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Raven Capacitor and a General Querry on Education

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Posted on March 14, 2016 at 13:34:20
Prospect
Audiophile

Posts: 38
Joined: September 7, 2002
1) I was looking at Lynn's Raven preamp circuit, trying to figure everything out. I think I understand most of it, but what is the purpose of the large capacitor between the centertap of the output primary coil and the junction of the two cathodes and their bias resistor? Wouldn't the circuit work without that cap?

I assume it would block DC between the plate supply and the cathode, but it would let AC signals through. Why would you want that, and why is the cap so big?

2) My more general querry is about education. I have a rudimentary understanding of simple tube circuits. I've built several amps using various tubes and 2 or 3 different topologies. I've read most of the articles in Sound Practices (I had a subscription!) and I've paged through parts of two books (Morgan Jones and Bruce Rozenblit).

Very few of these sources talk much about designing with coils (interstage transformers, chokes, etc.) and I would like to learn more. I read forums like this one and keep running into concepts and terms I don't understand. I could bother everyone by asking an endless series of questions, or, perhaps more productively, I can ask for some advice on what resources I should turn to next. Does anyone have suggestions on where a relative beginner can get an education about designing tube circuits with coils (books, webpages, etc.)?

Without at least some knowledge, I don't even know how to pick the most appropriate Lundahl product for my next project :) I could ask Keven, but I would prefer to ask him from a position of basic knowledge rather than just having him pick something for me.



 

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Question 1. Answer. It is an ultrapath capacitor, posted on March 15, 2016 at 05:37:15
Bas Horneman
Audiophile

Posts: 4085
Joined: March 28, 2001
and it would work without.

http://www.tubecad.com/2008/08/blog0147.htm some theory.

 

RE: Question 1. Answer. It is an ultrapath capacitor, posted on March 15, 2016 at 09:47:41
Prospect
Audiophile

Posts: 38
Joined: September 7, 2002
Thanks! That explains it.

I gather from reading other posts on this forum that folks have moved beyond the Raven's ultrapath setup and are now using something different. This article suggests why, perhaps.

It also gives me a website full of articles worth several more days of reading.

 

RE: Raven Capacitor and a General Querry on Education, posted on March 15, 2016 at 13:03:42
KevinC
Manufacturer

Posts: 2984
Location: NC
Joined: April 19, 2001
I don't know of a comprehensive source such as you describe the desire for. There is some info dispersed among the chapters in the Radiotron Designer's Handbook, 4th Ed. The articles linked to on my website are probably not aimed at target you've presented, either.

I began my blog with the intent to add "transformer tutorial" installments from time-to-time, and I have the first two installments roughed out, but careful, clear technical writing is time consuming, so they haven't made it out of editing yet.

You are always welcome to contact me....

Kevin Carter
K&K Audio
www.kandkaudio.com

 

RE: Question 1. Answer. It is an ultrapath capacitor, posted on March 17, 2016 at 01:27:04
Boli46
Audiophile

Posts: 91
Location: Uppsala
Joined: March 6, 2015
There is hardly a consensus among tubebuilders on the (de)merits of ultrapath. Take a look at Thomas Mayer's Vinylsavor blog for a different take. Thomas Mayer builds top of the ladder tube amps and he uses ultrapath in most of them.

 

RE: Raven Capacitor and a General Querry on Education, posted on March 17, 2016 at 08:42:46
Prospect
Audiophile

Posts: 38
Joined: September 7, 2002
Kevin,
A set of short tutorials would be a wonderful addition to your website (or as stickies to this forum). Your offer to receive questions directly from me is most kind and welcome. I'd be happy to send you a set of questions that would cover the mysteries I confront when I'm trying to design with choke and transformer loads. There are probably only 5 or 6 questions, if I can structure them properly. They might even help you cross-check the coverage of your tutorials.

In the meantime, I just received a copy of Morgan Jones's book, Valve Amplifiers, 4th addition. It is almost twice as long as my 1st addition of the same book. The writing is much improved, and more thorough as well. This will keep me occupied for at least a few weeks :)

Around 2002-2004, I bought a few Lundahl products (probably from you) for two projects I was planning to build. I even had the chassis started, but then life threw me a sharp curve and I completely dropped out of electronics until just this year. I am now reviewing my journals, re-reading my magazines and reading lots of posts on this forum (and on Audio Asylum) to get back up to speed (I've forgotten Soooo, much!). I still have a pair of LL1660s (10ma), a pair of LL1676-AM and a pair of LL1660-PP, all fresh and unused (never soldered or mounted). They serve as incentive.

Again, thanks!



 

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