John Curl's Blowtorch preamplifier part III

[john curl]

I agree with you, ridikas. These steep slope xovers screw up the transient response too much.

 

[john curl]

My xover preferences over the years has been, 1. Transient perfect (derived). 2. 6dB/oct ---------- 3. three pole Bessel

 

[Waly]

Well I am both an audiophile and an engineer so this keeps me on my toes.

I find trying to teach engineers that their textbook theories are not adequate quite arduous at times. At all times.

Then you waste time annoying yourself. Marquise de Sade would be proud of you.

 

[ridikas]

I agree with you, ridikas. These steep slope xovers screw up the transient response too much.

1st order acoustic slopes are exceptionally difficult and usually require many parts in the crossover. With proper driver alignment, they can sound wonderful, Thiel, Vandersteen, etc.

 

[DPH]

Who else is amusedly waiting for the hubris of ridiklas waxing lyrical about a speaker with lr4 acoustic filter (s). It must be difficult maintaining that kind of consistency in ideology. 😉

 

[ridikas]

Who else is amusedly waiting for the hubris of ridiklas waxing lyrical about a speaker with lr4 acoustic filter (s). It must be difficult maintaining that kind of consistency in ideology. 😉

I enjoy and use plenty of LR4 speakers, such as Bowers & Wilkins and Focal. Lazy doesn't mean that it can't sound good. Plus they R&D new driver technology/materials. But the art of designing complex crossovers to hit 1st order acoustic slopes and proper time coherency is pretty much dead.

No doubt DSP is the future. But so far I'm not overly impressed. Although I was tempted to get the Devialet Phantom Golds on a number of occasions to play with...

 

[morinix]

This Teflon business is a tough one. IF you can source premium Teflon caps, it is difficult to fault them. However, I would prefer only REL Teflon caps and they are hard to get, AND EXPENSIVE. Especially for production. I just spoke to Bas Lim of Rel Cap about it today. He sampled me Teflon, years ago, but against his better judgement. I now agree with him to stick to quality polystyrene, like RT, or even RTX. They are a little softer on the transients, but they sound smooth and 'right'. It is a bit like we when used to change cams in our cars. A slightly modified cam (sports cam) might not do all that a 3/4 cam would do, but on the street, it is the best choice. Only racers would find 3/4 to full race cams useful. It is the same with the difference between Teflon and Polystyrene, even from the same manufacturer. Also, not just any Teflon cap will sound good for audio, watch out for magnetic leads, etc. The military might approve them, but not audiophile ears.

I only use Teflon in one position of the LCR Gold right now. It is doing the active bass boost needed to push low frequencies through the ESR of the inductor I use. Nothing resolves like Teflon. All my good caps come from soviet block countries so I guess the leads are magnetic.

Rel is just too expensive.

 

[ridikas]

CRC used to make good military capacitors, including Teflon. SCR/Solen can custom make just about anything, for a hefty price.

Anyone know where (and if) the US military is sourcing Teflon caps from?

Looks like RTI can custom make Teflon caps. I'm wondering if that's where most audiophile Teflon capacitors come from?

 

[31697B]

The prices of military Teflon caps are insanely expensive, as expensive as any audiophile caps.

yes they are. I use for a Standard cap, a 1.0 mfd/600v Teflon in military hermitically sealed package.

$$$



-RM

 

[gpapag]

(And yes for many of you I am discussing advanced Turd Polishing, but it's an enjoyable diversion).

How can it be enjoyable if it has not a mole of esoterica? (you boring determinists)

The resulting effect on image makes it wander around and flutter a bit proportional to the movement.

A phase meter shows this clearly, particularly on low to mid music levels (screenshots from a mono vinyl recording)

George

 

[scott wurcer]

yes they are. I use for a Standard cap, a 1.0 mfd/600v Teflon in military hermitically sealed package.

NIST uses fused silica, nitrogen, or dry air.

 

[rayma]

Rel doesn't take small orders and Michael Percy is a distributor.

Also the Parts Connexion. Rel-Cap Film Capacitors

 

[DPH]

NIST uses fused silica, nitrogen, or dry air.

I haven't looked, but I'm surprised they're not using UHV instead. Maybe they're doing both (although the link seems more for defining a Farad from electrons)? An Upper Bound to the Frequency Dependence of the Cryogenic Vacuum-Gap Capacitor | NIST

Also, thanks Rayma. Hopefully others find it useful. I'm more of a "if it doesn't exist at Mouser/Digikey/Allied/Jameco/etc, I don't buy it" type. 🙂

 

[rayma]

Hopefully others find it useful. I'm more of a "if it doesn't exist at
Mouser/Digikey/Allied/Jameco/etc, I don't buy it" type. 🙂

Parts Connexion has a new web site, and will be much easier to deal with now.
They and Percy do stock differing Rel Caps.

Also Handmade Electronics sells some Rel Caps.
Reliable capacitor- PPFA,PPT, RT,PCU audio grade capacitors

Try Arrow Electronics sometime. https://www.arrow.com/

 

[DPH]

^ Yup, Arrow is in that list of etc, but good to know about Parts Connexion!

This guy is great: Datasheets, Electronic Parts, Components, Search - Octopart

 

[jneutron]

Well I am both an audiophile and an engineer so this keeps me on my toes.

I find trying to teach engineers that their textbook theories are not adequate quite arduous at times. At all times.

Interesting. I spend a lot of time re-teaching engineers the textbook theories because they either forgot them, or slept in class.

Jn

 

[elektroj]

Since whed did the WonderCaps went out of fashion? What's wrong with them? Just curious..

What did I say. 😉

What did you say, Scott? Would you remind me, please?

 

[scott wurcer]

What did you say, Scott? Would you remind me, please?

Just a joke re: capacitor sound and disagreement i.e. one appeared within minutes.

 

[scott wurcer]

Interesting. I spend a lot of time re-teaching engineers the textbook theories because they either forgot them, or slept in class.

their textbook theories are not adequate

I would like to know adequate for what? Most of the time here is spent arguing about how "text book" theories don't help design for the "best" sound. Is there a book of theories on that, I mean theories in the classic sense?

I did fall asleep in Millie Desselhaus' quantum mechanics class and I'm sure that's part of my problem.

 

[Markw4]

@traderbam, Please clarify which theories you have in mind as being inadequate? Do you mean something like over-assumption of linearity? Or maybe you are thinking of something like fundamental network theorems, or Maxwell equations, or what?