- presently my LCD4 headphones which I like very much -- and just to have fun tweaking stuff. Changes made prior to new plate chokes:

(1) A CLCLC power supply with (a) doubled capacitance of the voltage doubler (PSUD indicates that this cuts ripple in half) and (b) polypro filter caps including a 1500 uF as "reservoir" cap (it stores a lot of juice - if the power switch is turned off while music is still playing, the amp will continue playing normally for another 3 seconds!)

(2) 100,000 uF bypass cap across the TL431 regulated driver bias (I still want to try replacing the reg with a high quality resistor as one other forum member has done - just to hear)

(3) A 330 uF polypro 300B Kthode resistor bypass cap in place of the stock electrolytic.

(4) Nano-C core output transformers with nominal 3.3K primary and switchable 16/32/64 ohm secondaries, plus parallel load resistors across the outputs that can be toggled on/off to hit the target nominal secondary impedances in parallel with the 200 ohm impedance of my headphones.

(5) 7000H "supermalloy" grid chokes that replace the grid resistor that loads the driver tube (I still need to do some experiments with different interstage coupling cap values w/ and w/o damping resistor across the choke -- as suggested by PJ)

Plus a new bigger chassis and changing the interstage and parafeed film caps to my preferred flavor. I've posted before about my purely subjective impressions of all of the above.

The newest change was to replace the Lundahl 53H Si-Fe plate chokes with 69H Nano-C plate chokes from Monolith Magnetics. The new chokes only have about 10-15 hrs on them - but I am liking what I am hearing. Nothing totally game changing - it doesn't sound like a totally different amp. Instead there is even more and tighter low end bass (likely attributable at least as much to the increase in inductance as to the change in core material) and even more clarity and reduction in "glare" (which I attribute to the new core material).  Acoustic instruments in particular sound cleaner and more textured and full.

Here's the speculation part. I'm fascinated by the relationship between external stimulus (music sound waves) and internal ear-brain reaction/processing (what I hear).  Some maintain that much of the burn/break-in experience is really the brain "rewiring" itself to better process new stimuli.  (Still others believe that much or all of it is just a placebo effect -- sort of a matrix "there is no spoon" kind of thing -- I think this is possible but doesn't explain everything).

If we admit or at least hypothesize that the ear-brain "constructs" the experience of music on the basis of sound wave "inputs" then it follows that there are 2 sides to the equation: input and construction.  Is it all just "construction"? I don't think it can be. Music played through your car's am radio sounds crappy compared to the same music played through, say, a BH Crack with Sennheisers. You can spend 20 years listening to that am car radio and your brain is not going to turn it into a "HiFi" experience.  So the input matters a lot.

So is it really all just about the input - with the ear-brain, if functioning properly, doing nothing more than translating eardrum enervations into the experience of sound according to a fixed, automatic process -- i.e., by a non-adaptive process?  I don't think that can be right either.  Consider hearing aids - I don't yet need them, but they strike me as providing a good example of how the brain "constructs" the experience of sound through some sort of iterative learning process. Do a search for "getting used to hearing aids" and you'll see a ton of info online to the effect that, initially, using a hearing aid can make some sounds incredibly loud, difficult to locate in space (where it's coming from), and even leave one feeling disoriented.  But with repeated use, those problems resolve. The inputs don't change (a bird chirp is no less loud one month later); the ear-brain "construction" operations do. 

Here's another potential example of the same adaptive learning phenomenon that's probably a little more relatable to BH forum members. Have you ever changed something in a BH amp -- e.g., volume pot, film cap for electrolytic, fancy "low noise" bias resistor, etc. -- and experienced a huge change in sound between how the amp sounded before turning it off on Day 1 and after warming up on Day 2?  Now, I think that in some cases some of the change may be due to an actual physical change -- e.g, in the case of caps, "cap forming" or some such.  I've "broken-in" teflon caps over a period of 100+ hours using dummy load resistors during which time I only briefly listened (matter of minutes or even seconds) once a day or so to see how the amp sounds. My experience with teflon caps is that they go through an extended period of 50+ hours where they don't sound so good, and then gradually start sounding better and better. This gradual change coupled with very little listening suggests to me that the sonic behavior  of the cap (the "input") is indeed changing.

But what about a volume pot, a resistor, or even some new iron? [Edit: In cases where it is not simply the placebo effect or "confirmation bias"], I suspect that any experience of additional "detail" is in fact the result of a physical change (change to the " input")-- but that at least some, and perhaps all, of the subsequent experience of the sound becoming more "coherent", "even", "separated in space", etc. is ear-brain learning.  I'm no neurologist or psychologist, but I've seen and read a number of docs/articles exploring the important role of sleep in learning. I wonder whether much of the "next day improvement" is result of brain adaptations during the intervening sleep?

Potential case in point: When I turned off the Kaiju last night I was hearing lots of new detail and clarity, but the "imaging" and "soundstage" was really off -- sometimes instruments seemed superimposed in the same space and others were just difficult to "locate".  And some of the highs even sounded a bit shrill.  Complete change this morning: sounds really good, soundstage and separation are "returning" and no shrillness. 

All of this is just a long-winded way of saying that my working guess is that physical soundwaves (inputs) provide the raw data and basic skeleton upon which the ear-brain constructs the experience of music -- fleshing it out, so to speak.  The ear-brain can't create detail without a stimulus, but it has some play in how it can arrange that detail into a more or less coherent soundscape.

A neat way of excluding (controlling for) the effects of any physical changes due to turn-off/cool-down would be to: (a) make a change (e.g., new choke or output trafo); (b) listen for a number of hours; (c) take a nap while the amp keeps playing (eg., with dummy loads in place of speakers, or just in another room if using headphones); and then (d) relisten.  If there's a big improvement, my money would be on it being the result of brain adaptation. 

Any tweakers out there that are also fans of midday naps? If I remember, I will try this the next time I make a significant change or build something completely new.

cheers, Derek
« Last Edit: January 20, 2021, 04:28:08 AM by Deke609 »



Offline Paul Birkeland

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Reply #1 on: January 19, 2021, 01:05:24 PM

Paul "PB" Birkeland

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Deke609

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Reply #2 on: January 19, 2021, 01:22:13 PM
Well, yeah, I guess that might be an audience for such experiments ... but I kinda had in mind those with slightly more "mainstream" tweaking inclinations -- not a crowd that's inclined to seriously wonder and experiment with whether, just for example, replacing aluminum screws with titanium in a carbon fiber wall receptacle improves the sound.

cheers, Derek



Offline Paul Birkeland

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Reply #3 on: January 19, 2021, 01:22:58 PM
Don't forget to tell them what kind of laundry detergent you use.  That's apparently also critical.

Paul "PB" Birkeland

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Deke609

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Reply #4 on: January 19, 2021, 01:29:31 PM
Damn right it's critical.  But I won't be telling anyone else about my homebrew recipe for laundry detergent. Not b/c I'm a hoarder of my hard-won arcane knowledge, mind you, but b/c it only works if no one else knows about it. Otherwise I'd share.  ;D



Offline mcandmar

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Reply #5 on: January 19, 2021, 01:52:11 PM
not a crowd that's inclined to seriously wonder and experiment with whether, just for example, replacing aluminum screws with titanium in a carbon fiber wall receptacle improves the sound.

cheers, Derek

I thought you were joking until i had a browse, are they having a laugh?

One thing i have found about modifications, or even just substituting parts is that it always takes me a week of listening to come to any sort of conclusion.  You may notice a difference immediately and decide if that change is good or bad, but with time you might notice other changes that are more subtle.  Even different room temperature makes my speaker system sound different, hence living with it for extended period of time to evaluate.  I am currently wrapping up a build of a line stage pre amp which has taken me 3-4 months of incremental changes to get to where it is now...

M.McCandless


Offline johnsonad

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Reply #6 on: January 19, 2021, 01:59:26 PM
I'll second that.  Weeks if not months.  I get upgrade-itis and convince myself it must be an improvement.  After you walk away and come back to it after a while, you have a little different experience.

I applaud you Derek for your tweeking.  Don't forget to have fun and watch your back ;)

Aaron Johnson


Deke609

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Reply #7 on: January 19, 2021, 02:27:13 PM
... are they having a laugh?

Can't say for certain, but I doubt it. Way crazier stuff gets discussed in apparent seriousness. 

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One thing i have found about modifications, or even just substituting parts is that it always takes me a week of listening to come to any sort of conclusion.  You may notice a difference immediately and decide if that change is good or bad, but with time you might notice other changes that are more subtle.

I'll second that.  Weeks if not months.  I get upgrade-itis and convince myself it must be an improvement.  After you walk away and come back to it after a while, you have a little different experience.

Yup. I agree.  No final judgments.  I'll give the new chokes a solid 100 hrs before venturing there.  But after the time, effort and expense of such an experiment, I am compelled to give the amp a bit of a critical listen with certain tracks that I know really well with certain features that let me know what the amp is doing.  So far so good. 

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I applaud you Derek for your tweeking.  Don't forget to have fun and watch your back ;)

Just following both of your good examples! So far back is fine.  But boy am I breathing hard after moving and lifting the amp.  Not unlike finishing a set of deadlifts -- except that it reminds me that I should really be doing more deadlifts. ;D

cheers, Derek